Expansion and contraction in OSB is not a problem ( I think) As far as I know, no gaps needed in 18mm T+G OSB the expansion is built-in. The lower part of the T+G this doesn’t meet the other side; however, the top use so I don’t understand how that works! I know they are moving over to a new under T+G soon, but that’s all I know. I’ve tried reading the BS EN 1995-1-1:2004+A1:2008 Eurocode 5: ( 145 pages but went to sleep) Tongue and groove do I leave expansion joints The expansion per meter if it gets damp is recorded at.03mm so it’s not much we always leave a perimeter gape of 10 mm and push the bards together lightly; some never go tight as the edges are fragile and brake and bind. I’ve covered roofs over 100 m² and never had a problem, that said we don’t put rigid roofing material on the roof its normally rubber. I get lots of complaints from people that have had GRP glass reinforced plastic flat roofs installed. They constantly complain about the banging noise that comes from the contraction and expansion. Nobody seems to know if this is because of how the boards have [...]
The builder has built a new side extension and we left the decking open ready to lay a new single ply EPDM rubber flat roof. Here is a series of photos along with guidance on lining the box gutter with EPDM.
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 old flat roof above a shop in Pinner was leaking for some time. As it’s a walkway to the flat above, the new roof had to have tiles over the top. This roof was well constructed so we were able to use normal concrete tiles rather than promenade tiles. The roof walls were insulated using Kingspan insulation to a depth of 100mm, then a new decking over the top with the Kemperol V210 System.
The decking to this flat roof has completely deteriorated. Back in the 70s it was the custom to lay flat roofs on chipboard or straw board. As you can see in the video, when water gets through to the roof decking it’s completely destroyed and cannot even support the weight of the roof laid upon it. The entire roof collapses and there is no alternative but to completely strip the roof back to the bare joists and start again.