How to fill this window gap to stop water?

[Prusassy]

We have bought into a lovely Victorian house. Our flat is on the first floor. We have a huge gaps on a few windows between the brick and sash. I believe that the window has been internally fitted. The problem historically is when the gutters block the overflow the water pours down onto the brick, window and sill and into the wall cavity. The down stairs flat owner does complain of damp. I suspect one reason is the over flow. How is it best to close the gap? Expandable foam has been offered as a solution. I suspect that this may not be the best solution.
Cheers

 

[a twig]

This thread might be useful

 

[TudorCottage]

I’ve used Oakum on several window frames in our cottage and love its flexibility. I purchased a set of vintage oakum chisels from eBay which really help, they have rounded edges so bang the oakum home nicely without tearing it. I finish off with some Burnt Sand Mastic.

Time will tell how successful it is but some were done over 2 years ago and there’s no sign of any tar seepage or damp in those areas and most importantly the draft around the frames have been eliminated.

 

[TudorCottage]

Regarding expanding foam. When we first moved here I was constantly checking the wooden frame for rot and damp, thankfully it seems to have done well considering it’s stood here for 500 years.

But I did find one small area where foam had been used. A piece of the sole plate had suffered a bit of rot and foam about the size of a tennis ball had been used. I’m guessing it was a quick fix to present the house for sale. I removed all the foam. The oak surrounding the foam was damp for approximately 2 cms away from the foam. That was 18 months ago and I haven’t touched it since, it’s a relatively small area and doesn’t compromise the structure.

Now the oak has been exposed to fresh air it has dried out completely and is rock hard again. Scarfing in the new bit of Oak to make it look neat and tidy is on my ‘to do’ list.

Currently about number 7 in the list

Just goes to show though Old buildings do love fresh air to keep them in shape.

 

[aockenden]

I’ve used Oakum on several window frames in our cottage and love its flexibility. I purchased a set of vintage oakum chisels from eBay which really help, they have rounded edges so bang the oakum home nicely without tearing it. I finish off with some Burnt Sand Mastic.

Time will tell how successful it is but some were done over 2 years ago and there’s no sign of any tar seepage or damp in those areas and most importantly the draft around the frames have been eliminated.

Interesting you haven't had any tar leaking through like we did. I wonder if the burnt sand mastic is not as capillary-active as the lime mortar fillets I used, so it's not sucking it through to the surface. I've never used burnt sand mastic. I expect that reduced capillarity would also be accompanied by some reduction in breathability? Either that or you don't get as much driving rain blasting onto your windows as we do on ours?

 

[Prusassy]

That's great everyone who replied. Got the info we needed. Much appreciated and thanks. No foam required.