Advice on felting & battening detail for a hiproof exten

[RomanAbramovich]

small roof extension (for recently built garage) which meets the existing roof on 2 planes. On one plane a new valley is formed while the other plane is simply a continuation of the existing roof line. It is a hipped roof and new roof is hipped also. Tiles have been parted/removed on one plane to accept the new roof structure.

question is, how far back should I strip back tile (plain conrete) and battens where new roof meets old? the new valley is formed with 6by1 and I've lined it with tyvek, i've also applied temporary batten and felt to the new roof structure - just not sure how to deal with felting & battening where new meets old - is it common place to remove a couple of feet of tiles and somehow apply the tyvek under the existing battens? or do i just cut off the tyvek where new meets old (at an existing hip, for example)?

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• RomanAbramovich
• 10 Mar 2011
• 1

 

[BethesdaSlate]

Personally I would strip back to a do a vertical join at a rafter just to the right of the junction of the new ridge and existing hip that runs into it.

This will allow the new Tyvek to drain any condensation vertically from from ridge to gutter. If there is existing felt running to the old hip then it wont do any harm to have the Tyvek go over it to this vertical point.

Regarding the new valley, I would strip back at least 4 or 5 tiles to the left side, run some new felt under any existing felt (this will mean lifting battens) and over the new lead in the valley.

Run a batten up both sides of the valley on top of the felt just outside the valley boards which will prevent the ends of the battens piercing the felt and give an extra fixing point for valley cuts.

Also, 6x1 valley boards too narrow, so (before any of the above) I would put a 2x1 batten up the side of these to allow for an adequate width of lead.

 

[RomanAbramovich]

great advice - thanks.

tbh for the valley timber section (6by1) i copied the carpentry from an existing valley elsewhere on the roof! will extend 2" either side as suggested.

main problem i'm having with getting under existing battens and felt is that they are so brittle. battens are approx 19mm square and felt is bituminous type, all around 50 years old. any attempted strip back around the new/old junction inevitably causes piercing of the old felt

will make good today....