Lead flashing to neighbour's garage roof

vallo

My over garage extension has a concrete reinforced ringbeam between the ground and 1st floors. This is about 2 feet higher than the old garage roof so a lead flashing is hooked over the top of the ringbeam and dressed down to meet with the garage roof of my neighbour. The builder has done a very tidy job BUT has fixed the lead to the ringbeam with steel masonry nails at about 300mm intervals. I thought you weren't supposed to puncture the lead - how should I remedy this?
Ta

rooferPete

Hi,

I presume the wall will carry on up on top of the ringbeam ? in which case the block work will hold the lead in place anyway.

It depends on the size (guage, width and length) of the lead as to whether or not it will crack from expansion and contraction.

The text book way to fit a flashing is to use one piece as the flashing and then fit a cover flashing welted and fitted into the joint of the block work.

That said if the finished lead is only going to show 100 mm or less after the plastering is finished then you should not have any problems, in fact most use the cheapest way possible and lead is not one of them.

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vallo

Thanks Pete. There will be more than 100mm visible, probably more like 250mm! I am also a bit worried whether it looks like a botched job. It is the one aspect of the extension that my neighbour is entitled to be concerned about and if he looks out his landing window he'll see the strips of lead all nailed in place.
My understanding was that you shouldn't pierce the lead or nail it in place as it needs to expand and contract. I don't know if this is really a concern or if it's a theoretical problem in a climate like ours.
Anyway, thanks for your help.

rooferPete

Hi,

We did a job last year where the neighbour paid for his builder and Architects mistakes.

I thought the wall was going up on the ring beam, what you are describing now seems to be a capping cast in place.

The lead will crack in our climate, I made a living out of fixing mistakes like it for years, if in any doubt bring it to your Architects attention, nails should not be exposed in a flashing.

The 250 mm would be ok if fitted using code 5 lead at lengths approximatley 2 metres with the laps either welted or a water check at the overlaps.

What is supposed to stop the water travelling behind the flashing ?

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vallo

Hi rooferpete, thanks again for the reply.
The wall is built on the ringbeam as you originally thought - I haven't described it very well.
We bulit a new gable wall right inside the party wall (no gap) and this goes up to attic level. Where this wall starts being higher than the party wall and garage roof there is a structural ring-beam and the lead flashing laps over the top of the ringbeam and about 1ft down onto the top of the party wall and neighbours garage roof. It is grade 4 lead and there is rather a lot of it in lengths of 1.5m to 0.5m.
If I get the builder to remove the exposed nails will that help? He has now started the blockwork above the ringbeam (and the top edge of the flashing lead) so I'm looking for the best remedial solution.
Thanks again.

rooferPete

Hi,

There should not be any nails exposed in the flashing, the nails on the ringbeam are ok if they are under the blockwork, if they are in the face of the lead then your builder may intend on sealing them when he plasters the new gable wall.

If that is not the case then the best I can think of is remove the nails and use lead slips under the flashing with water checks on both sides, if the nails in the top will remain exposed it is possible to solder them.

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