how to cut coving for a bay window?

The one and only way to affix coving with irregular angles on a bay window is by either using a magic mitre or the more expensive trigjig - unless you want to make a mess of it or you understand trigonometry and can work out Cosin, Sin and Tangents and if you can do that then you wouldnt be a plasterer, you'd be aan engineer - the reason is because of the compound angle required - the mitre and the bevel angle.

TheExpertPlasterer
July 2019

Find your angle half it and that will give you the angle to cut. Any gaps simply fill with decorators calk.

Old Job Bob
May 2009

Also...

A mitre saw like the one here will help a lot...

http://www.ultimatehandyman.co.uk/tiling/mitre_saw.jpg

They can be bought quite cheaply and even cheaper to borrow one - accurate cutting and easier to keep the piece properly upright as you cut.

When you cut the lengths of coving - this will sound obvious - aim to cut exactly to length (which is difficult) but do not cut over long because they will never fit. If you cut slightly short, say1 to 2 mm, they will fit and any gaps (you will always have some gaps) can be easily filled before decorating.

Good luck...

Peccavi
April 2009

Measure the angle formed by the walls/windows in pairs. Divide the included angle by 2 and that will be the bevel cut required on each piece at that joint. Don't assume that all parts of the bay are at the same angles - even a couple of degrees of a difference will result in a gap in your joints.
E.g. if the 2 sides of teh bay are at 45 degrees to the front, the included angle is 135. Half of that is 67.5 degrees and this is the angle to cut the coving at.

JD
April 2009