I'm fitting a kitchen workbench in a cupboard under the stairs which houses the washing machine and all the usual cleaning paraphernalia. Size approx 1400 x 1200mm. The bench will go all along the 1400mm side. The problem is that there's no right angles anywhere. The 2 side walls are not perpendicular to the back wall. The width of the cupboard is about 30mm less at the wall where the back of the bench will be than it is in the middle of the cupboard where the front of the bench will be.
How do I measure and cut the workbench so that it is a good fit? Where do I take measurements from and how do I transfer these to the workbench for cutting? Is there a general solution to this problem?
You may well need what engineers call CAD - that's cardboard aided design! ;-)
Measure the length of the wall that the worktop will go against - that gives you a starting point. Now with some bits of cardboard, cut then to fit (trial an error) into the angle made by the side walls to the back wall on both sides.
Now you can mark out the work top. Start at say the right hand end, and use your card template and a straight edge to mark the first back "corner". If the back is narrower than the front, then the worktop will be a trapezoidal shape when done, and the back right corner will end up being a bit inset from actual corner of the rectangular shape you start with. Next measure the length along the back, and mark out the other corner with your second template.
For best results flip the templates left to right and mark out the underside of the worktop. Then cut from that side with a circular saw (or jigsaw if the walls are that wonky!). That way you won't get chip out on the laminate.
If it's an expensive bit of worktop, another way to get better accuracy might be with two bits of MDF, each a bit over half the width of the space. Say 6mm or 12 mm. Or plywood.
Put one into the right hand side and scribe and cut the side (and back, if necessary, separately). I strongly recommend the Trend scribing kit.
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Put the second bit into the left hand side, and repeat.
You will now have two bits which should fit perfectly at the back and sides. Put them both in place, and mark the overlap line. Cut along this, you now have two pieces which exactly fill the space. You could fix them together with a lapping piece for really accurate finishing.
You might well find at this stage that your original bits were not quite deep enough. Something I have learned from repeated failures of "just trying to do it by measuring".
Now you can mark up your worktop for cutting, and arrange for the front edge to be just where you want it.
You *do* have a sawboard for making the straight cuts, don't you? Check DIY Wiki for details.
If the cut sides and back are only slightly wavy, I usually find it easier to cut straight, and oversize, and then trim to shape with a sanding disk in an angle grinder, rather than trying to use a jigsaw. Real carpenters might finish with a router, but I know my limits.
And +1 for flipping so that you cut from the underside with a circular saw. Just check very carefully before you start.
Some good answers above, but there is no single solution. The granite worktop people have a wonderful tripod mounted pointer connected to a laptop which enables them to quickly record a series of points and then cnc cut the worktop to fit. Unfortunately the more accurate the fit the more likely you won't be able to manoeuvre it into place.
If it's under the stairs then fill the gap with something from a sealant gun and cover it with an upstand.
The fact that it comes with several spacers that just fit perfectly makes all the difference to me. I know I could make one much cheaper, and I do sometimes make tools rather than buy them, but this one just isn't interesting (to me).
I had the same problem when building some heavy duty shelving under a set of stairs, the main issue being that the side wall was an old chimney breast, rendered, which wandered around by up to 3 inches in both the vertical and horizontal planes. The way I tackled that was to box it in with a false wall which I wanted to be both accurately vertical, and perpendicular to the back wall. So I needed to fit some substantial horizontal battens using offcuts of 3x2 and 4x2.
The tool I found *really* useful was a laser level. I first scribed the battens and fitted them temporarily to the wall. Then I used the laser pointer scanning a vertical plane going into the alcove, perpendicular to the back wall. This let me mark up on the battens exactly where the outer edges needed to be trimmed so that the false wall was vertical and true.
The false wall and all the shelving were built in 18 mm ply.
I just wanted to say thank you to all the people who relpied, particularly John. A bit of a fiddle as the most uneven wall was the long back wall. It's all done now, not perfect but the best I can manage.
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