Leaking Flat Roof

927465 · 4 Jan 2009

I have recently discovered my wimpy chalet style house has a leak in the flat roof. I have only been in the house for 4 months. On discovering the leak I went onto the roof to find that it has seen better days and has been patched up considerably already.

Can anybody suggest some advice on the best course of action. I'm hoping I can seal it enough until the summer(time will tell) but was wondering about a new felt covering, or fibreglass covering or epdm rubber or modifying the roof using a frame and making the flat roof pitched(this may have a name and isn't something I've seen before) but I can't see why it can't be done. The pitched roof would also have the advantage of giving me the ability to insulate the roof, as the current flat roof basically has no insulation which is about half my roof area.

I suspect a diy job is not really an option for this problem, as I have never done anything like this before.

All suggestions greatly received. I live in Renfrew by the way if anyone can suggest good local roofing companies.

masona · 4 Jan 2009

Just temporary repair with any roofing compound, plenty products out there and as you says a low pitch roof is the best way to go for maintenance free

http://www.screwfix.com/prods/57518...cals/Flexacryl-Roof-Repair-Compound-Black-1kg

927465 · 5 Jan 2009

Thanks for that link its a lot cheaper than some of the other stuff I've seen. I've put some bitumen based paint(that I had in the garage) on for the moment and it appears to have sorted the leak at the moment but I'll buy some decent stuff(and put that on, as soon as its dry and a weekend) in the hope that it lasts till the summer. Regardless, I need to sort the roof more permanently.

I've found more leaks(all weeping through slowly, not torrents) now that I have looked more thoroughly.

Therefore to narrow down the discussion some what. Is there a reason that people don't put pitched roof's onto wimpy chalet style 1970's flat roofs. I can't really think of a reason why this can't be done, but I have never seen it on this style of house, therefore suggesting there is a reason for not doing it. Is it too costly? Is it frowned upon by councils? Is it not possible? etc.etc

I've posted a similar type of house so people understand what type of house I'm talking about

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927465
5 Jan 2009
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masona · 5 Jan 2009

927465 said:
Is there a reason that people don't put pitched roof's onto wimpy chalet style 1970's flat roofs. I can't really think of a reason why this can't be done, but I have never seen it on this style of house, therefore suggesting there is a reason for not doing it.

No reason at all, it's really down to who did the drawing plans. It's the norm theses days

Is it too costly?

When they were building it, I would say it cost slightly more for a low pitch roof. And now, well depends how you look at it, a flat felt roof have a life span of 10-15yrs so renewing the flat roof could be cheaper in the long run.

Is it frowned upon by councils?

Sometime yes, every area is difference

Is it not possible?

Yes it is possible but would looks better if your neighbour have it done as well.

Xenon · 5 Jan 2009

You can put an insulated flat roof system on it quite easily.

927465 · 6 Jan 2009

Can you provide some links/info on an insulated flat roof system? Thats the reason I found the leaks, because I was trying to investigate how I insulate the flat roof space better. My heating bills are astronomical at the moment!

The flat roof area is basically(going upwards from the ceiling) plasterboard onto the underside of joists of the house frame, then plywood on top of the joists with felt covering(to the outside world) on the plywood. There is currently 25 mm fibre glass insulation stapled to the underside of the plywood. There is currently absolutely zero ventilation in the roof space. There is also no slope on the flat roof at all. Hence water just collects there. Therefore I want a cheap but durable system for weatherprroofing the flat roof, that provides good insulation and also a method of ventilating my roof/flat roof.

All suggestions greatly received!

Xenon · 6 Jan 2009

http://www.insulateonline.com/index1.htm?flatintro.htm~main

927465 · 7 Jan 2009

Please correct me if I'm wrong as I'm a bit of a novice when it comes to roofs, but this would require me to seal off the flat roof from the main roof. Currently they are as one. i.e. The same air is in the main roof as the flat roof. Also with that sort of roof where would the water go if there was a leak.

Also with the hot roof construction can you put insulation in the unventilated cavity?

Although I don't like my current situation at least I can tell there is a leak before too much damage is caused. With a hot roof construction my concern is when a leak does appear it won't be found until considerable damage is done.

I know if everything is done correctly I'm not likley to get a leak for at least 10 years, but if there was dodgy workmanship it could result in more work and cost. Sorry to all good tradesmen out there but I do feel there are more dodgy/useless tradesmen than there are good tradesmen.

Sorry for all the questions, but I do like to know as much as possible before I comit to something.

chappers · 8 Jan 2009

to be perfectly honest the most cost effective thing to do is to just get the roof refelted(try and get your neighbour on board too to split the cost, if it is joined like the photo).
Modern materials will last another 30 odd years

topend · 8 Jan 2009

should b able to insulate dormar roof no problem with coolaginsulation and a built up roofing system with a 10 year guarantee

927465 · 10 Aug 2009

Hello Again,

It is now late summer and I still haven't fixed my roof yet.(I have sealed it temporarily) I have a quote here where they will replace the felt covering with a warm roof construction(built up from a new Vapour layer, 1 inch Perlite insulation board, 2mm fibreglass underlay with 4 mm Paralon Cap sheet). The quote is £1620 + VAT. (This is the best quote I have had)

I think the price is steep, however if I did take this option. I would need to seal the flat roof from the apex roof(which I can do myself).

Ideally I would like thicker Perlite insulation which I can get but it will cost more. Hence I've been thinking... If I filled the void between the ceiling and the flatroof ply with insulation(before I sealed it) would I get a condensation problem on the underside of the ply?? ... I'm not convinced I would!! There would be little air movement and less temperature differential due to the warm roof construction.

I know the stock answer is yes you could get condensation because there is a difference in temperature, hence vapour can condense at the dew point. I'm just not convinced that scenario would be reached(due to the warm roof construction above) even in Glasgow.

Can people please, please pass on there comments. I really can't afford to fix my roof and need to penny pinch as much as possible.

topend · 10 Aug 2009

hi should b able to use 50mm coolag with vapour barrier then 3g felt and glass fibre under lay finished with torch on mineral finish last at leat 25 years depends on heights on ur up stands on roof with thickness of insulation .then cost more to start to raise facia boards at front so water goes of end of roof

927465 · 18 Aug 2009

As suggested I will have a problem with the front facia boards with 50mm insulation board.

Therefore I repeat my last question. Would I get an condensation problem if I insulated the void between the ceiling and the underside of the of the plywood roof(which would now have a vapour layer, insulation and a top sheet above)??

Nige F · 19 Aug 2009

927465 said:
Please correct me if I'm wrong
but if there was dodgy workmanship it could result in more work and cost. Sorry to all good tradesmen out there but I do feel there are more dodgy/useless tradesmen than there are good tradesmen.

.

I agree with you

When it comes to roofing . It`s the ***** Prefered way to get money. Even some established roofers have ancestral travellers

vinty · 19 Aug 2009

I live in the same type of house as your self, a chalet bunglow with a dormer. I had only been in the house about 6 months when i discovered a leak in the front bedroom, the water was running down the light flex in the ceiling.
so next day i got onto the dormer and found that the felt was starting to crack and blister a bit, but the deck itself was sound so i cut open any blisters on the roof and then i recovered the whole roof using 4 mm cap torch on sheet, including under neath the tiles on the main roof .

It was only supposed to be a tempory solution but that was 10 years ago, i have been back up from time to time to check the deck and it seems ok, my dormer is approx 18sqms, if your dormer is around the same size then the price you were quoted seems a bit excessive, maybe the price quoted was foe redecking as well.

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Leaking Flat Roof

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