Roofing Question

Epdm on concrete roof

I was going to fit a one sheet epdm room for a concrete roofed extension, out house converted to utility room, I've gone for contact adhesive and was going to lay it straight on.
Currently it's a felt roof, which I was going to scrape off, but that will leave small amounts of bitumen which is stated dosn't react well to EPDM.
my question is whether the trace amounts will be an issue (if dry) how can I get the roof clean enough or what other alternatives do I have.

Going to board first as suggested, what about the house wall, will boarding that cause any issues

3 Answers

Best Answer

There are various overlay systems available on the market, but as you are opting to remove the existing felt roof, a replacement system is the better option.
However you may want to consider that as you are removing more than 25% of the roof coverings you have to replace to current building regs which will require the deck to be insulated and adequately vented.
This is one of the reasons overlay systems are now more popular!
Bertie Donovan
Donovan Contractors

Answered 23rd May 2013

Donovan Contractors Limited

Member since 9 Jan 2013

Clean as best as possible & then cover with thin ply fixed to the concrete & lay EPDM to the ply

If you mean you also can't clean the house wall , you could cover this area with thin ply up to a suitable brick joint into which the epdm will be turned.
The ply does not need to be very thick just well fixed to avoid movement under the epdm

Answered 14th May 2013

Norjan Properties Ltd

Member since 20 Jan 2010

The deck needs to be cleaned, then a vapour control layer fitted. If a 100mm slab then you will need 140mm Kingspan to comply with approved document L of building regs. Then new decking, then your covering. This then gives you another problem - you need to increase the depth of your fascias to compensate for the increased depth of insulation.

This will then prevent you getting condensation, reduce heat loss but cost you a tidy sum of cash.

If you put a piece of ply onto concrete with no vapour barrier or insulation and the use of the room is a utility it is likely to fail earlier than anticipated. Interstitial condensation will occur in the concrete / wood and dependent on the relative humidity within the room you will end up with wet rot / mould on your deck.

Answered 10th Jun 2013


Member since 26 Jul 2012

Need help with your project?

We have tradesmen ready to help you. Post a job, read reviews and hire today.

Post a job

Need some help?

Post a job on MyBuilder to find quality, local Roofers who can help you with your project.

Search all questions