Enlarging a Window

[CHarr]

I've knocked together a small bathroom & toilet. The toilet had a small square window, and the bathroom a deeper rectangular one. They're on the same wall, about 18 inches apart.

I want to enlarge the opening of the smaller window so that it is the same depth as the larger one, and then have two new uPVC windows fitted, as the differently sized windows look very odd from the inside.

The wall is of standard brick cavity construction. Is it OK to cut the face of the external bricks with an angle grinder (to get a neat edge) before splitting the unwanted part of the bricks out? How should I go about forming a cill (bridging the cavity)? I was thinking of taking out one additional course of bricks internally, and then replacing them, turned 90 degrees, so that their length spanned the cavity (I'll need to trim them up a bit), butting them up against the inside of the external wall with mortar. Is this acceptable?

Lastly, I was going to use expanding foam to seal off the open sides of the cavity, and then after the windows are in, plaster internally to make a neat job and finally fit MDF internal cills & decorate.

Is there a better way?

 

[dann09]

1. A pic of the bathroom exterior & interior with the two frames would help.

2. Presumably the window heads are at the same level height?

3. Its OK to cut brick with an angle grinder. Practice on the interior skin before cutting the exterior face.

4. google pics of reveals, and cavity closures, and cavity insulation at reveals & openings, these will give you a mental picture of possibilities.
The new frames will have cills.
Talk to the window fitter(s), who come to measure up, about your proposition.

5. Before any of the above: do you have a firm plan for the new bathroom layout?

6. Have you thought about joining the two openings for a single frame installation?

 

[^woody^]

Yes you can cut the bricks with no issues, and do the rest of the stuff you planned

I would not bother turning the bricks around at the cill. Just fill with foam like the sides

Just don't forget to fit a polythene DPC up the inside of the cavity to form a barrier to damp coming across the wall

 

[CHarr]

2. Presumably the window heads are at the same level height?

Yes, they are.

3. Its OK to cut brick with an angle grinder. Practice on the interior skin before cutting the exterior face.

4. google pics of reveals, and cavity closures, and cavity insulation at reveals & openings, these will give you a mental picture of possibilities.
The new frames will have cills.
Talk to the window fitter(s), who come to measure up, about your proposition.

I'm not thinking about the external cill, but the internal one. I'm seeing the window company in the morning.

5. Before any of the above: do you have a firm plan for the new bathroom layout?

Yes, and the two windows will fit with our intended layout perfectly.

6. Have you thought about joining the two openings for a single frame installation?

Yes, but decided against it because a) we would need to take out considerably more brickwork and have a lintel put in, and b) the proportions of the resulting window wouldn't match the rest of the house, or its neighbours.

 

[CHarr]

Yes you can cut the bricks with no issues, and do the rest of the stuff you planned

I would not bother turning the bricks around at the cill. Just fill with foam like the sides

Just don't forget to fit a polythene DPC up the inside of the cavity to form a barrier to damp coming across the wall

I hadn't thought of foam all round: sounds easier! Would the foam not provide an effective moisture barrier? The existing internal cill of the larger window has a great thick layer of mortar and the two skins of the wall are bridged by it (but there's never been any sign of damp penetration).

 

[dann09]

Ref. the window fitter's appointment: the new frames should sit back approx 75mm from the face of the brickwork.