I have water dripping in my extension under some brand new lead flashing (which I cut into the exterior render of the main house wall). I pointed this with a mortar (4 parts sand, 1 cement) and painted with masonry paint. It is generally water tight but when the rain is very heavy combined with a strong wind I get water dripping on the inside of the extension from underneath the lead flashing. I have literllay spent hours with a hose trying to work out where the water is getting in but I'm now thinking it is soaking through the pointing - is this possible? If so, what is the best way to seal it?
Many thanks.
Tim.