On Mon, 28 Apr 2008 19:16:07 +0100, a particular chimpanzee, "Tanner-'op" randomly hit the keyboard and produced:
AFAIK it is a requirement for all new roofs in Scotland, not so in the rest of the UK. It may have been used on higher status buildings in the past where a higher standard of weatherproofing may have been needed (by the coast, for example), but it was by no means common, and it is virtually unknown these days (except when the roofer is Scottish).
Exactly,. By having the felt, you also guarantee that the air inside the loft at a higher pressure cant travel to wards that low pressure and push te slates off. I.e. the felt allows a low pressure area in BITH sides f the slates.
No, it is not. It is there to prevent the above. It does very little to prevent water ingress which is why we dont have fully felted rooves, and we do have many tiled rooves without felty.
I know that: that's the big danger point. It allows the inside pressure to be at atmospheric when a low pressure zone exists outside: thats why the felt is needed, to stop that blowing back out except via the eaves..
So have I, when its eithetr not raining or its all soaked into the insulation/
Permeable membrane is not needed in a 'cold roof'
Its there to vent 'warm roof' spaces where the joists are covered and there is very little movement past them as they are insulated, with a small air gap.
CUT.
NO!! don't get your local builder to do the job. Get a recommended roofing contractor.
As far as spray on, it only holds on the underside of the slates or tiles on in the roof space. When the exposed bottom half falls out where does the rain go. From professional experience getting a tile or slate out, of a sprayed roof is a nightmare. You have to go inside and cut away all the foam about 18" all round to release one tile or slate. If you ever have to strip a roof all the slates or tiles are covered in the crap. Everything is stuck together, spars, lath's and outer covering.
From a professional, KEEP WELL AWAY FROM SPRAY ON
By the way any roof either new or re roofed must by regs have a vapour barrier underlay.
I'm very happy with my DuPont Tyvek Supro sealed counter-battened permeable membrane system, this tells you everything you need to know:
On the slate front I'm very pleased with Spannish Forna, you might want to have a word with these guys:
One word of caution, be very careful with how your contractor intends to deal with the edges, abutments, verges, valleys, whatever. A number of GRP products, such as secret gutters for abutments are available which ensure you don't get leak problems, far too many try to bodge flashings without soakers or secret gutters. I had to re-timber a roof because of lack of attention to detail in this area. Roofing really seems to be a case of the devil being in the detail.
what is 'close boarded' ?
Indeed, making it future proof in case you want to build into the roofspace and want to maximise the usable space.
In article , Hugo Nebula writes
I've never seen an unboarded roof in Scotland but that's not authoritative of course. Tell a lie, I have, but it was a barn.
This is, looking up at my roof from the loft
aka sarking. Sarking boards can help strengthen the roof by bracing it - see
I thought Ballachulish was best :-) ...
Welsh slate is a smooth, rectangular, regular sized slate but the top or back of typical Scottish slate is usually rugged; only the underside or bed is smooth. As a result, most Scottish slates are shouldered or sloped off at the top corners to help them lie flat.
Owain
Its always in the builder's interest to recommend this, as they get
4 figures rather than 3. IMLE most of these recommendations have been inappropriate. Slate roofs shed slates over time, and the point at which its best to reslate is purely economic, ie when the cost of replacing a handful of slates every so many years works out to more than the cost of a reroof. One house had around 20 slates replaced several years ago after decades of neglect, and hasnt had any more work needed since. I havent seen or know the history of the roof, but more often than not just replacing missing slates is the more economic and satisfactory option.felt is a good backup, though not essential functionally.
yes, fibre cement. But it costs, and the cost isnt normally warranted.
I hope you stay well away from foam. There are more probems with it, such as the fact that it becomes impossible to inspect the roof structure, hence if structural rot occurs, you wont know until there is an eventual complete collapse. And it does significantly raise the chance of rot.
NT
The message from Hugo Nebula contains these words:
My first experience of building work was helping out on a house reconstruction in Argyll one summer holiday in 1961 or 62. Even then that roof was boarded first, and by a English Builder from Stoke-on-Trent of all places.
I can heartily endorse this: I had some good people and some not so good people working on my tiled roof. The not so good did one side, and the rain came in, at which point the good pair lifted the tiles and showed me the crappy soakers that were totally useless. And made some new ones.
The final demise of te old hose was in fact a valley that no one seemed able to fix. The new house that replaced it has two similar valleys, with lead going infeasible distances under the tiles and thatch (its where a tile section now abuts a thatch section: blame the council planners for wanting it that way).
The very best way to stop tiles being blown off. And limit arctic gales in the loft.
And, in the context of a complete re-slate, not that expensive to do.
There are rotten roof rafters with woodworm because of decades of leaks, so i think the whole lot of slates should come off and the wood be patched, replaced, and sprayed.
It's quite a steep roof, half of a large victorian house. We're half way up a hill, wth trees behind the house, so i dont think that sarking/boarding will be necessary.
The advantage of having no felting seems to me to be that when there is a small leak I can find it from underneath, damp patches in the attic and ceilings, whereas with felt the damp problem would be hidden, and may be rotting wood away secretly.
But most of you recommend a modern felting material. There are a few roof spaces that could in future be converted to living spaces, that's a future project, this summer I just want to get the roof derotted and watertight. And maybe get the hot water working.
Do the job properly then. Strip it. New timbers or treat the old, and FELT it with at least a breathable membrane. Proper eves vents with insect mesh, and maybe a ridge vent or two.
At this level it s probably a Building Notification matter, and I suspect they wont let you do any less actually.
I would even consider boarding it frankly - exterior grade ply ..adds a lot of strength and windproofing.
If you have the budget, and its sensible given the construction, I would also insulate between the rafters and board it out inside.
Make a nice room out of a crabby old loft.
stuart's reminder of it raining halfway through is the strongest argument for felting...
i guess the roofer will take the slates off first, cover it with plastic, then the wood people will replace the rotten rafters and spray them then recover with plastic, then the roofer will put in battens and felt then slowly fit slates over the top...
it's a complicated roof, and last summer it rained and rained, and i have computers and books etcetera in the rooms below, and very fancy plaster in some of the rooms below
what do roofing contractors do in rainy weather?
wrote : also insulate between the rafters and board it out inside.
That's something I can DIY in the winter after they're gone isnt it? Whether or not it's boarded on the top?
And even maybe give it a year or two first to see if there are any leaks where they forgot a few nails.
ive just uploaded a picture of the roof
Do yourself a favour and get all the wood you're likely to need into the roof space while they're redoing the roof. The access is much bigger than your loft hatch, meaning you can get nice big sheets up, which will save you an arm and a leg, and a LOT of time!
Jon.
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