cold deck approval with building control

[ceiseihubabra-4374]

our structural engineer submitted warm deck roof to building control.But our builder build cold deck roof.
Now building control is raising concerns on this and would like to know how the air circulation will be for the flat roof section.
They are asking to submit extra structural engineer approvals.once the structural engineer approved the change, how this is going to impact on the build control certification? are they going to include all this in the final report? Is this going to impact my mortgage?

 

[Notch7]

I presume you did a full building regs application, if so then building control approved the spec submitted which was designed by a SE….but what was built is different, so BC want SE to provide new drawings.

Assuming everything is ok, you will just get your final cert, there would be no impact on anything.


The question is why did the builder decide to build something different: was there a height restriction?

Cold and warm roofs are often built wrongly - have a look at Steve, London roofing on YouTube

cold roofs need adequate ventilation, they need correct detailing of soffit / fascia vents. Downlighters in cold roofs can be an issue, so can flat roofs that join a pitched roof

you really need to know what the builder has done, find out what the detailing is esp ventilation and vapour barri… it’s not good enough just to get building control to sign it off, you need to know it’s built correctly done wrong you might get condensation issues requiring remedial action.

 

[^woody^]

The only difference with a cold roof is the need for through ventilation. There should be no need for a structural engineer to recalculate anything.

The certification is not altered either, the design is approved and the completion certificate issued.

 

[ceiseihubabra-4374]

The only difference with a cold roof is the need for through ventilation. There should be no need for a structural engineer to recalculate anything.

The certification is not altered either, the design is approved and the completion certificate issued.

Looks like ventilation is the issue because we have a pitched roof on the sides and the middle is the flat roof surrounded by steel beams(15cm). BC is concerned about the flat roof ventilation. Is there any workaround as I am not sure we can increase the height now?

 

[^woody^]

Can you post a plan or section?

 

[ceiseihubabra-4374]

Can you post a plan or section?

Sorry, I couldn't able to attach the files. Not sure what is the issue. I can see that we can't increase the roof height But we have enough space to accommodate a warm deck as we have plenty of internal height. Can a warm deck be built within the steel frame? Also, can this warm deck be built from internally as the outer roof is already sealed with fiberglass?

 

[noseall]

Also, can this warm deck be built from internally as the outer roof is already sealed with fiberglass?

No.
A 'warm deck' means that the insulation sits on top of the joists and the roofing material directly on top of that, so that everything below the insulation is the same temperature as the room below - hence no need to vent.

For your builder to build a cold deck, without once considering the venting issues, is ridiculous.

 

[Notch7]

No.
A 'warm deck' means that the insulation sits on top of the joists and the roofing material directly on top of that, so that everything below the insulation is the same temperature as the room below - hence no need to vent.

For your builder to build a cold deck, without once considering the venting issues, is ridiculous.

I supplied the joinery for an orangery once, the clients builders were doing the flat roof - they built a “warm roof” but they put the firrings on top of the insulation leaving an invented void - god knows what problems it had afterwards

 

[ceiseihubabra-4374]

No.
A 'warm deck' means that the insulation sits on top of the joists and the roofing material directly on top of that, so that everything below the insulation is the same temperature as the room below - hence no need to vent.

For your builder to build a cold deck, without once considering the venting issues, is ridiculous.

Thanks @noseall. Can a warm deck be built within the steel frame?

 

[noseall]

Thanks @noseall. Can a warm deck be built within the steel frame?

I don't know what that means, sorry.
A steel frame would Need to be wholly beneath the insulation and not within it.