Search the Community

Looking for some advice on roofing if I may: I’m building a cabin with cold roof in SW UK and concerned about the air gap between insulation and OSB deck. The roof comprises (inside to outside): 12mm Q mark plywood Thick vapour barrier (black DPM) that is fitted best I could but without butyl tape to seal screw holes and stapler holes. 170mm deep rafter filled with 150mm PIR insulation which only gives me a 20mm air gap (50mm is recommended building regs). I messed up the materials order. That’s where I’ve paused building. Roof is 10 degrees single pitch roof Spans 4.2 meters I’ve already ordered 32/1000mm box profile metal roofing sheets High usage holiday cabin I can see 3 options going forward: A) No OSB on top of rafters - just membrane, counter battens then metal roofing Q) is this weather proof enough? Warm enough? Too much airflow? B) OSB fixed to rafters (20mm air gap), breather membrane, cross batten then metal box profile roofing. Gaps on front fascia and eaves for airflow. Q) enough airflow? 50mm is most people's recommendation. C) option B but with battens on top of rafters to lift OSB and increase air flow (cross and through ventilation) Q) is this too much airflow?) Any advice or thoughts much appreciated. I know cold roofs are prone to moisture build up so I want to get this right. Cheers, Jake

Hi, We are getting conflicting advice so any thoughts that might help us get through this very much appreciated. We are building a 4m deep x11m long single story extension on the back of our house, mono-pitched roof joined to the exiting house. Due to the lay of the land and upper story windows we are limited for height at the back/house side (3m) and still want to achieve a fall above 5 degrees. There are two questions this raises. 1. One installer recommended a vented or cold roof zinc installation (something to do with moisture trapped during installation of the zinc) where as our design/architect guy recommended a warm roof i.e. unvented. Has anyone got views on which is better and/or any advantages of each? 2. If we were to go down the vented route. I have been unable to see how the back/house side of the venting would work and upstand for that matter. I have seen venting details on roof ridges. Has anyone got any experience of how that might work? Again any help much appreciated. Thanks Graeme Extension 26-01-21 - Drive side view.tif

Hello, I would like some info/advice regarding a cold concrete flat roof. Sorry for the length of explanation.... But first a little background info...... The house we purchased was gutted, renovated and then sold on to us by a local building company... All certs for all upgrades and works were checked and passed.... Our problem.... 1 We moved in Sept 2107 all is fine until the first frost off this winter late 2018..when we started to notice a water stain in the rear utility ceiling (formerly downstairs rear loo and storeroom). These rooms were incorporated in to the house via the kitchen to form a utlity/cloakroom and extra kitchen space..... The roof itself is around 8 inches of concrete topped off with felt.. This was refelted just before we moved in... And the rooms below batterned, insulated, boarded, skimmed and redecorated. Oh and rads fitted. Since this watermark has appeared and got worse over the last month or two.. I cut a peice of board out, to be greated with a soaking wet inner roof, droplets everywhere.... Our problem 2.... The house is a semi formerly a council house, we have great neighbours who are council tennents... They have the same sort of rooms as us but still the original loo and store (no heat sourse).. And attached to ours So taking advise online of fitting a VCL then a thick insulation then watertight layer is not really an option without affecting the council properties roof.. So I am left with trying to sort the problem from inside.. Although there is much advice regarding how this is now not advisable.and insulating from outside is they way to go... Is there anyway I can fix this from within... I am happy to take down the internal ceiling and start again. But what would be the recommended materials etc etc.. To ensure no water ingress... You can see by the images that there is no VCL inside and the insulation is very thin and not sealed in anyway. Just placed in the roof void not a good job at all.. ... Please please any advice would be gratefully received.... Mark

I have a small flat roof to build. Nearly sorted everything out - one last detail niggles, though. The roof abutment ventilator. There are lots tof choose from. But the ones I have seen require a lead flashing. Is there any way I can avoid fitting a lead flashing?

My house design has 2 deep, long balconies off the bedrooms on the upper floor. The decks have been designed with parapets; the build is by MBC Timber Frame and it will be a cold roof construction. The architect is doing all the necessary for building regs sign off and it's nearly there, but they are flapping about ventilation of the decks. Their concern is that the cold roof on the decks must be vented, but they don't want to put any vents through the vertical face of the cladding that will be on the outside of the parapet. As yet, I haven't seen the type of vent that they are trying to avoid, but does anyone have any other solutions for venting the roof other than going through the cladding? I've seen a few ideas where the air flow goes to the edge of the deck then up through the inside of the parapet, but I'm not sure if this would give sufficient air flow and achieve the necessary ventilation level. Any suggestions welcome.

Currently at structural engineering stage for building regs submission and looking at roof covering loading. The choice of waterproofing is subjective and well documented; single ply, bituminous, EDPM, GRP - seems that everyone has a preference or horror story. Anyway more fundamentally my design is showing a cold roof design for a new build flat roof extension (parapet roof), however having researched flat roofs the majority of advice is to go for a warm roof to eliminate interstitial condensation (eg Bauder, NFRC) . As I chose the timber frame provider to avoid this issue at the sole plate I'm thinking that I'm walking into this problem up above. Any experience or thoughts welcome.