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Rain leaking from joint between top of window and brickwork. best approach?

Rainwater is penetrating above the window and running down the inside face of the window. This is a uPVC window about 7-8 years old I think, possibly a replacement for the original window, and the leak has only shown itself in the last few weeks. The house is brick construction, and there's a 'soldier' course of bricks above the window with a course of mortar between the bricks and the head of the window. There is also a bead of sealant between the window head and the bottom edge of the mortar course. It's probably about 1" between the bottom of the brickwork and the top of the window.
The sealant seems sound, but mortar course shows some slight cracking along the top edge - nothing terrible, but with the wind and rain we've had lately it could be enough to let wet in.
Problem is, what to do. Things I've considered:

1. Given that the cracks in the mortar are not severe and the sealant is good I've wondered about applying something like Thompsons Water Seal, the reasoning being that it's quick, cheap, and just MIGHT solve the problem - at least until the weather improves.

2. Digging out 1" - 1.5" the old mortar and applying new. Most of the mortar seems sound so it will be hammer and chisel (which may loosen the bricks), or small angle-grinder. My least favourite tool, dust everywhere, but less likely to disturb brickwork above. If I repack with new mortar that too may crack, but with a gap of around 1" to fill that may be too wide for sealant alone.

3. Dig out as in (2), but insert a narrow lead flashing into the gap. Secure it with lead wedges and Lead Mate sealant. A bit more work but maybe a better long-term solution.

What do you think folks? By the way, this is my daughter's house. She's broke so this repair will mean 71-year old Dad and a set of steps. Hope you can help.


Thanks for your reply and suggestion. The problem is on a ground-floor window which I should have mentioned in my original post. I've had the perished felt problem on my own roof and agree with you. However, there's an upstairs window directly above the window with the problem and if there's water leaking down the inside of the cavity i'd have thought it would show on the upstairs window too?
The weather here is awful at the moment so the affected area is going to get a dose of Thompsons Water Seal on the inside and reseal the window frame on the inside until the weather picks up. ******
Thanks again for the replies. Have dug out/resealed the inside of the window and applied Thompson Water Seal on outside. That's all I can do for now. Will aim on something more permanent in summer unless the problem reappears immediately. All the best!

5 Answers from MyBuilder Window & Door Fitters

Best Answer

You normally find the bottom 12"'s of felt on your roof has perished so the water comes from the bottom of the roof needs stripping and 1m of so me kind of roofing felt to be fitted


Answered 13th Feb 2020

Is the paster wet on the inside head ?
I’d go with your second fix. Dig out any lose mortar and point it bk up if the gap is to much for mortar alone then first put expanding foam in let go off and then repoint. But I do agree with s.jansen if it was an upstairs window


Answered 21st Feb 2020

Hi there, number 3 seems a good option,if you have checked all the external sealant, then the cement pointing is letting the water in, a small lead drip and a reseal will do the trick


Answered 21st Feb 2020

Are their any air joints between the bricks the plastic type if so they may be leaking due to volume of rain we have had

Also again it could be one or two bricks that are not so compact in side thus letting water pass into the inner skin into the room

Sealant May need redoing
Yes repointing and a good masonry weather sealant May help
Also check the gaskets are tight when window is locked to keep Water out
Hope this helps
Be carful on that ladder


Answered 25th Feb 2020

Hi first check roof .. under tiles make sure felt under tiles hasent perished.. or flat roofs are sealed with a bit bitchamin black paint .. then move to pointing above window a posability could be up stares window could have a fixings hole in bottom off it take glass out and check that the fitters haven't drilled any unwanted holes or cracked frame were glass gose and that window is drained properly and working correct. .. then check window seals and silicone seals .. if continues remove solder corse using strong boYs on a acrow props to support the rest off bricks above wilst you remove them then grind a damp corse in iner wall and place a 300 damp corse to brick work and replace brickes leaving the damp corse on top off window and install weephole joiners in solder corse n you should soRte yr problem out thanks Colin p.s start from roof then work yr way down alimanating each problem should sort this for you thanks Colin. ..


Answered 6th May 2020

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