Seeking advice on replacing lead on valleys.

[Munchincocopops]

Hi – I am looking to replace lead valleys as one failed (split) and I did not know until it bowed the bedroom ceiling.

Anyhow leak is temporary fixed but now I have decided to replace all 6 valleys.

I noticed the wood valley probably needs replacing and am thinking of 9mm OSB….is that ok.

Currently it looks like flooring T&G.

Also I expect the water got in as there is nothing below the lead on the valley.

So I’m after “belts and braces” solution and am thinking of new 9mm OSB valleys, new sarking underneath on top of 1.5mm Classicbond rubber running down the valley OSB and 2ft or so either side, then code 4 lead on top of that.

 

I’d appreciate any comments on this and can anyone recommend a good quality sarking.

 

 

The house was built in 1989 and the sarking is that bitumen based product that rots as it reaches the gutter. So I plan to fit new sarking under the old as it meets the gutter too.

 

 

I’m no roofer but I am a serious DIY who has bult a large garden room and I used Classicbond on OSB for that roof as it’s a 7 deg slope.

 

 

Thanks for any advice.

Edited Tuesday at 14:57 by Munchincocopops

[Nickfromwales]

8 hours ago, Munchincocopops said:

am thinking of 9mm OSB

It'll need to be OSB3 to be specific  You can't use regular OSB externally.

 

8 hours ago, Munchincocopops said:

Currently it looks like flooring T&G.

So will be 3/4" imperial, which means 18mm OSB3 is the thickness you need. Not sure why you suggest 9mm board?

 

This should form the sarking, so kills 2 birds. Membrane over, and away to go.

[Munchincocopops]

Hi Nick – thanks for the reply. Yes OSB3….I should have been more specific.

I was thinking OSB 9mm should be suffice as no-one will walk on the valleys unless your comment which has me at a loss “This should form the sarking” refers to 18mm OSB profile?

So I will use 18mm OSB 3 and I was thinking Classicbond glued to OSB, then sarking(felt?) running along roof from left to right is overlapped the valley and 2ft or so to the other side and again from right to left and overlapping the valley and beyond 2 ft or so. Then the code 6 lead on top of this. I know there is a maximum length (I need to check) in which case overlapping is required (again I need to check how much).

Reading your comment again and thinking about it I will run in sarking first over the valley then install Classicbond over the top of the sarking then lead on top of that in which case any water that manages to get behind pointing will not wet the sarking but run down the rubber to the gutter….Thanks for the advice.

I was also thinking of running eves comb filler under the tile down the valleys as my tile is a bold roll and it will give something to point against with 3:1 sharp sand:cement ……also thinking of maybe pea gravel concrete…..it just need to last another 30 years and I’ll be gone! LOL.

 

Thanks again for the advice and any further comments.

Kind Regards.

[Munchincocopops]

If I can ask some more questions.

 

I was thinking sarking is the correct name for the felt fitted under the tiles....but I think I'm wrong?

 

I've been in the loft today and can see somehow with this constant rain water has gotten behind the tiles and is staining the roof felt/sarking under the tiles on the larger valleys.

 

So a question.....can I use Classicbond instead of the sarking/felt when the valleys are redone. I realise sarking/felt allows air through and rubber will not so is this an issue? The larger valleys are an extension above the garage which protrudes from the front of the house hence 2 valleys.

 

These valleys meet at the ridge of the house whilse the other 2 pairs of valleys of the original house meet before the ridge.

 

The roof is Marley Bold Roll dry verge installation.

Looking at the felt in the loft it looks like water is getting in at the top and also lower down. Lower down could be valley pointing I guess, but at the top?

 

It will last the winter but needs doing this year.

 

Thanks for any advice.

 

Kind Regards.

 

Edited Wednesday at 17:30 by Munchincocopops

[Temp]

This bloke seems to know what he's doing. See if he has a vid on valleys..

 

https://youtu.be/srpMbLCTnMg?si=hFricBFGC_FSeikN

 

[Temp]

It could be the lead valley was designed/installed incorrectly so perhaps don't just copy what you have with new. Why did it split? Were the strips of lead too long (thermal expansion)?

 

No expert but I know lead work is a bit of a skill/art.

[Nickfromwales]

Sarking is the sheet board that goes (in some instances) over the roof rafters. 
 

If no sarking then the breather membrane is there instead. If sarked, the membrane sits directly onto the sarking.

 

Then roofing battens. 
 

 

[Russell griffiths]

Just be aware lead should not be longer than 1.5m, I’ve seen lads run a roll of lead from top to bottom of a valley, as it’s long and thin it looks like the obvious thing to do, but expansion kills it. 

[Munchincocopops]

Thanks for the great replies and thanks for clarification of sarking.

Lead that split is original as per house built in 1989 and south facing no more than 1.5m or I think & one piece. 

 

Valleys above extension over garage are much longer but are fibreglass valleys, again in lengths - cant recall what length...but was a kit from well known builders merchant at the time so I guess ok. These valleys themselves are not leaking but I do see signs of damp on sarking/membrane so water getting in somewhere over the years and in this constant rain....so plans to replace.

 

As I mentioned .....just got it into my head now to replace all with Lead on top of Classicbond as I want belts and braces.....do it once and forget it for rest of my life anyhow.

 

Thanks again.

 

Kind Regards