Yes me too. Sips using a Sip company designing, cutting and installing vs Sips designed by yourself, cut in factory and delivered to be self installed.... And... Sips delivered to be cut on site 😊 not the ideal use of such a great off-site product and a big mess on site, but could be a cheap alternative.
Yes, I made a comparison of sips and timber frame recently, here’s the link to the video What's best SIPS v Timber Frame - You won’t like what I’m going to tell you ua-cam.com/video/xW-ePTqDaAU/v-deo.html
A huge help, I'd come to my own conclusions on similar lines, but confirmation bias drew me to find your video. Really excellent, looking forward to watching more of your content.
Great walk through comparison. Interesting to see that you fix insulation external side of the osb sheathing. Is there any particular reason you prefer that arrangement as I have typically seen insulation only installed between the studwork with battens then nailed internal side of the stud to provide the cavity. Keep up the good work fella!
The reason to aim for fixing insulation to the outside is because you want the structural element as much as possible close to the internal room temperature. This is because of two reasons, first is to prevent differential movement…so where the structure moves at a different pace to the internal cladding causing those corner micro cracks in the plaster, and second is to ensure any possibility of a dew point (where warm air meets cold causing it to condense and create moisture) occurs as close to the outside and as far from any timber structure. Sometimes it unavoidable, for example in an attic conversion, and whilst a breather membrane will help if it’s just a wall, I’ll always aim to ventilate these cold voids on the inside face of the osb otherwise you’re asking for rot. Just because it’s a detail drawn in the insulation manufacturers’ specifications, it doesn’t mean it’s al all optimal. Hard to explain in a comment here.
@@build-better-things Thanks for the detailed response. Yes makes good sense doing all you can to move the dew point away from the TF. I am a chippie and I have done a couple TF stick frame extensions. I'm starting a TF extension (with brick external leaf) in a few weeks on my own house and I think I'll go with your method, it makes sense. I wonder how the large TF supply companies detail it, I must have a look. 👍
Many of the bigger timber frame companies supplying volume house builders have their own form of cassettes and panels that are a sort of hybrid SIPs where they create a timber frame with OSB and stud, and then put some form of synthetic inside the void, either by injecting or by compressing. They guarantee a certain u value and structure, although you then need to create a service void. However they won’t supply self builders. The sips panel providers do that, but I’ve made a separate video on that route, with costs and recommendations.
Thank you for the very thorough Video, the only thing I would have liked to see discussed and factored into the costs is the relative groundwork for both methods. I'm assuming the foundations required for Timber frame are shallower and required less material and time /labour to implement.
Hi. Foundations for both are broadly similar in design and dimensions so cost would not be a factor. Whilst it’s true masonry is heavier than timber frame, the foundation design is primarily determined by the loadings, both live and dead… (furniture, people etc and the roof and floors above, along with snow loadings).
Great content. Have been looking for something like this and it's more informative, thorough and graphic than expected. How about weight comparisons? Seems relevant for extensions over existing constructions. Cheers!
Hi. It’s not really weight, it’s loadings, which is measured in kilo newtons per metre square. The dead weight of the materials themselves isn’t such a big deal, and anyway, very easy to measure. It’s the combination of live and dead loadings and the way different materials react to the various stresses and moments. That’s why, for that part, we need our engineers. !!! So for the example you give, you method would be the same, calculate your loadings then see if your existing construction/foundation dimensions and design is able to take them. Hope I’m understanding your question properly.
@@build-better-things thanks for your reply, but I was referring to the actual weight per sqm of each system. As to which one is the lighter construction method and by how much. For context, I'm adding an extra room over an existing old masonry and concrete ground floor. There are no structural plans and it's actual construction is not the finest, so even though masonry additions are most usual where I live, I'm thinking of using timber to reduce the load on top of the existing home.
I’m not an engineer, but my initial answer is still what’s relevant, even for building on top of existing walls. . You need to forget about weight per square metre of the system and focus on the loadings. Timber frame is lighter than masonry. However the system’s weight is pretty much irrelevant. But you need to talk it through with an engineer.
Can a timber frame rear extension still work for terrace houses where you’d be building right up to the boundary, with no access on the neighbouring side? Could you build the outer leaf in block or facing brick first then build the inner frame? Thanks for the videos - super insightful for self builders 🙏
Brick is non combustible, the outer leaf, and even though the inner leaf is combustible if timber, If a fire started on your side, it would take more than 60 minutes to get through. Standard kiln bricks I think are 90 minutes. If fire started on your neighbours side, same would be true, since brick works both ways. 60 minutes is the standard. However, some local authorities take the view that ANY combustible element with a wall is detrimental to the integrity. Brick is such as inert material I would be very surprised if they took that view, but anything is possible with these officers. Normally it’s when you propose metal sheeting or similar however that they have concerns, which have radiant issues. I would be very confident and expect their approval by asking the question. To your other question, yes, I don’t see why not, although you’d also need to check any party wall agreements which can have some unusual conditions within them and are different for every circumstance. Remember you also need to show acoustic compliance for party walls.
My other question is about supporting the weight of the roof. Do you need vertical steel columns to take the roof load or is the timber frame strong enough for this on a 2 story extension?
Timber frame works fine for two storeys, and takes the roof loading. No need for steel in most circumstances, but as always get your engineer to confirm.
The inner leaf is always the load bearing leaf. The outer leaf is not. This sometimes confuses people. Therefore, the thickness of the inner leaf is defined by what it is holding up. 100mm is fine for some single storey situations, but for double storey and large single storey roofs, the engineers these days are insisting on 140mm. Great question since I didn’t clarify it in the video.
Thanks for the excellent video, very informative. How do brick ties get installed on the timber frame option? I would have thought the brickwork would still need to be tied back to the structure? Thanks
Yes, you need to tie brickwork in to the timber frame. There is a few ways, you get these cork screw ones that have the plastic washer for the insulation, I always put my insulation on the outside of the frame. The brickwork is essentially just a rain screen and needs securing up its height.
Thanks so much for the video. This is really interesting. My architect has specced masonry walls. 100mm cavity, with 90mm kingspan k106 to meet the latest u values of 0.18. this only leaves a 10mm void. You also say for a timber frame you can build the timber frame structure and get the roof on and windows in without having the outer brick skin done. This suggests the windows are fitted within the inner leaf rather than outer leaf as with standard masonry construction? Great video as always.
It's also worth mentioning that the other option my architect gave is a 150mm cavity with full fill cavity batts. No ventilation space at all which from looking around seems to be typical. I'm in North West England.
K106 complies within a block brick wall with a 10mm gap, the reality is it’s not really a ventilated cavity, it’s what’s called residual airspace and I think it’s a poor detail that leaves you open to cavity bridging, think about all those blobs of mortar that will slop down the tiny gap, unseen and against the PIR, as the block/brick is being laid. Fantastic route for cold damp, you’ll be blissfully unaware and there will be nothing you can do about it anyway. If space is a premium, use timber frame and a 50mm ventilated cavity, which is environmentally more efficient. In areas of higher exposure, it’s not compliant anyway, and you need a 50mm cavity, check out NHBC guidance. Your question on windows….if you’re using timber frame, you always should fit them prior to the outer leaf. Check out the volume house builders and you’ll see them doing just that. Your question about fixing them, use offset jamb fixing brackets, which allows flexibility in terms of where they sit and allows them to cantilever beyond the inner leaf and over the cavity. You fit your cavity closers and DPC first of course. Brick outer can be done anytime
Your full fill alternative solution is the lesser of two evils, but I would rather design out what I see as real world problems rather than these minimum standards.
Thanks again for your replies Jeremy. I asked my architects preferred structural engineer if changing my design to a timber frame inner leaf would change his calcs cost... He replied 'I wouldn’t recommend timber frame for a two-storey extension - inferior system all round and only suited for dorma cheeks and garden sheds'. So I assume I need to find an SE that thinks otherwise? I thought it was a strange opinion since a lot of very large houses are built with timber frame and work just fine?
@tomoose22 without seeing your project it’s difficult to give a view, but in general, that’s a strange comment by your engineer. As you say, 2 storey timber frame is everywhere. You can actually go up further too. Perhaps all his standard details are for brick and block, who knows. You’re the client, you’re paying him. Insist on a clear answer as to why, can it be done the way you want it…or not. You shouldn’t need to get a new engineer. People sometimes don’t like to deviate from what they are used to, regardless of the optimum solution, especially in the building industry
Hello there, In the case of constructing a single story extension (wooden frame with a brick outer leaf -Total width = 350mm) over a floating RSJ steel beam support beneath. How is the outer leaf brick supported if the RSJ is only 203mm wide to support the wooden frame and roof? Is it that a steel flange approx 150mm needs to be typically welded onto the RSJ to increase its width? Or it is that wider RSJ is required? Do you have an example of such in your videos? Thank you for your great content.
I might use a steel angle to support the outer leaf, but you need to properly design in the connections to the big beam so as to control thermal bridging.
Looking to build an outbuilding around 9m x 8m, with vaulted ceilings. Planning with architect is underway and in early stages so im doing loads of my own research in the mean time. Wondering if timber frame would be suited for the size of outbuilding i'm going for? loving your videos, great knowledge, subbed! thanks
Thanks a lot for your comment and subbing. Timber frame total suited to what you’re doing. Things to think about are the roof design in timber, prefabricated (trusses) or cut rafters and collars on site using speed squares. Trusses always seem a great idea until you realise the logistics issues. Rafters enable much more freedom with the roof space but will probably cost more. But the main difference between a flat roof of that you don’t have the issues of condensation as you don’t have a water membrane. You have tiles or slates with a breather membrane. Good luck with it.
So I have just bought a plot and the array of options out there is staggering! The temptation to just get a turn key job is high but so is the price! I hate paying for something I can do myself and historically I've paid good money to get shoddy workmanship. Where can I get 3 bedroom timber frame house designs including the engineering drawings to cover everything from founds to roofline for a home in scotland?
Companies like Scotframe publish their house plans on their website , you could just use those as your basis and then do the layout yourself. You’d need to learn the basics of Sketchup but I’ve made quite a few vids showing how easy it is for a self builder. Process would be…get a 3d measured survey of your plot that you can put into sketch up, (they’ll give you the dwg file), make your preferred layout, send off your layout to engineers and brief them to design it in timber frame. Once they come back with wall and floor makeups and foundation you add to your drawings. Then submit for your permissions. You might need an architect to help with the warrant application for things like u values etc. it may seem like a hassle but if you do it yourself, you’ll then find that building it yourself is a breeze.
So the plot has planning and designs for a 3 bed house which I like the bones of, however, I have tweaked it in MS Paint and I have additional features I wish to add. I am watching my way through your videos (great content btw) and I am now looking at how to use the software.... How do I go about capturing a 3d survey of the plot? is this something I can do with an IPad? @@build-better-things
I use a combination of a drone, a 30m tape and a staff with level to do my own surveys, but for anyone without much experience, just pay to get it done. They will give you a cad file which you import into something like sketchup.
I've just stumbled upon your channel. Really useful! Thanks! Just one question: do you have to do anything with the vapour barrier where services penetrate through e.g. electrical back boxes etc?
Great question. Yes, you should seal around all penetrations. With timber frame, you’d likely be using drywall boxes rather than metal back boxes. The best way is to avoid the hassle and create a battened service zone but that can be at the expense of floor area if space is a premium.
On your build up on the timber frame, you have 50mm insulation on the external side of the stud. I haven't seen any of the timber frame companies in Ireland do this; I can see the logic - but should the vapor barrier be moved from the OSB to the outside of the insulation? I am not keen on having PIR degassing into the house. I am okay with it on the external part of the stud, but inside, what are the best options, mineral wool? I don't have the space for cellulose.
I think when you say the vapour barrier, you mean the breather membrane. The breather membrane always needs to sit to the cold side of the OSB. As long as you stick to that principle , it’s not a huge deal whether it’s sitting directly on the osb, or, as i think suggest, sit it on the outside of the 50mm insulation. If you look at Unilin, which i believe were formally an Irish company, you’ll see their standard details for their XPS range of PIR and they will have it in the arrangement I suggest. The big mistake people make in these timber frame structures is underestimating the effect of cold / heat bridging that wall and roof studs create. They don’t bother with that 50mm layer you mention. They then compound that with an incorrectly placed breather membrane, shoddy vapour control, and no cavity ventilation. I hope I’ve understood your question correctly.
@@build-better-things @build-better-things - looked up the Unilin site, they do indeed give the same detail. I 100% agree on the cold bridging, amazing how many timber frame companies don't use something to break the cold bridge. On the breather membrane, as it's not really an insulator, is there potential for condensation between the membrane and the OSB? That's why I was thinking it would be better located on the external face of the PIR. I assume the minimum cavity should also be 50mm?
Assuming you’re using a breather membrane, the whole purpose of its construction is to keep moisture out whilst letting vapour from inside through. When you’re calculating your dew points, as part of the u value, as long as that dew point is past the cold side of the osb and the breather membrane, you don’t really need to worry about it.
I can see the benefits of timber frame, especially since as a DIYer I'm far more confident working with wood than with block, but in the context of the project I'm planning - 1950's brick cavity semi already full-fulled with blown in EPS gluemix by previous owner, which I'll be adding EWI to in an attempt to push the condensation point out of the fabric - I suspect I'd be better off replicating rest of the structure with the extension(though with blocks to save a bit of cash). Any thoughts?
I don’t see why you wouldn’t use timber frame with non loading brick outer leaf. I would. Be careful with your dew points with external wall insulation where you have existing cavity insulation.
@@build-better-things Even though I'm DIYing as much of the work as I can to save costs I do intend to have an eco-retrofit specialist architect & engineer do the planning and specs, so they'll be doing FLIR examination of the existing structure, probing the cavity to get current moisture levels, and doing some computer modelling, and the final result will have a contiguous warm roof and whole-house ducted MVHR plus a passive radon venting setup that will also help keep the ground beneath the structure dry(it's not really wet anyway, but belt & braces), so I'm confident the final result will be pretty bombproof in terms of moisture. In terms of the timber framing my worry was around interfacing the EWI with the new build effectively while also preserving the rendered exterior finish(the house is already fully rendered and the EWI requires it on top anyway for weatherproofing), if I add a timber frame to existing masonry wall will I not face issues with different expansion rates in the materials relative to the existing masonry it's fixed to(I don't intend to open the rear wall, the two existing windows will just be cut down into openings to avoid structural steelwork)? And I'm struggling to visualise how I could maintain a vented cavity for the timber extension - which I understood was an absolute necessity for timber, I can't fill the cavity like the house has been; unless I'm mistaken in that) - and use EWI on the facing brick as well, without which there would be a 150-200mm misalignment. With a masonry cavity construction I can build to modern code, pass the inspections, then just add the same EWI as the rest of the house as permitted dev.
Timber frame for a full new build all day. Economical, better energy options, easier, faster. Less reliance on trades holding up each other on the critical path. It surprises me that it remains so popular in the UK, but this is symptomatic of the industry and its appetite, or lack of, for change and innovation.
Hi, I had an engineer survey my house today and he thinks doing a timber frame extension to a block build house is a mistake due to different settling. What's your thoughts. I want to go timber frame as getting a block layer will be tricky and I'll get better insulation from timber frame and speed is better. Thanks
You always build up to DPC level in block brick anyway, with your timber frame starting above that. Any differential settlement would occur from the foundations up through the trench blocks. Your foundations are tied into the old foundations with anchors and rebar. Above the DPC The timber frame is tied into the existing block inner leaf with straps. For the outer leaf you either tooth in or use starter kits. There are thousands of extensions throughout the country built this way, into full masonry structures. Of course you should consult with a structural engineer, I’m not one, so don’t take my words as advice , but it sounds like your engineer may not be of the structural type? Timber is likely to shrink over is just year , so at the junctions with the plasterwork you make allowances for that, but shrinkage is inevitable anyway, and is not differential movement.
Yes but you need to vent the cavity top and bottom. You can use something like ryton slim vents, I think they make them for just a render board if you’re rendering into that, but they also make them for brick if you’re rendering into block…(both as part of a timber frame system). There is a rule for calculating how many you need if you phone the manufacturer but generally I just go every 9-1200mm. Alternatively you have a continuous 10mm gap top and bottom seal with fly mesh. You definitely need to counter batten your cavity to get it to the 50mm required for regulations. Best is 25mm battens and counter batten on top of breather membrane. Remember…never have horizontal battens directly onto breather membrane. Always start with vertical, with horizontal over
Amazing. Thanks for your help, your videos are extremely helpful and informative. I’m a carpenter with little general building knowledge, so this has all been a massive help and will enable me to carry out most of the works myself.
No it does not. Almost all of the volume house builders in the uk and usa are now using timber frame. What can affect the mortgage potential is the choice of cladding. For example, it was the case up until recently that if more than half of the property was clad in timber, for example cedar cladding, some lenders would be reluctant to commit. Not the case in USA but in uk. Most volume house builders in the uk choose to clad timber frame in brick, so you’d never know from looking that it was in fact, timber frame. Thanks for your comment.
Is it dangerous to drill holes in a timber stud wall and risk piercing the vapour barrier? How can we safely hang items like pictures, mirrors etc on a timber-frame wall?
Great question. Although there’s an argument that the nail or screw maintains the seal, in reality what you’re trying to do is prevent the majority of the vapour transitioning into the envelope. So one of the reasons we analyse the dew point, and use a breather membrane and then ventilate the cavity is because it’s virtually impossible to maintain the vapour barrier in the real world.
Ply board under plasterboard, allows you to hang mirrors and heavier items, I’d be very surprised if you manage to poke through the vapour barrier, specially when using 145mm CLS the screw/nail would have to be at least 170mm after it’s been boarded and plastered
Timber frame house. Air control, vapour control, thermal control, all much easier to achieve. Human beings can see kitchens and bathrooms, so that’s always been the selling point. Human beings can’t see environmental control, but that’s what makes you comfortable and healthy inside your home, and should be the main selling point.
We do 8 inch or 204 mm thick cmu block with vermiculite cores where not grouted solid with rebar, then 4 inches or 102 mm of mineral wool, low perm air barrier, 2 inch or 50 mm air gap, and masonry veneer rip rap limestone 40$ a ton. And use post and beam timber frame. I only did a masonry wall on my north wall. Have a skillion roof so snow builds up against north wall. I have 70 psf snow loads and 6 foot frost depths. My cottage was based off Goldie and Matt's earth ship but no berm or tires. I have 6 foot frost depths. And there framing was sub par for 70 psf snow loads.
It’s the insulation and u value that determine the wall thickness. Steel frame will make no difference to the insulation requirements and therefore your wall thickness would not change.
I don’t like it at all and I don’t think it works long term. It’s popular because it uses up less wall space in the makeup compared to traditional cavity fill.
@@build-better-things Yes I can see that. What about single skin blockwork with EWI? Again no air cavity but then the dew point is within the EWI meaning less risk of moisture damage inside the building.
Hi. Actually… the module you work from is 225mm, a brick is 215mm in length to take account of the stretcher bond joint on the centre line above it… if you measure it, plus the 10mm mortar joint, equals 225mm.
OMG! DEAD AIR SPACE between the vapour retarder and insulation is an absolute no-no in your stick frame wall. For Residential works especially, stick (timber) frame is the hand's down winner. I am staggered by the lack of insulation though. U-0.07 wall is poor even for Southern England these days . Air conditioning has to be considered today as well. Electricity is no cheap whether it's used to heat or cool. 38x140 stud at 400 o.c. provides U-0.05 with 140 batts of glass fiber (U-0.046 if using Rockwool). Your electrical service can easily be run before insulation (especially if you're using conduit). I refuse to specify rigid or spray foamed insulation when Rockwool or Glass Fiber is available and applicable. I only specify rigid foam (closed cell expanded polystyrene) for exterior below grade and underslab applications. In rare instances I will specify rigid insulation above grade where U-Value regulation compliance cannot be achieved any other way, but I try to design around those detail traps.
If the cavity is “airtight and sealed” as you advise, it means you have no weep holes, which means the moisture collecting from your cavity trays and DPC has nowhere to go. Damp and Rot will accumulate . For brickwork, for example in the timber frame scenario I describe and draw, you wouldn’t even get it past building regulations, because of the British Standard requirements for vents top and bottom to create airflow through the cavity for the rain screen, over and above the requirements for weep vents. This is done for every new house built today. Airtightness is a completely different thing you are confused about, that is about the inside envelope and nothing to do with the cavity. 40 years? Next thing you’ll be telling me you don’t need sand in your mortar mix.
Timber frame is just as strong as masonry if done correctly and much more labour efficient. Arguably more environmentally friendly but mostly much more cost effective from a construction standpoint.
What about sips instead of timber frame? Would love to see this cost comparison. 😊 Great video to see this trade off though.
Agreed would like to a sips comparison
Yes me too. Sips using a Sip company designing, cutting and installing vs Sips designed by yourself, cut in factory and delivered to be self installed.... And... Sips delivered to be cut on site 😊 not the ideal use of such a great off-site product and a big mess on site, but could be a cheap alternative.
Yes, I made a comparison of sips and timber frame recently, here’s the link to the video
What's best SIPS v Timber Frame - You won’t like what I’m going to tell you
ua-cam.com/video/xW-ePTqDaAU/v-deo.html
this stuff sounds so complicated
What an excellent video from a dedicated experienced one love it
Dude that was bloody brilliant !!! This is the second video of yours I have watced and I have to say, 10 out of 10 for both !!!
Thanks a lot. Appreciate it.
Great breakdown, convinced me!
Really useful information there, thanks for sharing 👍
Thorough and transparent. Thanks for making this video mate
A huge help, I'd come to my own conclusions on similar lines, but confirmation bias drew me to find your video. Really excellent, looking forward to watching more of your content.
Fantastic content as usual 👍
Great walk through comparison.
Interesting to see that you fix insulation external side of the osb sheathing. Is there any particular reason you prefer that arrangement as I have typically seen insulation only installed between the studwork with battens then nailed internal side of the stud to provide the cavity.
Keep up the good work fella!
The reason to aim for fixing insulation to the outside is because you want the structural element as much as possible close to the internal room temperature. This is because of two reasons, first is to prevent differential movement…so where the structure moves at a different pace to the internal cladding causing those corner micro cracks in the plaster, and second is to ensure any possibility of a dew point (where warm air meets cold causing it to condense and create moisture) occurs as close to the outside and as far from any timber structure. Sometimes it unavoidable, for example in an attic conversion, and whilst a breather membrane will help if it’s just a wall, I’ll always aim to ventilate these cold voids on the inside face of the osb otherwise you’re asking for rot. Just because it’s a detail drawn in the insulation manufacturers’ specifications, it doesn’t mean it’s al all optimal. Hard to explain in a comment here.
@@build-better-things Thanks for the detailed response.
Yes makes good sense doing all you can to move the dew point away from the TF.
I am a chippie and I have done a couple TF stick frame extensions. I'm starting a TF extension (with brick external leaf) in a few weeks on my own house and I think I'll go with your method, it makes sense.
I wonder how the large TF supply companies detail it, I must have a look.
👍
Many of the bigger timber frame companies supplying volume house builders have their own form of cassettes and panels that are a sort of hybrid SIPs where they create a timber frame with OSB and stud, and then put some form of synthetic inside the void, either by injecting or by compressing. They guarantee a certain u value and structure, although you then need to create a service void. However they won’t supply self builders. The sips panel providers do that, but I’ve made a separate video on that route, with costs and recommendations.
Thank you for the very thorough Video, the only thing I would have liked to see discussed and factored into the costs is the relative groundwork for both methods. I'm assuming the foundations required for Timber frame are shallower and required less material and time /labour to implement.
Hi. Foundations for both are broadly similar in design and dimensions so cost would not be a factor. Whilst it’s true masonry is heavier than timber frame, the foundation design is primarily determined by the loadings, both live and dead… (furniture, people etc and the roof and floors above, along with snow loadings).
@@build-better-things thank you for the comprehensive and quick reply... much appreciated
Great content. Have been looking for something like this and it's more informative, thorough and graphic than expected.
How about weight comparisons? Seems relevant for extensions over existing constructions.
Cheers!
Hi. It’s not really weight, it’s loadings, which is measured in kilo newtons per metre square. The dead weight of the materials themselves isn’t such a big deal, and anyway, very easy to measure. It’s the combination of live and dead loadings and the way different materials react to the various stresses and moments. That’s why, for that part, we need our engineers. !!! So for the example you give, you method would be the same, calculate your loadings then see if your existing construction/foundation dimensions and design is able to take them. Hope I’m understanding your question properly.
@@build-better-things thanks for your reply, but I was referring to the actual weight per sqm of each system. As to which one is the lighter construction method and by how much.
For context, I'm adding an extra room over an existing old masonry and concrete ground floor. There are no structural plans and it's actual construction is not the finest, so even though masonry additions are most usual where I live, I'm thinking of using timber to reduce the load on top of the existing home.
I’m not an engineer, but my initial answer is still what’s relevant, even for building on top of existing walls. . You need to forget about weight per square metre of the system and focus on the loadings. Timber frame is lighter than masonry. However the system’s weight is pretty much irrelevant. But you need to talk it through with an engineer.
Great analysis. Thank you.
Very interesting - thank you!
Glad it was helpful!
Can a timber frame rear extension still work for terrace houses where you’d be building right up to the boundary, with no access on the neighbouring side? Could you build the outer leaf in block or facing brick first then build the inner frame? Thanks for the videos - super insightful for self builders 🙏
Brick is non combustible, the outer leaf, and even though the inner leaf is combustible if timber, If a fire started on your side, it would take more than 60 minutes to get through. Standard kiln bricks I think are 90 minutes. If fire started on your neighbours side, same would be true, since brick works both ways. 60 minutes is the standard. However, some local authorities take the view that ANY combustible element with a wall is detrimental to the integrity. Brick is such as inert material I would be very surprised if they took that view, but anything is possible with these officers. Normally it’s when you propose metal sheeting or similar however that they have concerns, which have radiant issues. I would be very confident and expect their approval by asking the question. To your other question, yes, I don’t see why not, although you’d also need to check any party wall agreements which can have some unusual conditions within them and are different for every circumstance. Remember you also need to show acoustic compliance for party walls.
Do we need a damp proof course in foundation for timber builds ??
If you’re building a suspended timber floor off masonry you need a DPC.
My other question is about supporting the weight of the roof. Do you need vertical steel columns to take the roof load or is the timber frame strong enough for this on a 2 story extension?
Timber frame works fine for two storeys, and takes the roof loading. No need for steel in most circumstances, but as always get your engineer to confirm.
Amazing detail thank you😮
Great videos, why do you use 140mm block for the inner leaf rather than 100mm? Thanks!
The inner leaf is always the load bearing leaf. The outer leaf is not. This sometimes confuses people. Therefore, the thickness of the inner leaf is defined by what it is holding up. 100mm is fine for some single storey situations, but for double storey and large single storey roofs, the engineers these days are insisting on 140mm. Great question since I didn’t clarify it in the video.
Thanks for the excellent video, very informative. How do brick ties get installed on the timber frame option? I would have thought the brickwork would still need to be tied back to the structure? Thanks
Yes, you need to tie brickwork in to the timber frame. There is a few ways, you get these cork screw ones that have the plastic washer for the insulation, I always put my insulation on the outside of the frame. The brickwork is essentially just a rain screen and needs securing up its height.
Thanks so much for the video. This is really interesting. My architect has specced masonry walls. 100mm cavity, with 90mm kingspan k106 to meet the latest u values of 0.18. this only leaves a 10mm void. You also say for a timber frame you can build the timber frame structure and get the roof on and windows in without having the outer brick skin done. This suggests the windows are fitted within the inner leaf rather than outer leaf as with standard masonry construction? Great video as always.
It's also worth mentioning that the other option my architect gave is a 150mm cavity with full fill cavity batts. No ventilation space at all which from looking around seems to be typical. I'm in North West England.
K106 complies within a block brick wall with a 10mm gap, the reality is it’s not really a ventilated cavity, it’s what’s called residual airspace and I think it’s a poor detail that leaves you open to cavity bridging, think about all those blobs of mortar that will slop down the tiny gap, unseen and against the PIR, as the block/brick is being laid. Fantastic route for cold damp, you’ll be blissfully unaware and there will be nothing you can do about it anyway. If space is a premium, use timber frame and a 50mm ventilated cavity, which is environmentally more efficient. In areas of higher exposure, it’s not compliant anyway, and you need a 50mm cavity, check out NHBC guidance.
Your question on windows….if you’re using timber frame, you always should fit them prior to the outer leaf. Check out the volume house builders and you’ll see them doing just that. Your question about fixing them, use offset jamb fixing brackets, which allows flexibility in terms of where they sit and allows them to cantilever beyond the inner leaf and over the cavity. You fit your cavity closers and DPC first of course. Brick outer can be done anytime
Your full fill alternative solution is the lesser of two evils, but I would rather design out what I see as real world problems rather than these minimum standards.
Thanks again for your replies Jeremy. I asked my architects preferred structural engineer if changing my design to a timber frame inner leaf would change his calcs cost... He replied 'I wouldn’t recommend timber frame for a two-storey extension - inferior system all round and only suited for dorma cheeks and garden sheds'. So I assume I need to find an SE that thinks otherwise? I thought it was a strange opinion since a lot of very large houses are built with timber frame and work just fine?
@tomoose22 without seeing your project it’s difficult to give a view, but in general, that’s a strange comment by your engineer. As you say, 2 storey timber frame is everywhere. You can actually go up further too. Perhaps all his standard details are for brick and block, who knows. You’re the client, you’re paying him. Insist on a clear answer as to why, can it be done the way you want it…or not. You shouldn’t need to get a new engineer. People sometimes don’t like to deviate from what they are used to, regardless of the optimum solution, especially in the building industry
Hello there, In the case of constructing a single story extension (wooden frame with a brick outer leaf -Total width = 350mm) over a floating RSJ steel beam support beneath. How is the outer leaf brick supported if the RSJ is only 203mm wide to support the wooden frame and roof? Is it that a steel flange approx 150mm needs to be typically welded onto the RSJ to increase its width? Or it is that wider RSJ is required? Do you have an example of such in your videos? Thank you for your great content.
I might use a steel angle to support the outer leaf, but you need to properly design in the connections to the big beam so as to control thermal bridging.
Looking to build an outbuilding around 9m x 8m, with vaulted ceilings. Planning with architect is underway and in early stages so im doing loads of my own research in the mean time. Wondering if timber frame would be suited for the size of outbuilding i'm going for? loving your videos, great knowledge, subbed! thanks
Thanks a lot for your comment and subbing. Timber frame total suited to what you’re doing. Things to think about are the roof design in timber, prefabricated (trusses) or cut rafters and collars on site using speed squares. Trusses always seem a great idea until you realise the logistics issues. Rafters enable much more freedom with the roof space but will probably cost more. But the main difference between a flat roof of that you don’t have the issues of condensation as you don’t have a water membrane. You have tiles or slates with a breather membrane. Good luck with it.
So I have just bought a plot and the array of options out there is staggering!
The temptation to just get a turn key job is high but so is the price!
I hate paying for something I can do myself and historically I've paid good money to get shoddy workmanship.
Where can I get 3 bedroom timber frame house designs including the engineering drawings to cover everything from founds to roofline for a home in scotland?
Companies like Scotframe publish their house plans on their website , you could just use those as your basis and then do the layout yourself. You’d need to learn the basics of Sketchup but I’ve made quite a few vids showing how easy it is for a self builder. Process would be…get a 3d measured survey of your plot that you can put into sketch up, (they’ll give you the dwg file), make your preferred layout, send off your layout to engineers and brief them to design it in timber frame. Once they come back with wall and floor makeups and foundation you add to your drawings. Then submit for your permissions. You might need an architect to help with the warrant application for things like u values etc. it may seem like a hassle but if you do it yourself, you’ll then find that building it yourself is a breeze.
So the plot has planning and designs for a 3 bed house which I like the bones of, however, I have tweaked it in MS Paint and I have additional features I wish to add.
I am watching my way through your videos (great content btw) and I am now looking at how to use the software.... How do I go about capturing a 3d survey of the plot? is this something I can do with an IPad? @@build-better-things
I use a combination of a drone, a 30m tape and a staff with level to do my own surveys, but for anyone without much experience, just pay to get it done. They will give you a cad file which you import into something like sketchup.
I've just stumbled upon your channel. Really useful! Thanks!
Just one question: do you have to do anything with the vapour barrier where services penetrate through e.g. electrical back boxes etc?
Great question. Yes, you should seal around all penetrations. With timber frame, you’d likely be using drywall boxes rather than metal back boxes. The best way is to avoid the hassle and create a battened service zone but that can be at the expense of floor area if space is a premium.
On your build up on the timber frame, you have 50mm insulation on the external side of the stud. I haven't seen any of the timber frame companies in Ireland do this; I can see the logic - but should the vapor barrier be moved from the OSB to the outside of the insulation? I am not keen on having PIR degassing into the house. I am okay with it on the external part of the stud, but inside, what are the best options, mineral wool? I don't have the space for cellulose.
I think when you say the vapour barrier, you mean the breather membrane. The breather membrane always needs to sit to the cold side of the OSB. As long as you stick to that principle , it’s not a huge deal whether it’s sitting directly on the osb, or, as i think suggest, sit it on the outside of the 50mm insulation. If you look at Unilin, which i believe were formally an Irish company, you’ll see their standard details for their XPS range of PIR and they will have it in the arrangement I suggest. The big mistake people make in these timber frame structures is underestimating the effect of cold / heat bridging that wall and roof studs create. They don’t bother with that 50mm layer you mention. They then compound that with an incorrectly placed breather membrane, shoddy vapour control, and no cavity ventilation. I hope I’ve understood your question correctly.
@@build-better-things @build-better-things - looked up the Unilin site, they do indeed give the same detail. I 100% agree on the cold bridging, amazing how many timber frame companies don't use something to break the cold bridge. On the breather membrane, as it's not really an insulator, is there potential for condensation between the membrane and the OSB? That's why I was thinking it would be better located on the external face of the PIR. I assume the minimum cavity should also be 50mm?
Assuming you’re using a breather membrane, the whole purpose of its construction is to keep moisture out whilst letting vapour from inside through. When you’re calculating your dew points, as part of the u value, as long as that dew point is past the cold side of the osb and the breather membrane, you don’t really need to worry about it.
I can see the benefits of timber frame, especially since as a DIYer I'm far more confident working with wood than with block, but in the context of the project I'm planning - 1950's brick cavity semi already full-fulled with blown in EPS gluemix by previous owner, which I'll be adding EWI to in an attempt to push the condensation point out of the fabric - I suspect I'd be better off replicating rest of the structure with the extension(though with blocks to save a bit of cash). Any thoughts?
I don’t see why you wouldn’t use timber frame with non loading brick outer leaf. I would. Be careful with your dew points with external wall insulation where you have existing cavity insulation.
@@build-better-things Even though I'm DIYing as much of the work as I can to save costs I do intend to have an eco-retrofit specialist architect & engineer do the planning and specs, so they'll be doing FLIR examination of the existing structure, probing the cavity to get current moisture levels, and doing some computer modelling, and the final result will have a contiguous warm roof and whole-house ducted MVHR plus a passive radon venting setup that will also help keep the ground beneath the structure dry(it's not really wet anyway, but belt & braces), so I'm confident the final result will be pretty bombproof in terms of moisture. In terms of the timber framing my worry was around interfacing the EWI with the new build effectively while also preserving the rendered exterior finish(the house is already fully rendered and the EWI requires it on top anyway for weatherproofing), if I add a timber frame to existing masonry wall will I not face issues with different expansion rates in the materials relative to the existing masonry it's fixed to(I don't intend to open the rear wall, the two existing windows will just be cut down into openings to avoid structural steelwork)? And I'm struggling to visualise how I could maintain a vented cavity for the timber extension - which I understood was an absolute necessity for timber, I can't fill the cavity like the house has been; unless I'm mistaken in that) - and use EWI on the facing brick as well, without which there would be a 150-200mm misalignment. With a masonry cavity construction I can build to modern code, pass the inspections, then just add the same EWI as the rest of the house as permitted dev.
Would you consider timber frame for a full new build, or do you think block work has the edge here?
Timber frame for a full new build all day. Economical, better energy options, easier, faster. Less reliance on trades holding up each other on the critical path. It surprises me that it remains so popular in the UK, but this is symptomatic of the industry and its appetite, or lack of, for change and innovation.
Hi, I had an engineer survey my house today and he thinks doing a timber frame extension to a block build house is a mistake due to different settling. What's your thoughts. I want to go timber frame as getting a block layer will be tricky and I'll get better insulation from timber frame and speed is better. Thanks
You always build up to DPC level in block brick anyway, with your timber frame starting above that. Any differential settlement would occur from the foundations up through the trench blocks. Your foundations are tied into the old foundations with anchors and rebar. Above the DPC The timber frame is tied into the existing block inner leaf with straps. For the outer leaf you either tooth in or use starter kits. There are thousands of extensions throughout the country built this way, into full masonry structures. Of course you should consult with a structural engineer, I’m not one, so don’t take my words as advice , but it sounds like your engineer may not be of the structural type? Timber is likely to shrink over is just year , so at the junctions with the plasterwork you make allowances for that, but shrinkage is inevitable anyway, and is not differential movement.
If you were to build a timber frame to have a rendered finished, how would you create a vented cavity? Would counter batten suffice?
Yes but you need to vent the cavity top and bottom. You can use something like ryton slim vents, I think they make them for just a render board if you’re rendering into that, but they also make them for brick if you’re rendering into block…(both as part of a timber frame system). There is a rule for calculating how many you need if you phone the manufacturer but generally I just go every 9-1200mm. Alternatively you have a continuous 10mm gap top and bottom seal with fly mesh. You definitely need to counter batten your cavity to get it to the 50mm required for regulations. Best is 25mm battens and counter batten on top of breather membrane. Remember…never have horizontal battens directly onto breather membrane. Always start with vertical, with horizontal over
Amazing. Thanks for your help, your videos are extremely helpful and informative. I’m a carpenter with little general building knowledge, so this has all been a massive help and will enable me to carry out most of the works myself.
Whats the website you used to look at the different types of cavity wall?
It’s the Kingspan one, but there’s also Knauf, Isotherm, Rockwool etc. I’ve got no preference for Kingspan, it was just the first one that came up.
Does the timber frame effect the mortgage of the property?
Thanks
No it does not. Almost all of the volume house builders in the uk and usa are now using timber frame. What can affect the mortgage potential is the choice of cladding. For example, it was the case up until recently that if more than half of the property was clad in timber, for example cedar cladding, some lenders would be reluctant to commit. Not the case in USA but in uk. Most volume house builders in the uk choose to clad timber frame in brick, so you’d never know from looking that it was in fact, timber frame. Thanks for your comment.
Is it dangerous to drill holes in a timber stud wall and risk piercing the vapour barrier? How can we safely hang items like pictures, mirrors etc on a timber-frame wall?
Great question. Although there’s an argument that the nail or screw maintains the seal, in reality what you’re trying to do is prevent the majority of the vapour transitioning into the envelope. So one of the reasons we analyse the dew point, and use a breather membrane and then ventilate the cavity is because it’s virtually impossible to maintain the vapour barrier in the real world.
Ply board under plasterboard, allows you to hang mirrors and heavier items, I’d be very surprised if you manage to poke through the vapour barrier, specially when using 145mm CLS the screw/nail would have to be at least 170mm after it’s been boarded and plastered
@Qizhang1 think you’re confusing vapour barrier with breather membrane.
Is the outer leaf not tied to the inner?
Yes, that’s right
Do you have any experience of building an extension using sfs / medsec
I don’t have direct experience . I’ve never built anything with either system although I nearly used metsec once.
@@build-better-things I use it on the commercial jobs I work on, it’s a very fast system
@@build-better-things would you prefer a brick house or timber frame house ?
Timber frame house. Air control, vapour control, thermal control, all much easier to achieve. Human beings can see kitchens and bathrooms, so that’s always been the selling point. Human beings can’t see environmental control, but that’s what makes you comfortable and healthy inside your home, and should be the main selling point.
We do 8 inch or 204 mm thick cmu block with vermiculite cores where not grouted solid with rebar, then 4 inches or 102 mm of mineral wool, low perm air barrier, 2 inch or 50 mm air gap, and masonry veneer rip rap limestone 40$ a ton. And use post and beam timber frame. I only did a masonry wall on my north wall. Have a skillion roof so snow builds up against north wall. I have 70 psf snow loads and 6 foot frost depths. My cottage was based off Goldie and Matt's earth ship but no berm or tires. I have 6 foot frost depths. And there framing was sub par for 70 psf snow loads.
What if you use steel profile insted of timber? You could save on internal wall thickness?
It’s the insulation and u value that determine the wall thickness. Steel frame will make no difference to the insulation requirements and therefore your wall thickness would not change.
Full fill cavity seem quite popular these days but seems like you are not in favour?
I don’t like it at all and I don’t think it works long term. It’s popular because it uses up less wall space in the makeup compared to traditional cavity fill.
@@build-better-things Yes I can see that. What about single skin blockwork with EWI? Again no air cavity but then the dew point is within the EWI meaning less risk of moisture damage inside the building.
A bricks width is 102.5mm so that two bricks width and 10mm mortar is 215mm, the length of a brick.
Hi. Actually… the module you work from is 225mm, a brick is 215mm in length to take account of the stretcher bond joint on the centre line above it… if you measure it, plus the 10mm mortar joint, equals 225mm.
OMG! DEAD AIR SPACE between the vapour retarder and insulation is an absolute no-no in your stick frame wall.
For Residential works especially, stick (timber) frame is the hand's down winner.
I am staggered by the lack of insulation though. U-0.07 wall is poor even for Southern England these days . Air conditioning has to be considered today as well. Electricity is no cheap whether it's used to heat or cool. 38x140 stud at 400 o.c. provides U-0.05 with 140 batts of glass fiber (U-0.046 if using Rockwool). Your electrical service can easily be run before insulation (especially if you're using conduit).
I refuse to specify rigid or spray foamed insulation when Rockwool or Glass Fiber is available and applicable. I only specify rigid foam (closed cell expanded polystyrene) for exterior below grade and underslab applications. In rare instances I will specify rigid insulation above grade where U-Value regulation compliance cannot be achieved any other way, but I try to design around those detail traps.
Cavity is supposed to be airtight and sealed .bricklayer 40 years City and guilds
If the cavity is “airtight and sealed” as you advise, it means you have no weep holes, which means the moisture collecting from your cavity trays and DPC has nowhere to go. Damp and Rot will accumulate .
For brickwork, for example in the timber frame scenario I describe and draw, you wouldn’t even get it past building regulations, because of the British Standard requirements for vents top and bottom to create airflow through the cavity for the rain screen, over and above the requirements for weep vents. This is done for every new house built today.
Airtightness is a completely different thing you are confused about, that is about the inside envelope and nothing to do with the cavity.
40 years? Next thing you’ll be telling me you don’t need sand in your mortar mix.
Who taught you that?
"Promo sm"
All the extra steps needed and the delicacy of timber frame, why would you even bother. Saving pennies now will cost you in the future.
What would you suggest?
Timber frame is just as strong as masonry if done correctly and much more labour efficient.
Arguably more environmentally friendly but mostly much more cost effective from a construction standpoint.
Wow can I borrow your brain
Excellent presentation, thanks for sharing :)
Many thanks!