Hi there,
my first time on here. I have a single storey building with a flat roof. We had to move out due to damp/condensation. I am now completely refurbishing. I have removed the ceilings. The parapett has been letting in water due to non existent pointing and the joist are black and rotten on the ends. There is no insulation whatsoever, and the present covering is 3 layer buoilt up felt on t & g timber (approx. 5 inch strips). Damp has
also spread across this and the joists a couple of feet all round so I'd like to replace the lot.
So if I remove the old roof, lay 8x2 joists across and ply on top (.75 inch? ) what should I do next to create a well insulated and watertight roof. I've had several suggestions, and I
am not a lover of 3 layer felt. I've looked at Weber system but its quite expensive, I would appreciate some advice, thanks,
regards Luke.

Luke, I would suggest a TPO roof over a layer of 3" of polyisocyanurate insulation (R-24). The life span of a flat roof system is usually no more than 25 years-regardless of which system or manufacturer. The TPO system will provide the same life span, but will also allow a second TPO roof to be installed over the first one. TPO is usually white, so the membrane should qualify for a cool roof tax credit as well as save some cash in the heating/cooling area. There is also possibilities for a live roof, where your roof becomes a garden.

Other systems can be better for your location. If you live in a colder climate, then an EPDM roof may be the way to go.

I would steer clear of any asphalt applied systems. The price of asphalt is on the rise and the labor to install a full system usually costs more than membrane roofing.

Be sure to ask about warranty options for any system you choose. Here is a link to a TPO roof: http://www.gaf.com/Content/Documents/10571.pdf.

Since roofing is my business, I have to consult for residential roofing all the time. Feel free to contact me with further questions. Hope this helps.

Hi Dawgnskats,
Thanks for that. I've been looking at this website with instruction video EPDM rubber flat roof supplies for DIY from Rubba-seal (http://www.rubba-seal.co.uk) .
Not quite sure about insulation in this case or what goes on top (reflective material )
As I haven't watched whole video yet, but the initial application looks fairly straightforward.
Is the TPO system available in the UK ?

Luke, I know that Firestone Building Materials has TPO in the UK. I also think that GAF/US Intec and Carlisle has TPO available in the UK. If you are planning on doing the install yourself you probably need to stick with EPDM. Welding the seams of TPO is important and it does take some practice to get right. Finding out you made a mistake after it rains is not fun. EPDM comes in white also.