New Build Passive House Roof Leaking or Sweating?
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- Опубликовано: 5 фев 2022
- New Build Passive House Roof Leaking or Sweating?
This house was probably built to what's known as Passive house standards, i.e. extremely high standards of airtightness and insulation. We don't know if the problem to the roof was totally caused by leaking, or if it was the way the membranes over the roof were fixed, that stopped the Passive house from 'breathing'? Although I agree with the idea of Passive house standards, extreme care has to be taken when building a house with so much insulation. Management of the internal environment has to be strictly managed, the transfer of energy to the outside is severely reduced because of the insulation, this also severely stops the transfer of moisture that has to be managed iternally to stop interstitial condensation from happening. When we stripped this flat roof, we found different membranes fitted in the incorrect place, thus holding back any moisture that got into the roof.
The other thing to take into consideration is that this roof is formed from cross-laminated timbers and is fully structural. This is a good strong platform from which to form a roof's sub base. However, if the roof leaks and the timber is compromised by rot, then the cost to replace it will be enormous. If we had to replace the cross-laminated roof section on this roof, we would have had to completely dismantle the stairwell and the surrounding areas.
Building in redundancy into a building should be a big factor in the design. When we re-roofed this roof we made sure that the falls to the roof were extremely good; any small settlement in the building would not change the falls to the roof, and the roof would still drain. We enlarged the scupper (rainwater outlet) so that it would drain more freely and be less likely to get blocked. We added through-ventilation all around the roof so that if the roof did get wet or there was moisture that needed to escape from the roof, it could freely get out of the structure. We covered the roof in a roofing membrane that was laid in one piece so as to make maintenance and roof inspections easier in the future. The decking that was placed over the top of the flat roof was laid on plastic supports and the decking itself is plastic so that it will be maintenance-free for its lifespan.
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Steven Dickinson
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Really enjoy your videos, I don't have anything to do with roofs, juat a casual viewer. It's really interesting to hear from a professional how different roofs should perform and how to combat issues. This particular job must have cost a fortune, but the work looked like it was a necessity. What I don't understand is why the original builders are not held to account or the local building authority who sign off the work.
Building control is not clark of works. There is no comeback to Building control there job is pretty much only safety IE making sure the building want fall down or burn down or harm anybody
@@SteveRoofer thanks for the reply, So can the original builders or project manager be held to account for the failings then?
@Nick Jeffels All new builds shoud come with a ten-year insurance backed guarantee NHBC is probably the best known. Generally, the defect period where the builder has to pick up the problems and snag is 24 months after that its down to the insurers, how I actually got into all of this was being one of the building companies working for the insurers going around putting right the so-called house of horrors. As you can imagine the insurance companies don't want to pay out for much and you have to have a big problem and a watertight ( excuse the pun) claim for them to payout. I would say when I was doing that sort of thing generally the claim was always between two and 6 years old before it was settled and we went in to put it right
2-6 yr old claims, wow!
Great investigations. The Sherlock Holmes approach😃. Nice!!
Thanks for coming sometimes some really interesting jobs come up and I'll do my best to try and record them speak soon
Great vid Steve and a superb example of just how much work has to go in to correctly diagnosing the problem.
Thanks 👍
Great video as normal, the end result looked brilliant !
Glad you enjoyed it
What a great channel you have Steve and tidy work . Great info for remedial contractors like myself, there will be ever more problems like these appearing.
Glad you enjoyed it
Incredible level of detail, amazing.
Thank you very much!
I love finding strange errors and stopping leaks no one else could. It what makes the gruelling part of the job worth it for me.
Thanks
Real nice content, keep it coming
Thanks, will do!
I had a similar issue recently to deal with on a hospital. Seemingly water getting behind the system everywhere. Re profiled and that was covered in a Triflex system. With grit added to walkways.
I’m always amazed at how previous people complete roofs when I start to strip them. Often feels that a lot is an after thought. When the roof is one of the most important parts of the building.
absolutely
The 2nd layer of firring strips are way too thin on the low end to be self supporting and get a good fixing in to, should have had a noggin underneath, the deck is going to sag over time. Fixed one problem and created others!
Good point however OSB is designed to span 400mm center to center, if you look closely this span has been reduced at that end therefore offering more support where we cross the battens. Theres is more support than meets the eye at this point, extended pinpoint loading with decreased unsupported area of OSB.
@@SteveRoofer The areas where the battens cross are extremely small and would provide significantly less support than would be required to prevent sag in the OSB, also fixing of the sheets would be a major issue as the firring strip has no substance, this type of firring strip should be fully supported along it's length. This problem will cause issues in the future, a poorly thought out solution in my opinion.
Really good knowledge transfer, I'm not roofer but the investigation and remedial actions to correct the faulty roof helps the every day lay person understand the principles of having good air ventilation! Keep up the good work!
Thank
Great video Steve. On a traditional felt roof flashings would be used from the roof up the wall and under the copings so water couldn't run down
Good tip!
That looked a complete nightmare to do, but looks superb now it's complete. I've never seen wood that deep and continous before either. 👍Great video.
Glad you enjoyed it
Based on the previous hole that you found, I wonder if those tiles were a recent addition to sell the house and cover up the problem by looking shiny.
Just an interesting point on this one is that you still have to make sure that the height of the guarding is not compromised to the parapet walls as you have raised the level of the deck by probably 100mm.
Also to say that there should be detailed drawings lodged with Building Control for the build up, unless it was built by NHBC.
Its possible re the tiles however I don't know. Good point about the hand rails, it was already high enough the depth of the wall is amazing there is the timber inner frame with an insulated cavity before you get to a normal cavity wall with block inside and outside and then some sort of external rendering suggest 500 to 600 depth, its also at an angel sloping inwards, this didn't help as rain hit the top and then came in under the tin roof and plastic
Another really interesting video. Having completed a large CLT project (with a warm roof) I am aware that all openings in the CLT (ideally) need to be made in the factory. Being the main structural element the number, size and position of the openings need to be checked by an engineer, so given how neat that hole was I wonder if it was originally intended to be the position of a roof outlet?
Possibly
Over engineered and design flaws. I'm constantly battling with architects /builders over detail they've downloaded or been given by architects. Which is for a standard warm or cold roof, with out parapets or skylights or screeds or tiles, decking etc. And details from 10 yrs ago. Anyway thanks appreciate the videos. As always extremely beneficial
Yes its a constant battle
Very interesting video and very well explained. Really feel for the homeowner they must have really through the mill with this. The use of plastic sheet against a vapour barrier (alone) indicates the installer did not really understand these construction methods.
Glad you enjoyed it
Good video , timber structure really needs to be done correctly ,if possible follow engineer or architect drawings 👍🤟🇮🇪☘️👏
As long as they get it right
Hi Steve, currently doing a flat roof of my own for the first time, found all your videos very helpful.
I have gone down the cold roof route, just a quick question, when putting a vapour barrier on a cold roof are you fixing the vapour proof barrier to the joists before plaster board?
Also would you recommend a vapour barrier please
Cheers
Luke
Yes you fix it to the joists there are lots of AVCL (air vapour control layer) out there I will be doing a video on some shortly however ive been working with Novia recently and they have been really helpful try the 1200g VCL don't forget to get the tapes Novia Butyl 30mm x 30M and Novia BOPP tape 60mm x 50M get back to me if you have any left over as I can put you in touch with outers that may buy from you steve@londonflatroofing.co.uk
Was hole in the middle intended for an outlet then changed their mind as it looks like it was built that way not cut out ,too neat
Possibly
I need Matt Risinger to chime in
He is a good man
Hope you made sure that there was no airflow possible from inside the envelope to your vented space.
Unfortunately we didn't have access to the underside however the think was solid with no obvious gaps
If I've learned anything over the years, it's that every exposed wall, roof, or floor assembly should be cross vented. Great video!
Thanks 👍
Hi steve.
Great video.
How did you prevent the water coming off the coping stones and down behind d the parapet cladding, which was the cause of the water ingress?
We applied rubber sealed to all the joints of the zinc cappings and told the customer to get them changed Will they I don't know? probably be back in a year or two
Hi great video - really informative but a few details at the end were skipped over. Can you explain if there was a membrane or flashing down the parapet to stop any driving rain running down the vented edge strips? Would be great to see a full roof to parapet detail
I had to cut out so much as the video was getting extremely long, the parapet walls had plastic and a breathable membrane on them also. Internally we had to do lots of repairs and treatment to the mould on the walls, just to much to go in one video
Surely wrapping bottom furings where it sits on wet deck would have been better just to rule out further seepage from roof underneath as it looks soaking wet?
It's wet because of the rot treatment we put on it. All the timbers we put in are treated also so that won't be a problem. The ventilation around the outside is enormous, so the internal timberwork will be back to some sort of equilibrium extremely soon. Even in the winter, the surface temperature of the roof is quite high that will help with evaporation and the venting will deal with the rest
We've had a job recently, on a 10 year old roof, completely rotted out. But looking at it it's the architects design error with oak frame not deep enough to accommodate warm deck and doors to low onto balcony through more leaky oak frame. Without Ripping the whole extension down and starting again, not much we can do. Classic insulation between 4 inch timbers downlights cut through any vapour barrier, not being able to flash a mortice and tenon oak frame. A whole list of rubbish to be honest. Anyway great video, I do enjoy your analysis videos.
Yes a lot of this is because of the design some people just don't live in the real world
Do a video on new build decorating and the endless snagging especially the tape & joints which are still visible after having been painted.
its not good out there
Hey Steve. Great content as always. Just a question regarding some videos I saw from a chap doing garden rooms in Leeds. He has been doing hybrid roofs due to height restrictions for outdoor buildings. This hybrid roof consists of pushing the pir up against the roof OSB and creating an air gap between the plasterboard and PIR...his school of thought is because the PIR is pushed firm against the OSB, there is no room for moisture to get trapped between this and the OSB. What's your thoughts on this way of doing the roof and of this works, why wouldn't you push all pir in cold roofs up against the roof to make it hybrid. Your opinion on this would be interesting. Many Thanks
Everything works until it doesn't a garden shed doesn't come under building control so they can do what they want. WIll it work? If the building is not heated or lived in possibly
@@SteveRoofer thanks Steve. Definitely heated and many used as offices and gyms. However, does state they are low occupancy, but then again if your making a garden office. You are probably going to use it everyday. Worryingly according to him some building regs agree with this school of thought. First 10 mins - m.ruclips.net/video/mLi1rTQAKKo/видео.html
As an old roofer told me many years ago "there are only 3 things that are certain in this life, 1. You have to pay your taxes, 2. you will die eventually and 3. your flat roof is going to leak"!! I work in the industry and with most projects we see, there is very little thought by architects/ designers to ensure they detail the flat roofs robustly for enough fall and ventilation/ vapour barriers. Problems waiting to happen!
Yes for some unknown reason the falls are alway to small
Hello Steve!
Great channel.
My question is, that you shown the timber matrix that allowed the roof to be sloped tovards the water outlet. Do you put plywood or osb down on that timber matrix and than attach your epdm on top of that? There was no photo of that step, and just wondering how that looks like.
Look again I do show the OSB over the matrix before the EPDM
@@SteveRoofer Sorry than, my mistake, I understand everything now. Tanks!
Great video. Is there any protection between the plastic supports for the decking and the rubber membrane?
yes there are soft rubber pads under each pedestal they come with the decking pedestal kit
Does the composite just sit on the epdm on the feet then? Always extra careful when I go up on my epdm roof even though it's pretty thick rubber, maybe it can put up with more than I think!
Yes it can put up with lots ive had some in my drive and driven over it for a year or so and its just about OK still
So that put a block of wood in a plastic bag then feed water into it, covered it all to keep it nice and sweaty, surprise! It rotted, well I never, who knew wood and water don't mix well. I am totally surprised, not!
The first clue was at the beginning when he uttered those famous last words " couldn't find any drawings" as you know a recent build like that would have architects details which are translated into manufacturers production drawings to be at least signed off by the builder or a qualified consultant, usually architect/ structural engineer and often the product manufacturers involves.
Looks like a D&B contact, where these processes are cut out to save money, win the job with lowest price. Old saying that never changes "you get what you pay for". In this case the materials seem correct but the construction method wasn't.
A nice renovation by your company, a bit more than just a repair.
Hi Steve,
Trust you are well.
Is there a drawing/illustration I can use as a keen DIY enthusiast, for walls, breeze block single skin, which shows how to correctly insulate externally. Your help and guidance would be appreciated.
I have the said wall which is a dew point in my home! Causing damp in this area.
Thanks Harry
Sorry I don't know much about external insulation obviously google it
nice door, where are they from please
Yes lovely door and really nice people to work with i you email me I will give you there details I cant post here as havet asked them steveroofer@gmail.com
Hello, I just had my garden house roof built ( warm roof ). At the time the underlayment got a bit wet before placing the roof. Now there is a bit a mold growing on the underside of the underlayment. Should i be worried about this ?
No dot think so we are moving to the summer so re assess it next year it will probably dry out over the summer
Did you need to raise level of parapet wall or was it high enough already?
Good point, it was already high enough the depth of the wall is amazing there is the timber inner frame with an insulated cavity before you get to a normal cavity wall with block inside and outside and then some sort of external rendering suggest 500 to 600 depth, its also at an angel sloping inwards, this didn't help as rain hit the top and then came in under the tin roof and plastic
If the original source of moisture was identified as water running down the inside face of the parapet, what measures are in place to stop this happening again? Does the epdm sheet on the deck extend the full height up the parapet? Or is there a parapet covering that drapes over the sheet on the deck?
We have fixed the leaking parapet copings and told the customer she should replace them Thats as much as we can do for now
Interesting job & hopefully it paid for a new tape measure 😜
Second person to spot that Ill go get one for the next job
@@SteveRoofer or you could just keep it for measuring stuff that happens to fall on the bits of the tape that still has markings on it 😅dare say I have a few tapes as bad if not worse lying around to be fair!
Top job again! I thought this job would be perfect for liquid applied?
Sheet rubber all day long as no detailing only took 1/2 a day and rubber down
Quick question, since you figured water was dripping on the parapet walls, wouldn’t that mean it can now drip straight down into the timber roof ?
No as we fixed the leaks to the parapet walls
Can you use visqueen as a vapour barrier
Yes they have a good selection
Thank you for your reply is it good to use a Dpm black visqueen on the walls
Not quite sure why you think it’s a Passive House? If it was it would be on the Passive House database and certainly wouldn’t have problems with sweating from the inside as the Mvhr would create a dry internal atmosphere. Well insulated does not mean passive house. The whole point of passive house is that there is a robust check on all design and construction
I do say like a passive house or close to passive house
@@SteveRoofer but it is neither like or close to passive house for the reasons I stated. The title of your video implies passive houses are more prone to roof problems and they are certainly not going to sweat.
A very Austrian type of build but they are normally vapour open! I think its the plastic that has killed it.
Yes thats my thoughts
You need a new measure tape 😱
Third person to not that, thinking of adding a little spot the poor roofer spot in next video