As it says really. Has anyone got an old slate roof on their house and had the spray foam used on it for insulation and bonding? More interested in the bonding side of things as the roof is about 100 years old and I don’t want to buy a new one. I know one person who has had it but looking for more opinions. I shall carry on with wine and cheese and await wisdom.
I have a lot of cheese.

If you use spray foam the slates can not be re used when re roofing.
You may also loose ventilation and the roof structure can then suffer from condensation. The insulation may also have poor insulation properties.
There are alternatives such as this

http://www.stormflex.co.uk/system.html

House opposite ours had it done and it was a big reason it didn’t manage to sell several times.

Why would it put off buyers. The house is bog standard semidetached the slate roof does not really add to the character at all.
The spray foam is breathable so should avoid condensation, its a long term rental so mainly interested in avoiding future roofing costs.

What’s the main reason for wanting it done ?

Does it leak ?

why would it put off buyers

f you use spray foam the slates can not be re used when re roofing.

mainly interested in avoiding future roofing costs.

You would be creating future roofing costs, when the time comes to re-roof properly the slates will be un-usable and everything will have foam stuck to it that will need stripping off before and future work can commence, so the who process will more costly.

The house is bog standard semi-detached the slate roof does not really add to the character at all.

Do you live in a conservation area? If not, a decent roofer could replace the slate with tiles and use the value of the slate to offset the price of the work. A lot will depend on the quality of the slate. One of my mates’ does a lot of this type of work on farms/barns…that’s for high demand, Buttermere slate though.

^^^^ not very often ^^^^

It’s shit avoid at all costs. I basically see it as a short term bodge!

Double

Who told you it was breathable?

I used it on my campervan (also commonly used in boats and warehouse roofs) and one of its selling points is that its closed cell foam, so can’t absorb water. I’d hazard a guess that this means its not breathable.

Who told you it was breathable?
I used it on my campervan (also commonly used in boats and warehouse roofs) and one of its selling points is that its closed cell foam, so can’t absorb water. I’d hazard a guess that this means its not breathable.

Polyurethane foams are not all the same.

Some are are closed cell and not breathable.

some are open cell and breathable.

Building regs require 50 or 75 mm air gap, foam gives zero circulation and if open foam worked th BR would allow it with zero air gap. Breathabilty only works for membranes not thick layers

If the rafters are open to allow spraying the foam breathability wont be much of an issue. I’d stay clear of the foam myself though, it’s a bodge job.

A few yrs back we did a re-roof and used a foam, not sure which one though but the client had his own ecofit/insulation/heat recovery business and he also didn’t want the ceilings damaged inside. The fool had decorated the whole house then thought about insulating the roof and as it was a vaulted ceiling this was the best option and as the roof was in poor condition it was a 2 birds 1 stone.

Afaikr it didn’t have any bonding properties, but is breathable.

It went something like – strip roof, clean out between spars, lay a breathable membrane onto ceiling and over spars, lapping the edges, lay another membrane put pulled taut, felt and batten as normal, inject/spray or whatever the foam then re slate using the existing tile replacing any that were shot.

Have it in ours (was there when we bought) looking at replacing the roof and we have to count on not reusing the slate. It’s going to cost much more.
As for leaks….you are stuffed when something eventually comes through as you can tell where it’s coming from and it makes it more difficult to repair if take a guess at where the leak is.

Seriously avoid.

Why would it put off buyers. The house is bog standard semidetached the slate roof does not really add to the character at all.

I have no qualified idea, I just know it led to potential purchases fall through so it can’t be a good decision – why do something to your house that will come up come house valuation time when you want to sell it?

avoid, its an expensive bodge, fix it properly.

the roof is about 100 years old and I don’t want to buy a new one

Why would you have to? It’s the nails that fail; get a roofer and get a price to reroof. It might be less than you think.

My first house was a Victorian terrace; I looked at the all the shortcuts, and ended up having it done properly. They use your slate and just replaced the ones that were broken. New felts/leading etc and it looked great.

It wasn’t that much more and was a great selling point when I finally moved.

slate can be reused – done it on my terrace, over 100 years old as well

strip the roof, fit breathable membrane, new battens, re-use the ridge tiles and 90% of the existing slate, pray it doesn’t rain

when it comes to resale – they can’t deduct £5k+ off the offer amount after the survey, because the original roof nails are over 100 years old etc etc

Never ever believe manufacturers claims, as with all building products check to see that it has a British board of agrement certificate and it is installed as per that certificate, google BBA certs

Reason most of these cause problems selling in the future is that building control completion will be required and may be very difficult to get for spray foam insulation

Reason most of these cause problems selling in the future is that building control completion will be required and may be very difficult to get for spray foam insulation

Are you sure for a retrofit? For a new build yes, but AFAIK if you want to insulate the inside of your existing roof, you don’t need to involve building control.

It’s a bodge job now move on!
And yes footflaps you are right.

Thanks very much all. Good points. I had never heard of this till about a month ago and had a conversation about it with a mate after a few days of very strong winds and was looking at it as prevention really. I do like my slates though and re-roofing with them all is a fair point. The wine was fine and so was me cheese.

Don’t do it mate!
I have my own construction buisness , last year we were called out to a roof leak, so up we went and stripped out a square metre of tiles and shock horror all the battens and rafters in that area were soaked and rotting we stripped off some more same there, the problem is theres no air space so it condensates like mad,.
The couple had paid 5k for the spray foam which ultimately cost them another 10k to put right. We had to completly reroof the property.then reinsulate with 120mm kingspan with 50mm air gap between roof covering and insulation. Its absolutely criminal how these people can go round spraying foam between rafters knowing what it does to the timber work. It should be banned !!!!

Hey paul, if we left some space for air to minimize the condensation will roof leaks by that time too?

thread resurrection without a spam link. unusual.