Valley advice!

[larry]

Hi all,

I have a pan tiled roof with bitumen felt underneath.

We've got four lead lined valleys.

One of the front valleys has started leaking - not "need a bucket" level, but basically visibly damp valley boards (quite localised).

I've had two quotes back for repair - both of which are obviously more than I'd like, but the second chap just now has said that if he replaced them he wouldn't use cement underneath the tiles, his point being that the lead will expand, the cement will crack etc. He said lime wasn't any help either. So he would replace the valleys but with nothing around the edges tucked under the tiles.

The first chap was planning on using cement around the edges of the tiles.

Can I ask what is accepted/standard practice and what should I be expecting?

We had one pther valley done a few years ago and this was with nothing under the tile edges. It hasn't leaked, but it isn't pretty, and there's a few bits of tiles which it looks like the roofers stuck underneath other tiles to try to prop the tiles into place.

Thanks for advice!

 

[Flyfisher]

Interesting question, for which I don't really know if there is an accepted/standard practice.

We also have a pantile roof with lead valleys where the edge tiles have been finished with lime mortar, though none of them are more than about 18 years old as we stripped and re-layed the roof after adding a breathable membrane. Do you know how old are your leaking valleys?

Our roof work was done in phases, some by me and some by two different local contractors, one of which is a heritage specialist firm. The fact that they both used mortar under the edge tiles suggests to me that it's the standard practice - plus, as you say, it does look better than leaving the tile edges open.

I use builders paper under lead on the understanding that it allows the lead to freely expand/contract so that it doesn't split if it becomes partly 'stuck'. I wonder if if it could be used on top of the lead so that the mortar sits on the paper allowing the lead to move slightly underneath and not cause any cracking? Just an idea as I've not done that myself so just thinking out loud really.

 

[larry]

Interesting question, for which I don't really know if there is an accepted/standard practice.

We also have a pantile roof with lead valleys where the edge tiles have been finished with lime mortar, though none of them are more than about 18 years old as we stripped and re-layed the roof after adding a breathable membrane. Do you know how old are your leaking valleys?

Our roof work was done in phases, some by me and some by two different local contractors, one of which is a heritage specialist firm. The fact that they both used mortar under the edge tiles suggests to me that it's the standard practice - plus, as you say, it does look better than leaving the tile edges open.

Hey, thanks for such a quick reply - that's really helpful, as I suspect building practices might be aligned in this part of the world.

This is definitely for me outside any DIY expertise - I don't do heights!!

If I'm honest I've got no idea how old the valleys are, but does the Bitumen felt date it? The house is 100 years old (I know, basically a new build compared to some on here) and if I had to give a massive guess I'd say they might have had it all replaced with the felt maybe in the 80s or something. I'd certainly be surprised if it was less than 30 years old looking at it and if somebody told me it was 50 years old I'd believe them. But that's also because I've really got little to compare against.

If you've got any tips for local firms who might take a look and who are likely to be at least reasonably costed do buzz me a PM!

 

[Cubist]

Well your chap is right about the lead expanding but I believe he's wrong in his thinking about the mortar. As I understand it the purpose of the mortar is to prevent 'driven' water ingress and reduce the potential for wind to either lift the tiles or get under the lead-work. The mortar will bond initially to both the underside of the tiles and the lead but, as your guy says, repeated expansion and contraction will operate overtime to 'shear' the connection to the lead sheet. Whilst that would permit the possibility of some driven water penetrating beneath the tiles this would/should be minimal.

Happy to see the above corrected as its pretty old data but its always made sense to me.

The discussion has prompted me to think though that if the lead sheet were to be 'lapped' over any water proof membrane beneath the tiles then perhaps the mortar would become superfluous?

 

[a twig]

Admittedly clay double romans rather than clay pantiles but all our valleys were done by running the membrane down and overlapping the edges of the lead valley (which themselves ran about half a tiles height up underneath the tiles) and then using plastic fingered trays over the top of the membrane/lead interface to prevent damage to the membrane and hold the membrane down in the event of driven rain.

The fingers then prevented animal / rodent ingress into the roof.

I’m sure it is not “approved” but it was very effective