Window frame sealing

There shouldn't be too much space between the frame and the brickwork as the outside lining is part of a box that holds a sliding mechanism and space is a premium.

You may find silicon effective but if there is a larger than normal space mortar is the more effective filler.

I'm just completing more or less the same process. I ended up with a gap between the brickwork and the frame that varies between about 7 to 10mm. What I did was to fill this with mortar (1:4.5 masonry cement:sand) using a dry mixture (to avoid it flowing out of the 6 ft verticals and the upside-down bit at the top) and a pointing trowel. This mix is (supposedly) equivalent to the 1:1:6 OPC:lime:sand mix usually suggested.

If it eventually shrinks back and opens a crack between the window and the mortar, I'll follow up with a bead of frame sealant.

However, the problem I have is that a hairline crack has opened between the new mortar and the brickwork in some areas. Is this because I was using a dry mixture over the hot weekend and it's dried out too quickly ? Is there anything I can do about this apart from chisel it out and try again ? Sealant wouldn't look right here.

Cheers,

Phil Young

Hi,

I'd stick a strip of wood/foam etc round the frame that goes 5mm deeper than the surface of the brick. Then when the cement dries remove it to leave a 5mm deep channel, put a strip of PVC at the bottom then fill with sealant to create an expansion joint.

A wood/uPVC frame will move with humidity/temperature so cement alone will never give a good seal.

cheers, Pete.