Cutting 150mm hole in lath & plaster ceiling

[Taylortwocities]

Yes, well I was being a little harsh (BAS is back so gotta polish up my act )

When using holesaws in lath & plaster, I find the best methgod is to use a blunt one to chomp through the plaster, then swop to a sharp one for the laths.

It's not so good tryiong to do it in one go, as the plaster blunts the hole saw before it has a chance to get to the wood.

 

[LeeDowner]

Thanks for all the replies.

I will try cutting through with a holesaw, is it vital that the ceiling is supported from the top ?

Has anyone done this job or similar job without supporting the ceiling ? There's the weight of the extractor fan unit and the plastic ducting that will slot onto it. All supported by the plaster surrounding the hole.

 

[bernardgreen]

If the laths are not held securely then the vibration from the saw as it cuts one lath will cause the plaster to break away from the other laths.

The advice to re-inforce by glueing from above is good advice.

For cutting a large hole in an old lath and plaster wall this was reasonably successful.

Cut a hole of the same size in a piece of plywood Then Drill a ring of small holes around that hole about an inch away from the rim of the large hole. Then using small diameter sharp screws through the small holes screw the plywood to the wall with the screws going into the laths. It helps to drill pilot holes into the plaster and lath for the screws.

Once the plywood is firmly fixed cut the hole with with a pad saw with the saw set to cut as it is pulled out of the wall.