There are lots of slipped slates on my roof, with rusty nails, the local builder recommends reslating the whole roof rather than patching it again and again.
At the moment there is no felt, he advises felt, is there any reason not to use felt?
or is there an even better option?
I will use a professional for this as I almost broke my back in a fall a few years ago, and ladders scare me!
George (dicegeorge) wrote in
I'm with you on that - being scared of ladders is nature's way of stopping you plunging to the ground from one.
As far as the roof is concerned, have you thought about sprayed foam insulation? I have to admit to having had something to do with these folks on a commercial basis a while back but they do claim that it's cheaper than having a re-roof and there's the benefit of insulation and a permanent fix for the tiles.
day...)
Seems fine, *but* almost anyone I mention it to sucks their teeth and says 'ooh the damp gets into the joists'.
Any first hand experiences, good or bad?
A good decision.
There is every reason to *USE* felt. The main one is that if a slate slips or breaks then the felt (if properly fitted) will prevent water from entering the roof space until the slate can be replaced.
A close boarded roof with felt and slate (Welsh slate being the best) but the cost will frighten you! :-)
That's a good idea anyway.
Tanner-'op
Totally agree, a failsafe (faildry?) system has to be better than one which allows damp ingress on a single point of failure.
I thought all slate roofs were close boarded but that's what living in Scotlandshire does for your perceptions. If cost isn't an object and you might insulate or convert the loft later then a breathable membrane in place of felt would be a further improvement. Any (unlikely) damp ingress below the membrane would have a chance of escape in warmer weather, saving timbers from potential rot.
The danger is that any rain blown under the slates will be trapped for much longer than normal between slate and insulation and will lead to wood rot in the rafters.
Building next to ours had the foam treatment about 15 years ago. I sucked my teeth at the time but it appears I was wrong.
Except a single point of failure (a single slate slipping) does not result in a leak unless the slate below is also faulty.
Anyway I fail to understand the reliance on a material with a much lesser life than the 100 years plus of 2 layers of slate.
OK there are now better materials than traditional felt.
Jim A
Well that's what the felt is there for - just in case more than one slate breaks or slips!
Slate is a rather brittle material, especially if a ridge tile blows off and bounces down the roof or, frost gets into a small crack and does it 'dirty work' over a period of time!
You have to use a 'permeable membrane' material now rather than the old bituminous felt.
Tanner-'op
Without felt you'd be in trouble if it rained halfway through the job. Certainly easier than lugging tarpaulins over the roof
Fred,
No not all slate roofs are close boarded - that is usually reserved for the 'better' class of building and the 'normal' house these days (and in the past) is simply trussed, felted, battened and tiled - using a permeable (breathable) sraking felt as a matter of course.
Tanner-'op
If you watched any consumer advice programmes you would avoid spray on insulation at all costs! Keep well away. Get your local builder to do the job and use what he suggests.
Are you sure that doesn't just mean stay away from cowboy contractors? The principle seems to work well enough though I wouldn't risk it myself.
A friend also had foam on the back of unfelted slates. That seems to have been good for many years.
However 15 years isn't long in the lifetime of a roof - and usually there is some hope both of reusing roof coverings and that the rafters will not need attention - neither may be possible when a foam treated roof finally does need attention.
Another factor is professionalism. I would suspect that a foam treatment could be used to patch up a failing roof without fixing the real problems - rain leakage may no longer be seen - but rafter damage may be occurring.
If you have this situation it is indicative of the current roof reaching the end of its useful life. It is certainly better to re- cover that just patch.
I would suggest that a breathable membrane is better than 'felt' see :
Whatever you do don't use that stick-on-foam stuff it will rot the woodwork.
best of luck
Well there are better materials that last longer, and yes you should use SOMETHING.
No criticism on that score from me.;-)
The point is te roof is a cold roof typically, so the insulation does bugger all.
On sound timbers, it probably means they will rot in 25 years instead of
100 years.
The purpoe is to avoid low pressure over the slates due to wind ripping them off: the felt later is not for waterproofing, it is for windproofing.
By and large there are too many holes in it where nail;s get driven through to rely on it for waterproofing. I know then when my roof was felted up before tiling, there were loads of leaks when it rained, pissing all over the timbers.
You cannot avoid "low pressure over the roof" - and it is usually the low pressure that lifts the slates off on the leeward side of the roof (this creates a vacuum and 'sucks' the slates upwards and snapping them) and not on the windward side. Direct wind pressure usually just pushes the slates down onto each other/
The felt is for 'windproofing' ?? Not sure what mean here as the felt has no wind proofong qualities as such in this situation - it is there simply as stop-gap against water penetration.
As a matter of interest, you need a certain amount of airflow under the edges of the felt/slates/tiles/eaves/cavites to prevent interstitial condensation forming on the underside of the felt in the attic. Stopping all that airflow can cause trouble - as people have found to their cost when insulating the cavities and loft space without leaving room for an airflow.
Then the felt was poorly fixed or nails have 'missed' the rafters - I have seen roofs around 20 tiles missing and no water in the attic!
Tanner-'op
On Mon, 28 Apr 2008 19:12:35 +0100, a particular chimpanzee, "Tanner-'op" randomly hit the keyboard and produced:
You don't "have to"; bituminous felt is still acceptable. I would go for a breather membrane, though.
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