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
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.
The original cavity for filling the flashing seal was wide but not deep, so I made it deeper with angle grinder and filled with mortar. The slot was too wide anyway for sightly or economical use of silicone. So now I'm after some silicone based product that can be absorbed by the mortar. I was under the impression there was one?
I can't see a surface coating being a long term solution.
Did the mortar not have enough cement in it? It should be pretty waterproof itself.
Christian.
Standard ready mixed sand/cement (no ratios on bag 4:1?) Plus addition of PVA, I slipped and put it bit much in I guess 100ml to 10mugs of dry mix. Perhaps its not fully set yet.
Hmmm. I'm no expert, but I suspect you may have to redo it, with a bit more lead in the wall. Also, how far do you go up before going into the wall?
For my conservatory flashing, IIRC, I went up just under 3 brick courses. I then buried about 30mm (or however far a 110mm grinder will go) into the existing mortar in an angle grinder slot and used silicone. No leaks that I've detected. I made sure the slot was slightly upwards into the wall, so any water drained outwards, not that it would have the chance with the silicone, though.
Christian.
You'v probably washed the mortar out of the joint... I would suggest taking it all off and starting again, no amount of silicone will ever seal it. If it's a long piece of lead (more than 3ft long) you will need two people to get it in to the right depth, (25mm+) use an angle grinder with a diamond disk in it (new, preferably so you get the deepest possible cut) and wedge it in with small rolled up lead wedges. Point with a strong mix 3:1 and hope for dry weather for 24 hours.
15mm turn in should carry ok, I've seen less turn in with no leak, yes I know its recommends 25mm. One of the problems with leaking lead/brick joints is that the mortar is not push in to the back far enough. If you cant get the recommended 25mm. Take out the next joint above and put an apron over the whole lot so it covers down to the flat, cloaking the joint below. This will give a greater up stand.
Yes I've come to that conclusion myself now, I think that's the best solution. It is quite possible that the problem is the joints above anyhow. Thanks.
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