old slate roof advice please

[Andy Hall]

Case of risk/return

[Andy Hall]

Case of risk/return

[George (dicegeorge)]

but if sarking stops wind then it wont it be hotter in summer cos the sun will heat the roof space air with less ventiation???

[<me9]

I don't know what type of foam they use, but surely a closed cell foam would make an impervious barrier above the timbers and act as a DPC/sarking felt, thus preserving th timbers from rot?

I know of a grade IIS listed building where a spray coating was done about 35 years ago. It was very successful, but was removed at great expense a year or so ago. The problem was that they'd used an asbestos based material, and the current owners wanted the building asbestos free. As far as durability was concerned,it was fine as it was.

[dom]

What is it that they guarantee for 25 years?

That the foam won't fall off, or that there will be no leaks through to the living space - or what you really want - that should a leak lead to rot in the rafters, they will replace the rafters?

[The Natural Philosopher]

Stops the slates lifting in the gales. That's the primary function.

[Owain]

But a good slated roof should last for 100+ years with minor preventative maintenance.

If it costs an extra £10,000 that's only £100 a year at current prices, and far less in the future.

IMO proper sarking boards give you quicker temporary waterproofing and a better area to work on.

I know we'll all be dead by then anyway ...

Owain

[meow2222]

I assume then you know that slate loss isnt a reason to reroof. Slate roofs go on for decades losing the occasional slate. When to reroof is purely an economic decision

NT

[Dave Liquorice]

Tell that to the slates on the barn roof in a gale, they rattle away nicely and there is sarking under them. Remember we get real gales several times a year up here and the occasional storm, not just a strong breeze that most urbanites experience. When there is a gale or stronger blowing one has to be careful not to step out from the shelter of the house or you get knocked off your feet...

[The Natural Philosopher]

Rattling away is not the same as being ripped off and landing 50 yards away..its the massive pressure drop you get in the downwind side of a roof that creates a huge suction on the slates..the sarking to an extent bows out and prevents that from becoming a minor explosion.

[The Natural Philosopher]

Or when the timbers have rotted due to using spray on foam ;-)