Thank you for the explanation Andy. As a practicing Chartered Structural Engineer myself it does all make sense. Not saying I'd have used timbers that large (preferring to sympathetically match the existing, cross battening where necessary for modern insulation so plate levels are maintained) but the basic philosophy is sound. Those uncoordinated details caused my eyes to bleed a little, the drawing checker wants their knuckles wrapped for that! What I find with a contingent of modern builders, and even some supposed experienced roofing carpenters, (and particularly the keyboard warrior experts) is that they don't understand thrust, spread and restraint. A fresh new roof may well look like it locks together without all that structural gubbins, but timbers shrink, joints open, relaxation and spread occurs, and then the householder sees cracks that repeatedly open until, sometimes years later, if at all, the roof reaches an equilibrium, and all the time normal seasonal thermal and humidity movement racks the unrestrained roof further. That early spread movement may have disrupted brickwork, and even rotated lintels. It's much better to properly restrain roofs during construction and mitigate all those nasty issues that will otherwise plague the building. And it rarely takes much more effort. As well as designing, we also write structural reports on (mostly) older properties for those selling and buying. Whilst many old roofs were build well and sound and have no significant issues at all, we make a good living out of appraising those other old roofs where the experienced carpenter thought he knew best and elected to provide insufficient restraint to rafter toes (particularly hips) leading to spread, internal and external cracking, bulging/leaning walls, or where purlins are undersized / insufficiently propped and have sagged and twisted, or ceiling joists bounce better than some garden trampolines - toe nailing through binders to hold up ceiling joist is a classic failure issue as the nails withdraw over time. The naysayers putting up roofs today with more confidence than skill, knowledge and understanding will continue to provide me with an income in sorting out their spreading roofs long in to my retirement and beyond. However, I can't see anyone having an issue with that new piece of roof, Andy. Aside from the somewhat chunky and generous timber sizes, well done for having it all put in. A good nights sleep will be had below those timbers. Thank you for sharing.
@@peterwooldridge7285 Hi Peter. For this addition, no. It's far too small and would have resulted in a considerable amount of hand cut anyway. Trusses are usually more suited to areas where full span trusses can be erected over a larger area. Hips always seem to involve a lot of cuts, and this roof seemed mostly a hip. Not to mention there would still be a need to provide support to the existing roof where the original hip was unpicked.
Fantastic response - thank you so much for sharing your insight. I'm involved in the peripherals of the construction trade (on the banking side...often pronounced with a soft 'b' ;) ) and have seen my fair share of Chartered Surveyor & Engineers reports where things have started to go wrong - it can get scary and result in the remediation works costing more than doing it properly in the first place (although it's never the person who cut the corners that gets to pay for it 20+ years down the line). As someone who relies on professional reports (and the Professional Indemnity policies behind them) it's a great comfort that the designs typically provided by the SE takes into account the natural lifecycle of a structure and dynamic nature of the materials used. Incidentally - how much consideration is given to dynamic loading for this sort of design? Presumably there is a great deal of torque applied to a structure in heavy winds via the roof in addition to the static weight of itself?
Thanks for explaining. Basically the ridge needed some support but there was nothing under it so the steels bridged the gap to get a solid base to support from. I am jealous of your slope insulation. I spent days up in my loft retro fitting that and sliding insulation down the gap and doing the jack rafter gaps from the outside.
@@GosforthHandyman This, along with the cavity filling has made a huge difference. As we have a steep roof and a deep overhang, the outer skin of the wall stopped about 50cm below the inside skin wallplate. So while repainting the outside I took off the fascia and insulated that gap too. I could not find anyone else who has done this!
Going through the engineers drawings… where he notes ‘pitch and plane of beam to match roof slope / rafters’ did he come out and measure the slope so that you had a beam design you could send out to fabricators, or did you get left to work that bit out?
Old ridge timbers were usually only 1" or 1 1/4"r inch thick as they do not support anything [the rafter each side support each other]. it is just there as something to fix the rafters to and stop them moving about.
@@GosforthHandyman There were no structural engineers involved when that place was built. They do tend to work it out. double it and add the date in. But as you say you have no way of doing it.
Using the, 'look these buildings have lasted 100 years + so old building methods were good, no need for all these calcs' argument, does not take into account those old buildings which fell down or were replaced because of structural problems. We are seeing the survivors, or satisfactorily remedialy fixed, today. Numerous Cathedral's roofs had to be re designed and replaced, as they were built, but these were well documented buildings. Modern materials are often heavier. Replace a slate roof with tiles and the structure needs redesigning, including the slope. Great video Andy.
Hi sir I think the engineer has been very wise , and has been very prudent not to take any notice of the existing structure . Just those last photos of the existing rafters is proof that he was right . Even my own house that was built some 40years ago has sagged slightly even though the house was designed with 18inc RSJs x 5 running the full width of the house . The reason being for sagging is the jack rafters were just not big enough , if it was being built to day they would be a lot bigger . Having said all that the roof is not going any were because of the massive steels used , but I just thought it was a good example of things that can appear in the future . Best wishes and kind regards as always 😀👍👍👍
We live in an old terrace where the roof has huge purlins (think that's the correct term, they look the size of large tree trunks) With a big triangle construction in the middle of the roof made from huge sawn timbers, with smaller rafters sitting on the purlins. All the timbers look more like logs than modern rectangular timbers, all the joints are dove tailed or mortise and tenon. In terms of craftmanship its a beautiful thing to look at (even if it does make feel somewhat unsure of its structural integrity after all these years). However this video got me thinking how you would marry that old construction with modern construction if you were to try and do a similar extension on a roof the age of mine.
The steels make more sense now, although I would have thought the existing timbers were very 'examinable' in situ and the steels would have been just as effective if they'd been tension bars spanning the house and attached to the roof spars to prevent the roof spreading under its own weight. But as you say, there's no point arguing.
I do structural engineering for ships, not houses, but your explanation was good. I enjoyed seeing the architect and engineering drawings. You’re absolutely right that the engineer had to assume the new structure needed full support. Without the as built drawings for the house originally plus a detailed survey to note any changes since build and the current condition of the structure as it stands, it would be irresponsible to assume the strength of the existing structure and then depend on that assumption for the new work. If anything were to happen down the road, they would be legally liable for damages because of that assumption. In my work, we actually do the surveys to determine current as built condition because it is EXPENSIVE to assume the worst and with large ships the job is already costly and materials are a much bigger portion of that than the engineering. As you said, those beams aren’t cheap! But in small residential renovations like this, I assume it’s more cost effective to make that assumption and pay the price in materials than to do the investigative work to determine the bare minimum support required.
Can see it has 'belt and braces' , a very solid construction apart from one thing - a purlin. Think I would be tempted to add one between the two vertical supports on either side to give additional support to the intermediate rafters. But suspect the rafters have been sized to allow for this? Love roofs. Always a mess of timbers !! :)
Thanks for the great videos, I'm learning lots! Also I've just found the measuring up podcast, only a few years too late..... Out of curiosity, how picky are building control? If the structural engineer specs 2x(100x50) and you use C16/24 it's actually 95x47(IIRC) are they going to complain or is this more of the typical building materials nominal sizes and you need to know what everyone actually means rather than what's written down?
I understand the structural proposal but I have to say that the sizes are much larger than I would have expected and certainly more than would probably have been specified by the various structural engineers I use. Unfortunately, some engineers design on a dot to dot basis and not holistically. An example of this is that is the size of the ridge beam than can either be assumed as carrying weight or as just a separator of the rafters, that is why traditionally the ridge plate was 200/250 deep x 25mm The 120x120x6.3 SHS is actually 120mm by 120mm by 6.3mm wall thickness Square Hollow Section. You also get RHS and CHS that are Rectangular and Circular respectively. I assume that the SHS was specified to get the steelwork within the depth of the rafters. Having now seen in detail the construction I assume that the central double beam doesn't support the enormous ceiling joists so that it and the steelwork only support the roof. If so, then there is no need for fire protection to the steelwork. I note that the roof has been sprayed with polyurethane foam, which is a real problem as the system is not vapour resistive and thus condensation will occur in the rafters but before then it would not surprise me if the tiling battens start to rot as any water getting through the tiles will run down the sarking but only as far as the first batten where the foam has taken the sag out that normally allows drainage of incidental water. If you were to retain the rafter level insulation it would be logical to extend that over the new roof, but be aware of the required detailing to prevent vapour passages and cold bridging. A good solution to this is to use multi-foil insulation/vapour barrier. and PIR board under.
Hi Andy. Great video. You said that you think that the cranked beam is overkill. What on the structural engineers calculations do you think he got wrong?
The timber and nails scenario just highlights at some points just how "rough and ready" the construction industry is. However, it's best to adhere to engineers guidelines and better to be safe than sorry Andy !
I find it quite interesting. Our home was built in the late 1800's. All the floor joists are dove tailed into two large beams that span the downstairs space. You can see old stuff beautifully crafted together, whilst the modern repairs just butted up against and scatter-gunned with screws/nails. I suppose its strong enough and time is money and all that
Wondering if you had stripped the entire roof back and rebuilt the roof structure, would it have been comparable to the cost of getting the steels done and in and all the engineering? And what was the existing stuff like? Seeing what you pulled out, it seems the rest might have been in quite good. condition
The existing timbers were perfect but stripping the whole roof off would have been very costly. The whole roof would have needed a temporary cover, complete re-tile, waste disposal of the old roof... probably looking at min £25k to do that vs ~£800 for the two steels. 👍
Fascinating! Will all that spray foam insulation on the original roof now be redundant? I pressume you either get the new roof sprayed or fully insulate the whole ceiling to current standards? Edit: Sorry I think I found your answer way below - Insulate whole ceiling. Cheers.
@@donald840 I sold my dad's house about 5 years ago and had 3 people pull out as their lenders wouldn't give a mortgage as it had foam spray in loft, had to change roof eventually to sell it.
On a slightly different question (and Im not an expert on this) having just had my loft extension completed I researched insulation and found that PIR sprayed insulation was a huge issue in roofing applications. Its stated that either open or closed cell applications do not allow the roof to breath and eventually rots the timbers. Did you do any research into the application and wondered what your views on it would be?
@@girlsdrinkfeck I think that its exactly the fact that we do have moisture in our air. When reading the foam reduces ventilation as it fails to leave any ventilation within the roof space, this then causes humidity and damp placing roof timbers at risk of decay. Im certainly not an expert but was interested in peoples opinion.
@@optic1972 yh this is why u have eve vents or vented tiles about 5 tiles up spanning every 8 tiles depending on width. Also make sure all, water pipes have proper lagging to prevent condensation forming and rising. Also should be no foam where the vents are obviously
@@GosforthHandyman, I’m in Ontario, Canada. We have a cape cod style house with 3/4 second story, so there are, I think, a total of 6 separate attic spaces, what with the dormers and all. When we had our roof done a few years back we had them take of the roof sheathing and spray foam all the little attic spaces (we still have loose insulation sprayed in the main top attic). It has made a huge difference in our energy bill. All that to say, no one batted an eyelid over spraying a roof. Our roofer had tons of experience working alongside spray insulation companies. So yeah, no one here seems to think it’ll cause damp and ventilation issues.
I think you could do that for the second steel but the first one has the old hip rafter running across. Other option is to chop the old roof back to the end of the old ridge and replace the old jack rafter with all new. You still get to the question if is the old roof being supported by the new and adding strength to cover this.
@@GosforthHandyman It’s almost impossible to meet CE/UKCA regs using onsite fabrication. Did the fabricator provide some kind of execution class compliance documentation?
SHS is square hollow section. I'm surprised the building inspector has ok'd the cranked beam sitting on a timber wallplate. SE's detail C shows sat on brickwork not timber. Timber can expand, contract or rot. The other side is sat on padstone. Plus I don't think architect is 'fobbing it off' to structural engineer. Architects and building control aren't usually qualified engineers and won't be insured for structural design.
You couldn't put it on brickwork without notching out the wall plate which is impossible since the hip sits directly on it at that point. SE was fine with this. The 'fobbing it off' comment was a joke. 🙄
@@GosforthHandyman this one sure is 'attack of the armchair roof construction experts', eh, Gosforth.....?!! Never heard so many 'I would've thought' s....!!!
peace of mind if Bob forbid it fails you can point to the the Structural engineer and say his fault and his insurance will cover fixing it thats why good structural engineers are expensive cause they have to pay for that insurance
Curious as to why you would pay a structural engineer to spec timber sizes - and then put bigger, heavier and more expensive timbers in the roof?! After all, according to the structural engineer, they're completely unnecessary....!!! Is it just that ' we've got a belt and braces - but we'd better just have another belt because ''you never know" ' paranoia some people have...?!
I don’t work in residential construction but I am a structural engineer. Often materials are sized up simply due to cost or availability. The engineer specs the bare minimum to meet the requirements, but it could be an uncommon size and hard to find. Or maybe the lumber yard was out when the crew turned up to the day before the job to get what they needed. Or maybe the roofers already had the larger timber on hand and it was cheaper to use it than to buy new. It may be that the larger timber’s are the more commonly used size and the roofer gets bulk discounts on buying big lots and didn’t want to bother with a custom smaller size order. Lots of potential reasons. (I can’t rightly remember who purchased the roof timbers, Andy or the roofers.)
Didn't put bigger timbers anywhere, but I generally prefer C24 to C16 as it's a lot more predictable for a few quid more. The joist spacing was just what worked for the joiners who did the roof. 👍 But yes, it can also be simply down to what's readily available at the time etc.
Bet the structural engineer's insurance premiums are low 🤭 the old roof had years of empirical loading attesting for it integrity. Although the cost of over engineering, is insignificant to the total build, not to mention the inconvenience if the new roof collapsed, which would likely take the original roof down with it. More importantly you don't want to risk Mrs Mack's hair do!🤔🎯🤣🤣🤣
Proof loading of serviceability limit state doesn't really prove anything. Structures are designed to ultimate limit state by applying partial safety factors to both loads and material properties. Therefore the proof load is no proof at all to comply with modern codes...
@@GosforthHandyman yeah Andy that was my point.👍 🎯 The sizing off timbers would be based on past experience and l bet there are many houses built at the same time around you and up and down the country as well with similar sized timbers. We have a 150 year old High Street shop that was originally a town house three floors with servants on the top floor, and that’s got a massive roof and the only problem has been were water has got in and rotted out a couple of rafters which then put additional load one the purlin on one side. Relatively easy fix with some sistering. I think that’s got a 1”x 10” ridge😱 strikes me that the ridge board is the least load part of the roof it’s only really supporting the ridge tile, and completing the roof triangle? Anyway great work❤️
The engineer will have checked the lintel. My observation is that the end of the cranked beam is bearing on timber. Again, assumed it was checked by the SE.
I am not even sure they are real structural engineers anymore. They drive spreadsheets with uber conservative safety factors bolstered to satisfy indemnity insurance. The RSJ I had to put in my gaff (extension) could have held up the piggin Albert Hall.😉👍
Your Structural Engineer is clearly not a modern 'spreadsheet driver' if they have specified an 'RSJ' which were superseded by Universal Beams 'UBs' decades ago!
Thank you for the explanation Andy. As a practicing Chartered Structural Engineer myself it does all make sense. Not saying I'd have used timbers that large (preferring to sympathetically match the existing, cross battening where necessary for modern insulation so plate levels are maintained) but the basic philosophy is sound. Those uncoordinated details caused my eyes to bleed a little, the drawing checker wants their knuckles wrapped for that! What I find with a contingent of modern builders, and even some supposed experienced roofing carpenters, (and particularly the keyboard warrior experts) is that they don't understand thrust, spread and restraint. A fresh new roof may well look like it locks together without all that structural gubbins, but timbers shrink, joints open, relaxation and spread occurs, and then the householder sees cracks that repeatedly open until, sometimes years later, if at all, the roof reaches an equilibrium, and all the time normal seasonal thermal and humidity movement racks the unrestrained roof further. That early spread movement may have disrupted brickwork, and even rotated lintels. It's much better to properly restrain roofs during construction and mitigate all those nasty issues that will otherwise plague the building. And it rarely takes much more effort. As well as designing, we also write structural reports on (mostly) older properties for those selling and buying. Whilst many old roofs were build well and sound and have no significant issues at all, we make a good living out of appraising those other old roofs where the experienced carpenter thought he knew best and elected to provide insufficient restraint to rafter toes (particularly hips) leading to spread, internal and external cracking, bulging/leaning walls, or where purlins are undersized / insufficiently propped and have sagged and twisted, or ceiling joists bounce better than some garden trampolines - toe nailing through binders to hold up ceiling joist is a classic failure issue as the nails withdraw over time. The naysayers putting up roofs today with more confidence than skill, knowledge and understanding will continue to provide me with an income in sorting out their spreading roofs long in to my retirement and beyond. However, I can't see anyone having an issue with that new piece of roof, Andy. Aside from the somewhat chunky and generous timber sizes, well done for having it all put in. A good nights sleep will be had below those timbers. Thank you for sharing.
Would you have recommended trusses for the addition as opposed to the stick build as an alternative solution?
@@peterwooldridge7285 Hi Peter. For this addition, no. It's far too small and would have resulted in a considerable amount of hand cut anyway. Trusses are usually more suited to areas where full span trusses can be erected over a larger area. Hips always seem to involve a lot of cuts, and this roof seemed mostly a hip. Not to mention there would still be a need to provide support to the existing roof where the original hip was unpicked.
It's really good of you to go into this much detail, well done 👌
Cheers Andrew - great info as always! 👍👍
Fantastic response - thank you so much for sharing your insight. I'm involved in the peripherals of the construction trade (on the banking side...often pronounced with a soft 'b' ;) ) and have seen my fair share of Chartered Surveyor & Engineers reports where things have started to go wrong - it can get scary and result in the remediation works costing more than doing it properly in the first place (although it's never the person who cut the corners that gets to pay for it 20+ years down the line). As someone who relies on professional reports (and the Professional Indemnity policies behind them) it's a great comfort that the designs typically provided by the SE takes into account the natural lifecycle of a structure and dynamic nature of the materials used. Incidentally - how much consideration is given to dynamic loading for this sort of design? Presumably there is a great deal of torque applied to a structure in heavy winds via the roof in addition to the static weight of itself?
Congratulations on reaching 198,000 subscribers and you will soon be at 200,000 subscribers and well done for all your continued hard work
Cheers Ben!
Could have called the episode "Andy's New Hip". Ha Good work, buddy.
Good idea! 😂
Thank you for this as I'm now much more understanding of why the steels have been put in.
No worries - glad it makes sense!
SHS - Square hollow section, RHS - Rectangular hollow section
RHS Right Hand Side SHS Stupid Homo Sapien 🤣
👍😎
Thanks for explaining. Basically the ridge needed some support but there was nothing under it so the steels bridged the gap to get a solid base to support from.
I am jealous of your slope insulation. I spent days up in my loft retro fitting that and sliding insulation down the gap and doing the jack rafter gaps from the outside.
Cheers! Yeah, the slope insulation is critical as it's the coldest part of the roof. Defo worth doing. 👍
@@GosforthHandyman This, along with the cavity filling has made a huge difference.
As we have a steep roof and a deep overhang, the outer skin of the wall stopped about 50cm below the inside skin wallplate. So while repainting the outside I took off the fascia and insulated that gap too. I could not find anyone else who has done this!
I do this for a living and you've explained it very well, good on you 👌
Thank you! 👍👍
Could have braced between the timber posts propping new ridge to give a bit more stability but otherwise looks solid. Great video and explanation!
A great detailed run through mate 👌🏼🧱👍🏼
Cheers bud! 👍👍
Going through the engineers drawings… where he notes ‘pitch and plane of beam to match roof slope / rafters’ did he come out and measure the slope so that you had a beam design you could send out to fabricators, or did you get left to work that bit out?
Just made a template 👍
Wow, my head hurts, great explanation matey. Less daunting now! LOL. Well a little bit!
Makes perfect sense, thank you. Should last quite a few lifetimes!
Should do! 👍
Great work and thanks for sharing this with us take care
Old ridge timbers were usually only 1" or 1 1/4"r inch thick as they do not support anything [the rafter each side support each other]. it is just there as something to fix the rafters to and stop them moving about.
Yup! The 9" ridge timber did seem a bit excessive. I guess it was partly to accommodate the bigger hip timbers and rafters. 👍
@@GosforthHandyman There were no structural engineers involved when that place was built. They do tend to work it out. double it and add the date in. But as you say you have no way of doing it.
Using the, 'look these buildings have lasted 100 years + so old building methods were good, no need for all these calcs' argument, does not take into account those old buildings which fell down or were replaced because of structural problems. We are seeing the survivors, or satisfactorily remedialy fixed, today. Numerous Cathedral's roofs had to be re designed and replaced, as they were built, but these were well documented buildings.
Modern materials are often heavier. Replace a slate roof with tiles and the structure needs redesigning, including the slope.
Great video Andy.
Hi sir I think the engineer has been very wise , and has been very prudent not to take any notice of the existing structure . Just those last photos of the existing rafters is proof that he was right . Even my own house that was built some 40years ago has sagged slightly even though the house was designed with
18inc RSJs x 5 running the full width of the house . The reason being for sagging is the jack rafters were just not big enough , if it was being built to day they would be a lot bigger . Having said all that the roof is not going any were because of the massive steels used , but I just thought it was a good example of things that can appear in the future . Best wishes and kind regards as always 😀👍👍👍
Yup! In this scenario better safe than sorry. No sagging of the original timbers in 100 years but it's only a small roof. 👍
We live in an old terrace where the roof has huge purlins (think that's the correct term, they look the size of large tree trunks) With a big triangle construction in the middle of the roof made from huge sawn timbers, with smaller rafters sitting on the purlins. All the timbers look more like logs than modern rectangular timbers, all the joints are dove tailed or mortise and tenon. In terms of craftmanship its a beautiful thing to look at (even if it does make feel somewhat unsure of its structural integrity after all these years).
However this video got me thinking how you would marry that old construction with modern construction if you were to try and do a similar extension on a roof the age of mine.
Old terrace houses often have huge roof spaces so the spans are much bigger. In a similar extension you'd need extensive steelwork. 👍
Andy-Assume the nominal sizes are similar to those here in the USA?
The steels make more sense now, although I would have thought the existing timbers were very 'examinable' in situ and the steels would have been just as effective if they'd been tension bars spanning the house and attached to the roof spars to prevent the roof spreading under its own weight. But as you say, there's no point arguing.
Yeah, I didn't really want to argue the point as he's worked in hundreds of these houses. 👍
I do structural engineering for ships, not houses, but your explanation was good. I enjoyed seeing the architect and engineering drawings. You’re absolutely right that the engineer had to assume the new structure needed full support. Without the as built drawings for the house originally plus a detailed survey to note any changes since build and the current condition of the structure as it stands, it would be irresponsible to assume the strength of the existing structure and then depend on that assumption for the new work. If anything were to happen down the road, they would be legally liable for damages because of that assumption. In my work, we actually do the surveys to determine current as built condition because it is EXPENSIVE to assume the worst and with large ships the job is already costly and materials are a much bigger portion of that than the engineering. As you said, those beams aren’t cheap! But in small residential renovations like this, I assume it’s more cost effective to make that assumption and pay the price in materials than to do the investigative work to determine the bare minimum support required.
Very interesting! 👍👍
Can see it has 'belt and braces' , a very solid construction apart from one thing - a purlin. Think I would be tempted to add one between the two vertical supports on either side to give additional support to the intermediate rafters. But suspect the rafters have been sized to allow for this?
Love roofs. Always a mess of timbers !! :)
The the rafters are sized to allow for no purlin, since there wasn't one in the existing roof. 👍
Thanks for the great videos, I'm learning lots! Also I've just found the measuring up podcast, only a few years too late.....
Out of curiosity, how picky are building control? If the structural engineer specs 2x(100x50) and you use C16/24 it's actually 95x47(IIRC) are they going to complain or is this more of the typical building materials nominal sizes and you need to know what everyone actually means rather than what's written down?
I understand the structural proposal but I have to say that the sizes are much larger than I would have expected and certainly more than would probably have been specified by the various structural engineers I use. Unfortunately, some engineers design on a dot to dot basis and not holistically. An example of this is that is the size of the ridge beam than can either be assumed as carrying weight or as just a separator of the rafters, that is why traditionally the ridge plate was 200/250 deep x 25mm
The 120x120x6.3 SHS is actually 120mm by 120mm by 6.3mm wall thickness Square Hollow Section. You also get RHS and CHS that are Rectangular and Circular respectively. I assume that the SHS was specified to get the steelwork within the depth of the rafters.
Having now seen in detail the construction I assume that the central double beam doesn't support the enormous ceiling joists so that it and the steelwork only support the roof. If so, then there is no need for fire protection to the steelwork.
I note that the roof has been sprayed with polyurethane foam, which is a real problem as the system is not vapour resistive and thus condensation will occur in the rafters but before then it would not surprise me if the tiling battens start to rot as any water getting through the tiles will run down the sarking but only as far as the first batten where the foam has taken the sag out that normally allows drainage of incidental water. If you were to retain the rafter level insulation it would be logical to extend that over the new roof, but be aware of the required detailing to prevent vapour passages and cold bridging. A good solution to this is to use multi-foil insulation/vapour barrier. and PIR board under.
Cheers Clive! 👍👍
Great video, I got a question is that spary foam open cell or close cell
Hi Andy. Great video. You said that you think that the cranked beam is overkill. What on the structural engineers calculations do you think he got wrong?
You could always put a durgo valve on the waste pipe
Loads of durgos but need at least one open vent apparently. 👍
Don’t forget that the older timber is usually very strong. I struggle to cut some of the older stuff.
You need to use an old saw.
Good firewood too!
@@ricos1497 Well said.
Did you say the steel was welded to the lintel. Maybe I heard it wrong. Great vid Andy, appreciate all the explanations.
No, there's a base plate welded to the steel... but it just sits on the lintel. 👍
Enjoyable video and informative.
Cheers Lewis!
Helicopters!!! Try living in Prestbury (Gloucestershire) gold cup week 100's of the damn things flying over all day for 4 days lol
I bet! Sounds entertaining! 😂👍
i take it you will doing spray foam on the under side of the new roof too, to match what has already been done ??
Probably not, the ceiling will be so well insulated there's really no point. 👍
The timber and nails scenario just highlights at some points just how "rough and ready" the construction industry is. However, it's best to adhere to engineers guidelines and better to be safe than sorry Andy !
I find it quite interesting. Our home was built in the late 1800's. All the floor joists are dove tailed into two large beams that span the downstairs space. You can see old stuff beautifully crafted together, whilst the modern repairs just butted up against and scatter-gunned with screws/nails. I suppose its strong enough and time is money and all that
That's when real artisans were working solely with hand tools, No electric drills and saws et cetera then Stephen.
Indeed! When you think this entire original roof was built only using hand tools. We've become lazy as a society. 👍💪
That indeed is the case Andy ! It's all starting to come together.
Only curious, but did you think of a dergo for the foul ventilation? Quite right it's better out the house.
We need at least one open vent apparently! Got other durgos on the system though. 👍
While you were talking about the helicopter passing by, there was a helicopter passing by here too. 🤯
Spooky! 😬
Wondering if you had stripped the entire roof back and rebuilt the roof structure, would it have been comparable to the cost of getting the steels done and in and all the engineering? And what was the existing stuff like? Seeing what you pulled out, it seems the rest might have been in quite good. condition
The existing timbers were perfect but stripping the whole roof off would have been very costly. The whole roof would have needed a temporary cover, complete re-tile, waste disposal of the old roof... probably looking at min £25k to do that vs ~£800 for the two steels. 👍
@@GosforthHandyman wow, didn't think steels would be so cheap
lovely channel mate, New sub here
Is the Quality record for the welded cranked beam required for the records
No
@@GosforthHandyman some people are just SCARILY nerdy aren't they.....!
0:12; humf. that's funny. when i close any door to any room, my cat goes off. go figure... :D
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Fascinating! Will all that spray foam insulation on the original roof now be redundant? I pressume you either get the new roof sprayed or fully insulate the whole ceiling to current standards? Edit: Sorry I think I found your answer way below - Insulate whole ceiling. Cheers.
Yeah, might take the spray foam out at some point. Keeping an eye on it. 👍
Did you have any morgage problems with the spray foamed roof?
@@donald840 I sold my dad's house about 5 years ago and had 3 people pull out as their lenders wouldn't give a mortgage as it had foam spray in loft, had to change roof eventually to sell it.
cheers, makes more sense now.
No worries!
On a slightly different question (and Im not an expert on this) having just had my loft extension completed I researched insulation and found that PIR sprayed insulation was a huge issue in roofing applications. Its stated that either open or closed cell applications do not allow the roof to breath and eventually rots the timbers. Did you do any research into the application and wondered what your views on it would be?
We didn't install it - was already in. I personally think the problems are over-hyped a bit. It's used extensively in the States and Canada. 👍
Timbers only rott if therr is a moisture problem in the attic space and if there are no vents.
@@girlsdrinkfeck I think that its exactly the fact that we do have moisture in our air. When reading the foam reduces ventilation as it fails to leave any ventilation within the roof space, this then causes humidity and damp placing roof timbers at risk of decay. Im certainly not an expert but was interested in peoples opinion.
@@optic1972 yh this is why u have eve vents or vented tiles about 5 tiles up spanning every 8 tiles depending on width. Also make sure all, water pipes have proper lagging to prevent condensation forming and rising. Also should be no foam where the vents are obviously
@@GosforthHandyman, I’m in Ontario, Canada. We have a cape cod style house with 3/4 second story, so there are, I think, a total of 6 separate attic spaces, what with the dormers and all. When we had our roof done a few years back we had them take of the roof sheathing and spray foam all the little attic spaces (we still have loose insulation sprayed in the main top attic). It has made a huge difference in our energy bill. All that to say, no one batted an eyelid over spraying a roof. Our roofer had tons of experience working alongside spray insulation companies. So yeah, no one here seems to think it’ll cause damp and ventilation issues.
What's the white ribbed ductwork in the attic?
Just duct for the bathroom extractor - will be getting upgraded shortly. 👍
Are you going to spray insulate the new roof?
Probably not. 👍
Hip hip hooray....sorry there's always one...😉😂
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It's a bit dusty, I should have cleaned it. It's up in the loft! Okay, the next time you're up there take your feather duster...
I will clean it. 😂👍
Belt and braces is always best.👍👍
👍😁
SHS = Square Hollow Section 👍
That's the fella 👍
I'm not new, and I don't remember ever seeing thecstee l beams going in. oh well.
Here you go 👍 ua-cam.com/video/850uXQ5QLzg/v-deo.html
I would have thought flitch beams would have been just as effective, cheaper and fabricated on site too.
Possibly! The steel was fabricated on-site tho. 👍
I think you could do that for the second steel but the first one has the old hip rafter running across.
Other option is to chop the old roof back to the end of the old ridge and replace the old jack rafter with all new. You still get to the question if is the old roof being supported by the new and adding strength to cover this.
@@GosforthHandyman It’s almost impossible to meet CE/UKCA regs using onsite fabrication. Did the fabricator provide some kind of execution class compliance documentation?
House is coming along really well now and are you going to keep it or sell it
We'll be staying put for a while!
SHS is square hollow section. I'm surprised the building inspector has ok'd the cranked beam sitting on a timber wallplate. SE's detail C shows sat on brickwork not timber. Timber can expand, contract or rot. The other side is sat on padstone. Plus I don't think architect is 'fobbing it off' to structural engineer. Architects and building control aren't usually qualified engineers and won't be insured for structural design.
You couldn't put it on brickwork without notching out the wall plate which is impossible since the hip sits directly on it at that point. SE was fine with this. The 'fobbing it off' comment was a joke. 🙄
Rhs is a rectangular hollow section,and chs is circular hollow section
@@GosforthHandyman this one sure is 'attack of the armchair roof construction experts', eh, Gosforth.....?!!
Never heard so many 'I would've thought' s....!!!
peace of mind if Bob forbid it fails you can point to the the Structural engineer and say his fault and his insurance will cover fixing it thats why good structural engineers are expensive cause they have to pay for that insurance
SHS is square hollow edition
That's the one!
Looks a bit overkill to me Andy?
Curious as to why you would pay a structural engineer to spec timber sizes - and then put bigger, heavier and more expensive timbers in the roof?! After all, according to the structural engineer, they're completely unnecessary....!!!
Is it just that ' we've got a belt and braces - but we'd better just have another belt because ''you never know" ' paranoia some people have...?!
I don’t work in residential construction but I am a structural engineer. Often materials are sized up simply due to cost or availability. The engineer specs the bare minimum to meet the requirements, but it could be an uncommon size and hard to find. Or maybe the lumber yard was out when the crew turned up to the day before the job to get what they needed. Or maybe the roofers already had the larger timber on hand and it was cheaper to use it than to buy new. It may be that the larger timber’s are the more commonly used size and the roofer gets bulk discounts on buying big lots and didn’t want to bother with a custom smaller size order. Lots of potential reasons. (I can’t rightly remember who purchased the roof timbers, Andy or the roofers.)
Didn't put bigger timbers anywhere, but I generally prefer C24 to C16 as it's a lot more predictable for a few quid more. The joist spacing was just what worked for the joiners who did the roof. 👍 But yes, it can also be simply down to what's readily available at the time etc.
Now that you are approaching 200,000 subscribers, UA-cam is sending that annoying helicopter to see what all the excitement is about.
Ha ha you're not wrong Bob! I'll have to watch out! 😂👍
Bet the structural engineer's insurance premiums are low 🤭 the old roof had years of empirical loading attesting for it integrity. Although the cost of over engineering, is insignificant to the total build, not to mention the inconvenience if the new roof collapsed, which would likely take the original roof down with it. More importantly you don't want to risk Mrs Mack's hair do!🤔🎯🤣🤣🤣
Proof loading of serviceability limit state doesn't really prove anything. Structures are designed to ultimate limit state by applying partial safety factors to both loads and material properties. Therefore the proof load is no proof at all to comply with modern codes...
@@skybenedict edited to empirical🎯
Modern codes are not retrospective.
100 years and the existing roof hasn't moved a mm! 👍😁
@@GosforthHandyman yeah Andy that was my point.👍 🎯 The sizing off timbers would be based on past experience and l bet there are many houses built at the same time around you and up and down the country as well with similar sized timbers. We have a 150 year old High Street shop that was originally a town house three floors with servants on the top floor, and that’s got a massive roof and the only problem has been were water has got in and rotted out a couple of rafters which then put additional load one the purlin on one side. Relatively easy fix with some sistering. I think that’s got a 1”x 10” ridge😱 strikes me that the ridge board is the least load part of the roof it’s only really supporting the ridge tile, and completing the roof triangle? Anyway great work❤️
You looked like Garth Brooks in the thumbnail
I'll take that 👍😂
@@GosforthHandyman glad u liked :)
Basically the structure is solid even if the old timbers weren't there.
Effectively! 👍
Hips don't lie.
I am surprised that a steel can go on top of a lintel.
I am also not a structural engineer.
Yup! HD lintel 👍
The engineer will have checked the lintel. My observation is that the end of the cranked beam is bearing on timber. Again, assumed it was checked by the SE.
I am not even sure they are real structural engineers anymore. They drive spreadsheets with uber conservative safety factors bolstered to satisfy indemnity insurance. The RSJ I had to put in my gaff (extension) could have held up the piggin Albert Hall.😉👍
In a completely unrelated matter, I see on the news that Royal Albert hall has collapsed.
@@ricos1497 🤣👍
Does seem a bit OTT! 😂
Your Structural Engineer is clearly not a modern 'spreadsheet driver' if they have specified an 'RSJ' which were superseded by Universal Beams 'UBs' decades ago!
@@LordLuggage Good catch- however all it proves is I am not a structural engineer and I was just using common parlance in the building industry.😉
Serious case of UA-camr thumbnail face in the thumbnail for this, can tell the project's taking its toll! 😆
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