Choice between valley tiles and open/lead valley

11 Apr 2006
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United Kingdom
I'm just finishing the roof carcass on a rear extension and I'm starting to think about roof coverings, and wondering how to tackle my 3.5M long valley. The idea being that I can prep any valley boards required at this stage.

I've not purchased any valley tiles or lead yet, and I don't think there's much in it cost wise which construction option I take.

So I think my options are:

1) Fit noggins between all my valley jack rafters to form two valley boards, and then construct a lead lined open valley. I presume this means running a batten down each side of the valley to form the sides of the lead channel and then cutting the tiles so they overlap these sides. What's involved in forming a lead saddle at the top of the valley? More than folding the valley lead over the ridge and beating/forming in to place?

2) Make the valley with felt and valley tiles. This seems like a far simpler construction, but is it considered inferior in terms of longevity? Am I right in thinking valley tiles don't need pointing?

The existing house roof has a 45 degree pitch, and this particular plane on the extension roof is 42 degrees (don't ask!) so I think the lead valley will be more flexible, but will the valley tiles really notice a 3 degree difference?


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Gary they do a g.r.p dry clossed valley, I have never used one but they look easy to fit.
Tiles would be my first choice, but they are harder to fit and align to get a nice result. If you can spend the time then I'd go with tiles. Valley tiles should last as long as the rest of the roof tiles, and don't need pointing

Next choice would be lead and last resort would be plastic - purely for its cheapness. You can get plastic valleys which don't need pointing too.

But lead valleys are just as easy as plastic ones.
Assuming it is plain tiles then the preferable option would be valley tiles in my opinion. As far as the differing pitch is concerned, it won't make too much difference but you should batten the lower pitch first then course round to the steeper pitch which will close the gauge (very) slightly
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Thanks guys. Yes they're just plain tiles. I think I'll go with tiles then.

Woody - in what way are they harder to get a nice result? I was wondering whether the fact that the existing house was already tiled would mean that it's a chuck of the dice whether the position of the valley is going to perfectly align with the existing bonding pattern of the tiles already laid on the roof. I suppose I can always by a stack of tile-and-a-halfs and cut them to fit...

It's good to know that a few degrees between the pitches wont amount to too much.

You just have to be more careful with the laths (level and gauge) and valley angle, as any discrepancies tend to be highlighted by the valley tiles

Its not so much the tile spacing as you can like you say, throw some cuts in
It might be an idea to get just a few valley tiles and see how you get on, then you could always have a plan B.
The existing house roof has a 45 degree pitch, and this particular plane on the extension roof is 42 degrees (don't ask!) so I think the lead valley will be more flexible, but will the valley tiles really notice a 3 degree difference?
Yes if you gauged up exactly the same.

As said, you need to set out the gauge on shallow pitch then close up or else you will be about 34mm out by the time you get to the top and this will look like a pigs ear with valley tiles!

Dry grp valleys are excellent and look ok when fitted, though you still need to use lead at the very bottom to deal with the fascia kick.
Carefull battening making sure your battens course correctly as SRE says lower pitch will govern your batten gauge. Set it out properly with care then vally tiles piece of cake.
There will always be a cut somewhere.
Yes if you gauged up exactly the same.

Right okay - that makes sense. Unfortunately the steeper gauge (the existing house) is already tiled, so I was hoping to do it the other way around. Will check the specs on the tiles to make sure the 42 degree gauge is going to give me enough head lap.

Valley tiles need a bonnet hip to make the roof look pukka.

That's the plan - two bonnet hips, and a valley, so hopefully it'll look smart!



Regardless of what the tile courses are doing, it is essential you keep the bonnets in line, central to the hip blade.

Whilst it is tempting to turn the bonnet one way or t'uther to try and match the tiles adjacent, don't do it. Keep 'em central on the hip. ;)
Ok as the steeper pitch is already tiled firstly you need to measure the existing gauge..
if your lucky it'll be under max gauge 100mm or less ( but doubt it will be less)
If it's max gauge and the lower pitch roof has a long rafter you may be stuffed
If its a short rafter then you might get away with..

no need to tip bonnets to one side ever.

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