PaddyP Posted November 4, 2020 Share Posted November 4, 2020 Hi all, Just looking for a bit of advice. After trawling through the forums and consulting with my builder relatives/ engineer we have settled on a rubber roof membrane. I will be doing the bulk of the building myself with my builder relatives and am trying to save money wherever possible. I have received back some ridiculous quotes so far for the installation of a rubber membrane, with some in excess of £100+ per m2. My roof is a very straight forward rectangle with parapet walls and no roof lights or other tricky details so I see no reason why I shouldn't be able to do it myself. I am looking at using a single sheet system such as Firestone or ClassicBond. Does anyone have any experience with either of these products? Firestone seems to be the most popular however the price of ClassicBond is very attractive. I have also attached our proposed roof build up if anyone had any feedback or advice it would be much appreciated. All the best and thanks for your help, Patrick Link to comment Share on other sites More sharing options...
Big Jimbo Posted November 4, 2020 Share Posted November 4, 2020 Patrick. I have done loads of Firestone rubber roofs. Some have been simple, and some have been complicated with multiple roof lights etc. If yours is as you discribe, then i would class it as an easy roof. The only thing i would say is that because of the time of year, you will have to use the contact type adhesive, rather than the water based adhesive. You can't use the water based adhesive if there is any chance of frost. The water based adhesive is great, because as you lay, if you get a ripple, you can pull it back and sort it out. With the Contact type adhesive, you only get One chance to lay, It sticks, and ain't coming back up...... You would have to use the contact on the vertical surfaces anyway, but it does make it much harder to do. Your rubber roof would also need to be taken up and over the top of you parapet wall, so your top trim would lap down over it. How is your roof being vented ? If your cladding is vertical, it would need another batten (Counter) in order to provide ventilation. 12mm Osb on your roof is to light for your roof top layer. Looking at your drawing, i don't see your ventilation, or construction working. Can you do a warm roof ? Link to comment Share on other sites More sharing options...
Mr Punter Posted November 4, 2020 Share Posted November 4, 2020 The membrane is heavy. Don't try to do it on your own. You need a fall on the roof of at least 1:60 so on your joists you could run firrings in one direction and then your battens at right angles to the firrings. If you go with the cold roof (which is far from ideal) you will need a very well installed vapour control layer under the joists to stop warm moist air condensing in the cellulose. Have a service cavity for light cables as well. The ventilation around the parapet is quite hard to achieve but changing the wall battens from horizontal to vertical would help. Link to comment Share on other sites More sharing options...
PeterW Posted November 4, 2020 Share Posted November 4, 2020 Not sure who has designed that build up, but there are layers missing. Cellulose won’t work in that situation for a ceiling, you will need some sort of OSB layer above the joists and below the battens to trap the insulation. You also won’t get to building regulations levels of insulation unless it is 350mm thick - that is a very thick and very heavy roof to try and do with standard timbers. If you are doing this yourself then make it easy. Build a standard flat roof and then use tapered PIR above the deck. This will give you the fall needed - you can slope it both ways from the middle - and then bond on 12mm OSB and the membrane ensuring it goes up and over the top of the parapet. This completely removes the need to have a ventilation gap anywhere, and seals the box tight. Also looks like you are missing a counterbatten in the wall build up - again, this needs proper detail as you will need OSB outer layers for racking strength and to contain the cellulose. Link to comment Share on other sites More sharing options...
SimonD Posted November 4, 2020 Share Posted November 4, 2020 3 hours ago, PaddyP said: Hi all, Just looking for a bit of advice. After trawling through the forums and consulting with my builder relatives/ engineer we have settled on a rubber roof membrane. I will be doing the bulk of the building myself with my builder relatives and am trying to save money wherever possible. I have received back some ridiculous quotes so far for the installation of a rubber membrane, with some in excess of £100+ per m2. My roof is a very straight forward rectangle with parapet walls and no roof lights or other tricky details so I see no reason why I shouldn't be able to do it myself. I am looking at using a single sheet system such as Firestone or ClassicBond. Does anyone have any experience with either of these products? Firestone seems to be the most popular however the price of ClassicBond is very attractive. I have also attached our proposed roof build up if anyone had any feedback or advice it would be much appreciated. All the best and thanks for your help, Patrick FWIW, I did do an epdm flat roof completely on my own and it's not a terribly difficult thing to diy. However, as mentioned above, I used the water based adhesive as when I was finishing around upstands and completing corner finishes, I did need to pull it up and re-do a couple of times. I also needed to resolve some bubbles when laying the full sheet. In my experience, it's not the general laying of it but the detailing to make it neat and tidy that are the major challenges. As for your drawing, there's obviously been a lot of comments about the build-up so I'll just chip in with the metal. What metal cladding are you using? If it's a standing seam type cladding you need to ensure it's fully supported by plywood or osb. Your ventilation gap at the top is too small and should provide 25mm ventilation gap along the top. The metal capping should have a slope and the down turn should be 60mm to the side of the flat roof and at least 75mm to the clad side. You also meed to make sure you have a weather check at the top of the metal cladding. The 50mm wall battens should be installed vertically. The detailing for metal cladding and coping says the parapet should be 150mm in height with, as @Big Jimbo already said, the epdm installed up and over the parapet. hth. Link to comment Share on other sites More sharing options...
BobAJob Posted November 4, 2020 Share Posted November 4, 2020 I had a rubber roof redone a couple of weeks ago. The roofer said there was no need to protect the wood on the gutter edge with a cladding, so he left it as bare wood. Link to comment Share on other sites More sharing options...
Dave Jones Posted November 5, 2020 Share Posted November 5, 2020 (edited) The way our roofer did this was to clad the fascia first with our choice of cladding then ran the rubber over and used a narrow trim that the rubber clamps into that is secured to the fascia. similar to this , I don’t think any glue was used on this clip so it allows fascia repairs without touching the rubber. https://www.rubber4roofs.co.uk/shop/sure-edge-gutter-drip-trim-2-5m Edited November 5, 2020 by Dave Jones Link to comment Share on other sites More sharing options...
PaddyP Posted November 5, 2020 Author Share Posted November 5, 2020 Hi all, Thank you all very much for your helpful replies they are very much appreciated. I am a complete novice to this so I may be explaining things wrong but try to learn and will answer questions to the best of my knowledge. Don't worry I have a builder and engineer to fall back on so I won't be allowed go too far wrong am eager to be involved and would like to learn! It's great to hear that people have been able to successfully DIY a rubber roof. Attention to detail seems to be the main thing. I will have plenty of help for installation so that should jhelp greatly. 22 hours ago, PeterW said: Not sure who has designed that build up, but there are layers missing. Cellulose won’t work in that situation for a ceiling, you will need some sort of OSB layer above the joists and below the battens to trap the insulation. You also won’t get to building regulations levels of insulation unless it is 350mm thick - that is a very thick and very heavy roof to try and do with standard timbers. I am eager to use cellulose in the roof mainly due to the cost benefits of it. At the moment it is coming in at about a third of the cost of PIR. As long as a cold roof is ventilated properly I would assume there should be no problem with it? Is the heat loss significant enough between a warm and cold roof to warrant a change? 23 hours ago, Mr Punter said: You need a fall on the roof of at least 1:60 so on your joists you could run firrings in one direction and then your battens at right angles to the firrings. I think calling it a flat roof was probably a bit off. There is actually a pitch of about 4 degrees on the roof so this should take care of that much. The fall of 4 degrees is over 15 metres so I presume that is enough to carry away the water? On 04/11/2020 at 09:54, Big Jimbo said: Patrick. I have done loads of Firestone rubber roofs. Some have been simple, and some have been complicated with multiple roof lights etc. If yours is as you discribe, then i would class it as an easy roof. The only thing i would say is that because of the time of year, you will have to use the contact type adhesive, rather than the water based adhesive. You can't use the water based adhesive if there is any chance of frost. The water based adhesive is great, because as you lay, if you get a ripple, you can pull it back and sort it out. With the Contact type adhesive, you only get One chance to lay, It sticks, and ain't coming back up...... You would have to use the contact on the vertical surfaces anyway, but it does make it much harder to do. Your rubber roof would also need to be taken up and over the top of you parapet wall, so your top trim would lap down over it. Thank you very much for your feedback on the membrane. Thankfully the roof isn't due to be done for a while yet. We are just clearing the site at the moment for probably wont be done until March/ April time. For applying the roof I would be planning to follow the approach here https://www.youtube.com/watch?v=YVU3ejUa2sA&t=211s. This involves using a water based adhesive in the middle and a contact type adhesive at the upstands/ edges. Would this be an ok approach? I plan to bring the membrane over the parapet so that detail will be updated thank you for pointing it out. Quote If your cladding is vertical, it would need another batten (Counter) in order to provide ventilation. 12mm Osb on your roof is to light for your roof top layer. Looking at your drawing, i don't see your ventilation, or construction working. Can you do a warm roof ? The cladding on the wall is vertical. Would it best to counterbatten the wall to assist with ventilation as mentioned elsewhere? Would I need to double the OSB? Nobody will be one the roof so I thought that would be strong enough. I am eager to use cellulose in the roof so felt a cold roof was best to achieve this. Thanks to all again for their help and replies hopefully I have helped answer some of the questions posed. All the best, Patrick Link to comment Share on other sites More sharing options...
PeterW Posted November 5, 2020 Share Posted November 5, 2020 1 hour ago, PaddyP said: I am eager to use cellulose in the roof mainly due to the cost benefits of it. At the moment it is coming in at about a third of the cost of PIR Have you factored in the OSB both sides to contain the insulation plus the machinery to blow it in, and that it needs to be roughly 2.5 times the thickness of PIR for the same insulation values..? When you factor all this in, it will be borderline that you can complete it for less than the cost of PIR. It is also much more labour intensive and you will need to detail that cold roof very carefully. Link to comment Share on other sites More sharing options...
Mr Punter Posted November 5, 2020 Share Posted November 5, 2020 I see MBC Timber Frame have a similar roof design: https://www.mbctimberframe.co.uk/passive-house/passive-roof/ Link to comment Share on other sites More sharing options...
HerbJ Posted November 5, 2020 Share Posted November 5, 2020 (edited) Yes and that is how my roof was built and insulated. I've attached a few photos, which may be helpful Edited November 5, 2020 by HerbJ Link to comment Share on other sites More sharing options...
HerbJ Posted November 5, 2020 Share Posted November 5, 2020 I forgot to mention that my roof doesn't have OSB on both sides to contain the cellulose. As you can see from the photos, (and detailed in the MBC Attic Trussed roof detail) there is a 22mm OSB sarking on the external face and the internal face of the airtight membrane held in place with the service battens. I think the photo attached shows the airtight membrane in place before the cellulose was blown in. There are a good few of us on Buildhub with MBC Timberframe houses and this construction detail Link to comment Share on other sites More sharing options...
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