Valley detail

7 Aug 2010
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United Kingdom

I am about to have the roof coverings fitted and would like to get some info on the different valley details.

I have recently seen a new build where the tiles have been cut very close together and you cannot see the valley at all. I have been told that this is a dry valley trough. I would personally like to have this as it looks the neatest way of forming the valley.

A roofer that I had to give me a quote said that I do not need one of these. He said that I can either use lead or a GRP trough and he will cut them tight together.

However, after speaking with a manufacturer they have told me that a normal GRP trough/Lead needs to have the sides cemented, so they can't be cut close together.

After telling the roofer this, he said that, that is what they advise, but he doesn't advise it. When the mortar finally breaks down it lodges in the valley and creates leaks, so he never cements the sides. He said he has been roofing for over 30 years and has never had a problem doing it the way he does.

Is he advising me correctly or should I just by the dry valley trough and make sure it's done the right way.

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Go with the dry valley system as it is maintenence free.
Also use dry ridge and verge systems,all maintenence free!

RoofDry have over 37 years experience in the roofing industry
and you should always point the valley and you never should cut
the tiles tight together because if it gets blocked with moss or other
sediment you will have to take the tiles out just to clear the blockage!!!

So use dry system but have a 4 to 5 inch gap with the tiles.
Better to have a functioning roof instead of a leaking one!!

You need a roofing specialist because the guy you have is clueless
and clearly doesn't know what he's talking about!!!!


RoofDry ( roofing specialist )
Personally I can't understand why anyone would want to use a product (like GRP) in the valleys that is not expected to last as long as the roof covering - seems mad to me. GRP - 20 years if you're lucky, you're concrete tiles could well last 60 years, that 3 times as long!!

The new-ish GRP troughs with close mitre appearance are asking for trouble in my opinion, won't take long to start clogging up.

Why not just use the traditional material that's tried and tested and has standard codes of practice -ie lead (or other metal such as copper)

Lead valleys installed correctly as per British Standard Codes of Practice i.e Open valley, tiles bedded onto slips (normally fibre cement these days) using good mix, will last as long as the rest of the roof without any maintenance.

Do it right, do it once!
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I agree, lead for the valley but traditional mortar always falls out with movement over time. If you use the dry valley you don't have to point the tiles and it doesn't fall out every few years!!

Also fibreglass last for 40+ years not 20. Most fibreglass flat roof systems have a 20 to 25 year guarantee, they don't guarantee things for its full life, or have i missed something!!??
This is a real learning experience. I don't think I've come across a trade yet where more than one tradesman agrees on the best way of doing something.

I do like asking a few people though and then making up my own mind.

I do like the way the dry valley trough looks, but if the tiles need to be cut back, therefore exposing the valley then I may as well use lead, considering that it lasts that much longer.

This is the finish that I wanted.


Those tiles look like ashmoor old english?? are they the tiles your having??
If so have you enquired about valley tiles??

Do they make valley tiles for that tile??

if they do that would be problem solved as you wouldn't need to cut the tiles in at all!! And you don't have to re point the valley every few years!

The tiles I've got are mini Stonewold.

I was just showing this image as the house I first saw it on looked like this and they were also mini Stonewolds.

I've just installed 4 8m valleys in stainless steel in west London. These have a guarantee of 100 years when installed correctly and weather the same colour as lead.

Stainless steel can be formed to have a rigid upstand each side which means there is no need for the cement finish to the tiles.
Thats what i meant by dry valley but got mixed up with actual dry valley!!!

Should have worded it your way lol.
Hi hardmetalking.

How much does that cost per metre?

Also when you say that an upstand can be formed, another roofer told me that he can also do this with lead by fitting a length of timber just in from the edges and forming the lead up and over it.

Is this an option?
another roofer told me that he can also do this with lead by fitting a length of timber just in from the edges and forming the lead up and over it.

Is this an option?

Yes a tilting fillet is fitted and the lead dressed over it. The eave tiles and first course then rest on the lead covered fillet. That's how I've always done it and the way it's been done for hundreds of years and no pointing to the tiles.

It's around £20 per metre for material and the same for installation with a lifetime guarantee.

Lead can be formed the same but can only be fixed in short lengths to allow for expansion and contraction. Lead also has a risk of theft. Stainless steel doesn't carry these issues.
Go with the dry valley in your pic..using mortar in valleys is old hat on a tiled roof.looks good when cut tight to the grp rib..
Plastic and grp have no place on pitched roofs, I don't know who is in charge of the current building regs but I do not know how it is justified with the longevity of the other materials involved.

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