Appropriate filler for large gaps around window frames. Fillers, sealants and adhesives for all types of DIY work. Help, advice and information on all aspects of this subject

[Melinda]

Hi everyone

I recently discovered some blown plaster in a ground floor room either side of a large window. Ive successfully repaired the leak outside which caused the problem.

While removing the plaster Ive been rather alarmed to discover *massive* gaps around the window frames. I can get a hand inside the gaps on both sides. The gap is at least a brick deep and at its widest is 2-3 inches.
The mortar flaunches on the outside of the window are weak and crumbly, so this is almost certainly how the water got in.




Will expanding filler be appropriate to fill the gaps by the window?

Is there any particular mortar recipe I need to fix the outside flaunching?

[Melinda]

Should I have posted this in the Plastering forum?

[JRS]

Fill the gap with expanding foam cutting excess off. then carry on with the repair of the wall.

[Pops Tripping]

Expanding filler is a good solution but if the external side is as weak as you say it is it may "blow" the render. My advice would be to try it sparingly to see if it's successful.

[Melinda]

Thanks for the responses. :)

Im going to go with a cement filler I think. Ive just had a look at the outside flaunching and it came away in my hand. If I tried Im sure I could stick my hand right round the window- With my fingers right inside the room while still standing outside.

Cement would make me feel more secure about it.