Flat roof to be replaced by a pitched roof.

[hardmetalking]

Just out of interest what stops the warm moist air condensing on the cold single ply membrane..........
.......there was no mention of vapour control layer or ventilation??

And don't even mention foil backed plasterboard.....about as useful as a chocolate teapot!

 

[AlphaTeamBuilder]

Hardmetalking - watch out. Don't try and say anything good about a zinc roof otherwise you run the risk of being well and truly got at by the felt traditionalists amongst us!

To answer your question. We dont specify cold decks for this very reason. If you cant guarantee the necessary airflow through the roof it can pose problematic. I like warm roof designs, quick, easier and need less insulation and disruption to the interior ceiling to meet the correct regs. VCL would normally go under insulation to stop said moist air going any higher. Although, Celotex specify that if you tape and seal between their boards then the double foil faces act as a suitable VCL.

As EPDM is vapour permeable any small amounts of moisture present below the membrane will work their way through. I believe the rate is something like 1.5g of water per metre squared per day. It's in the BBA certificate somewhere.

 

[Xenon]

You are obviously biased towards your preferred system

Hmmmm,

These are our preferred;

Permaphalt
Bauder
IKO
Langley
Sarna
Triflex
Flag
Icopal
Baileys
Etc Etc, all subject to weekly installation inspection, all fitted by time served badged operatives, all with a cast iron insurance backed single point guarantee.

How many EPDM Tenders come in from consultants? None. Now, as previously, i understand a tanner has to be earned by the small builder/roofer. EPDM gives better margins as its only a fiver M2 to buy. But trust me, it lags far behind in quality.

 

[^woody^]

And what are the projected life expectancies of those products and lifecycle costs of those systems per m2 compared to EPDM?

 

[Xenon]

And what are the projected life expectancies of those products and lifecycle costs of those systems per m2 compared to EPDM?

Lets take Bauder Total as an example.

Actual roofs in existence of 50 years plus old (It used to be used as a tanking membrane for reservoirs in Germany)

Insulated cost per m2 £85. Guarantee minimum 20 years extendable in 5 year increments subject to 5 yearly inspections.

Bit cheaper than the £139 m2 quoted previously even taking into account fascias/gutters in quote...

 

[noseall]

Its 2013 not 1913.

Building materials move on, roofers should too

Builders don't mind taking a forwards step regards 'moving on' Woodframe, but a sideways or backwards step......?

I remember using breathable membrane for the first time and vowed never to use standard sarking ever again. And i haven't.