fitting roof valley boards where different roof styles meet!

16 Apr 2010
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United Kingdom
first post.
new extension.i am fitting valley boards one side of valley roof is warm ie with counter battens so valley board can be fitted on top of rafters and tile battens sail over o.k.. other roof is standard so do i need to recess valley boards or can i use 6mm on top of rafters. also will it matter that the 2 sides of valley are 25 mm diff heights. this is a lead valley.
if you think i got it completely wrong please help . thanks in advance.paul.
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The heights of the rafters is irrelevant.

What it does mean though is, when you fit the material to the one side i.e. counter-battens insulation etc, it shifts the valley centre over.

You will still need to fit the valley boards so that they fit flush with the tops of the rafters, or if you like, so that they don't stand proud and interfere with the roofing lathes/battens.
thanks thats great
regarding the old style roof can i avoid the job of sinking the valley boards into rafters by using 6mm ply on top of rafters or would you not recommend this as it is a lead valley. ta paul.
The thing is you don't want to be lifting the lathes as this causes trouble with the way the tiles sit in the valley.

Granted, you could leave the lathes short so that they but up to the valley board but then you have the problem of catching the ends of the lathe, those that do not land on a rafter that is.

What we do is set the valley boards so that they sit flush with the rafter top and are set wide enough to catch the lathe ends also.
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Hi. I get various valley situations where we are asked to fit sheet lead to valleys. On occasions i have come across feather edge board used as valley board. The thick edges butt in the centre of valley. Although it takes out a bit of the rafter pitch it allows a small upstand and sufficient roof to form a worm on the lead without causing the tiles/ slates to lift.
Make sure your sections of lead are no longer than 1.5m,this is a common mistake for the DIYer. ;)

1.5m spacing applies (commonly) to code 4 lead.

However the greater the thickness/weight/code the greater the maximum spacing.
This is true but code 4 lead is ample for valleys .This length allows for thermal expansion and contraction ,prevents loosening/splitting of the lead.

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