Fitting window cill, not my normal work.

[Cabinetman]

Hi, just been asked to quote to make and fit an internal window cill in solid oak to a recess that is about 1.5 m wide and 450 mm deep the plaster on the side reveals goes all the way down to what looks like a plastered base as well, do I remove some of the plaster on the sides to enable me to slide the oak in or just fit it superbly brilliantly to fit, and how should I fix it in place – thinking more about how to attach it to the window frame. I am thinking it would be made having a wider and thicker front section. Or do I run away? Ian

 

[Doug71]

Well back in the day (I feel so old sometimes) when doing a first fix the walls wouldn't be plastered and there would be a nice groove in the back of the wooden window to take the tongue of the window board. You would cut a couple of twisted wedges with the axe and hammer them in to the joints in the blocks, cut them off level and nail down the board.

These days with plastic windows and things rushed on/done in the wrong order it's just do the best you can. Once you start chopping in to the plaster you can cause problems, especially if there are metal corner beads?

The easy way is make a template, cut board to size and glue down with fix-all.

The problem is Ian you do things properly and you are starting at the wrong point to do that.

 

[Cabinetman]

Well back in the day (I feel so old sometimes) when doing a first fix the walls wouldn't be plastered and there would be a nice groove in the back of the wooden window to take the tongue of the window board. You would cut a couple of twisted wedges with the axe and hammer them in to the joints in the blocks, cut them off level and nail down the board.

These days with plastic windows and things rushed on/done in the wrong order it's just do the best you can. Once you start chopping in to the plaster you can cause problems, especially if there are metal corner beads?

The easy way is make a template, cut board to size and glue down with fix-all.

The problem is Ian you do things properly and you are starting at the wrong point to do that.

Thanks Doug, The more I think about it the more I want to run away your last sentence summed it up completely thank you, and it’s somebody I know quite well so couldn’t just give her a silly price. I think I shall just say it’s outside my expertise. I have plenty to be getting on with anyway so thanks you’ve answered it perfectly. Ian

 

[Phil Pascoe]

If you do it don't forget that 450mm deep at some time it will be sat on.

 

[Cabinetman]

Thanks Phil, normally you would be quite right haha, but this is a window that is only 2 feet six high and about 4 feet off the ground – it’s a strange old barn conversion. The other reason I think I shall run away is the expansion/contraction problems in the future. Ian

 

[eribaMotters]

18mm Oak faced ply with a solid front lipping about twice as thick. I'd add a micro chamfer on the join line.
Pre-finish the woodwork, leave all existing plasterwork, scribe to fit and liquid nails into place.

Colin

 

[dzj]

One of those stair tread jigs might come in handy for such a job.

 

[Jacob]

Hi, just been asked to quote to make and fit an internal window cill in solid oak to a recess that is about 1.5 m wide and 450 mm deep the plaster on the side reveals goes all the way down to what looks like a plastered base as well, do I remove some of the plaster on the sides to enable me to slide the oak in or just fit it superbly brilliantly to fit, and how should I fix it in place – thinking more about how to attach it to the window frame. I am thinking it would be made having a wider and thicker front section. Or do I run away? Ian

It's not a "cill" it's a window "board".
Doesn't necessarily need fitting to the frame - just up to the frame will do if there is somewhere more convenient to pin the thing down.
A 450mm board is doomed to bend - the top face will dry faster than the bottom - even more so if it is on the sunny side. I'd look at oak T&G instead, if there is anything to fix it to.
Finish it off with a batten along the front edge wider than the board thickness - could be half round or just flat.

 

[stuckinthemud]

I always overthink stuff, had to make a window board in a hurry for my house when it became apparent the cill I was trying to fill and gloss was fibreboard over filler/cement/ rotten pine. Found a few lengths of 4x1 edge glued them scribed and fitted in an evening's worth of work. I was lucky the old board left a hole in the plaster which I made good. Point is, its not a difficult job, notch the plaster back a couple of mm, scribe the board into the notches, glue the board down well, if the board is at the right moisture content it won't move, don't overthink it... :-D