I had the conversion done 20 years ago. The flat roof has a very shallow slope and consists of joists, surmounted by furring pieces, transverse spacing battens for ventilation, ply deck with mushroom ventilators, and multiple felt layers. It is also penetrated by a soil pipe near the condensing boiler vent. The ply deck appears to be in sound condition but blackened, presumably by condensation.
I want to put a second layer of ply sheet on top of the insulation board, I can screw that down around the edges, but want to put a line of fixings down the middle, but this would mean going through the board until I get to the ply underneath.
I currently have a flat roof extension for my bathroom and kitchen, this is how I bought the house, but it has no insulation and it leaks also. My walls are cavity on the extension but they are not insulated, my question is, would I be better fixing the roof with a warm roof or filling the walls with insulation?
As you can see when I went to look at this roof it was cold and snow was still around. Apart from the flashings being all over the place the roof looked quite flat, an easy one to overlay! If you look at the roof around the pipe in the center you can see that its cracked and the roof is actually leaking badly from this area, its very hard to get the old type felts to dress around details like the pipe.
Note the little dots on the decking, indicating they opted to use a perforated 1st coat of felt. The idea behind this is that the 2nd coat of felt will only partially bond to the decking. This ensures that when it fails, the next roofer can remove the old felt without having to hack away at the decking. This can be a common problem, because when roofers don’t follow manufacturers’ instructions, and fully bond the roof, the cost of removing the old roof covering could be considerably more expensive.
The roof has been stripped and the insulation has already been taken up the scaffolding, ready to go down. You can see that the insulation has been laid out over the old decking and is being screwed down, ready for the finishing layer of EPDM single ply rubber to be laid.
This gives an idea as to what we were up against. Our specification for this new flat roof was to strip the old roof, apply insulation and re-roof using EPDM rubber. Just what we were going to do with the parapet walls and chimneys was always going to be up for debate and, as part of the pricing, we had discussed that a Provisional Costs (PC) sum should be put to one side to deal with the renovation of this area.
In this video I explain problems with insulating a roof using the warm and cold roof construction methods. Whatever new flat roof covering you choose, e.g. EPDM rubber, Kemper, Liquid Rubber Triflex, if the specification of the insulation is not correct you could have problems which could include rotting joists.