Idea of cost to enlarge a window (and add support if needed)...?

8 Sep 2010
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South West Wales
United Kingdom

We are thinking about increasing the size of the existing window in our kitchen. The current window measures 118cm wide by 116cm high. The new window would be 236cm wide by 94cm high. Not sure if this would need a lintel or additional structural support?

The wall is a cavity brick wall as far as we know but cannot be sure. External rendering.

We've absolutely no idea how much something like this would cost and would be very grateful if anyone would share their thoughts. We're in South Wales.

We've already been given estimates for the cost to supply and fit the window itself, so are looking for an idea of the building/structural work costs.

Many thanks

PS - I can post photos if that would help.
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Thanks :)

Here's some pics:

Kitchen Window - Internal.jpg

Kitchen Window - External.jpg
your present window board/sill is set lower than the work top - extending the opening over the unit at the present window board height will create a further problem to a w/t and sink thats already a bit odd?

the Tyrolean(?) render will have to be made good and a new - maybe extended - external sill will be needed.

as above, you will need a new lintel - you determine wall thickness by measuring the wall at any convenient opening.

propping (strongboys or needles) will be required, and will cause further difficulties - the sink unit will have to be moved out to allow work on the wall.

that RH corner of the kitchen is a very dark corner.
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Many thanks for sharing your thoughts.

If we go ahead with the job we'd bring the sill higher so that I'd be above the sink etc. Hence the change in height from 116cm to 94cm.

Totally happy to have a new sill outside and expected that to be the case. We'll be repainting outside at some point so that should take care of any mismatch in colour with new render.

Very helpful re the fact the sink would have to be out of the way. That's all on the way out anyhow. But we had considered getting the kitchen done sooner and reconsidering the window enlargement in the more distant future. Obviously we wouldn't want to move a new sink/unit etc once installed, so if that's definitely the case then very handy to know that it's now or never.

The corner is not as dark as it looks. To the right it is open plan to the dining room which has patio doors and a large picture window. But yes, it could do with being lighter still and the window would do that, although in all honesty the main reason would be to open up the view more.

It will come down to cost at the end of the day and that's why I thought it would be helpful to at least get a rough idea at this stage before calling anyone out. I really have no idea whatsoever. But other considerations are also very helpful, like the things you've pointed out.

Thanks so much for the help
Seen it a few times where the joists are propped over 600mm from the wall ie kitchen units left in place. I’ve never done it tho
Sorry for being thick but quite visualise what you mean...
The ceiling joists are acrow propped to support the inner skin (as close as poss to the wall, but seen it where it’s a worktop depth off the wall to avoid disturbing kitchen units). Strong boys used outside for the outer. Assuming the exposed joists in your picture are the actual ceiling joists running into the wall.
Aha - Gotcha. Thanks :)

No, those joists are fake / non structural.

So any rough idea of cost? Any kind of idea would be helpful, or at least a "it would almost definitely be more than £????"...

Pricing on jobs does vary greatly, according to area, size of company, how busy everyone is etc.
However I would expect you could be looking at least 2.5 grand.
Thanks Stuart, that's so helpful to get an idea. I asked on another forum too and no-one there would put a price on it. I totally understand all of the factors involved and how impossible it is to give a price. But even a rough idea is helpful as I've no idea whether it could be £800 or £15,000! And I'm sure you guys in the know can narrow it down a bit more than that. So cheers for that.
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OP, you must work to a measured whole kitchen plan - dont do things, or allow anyone else to do things, in dribs and drabs or you will end up doing the job twice.

propping from an outside, substantial scaff platform - a scaffed platform and maybe a RSJ lintel that BCO might want SE's drawings and calcs for?
further difficulties could arise with any cavity and perished cavity ties.
and ground level - how far below and possibly sloping away?
as for the 600mm business - while working over a unit, and attempting to insert a steel lintel - that approach could even be dangerous.

the safest but time consuming approach is to needle the support.

the above are just a few possible difficulties (there are others) so for me, ball park figures are not possible or are misleading - eyes on site is needed.

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