Warm Deck Dormer Roof - Is this correct?

andyuk2005

Hi all,

Got a question regarding the design and construction of a warm deck flat dormer roof.

We had a loft extension, was supposed to be top spec, but the company has been utterly rubbish every step of the way in short! They didn't put insulation in the floors, they got the measurements completely wrong, velux windows weren't installed properly and we still have water leaks 9 months on! I've managed to get them to fix almost everything now, and we're just short of taking them to court.

But I notice that the room is incredibly cold during this last few weeks, despite the 'top spec' insulation.

As the standard of work has been so poor, I wouldn't be surprised if they've missed lots out, as they have done in other areas.

I have found that at the front of the dormer, facing away from the house, their is only a thin plastic facia covering the front (see pic with arrows), no sub fascia or anything. So as you can see from the photos I took from poking my phone through the recessed lighting holes, daylight is coming through thin fascia and into the gap between the joists. The fascia is quite loose so there is plenty (too much) ventilation!

In the one photo with the hose, that is the bathroom vent going straight out from the bathroom through the fascia, there is nothing else there at all! In the other photos it appears just the joist blocking is slightly in front of the fascia.

So any heat which goes up into the gap between the roof joists, is swiftly flushed out the front via the gappy fascia and the fact that it is incredibly thin, almost making the insulation above it useless!

Can anyone please tell me if this design is correct and normal? Or should there be some sub fascia or other bit there behind the fascia to stop so much heat escaping?

Many thanks for any help!

Andy

System

what is the wall build up below?
that is definitely not right...




so either the structural wall should come up past the bottom of your rafter with the insulation too (almost to the underside of the insulated deck) or there should be insulation packed between wall head and underside of deck - either way you shouldn't see daylight in your ceiling!

andyuk2005

Thanks for the reply r sole!

The roof extension we have is different from your diagram however. Our extension doesn't use any bricks, just timber and plaster board. And the only bit I can get access to see is the front of the former (the bit with the white fascia as seen in the photos), so I can't see the sides of the dormer. I didn't even think about the sides!!

Thinking about it, I can only imagine the fascia is screwed onto the ends of the joists?

I understand there should be ventilation regarding warm deck roofs, i don't suppose that would result in the type of sunlight we're getting through like in the above photos?

Many thanks again!

Andy

teneighty

Don't take r-soles diagram literally, that is a tile pitched roof verge detail but the principal is still the same for your flat roof dormer. The insulation in the walls of the dormer should be taken up to meet the insulation above the roof deck to avoid any cold spots.

You do NOT ventilate a warm deck roof. I think you should seek some professional advice as it would seem the quality of your build is rather poor. What does the Building Control Officer have to say about it?

andyuk2005

Thank you teneighty, yep I'm getting the impression that I'm going to have to a professional surveyor in to take a detailed inspection of this!

We have had one of the building contractors affiliated body; build assure, to come and do an inspection of their work and they weren't happy with it either. However it wasn't the most detailed and he didn't even go out on the scaffolding because it wasn't properly safety tagged! He and as well as the building control didn't look at any insulation.

Could either of you suggest a suitable surveyor or inspector who could do a really detailed inspection and who would include paperwork which would hold up in court? Ie what type of inspector/surveyor that would be?

I would imagine I need a roofing specialist who can also get up there from the ground and have a look as I have no scaffolding anymore!

Thanks again guys its all very helpful!

andyuk2005

Hey again all!

I just went up to the loft again and as you can see from the photos, I tried to see if I could push a stiff wire through under the fascia and into the cavity.

As you can see, it goes straight through, I didn't have any problems there! The top of the wire thing can be seen quite clearly hitting the top of the board there.

Can one of you wonderfully helpful chaps confirm that this should not be happening? I gather from the last few posts that there should not be any gap or ventilation like this from the outside into the cavity area?

Many thanks for your help once again!

Andy

cyclonebri1

andyuk2005 wrote: »

Hi all,

Got a question regarding the design and construction of a warm deck flat dormer roof.

We had a loft extension, was supposed to be top spec, but the company has been utterly rubbish every step of the way in short! They didn't put insulation in the floors, they got the measurements completely wrong, velux windows weren't installed properly and we still have water leaks 9 months on! I've managed to get them to fix almost everything now, and we're just short of taking them to court.

But I notice that the room is incredibly cold during this last few weeks, despite the 'top spec' insulation.

As the standard of work has been so poor, I wouldn't be surprised if they've missed lots out, as they have done in other areas.

I have found that at the front of the dormer, facing away from the house, their is only a thin plastic facia covering the front (see pic with arrows), no sub fascia or anything. So as you can see from the photos I took from poking my phone through the recessed lighting holes, daylight is coming through thin fascia and into the gap between the joists. The fascia is quite loose so there is plenty (too much) ventilation!

In the one photo with the hose, that is the bathroom vent going straight out from the bathroom through the fascia, there is nothing else there at all! In the other photos it appears just the joist blocking is slightly in front of the fascia.

So any heat which goes up into the gap between the roof joists, is swiftly flushed out the front via the gappy fascia and the fact that it is incredibly thin, almost making the insulation above it useless!

Can anyone please tell me if this design is correct and normal? Or should there be some sub fascia or other bit there behind the fascia to stop so much heat escaping?

Many thanks for any help!

Andy

I have highlighte a few bit to aid my memory as I type so here goes.

The company being rubbish is your subjective comment, no one else can confirm that as it's down to your info and your view.

Insulation in floors? If that's in the floor level between the loft floor and the downstairs ceiling, then it isn't required, unless it was specifically in the contract. I would do it as a matter of routine, more for sound proofing than heat insulation.

Water leaks?, your comments about rubbish may be correct there.I have never known a "water" leak in any properly constructed conversion.

Then, you say you have got almost everything fixed but are still thinking of going to court????? Why, it's either gold digging or retaliative. I don't understand that attitude?

andyuk2005

Hi Cyclone!

Erm, thank you for replying, however my question was rather a technical query which I feel you may have missed slightly. I shall answer your question no doubt as I'm sure you're trying to help!

While you may believe that the company being rubbish is my own subjective comment, it has also been the view of the company's own affiliated building body who gave it a damning report and I understand brought the company an earful and they may even lose their affiliation it was so bad. The companies own workers knew they did wrong, the new workers which came onto site to clean up what the others did wrong admitted this, and both directors of the company also admitted they fell short of their standard of work. So they were definitely rubbish!! I have plenty of statements from their own director this is the case!

The insulation I was talking about with the pictures attached was that in the warm deck insulation. However the company did not put insulation with chicken wire between the floor and the ceiling below as per the own diagrams. I understand this may also be a regulatory fire requirement too. Well that's what one of their workers said! Either way it was in their own diagrams and we were told it was in there, but when I took up the floor boards it wasn't, so they tried to deceive us!

The water leak was when rain was coming through the new roof which they put on, something they haven't been able to fix for about 6 months despite repeated attempts!

Everything that I said was almost fixed was referring to the fact that I pointed it out to the contractors and they attempted to rectify what they had done wrong.

And the fact that I might be taking them to court would to be to recover money which I have lost out on (including lack of pay from taking time off work, relatives who had to stay in hotels instead of staying here because work took about 7 months, money spent on paying for surveyors who confirmed our worries about the standards of work etc). Seeing as they are unlikely to pay this if I billed them, I would most likely have to go through the courts to claim this. It isn't gold digging or retaliative, it's claiming what is rightfully mine!

I hope that clears things up for you cyclone, if you do have any information regarding the technical side of a warm deck roof then I would welcome your comments! Otherwise it would probably be best to PM me as it would be taking this thread off track!

Many thanks,
Andy

southcoastrgi

as per your drawing, the insulation doesn't go inbetween the joists but on top of the plywood & under the felt, so when you look inside you won't see any lagging, have they used the wrong size roof joists or is that timber on top used as an angled fillet for the slope of the roof ?

cyclonebri1

andyuk2005 wrote: »

Hi Cyclone!

Erm, thank you for replying, however my question was rather a technical query which I feel you may have missed slightly. I shall answer your question no doubt as I'm sure you're trying to help!

While you may believe that the company being rubbish is my own subjective comment, it has also been the view of the company's own affiliated building body who gave it a damning report and I understand brought the company an earful and they may even lose their affiliation it was so bad. The companies own workers knew they did wrong, the new workers which came onto site to clean up what the others did wrong admitted this, and both directors of the company also admitted they fell short of their standard of work. So they were definitely rubbish!! I have plenty of statements from their own director this is the case!

The insulation I was talking about with the pictures attached was that in the warm deck insulation. However the company did not put insulation with chicken wire between the floor and the ceiling below as per the own diagrams. I understand this may also be a regulatory fire requirement too. Well that's what one of their workers said! Either way it was in their own diagrams and we were told it was in there, but when I took up the floor boards it wasn't, so they tried to deceive us!

The water leak was when rain was coming through the new roof which they put on, something they haven't been able to fix for about 6 months despite repeated attempts!

Everything that I said was almost fixed was referring to the fact that I pointed it out to the contractors and they attempted to rectify what they had done wrong.

And the fact that I might be taking them to court would to be to recover money which I have lost out on (including lack of pay from taking time off work, relatives who had to stay in hotels instead of staying here because work took about 7 months, money spent on paying for surveyors who confirmed our worries about the standards of work etc). Seeing as they are unlikely to pay this if I billed them, I would most likely have to go through the courts to claim this. It isn't gold digging or retaliative, it's claiming what is rightfully mine!

I hope that clears things up for you cyclone, if you do have any information regarding the technical side of a warm deck roof then I would welcome your comments! Otherwise it would probably be best to PM me as it would be taking this thread off track!

Many thanks,
Andy

Sorry andy. I thought we were talking the inter floor insulation I was more familiar with dealing with.

Roof leaks are inexcusable, full stop.

The one thing I still dont get is that you say you have removed foorboards and there is no insulation? I thought you were talking about a flat roof system with an epdm membrane, the insulation would be as SCguy says, over the ply top skin and under the roof finish.

Or do you have more issues than we realise.

Just 1 final thing, if this is going to court, I wouldn't post anymore about it on here for what should be obvious reasons;);)

System

sorry, didn't mean for the diagram to cause confusion - it was the only warm roof edge detail I could find, it was more to show how the top of the wall head should be insulated to the underside of the warm deck - obviously the walls/roof build ups aren't correct in your situation, but the theory is the same...
the insulation "envelope" for the building should be as continuous as possible, and you have a massive gap in yours, there should be no reason to ventilate that bit of ceiling given the roof build up