Best way to add cold roof venting when its been missed on a flat roof.
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- Опубліковано 30 вер 2024
- Best way to add cold roof venting when its been missed on a flat roof.
If you need any information or help please dont hesitate to contact me.
Steven Dickinson.
London Flat Roofing
07802300099
info@londonflatroofing.co.uk
If roofers or builders incorrectly construct a flat roof without ventilation, adding ventilation can be done afterward. However, retrofitting cross ventilation into an existing roof is notably challenging and seldom achieves perfect results. Typically, only about a 50% success rate is possible when adding ventilation to a flat roof already built. Despite this, adding any ventilation is better than none.
In the referenced video, the process of installing mushroom vents on a flat roof is explained, showcasing a technique that reduces the number of vents needed. This method allows for ventilation at each rafter using just one mushroom vent for two vented spaces, a strategy that has received building control approval. Such a method not only effectively adds ventilation but also minimizes the aesthetic impact, which can be a concern with the numerous vents required for each gap between rafters.
Additionally, ventilating the soffit board end or gutter board end of a flat roof is often achieved with a strip vent that blends in easily, enhancing the roof's appearance. This type of ventilation, known as cold roof ventilation, is crucial for preventing interstitial condensation and mold growth.
It's unfortunately common to find newly constructed roofs without any ventilation, often due to roofers' lack of training and understanding in building a cold roof. This emphasizes the importance of proper ventilation in roof construction to avoid such issues.
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I think Steves videos are the best ecplainer on how to build a flat roof. Are mushroom vents prone to leaking, or is there a good way to ensure the roof covering around them is fully sound?
Thanks for the nice comments no they 100% waterproof fitted correctly
They are spaced the same regardless. Either between joists or straddling them. Or is it just me?
You'd use one less I guess?
Are you saying to put the vents every OTHER ceiling joist, or EVERY ceiling joist? Seems like you could skip a joist and go every other so end up having a hold on one side of the joist bay, not both. If you went with a vent on top of every joist, wow, that's a lot of holes....
Hi, how do I maintain cold roof venting when installing a roof window? As far as I can see, the trimmers will block off all ventilation? This is for a vaulted ceiling where I intend to use PIR insulation on the inside.
mate, i have a parapet roof on a new build and already had to replace the roof with a GRP, the problem is not i see NO ventelation to the cold system i think my only option is to use this method but its a balcony roof in an L shape and will take up alot of space.
I don't like these mushrooms. Terrible idea to cut such large or any holes on the roof . Flat roofs are rubbish in any event, despite that they are so popular in the UK.
People build outdoor toilets with flat roofs in Europe .😅
Not for houses or extensions .
Really appreciate your videos. These ‘Extra Aqua’ vents are the lowest profile mushroom vents I’ve found. Do you know of any even lower solution?
Steve, by using these mushroom vents will that mean I won’t need to use Vapor barrier the joists before re plasterboarding the ceiling?
Hi Steve. I am curious regarding how often you need to install this caps for proper ventilation? Can you provide any information from your experience? Each meter or more often or less?
Why is that a ridge ? That seams very odd, that should have a welted drip onto some lead then sheaded onto the slate or tiles
so you have cut down the total number of vent by 1? if you wanted to save vents surly you should do a half span solid half span repeat? that would save you half the vents but you wouldn't have a cross draft.
No because that way you're not venting the one that you're missing we're not missing anything we're venting everything
Hi Steve, i'm after some advice please, I am building an attached garage. It's going to have a cold roof fitted. It's primarily going to be used for storing a car and a workshop space.
Rather than fit an abutment vent to the attached wall, soffit vent to the opposite wall, could I counter batten with 2x2 (front to back of garage) then put soffit vents front and back of the garage? Thank you. James.
Yes, absolutely
Hi Steve. What would you do with mushroom vents if the roof has been cross battened to allow ventilation in all directions? I ask as I know my loft was cross battened but I've never noticed any ventilation for it so I'm debating retro fitting mushroom vents myself next spring. I was debating 1 vent in each corner, as it's approx 3m x 5m. Many thanks, Matt
Good question! If you've got no venting then mushroom vents is probably one of the only ways to Venter roof. So yes definitely use mushroom vents however building control don't like them to be the main source of ventilation but as a retrofit like you seem to have it's probably the best option
Hi Steve, all your videos are extremely well explained. One question, how do you feel about total fill with spray foam, with space blanket underneath the joists, to save space, like they spray boats?
I'm not a lover of spray foam. In fact I'll be doing a video soon about taking it out. I've been involved with three or four jobs recently where it has to be taken out, but I do love space blankets and multi foil and I do think that is definitely the way to go.
Hello Steve,
Just came across your channel by chance. I'm 3/4 the way through a garden room build that is mostly underground.
Roof is a combination of steel and timber joists with osb used to pour a concrete roof slab that is basically a dome shape. Its all tanked with good drainage. I planned to just cut some ridged insulation boards to best fit the tricky internal shape and plaster it and leave it at that. Having seen your channel I feel i have over simplified what needs doing and ill end up with moisture, mould and rot on the osb.
Cant see how I can vent such a roof. I'm just wondering if the amount of earth on the roof will help insulated the osb so its not such a condensation trap. Any advice?
Could well be right that the soil itself could give enough thermal insulation that you don't get sweating depends on how thick it is
Hi Steve, as a roofer l have seen many issues with flat roofs that have inadequate or no ventilation at all. Recently l complete a loft conversion and had the same detail that you are showing. I couldn't have the mushroom vents due to solar panels on the flat roof. Neither could l have a ventilation strip over the tiles beneath a lead flashing due to planning wanting ridge tiles. I was left with the ventilated dry ridge system. However l discovered that once installed the ridge only produced 7000 mm2 /m rather the 25000 mm2/m as building regs.
Well you are correct with the problem with dry ridge venting and the amount of venting that it gives I'm about to do a video shortly showing you the problem is that I'm finding with these so-called vented which systems firstly I'm finding if you go to a roofing company and want to buy a vented which system they tend to sell you a nonvented which system secondly I'm finding that the vented Ridge systems just don't have enough in team in them to come up to the correct standards for building control however they do their own testing and say they do so as a roofer what do you do as a consumer you end up with a vented ridge that is probably not going to cut the cookie and you could have problems how long in the future will it be until some of these vented ridges have got no air venting whatsoever because the holes are too small and I getting blocked?
@steveroofer, My unconsciously incompetent builder has completed my dormer loft conversion. I was showing him your videos and he still got it wrong.On my instructions he lowered insulation to create 50 mm gap and drilled holes in the noggins. I believe he used dry ridge system you describe. Three months in and I have first drip of the condensation in the loft on mine nose, I had peek and it looks the biggest problem is over the bathroom section. On my instructions he lowered insulation to create 50 mm gap and drilled holes in the noggins. I believe he used dry ridge system you describe. My questions is would the mushroom vent solution work on fibreglass roof. Secondly do you know reputable roofers in Peterborough area?
What seems to get me is houses built on next to no foundation are still standing , roofs built with no next to no venting have no rot , so somewhere down the line something has gone wrong
Why isn't that roof counter battened and ventilated properly
Because it's a mock up done incorrectly on purpose to demonstrate how things are not done
@@SteveRoofer cunning indeed
JUST what I was looking for!
I'm glad it helped it's something that I see all the time
smart
thanks
I love that brick wallpaper!
I felt like I'd just found out I was living in the matrix after reading that.
I have never put wallpaper up outside before it was quite a challenge
@SteveRoofer well excellent job and an excellent video as always!
Are you only venting every other section vs every section, I could be wrong but I'd have thought going over the joists rather than between them would only save you 1 vent, not 50%? Anyway I can see the benefits of cross ventilation so definately a good tip 😁
One mushroom vent vents two cavities
@@SteveRooferbut in the video you still applied a vent to the next joist. Thus you had two half vents in a single section, apart from the final and first section which only have half.
For example, if I have six sections of cavity/spaces between joist, then I'd either be using one vent in each space (6), or one vent on each joist (5). Is that correct? Or is it that you can have one vent for spaces 1+2, one for 3+4 and one for 5+6, giving 3 in total?
You're right, not sure he fully thought the saving through plus only half a vent in the end bays where a full one would be better for the cross venting