I've just redone the flashing seal with the brickwork on my flat bay window roof. The depth inserted is about 15mm so a bit less than recommended. I've directed a hose at highish pressure along the joint for a few minutes, but it still leaks. I've simulated I guess an attrocious storm but that's not really acceptable I don't think. Can I treat the mortar I've applied with some silicon treatment to reduce ingress further? Or what?
TIA, Mike W