Flat Roof System

Moggaman

Hi.
I am planning a new build. I want to build a box..12m x 10m approx.
I want to put a flat roof system on it that I can forget about as in...not a cheap torch on effort. I know there is zinc, copper etc. Have ye any recommendations. I dont want to take chances.
Also, could i have you opinion on what height parapet to allow, I assume a 200mm upstand above the finished roof would be sufficient.
Could u give me an idea also roughly what would be the distance from plasterboard in the upstairs ceiling to the top of the roofing system... or link me to a good site to study a few flat roof constructions.
Appreciate it

Shaunoc

Fiberglass is a possibility

Moggaman

The one thing I read quickly was that it was unproven,,,maybe unfounded

BryanF

Box 12 x 10m ? Have you got help with design ?

- Bitumen two layer system on torch on board 30mm
- 200mm parapet
- 1:40 over 5m 125 + 1:100 gutter over 6m (4outlets in corner) +50 +50 recess : 225mm for slopes
- I-joists circa 400mm (spans tbc)
- (Insulation cellulose full full between joists
- vapour barrier
- service cavity min 50mm
- plasterboard

Circa 800mm overall ceiling to parapet not including sucking zone for vent system.

Gumbo

Think about Home Insurance.
Some companies wont insure flat roof's over a certain % of the overall roof area.

Moggaman

therefore in the eyes of Insurance companies, flat roofs of any type are a risk, regardless of their quality ... bit harsh considering you could have a pitched roof built by a terrible roofing carpenter...

Metric Tensor

Insurance company's care about aggregated risk. In general, flat roofed houses cost them more.

It's the same with timber frame houses. They charge extra for these too even though there are plenty of high quality ones.

It's just maths to them - nothing that can be done about it other than shopping around. Car insurance and life insurance are the same.

hognef

Metric Tensor wrote: »

Insurance company's care about aggregated risk. In general, flat roofed houses cost them more.

It's the same with timber frame houses. They charge extra for these too even though there are plenty of high quality ones.

It's just maths to them - nothing that can be done about it other than shopping around. Car insurance and life insurance are the same.

Cost them more, or they don't have enough data, so they assume the worst.

Metric Tensor

Cost them more in both cases is my educated guess (but still a guess!)

There were quite a few shockingly poor quality flat roofs and timber frames in 70s/80s whereas pitched roofs were reasonably good because they were harder to get wrong. Likewise although blockwork construction would not have been to modern standards it would not have "gone wrong" as much.

Irish flat roofs in particular have come a long way in 20/30 years.