re-covering the roof
- Thread starter Hib
- Start date
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I don't really understand why you'd want to use 2 layers? Unless the roof's leaked at all in the last 20 years due to the tiles leaking I can't see the point! If (assuming this is your thinking and the 2 layers are on top of each other) any water gets through the 1st layer, hows the water going to run down the second layer, it'll just remain trapped or find its way through the 2nd layer too. The whole point of a breathable membrane is to do away with the ventilation void, just make sure its pulled taut. http://www2.dupont.com/Tyvek_Construction/en_GB/assets/downloads/guidelines_pitched_roof.pdf
Well it does sound like classic condensation to me but I can appreciate you're concerns.
After the insulation was removed, was there any evidence that water was still getting in/through the tiles? Even if water was to get through the tiles, Tyvek should be sealed with Tyvek Tape so as long as its been done well there should'nt be any overlaps or gaps etc to allow wind driven rain to get in anyway.
If you end up going down the multiple layer route Tyvek are recommending I'd get him them put it in writing.
After the insulation was removed, was there any evidence that water was still getting in/through the tiles? Even if water was to get through the tiles, Tyvek should be sealed with Tyvek Tape so as long as its been done well there should'nt be any overlaps or gaps etc to allow wind driven rain to get in anyway.
If you end up going down the multiple layer route Tyvek are recommending I'd get him them put it in writing.
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Two layers probably because (as I have said more than once) not all breathable underlays are waterproof.. many are simple water resistant and will let in when saturated.
Which concrete tiles are fitted at the moment?
Are you sure they are suitible for a low pitch like yours?
if so what is the gauge they are fitted at?
If you reuse them it might pay to close the gauge down giving more head lap.
finally when you buy your underlay be sure it has a CURRENT BBA certificate..
Which concrete tiles are fitted at the moment?
Are you sure they are suitible for a low pitch like yours?
if so what is the gauge they are fitted at?
If you reuse them it might pay to close the gauge down giving more head lap.
finally when you buy your underlay be sure it has a CURRENT BBA certificate..
J
justlead1
Hi Hib, The problem you have will remain using felt as the sole barrier. I have a catalogue of customers with similar problems. In view of the monies involved why not look at the probabilities of changing the pitch? The gain you need to bring it up to 22 degrees is approx 300mm in 3m. Sorry about the negativity but short term gain leads to long term pain.
Good luck.
Good luck.
@ datarebal: Is'nt there a technique called double boarding for low pitched roofs where you use a layer of ply beneath the battens or something? I was told how it worked by a BC inspector but I can't remember the exact makeup as I did'nt use it in the end as it was on a local authority building and the tile manufacturer would'nt give a warranty as it was below their recomended pitch.
I was suggesting this method was used with felt not Tyvek.
Thats the first time you've mentioned you have a room in the roof, I have no idea how the regs are applied in Ireland but over here you'd be likely to need to sling a layer of continuous insulation beneath the line of the rafters in addition to insulation between the rafters to comply. You could look at Triso if its allowed.
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