On Tue, 03 Oct 2006 13:26:37 GMT, . wrote:

don't use silicone, if you have to use a sealant on roofing/lead use
Leadmate and plenty of it. it does what it says on the tube.

Umm, Leadmate is a neutral cure silicone. So "don't use silicone" is a tad
self-contradictory. But the advice to use a sealant is sound. I suspect the
OP's headache is that he had already used mortar, and is I guess asking
about the use of a silicon liquid to waterproof the mortar.

It doesn't seem like a sensible suggestion to me, and from the description
it is difficult to tell where the water is getting in. It may be necessary
to seal over the mortar with Leadmate, it may be necessary to rake out the
mortar and remake the joint.