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Got a few jobs to do around the house and one is to fill gaps where mortar has fallen out where flashing is bedded above a bay window.
Can anyone tell me the correct cement mix? The lead plugs are still in place so I guess it's just a case of refilling with cement. Also, the ridge tiles on this window probably needed redoing as the mortar they sit on seems to be decaying. Any tips for redoing his too gratefully received.
Just did my ridge tiles and a bit of flashing (oo-eer mrs) this weekend. 3 parts sharp sand, 3 parts builders sand, 2 parts cement.
1part cement to 3 parts building sand.
Unless the rest of the pointing is lime mortar
You can add some PVA (Nicobond, Unibond type stuff) to the mix, especially for re-pointing the lead. This will give some adheshion / pliability.
It's common to use Leadmate sealant (sort of grey silicon that sticks to lead) for this job as lead expands and contracts and mortar tends to fall out.
I would be cautious with this, mortar attacks lead. When considering a new installation of lead flashing the lead should be protected with builders paper or other such medium to act as a barrier between the lead and the mortar. It would add time to your repair, but you could remove the lead packing cut the builders paper to fit insert it then repack the lead wedges back in and point.
Admittedly the detereation will take place over a protracted period.
An organisation such as the Lead Sheet Association based in Tonbridge Kent should be able to advise you (01622 872432).
The mortar mix should reflect the existing mix that has been used to bed your existing brick/blockwork, routinely this is 5 to 1 (sand to cement) but could be stronger say 3 to 1. I would suggest making some trial mixes at different ratios letting it dry and then see which one matches the appearance of your existing jointing/pointing. When you have found the right mix don't make it too wet as it will smear on the brick faces or lead sheet and look unsightly, it should be easily workable not sloppy, slightly less spreadable than butter is a good analogy.
Oh and as said above, if it is lime mortar then it'll be different again!
MUTDs
Builders paper! WTF? I presume youre just reffering to the sun??
Mate I used to do lead roofing for 14 years and it was only on conservation jobs that anyone went to that extent. The flashing was screwed into the joint, bitumen applied and then pointed with stone mix.
For the most part we would either used specific lead sealant, or 3 parts sand to one part cement with a good amount of PVA.
Take a look at the pictures on the bottom of this page to see the end result.
http://shireroofingltd.shortlandpalmer.com/recent-projects
Agreed mr palmer!