cavity trays

Hi all!
I am building our own extension with a gable end abutting the old house wall. We are starting to run out of cash for materials and are desperate to afford to get the roof on before the winter sets in ( I know its a long way off, but I'm only a feeble southern gal doing it all - so I'm a bit slow ). Building control have insisted on cavity trays. We have been given some brand new short lead cavitray X trays (cavity trays of yeovil) by a mate who never used them on his bay windows. Only problem is that he had a 50 degree pitch, and our roof is 30 degrees. The wall is in a fairly protected area, so we see the cavity trays as over' egging the pudding', but understand why we have to have them there. Basically, in a long winded typical woman way, what I'm saying is do you reckon we could bodge it with these - possibly using the short lead as a soaker, and dressing new stepped lead flashing over the top to create secret gutter as planned under the tiles. The trays would overlap each other by about 3". If I ask any one else I just get furrowed brows and long noisy intakes of breath - so any help would be greatly appreiciated! many thanks!

Depends if you think the cost of retrofitting them and getting walls replastered and painted should you get damp problems later is a risk worth taking. The Forum is littered with homeowners who have skimped on cavity trays in such situations. BC usually insist on them anyway.

karenandoz said:

bodge it with these - possibly using the short lead as a soaker, and dressing new stepped lead flashing over the top to create secret gutter as planned under the tiles. ! many thanks!

Click to expand...

the short lead wants to go Over the upstand of the secret gutter !. That was a trade secret until I read it on the cav.tray website What area of Sussex?

Thanks for the tip Nige - we're near Chichester. So do we make the secret gutter out of a couple of straight lengths of 1500mm lead, and then dress the short leads over the top of it's upstand? Do we need zinc soakers too if doing this (sounds like overkill)?

Freddie - don't get your point? We know we gotta have them - trying to work out if anyone has done the same as we are suggesting...

Anyone know the minimum recommended overlap for individual stepped leads? Haven't been able to find any info for this on the web?

You can make your own trays from a roll of 450mm wide polyphene DPC which costs about £20 for 30m, and then you don't have to mess about with pre-formed trays at the wrong angle

Chichester - not my area - but if you google calder lead guide - then look for "the calder guide to good leadwork ". There is an online copy of their book - and you`ll find all the details there The 1500 measurement is the max for a piece of lead- the overlap depends on the roof pitch - all in the guide . Only downside is that you have to buy whole rolls lead nowadays , as far as I know . Used to be able to buy it by weight . Also I don`t think cav. trays type x are pitch specific - maybe ask the manufacturers . Always a good idea to mock up the layout before you install . You probably sussed the trays are to cascade the water from one down to the next . They can indeed be made from some DPC if it`s folded correctly and slopes correctly . the overlap of the x trays should be obtainable from the manufacturers too - they might send you a booklet Good luck and feel free to come back

Thanks Nige again for your time, and Woody too!

Nige - you are a true star - that guide is brilliant - and tells us exactly the overlap we need - thanks a million!