Does anyone have any advice on the best tools and methods of cutting this large hole ? It's to re-locate my bathroom extractor fan.
Cutting 150mm hole in lath & plaster ceiling
- Thread starter LeeDowner
- Start date
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Chop out a large square of ceiling back to the joists on either side of the fan position/
Take the laths outside and make a nice bonfire
Screw a piece of 12.5mm plasterboard into the new square hole (you can cut the hole for the fan before putting it into place if you like).
Doing anything else will be doomed to failure.
Lath and plaster is (also) the spawn of the devil.
Take the laths outside and make a nice bonfire
Screw a piece of 12.5mm plasterboard into the new square hole (you can cut the hole for the fan before putting it into place if you like).
Doing anything else will be doomed to failure.
Lath and plaster is (also) the spawn of the devil.
Get a nice, new, sharp holesaw of 150 or slightly larger in diameter, and fit to your drill.
And wear a hard hat lest it snag on the laths, rip them out of place and dislodge chunks of plaster.
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I would cut a 150mm hole in a piece of plywood and stick using gripfill or similar, especially around the hole, above.
Wait until it has set and use a jigsaw from above.
You will need the plywood to fix the fan anyway.
Wait until it has set and use a jigsaw from above.
You will need the plywood to fix the fan anyway.
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Good advice there. Would prefer to use a hole saw afterwards to cut the laths, should cause minimal of damage.
I've heard it helps to mix up a weak PVA solution and flood the plaster area (from above) where you're going to drill. Once it's set you're less likely to lose the edges of the hole to crumbling. Not tried it myself but told it works.
pj
pj
I tend to find downlights and lathe/plaster are not the best of friends for a number of reasons. The very best possible solution would be to replace the area where the light/lights are to be fitted, with plasterboard or fit non-recessed lighting.
Here's what I did for 100mm duct (hole 105 or 110mm I think). Assuming this is going through a ceiling.
A variation on some of the themes already posted.
Lots of different opinions on how to approach appeared, when I was looking on the web. You need to go with what makes sense to you and modify based on your circumstance and situation.
I'm sure many will say this is OTT. But I haven't had to deal with replacing or repairing the lath and plaster - once those laths break away from behind, it all becomes very unstable and I wanted to avoid that at all costs.
Cutout a section of ply to fit between joists and cover a wider area than the hole you will be making. 12mm or thicker suggested - what ever you feel comfortable with.
Brushing as much of the grit from the top of the ceiling and PVA to seal remaining grit. Pour plaster adhesive and spread level covering the top rolls of the plaster to adhere to plaster rolls and to ply - see next step.
Lay the Ply over the top and press down. Screw into Joists with angle brackets or other method of securing.
Let set over a day.
Use a new Hole Saw on high Speed and cut from room side. I found it advantageous to begin the cutting drill in reverse, as the teeth are so aggressive forwards.
Notes:
May be useful to precut the hole in the ply before mounting. If you wish it can then be cut larger than the diameter for the air inlet to allow mounting of retaining flange etc. Depends on mounting flexibility. I used a jigsaw rather than buying another larger hole saw.
Need to keep in mind that if cutting through the ply and ceiling in one go, it is getting pretty thick for the inlet spigot and also for the holesaw depth to cope with going from one direction.
Suggest you drill a pilot all the way through the ceiling from either top or bottom in case you need to tackle from a different direction. Be prepared.
Came out cleanly for me no problems and no damage.
Hope it helps.
A variation on some of the themes already posted.
Lots of different opinions on how to approach appeared, when I was looking on the web. You need to go with what makes sense to you and modify based on your circumstance and situation.
I'm sure many will say this is OTT. But I haven't had to deal with replacing or repairing the lath and plaster - once those laths break away from behind, it all becomes very unstable and I wanted to avoid that at all costs.
Cutout a section of ply to fit between joists and cover a wider area than the hole you will be making. 12mm or thicker suggested - what ever you feel comfortable with.
Brushing as much of the grit from the top of the ceiling and PVA to seal remaining grit. Pour plaster adhesive and spread level covering the top rolls of the plaster to adhere to plaster rolls and to ply - see next step.
Lay the Ply over the top and press down. Screw into Joists with angle brackets or other method of securing.
Let set over a day.
Use a new Hole Saw on high Speed and cut from room side. I found it advantageous to begin the cutting drill in reverse, as the teeth are so aggressive forwards.
Notes:
May be useful to precut the hole in the ply before mounting. If you wish it can then be cut larger than the diameter for the air inlet to allow mounting of retaining flange etc. Depends on mounting flexibility. I used a jigsaw rather than buying another larger hole saw.
Need to keep in mind that if cutting through the ply and ceiling in one go, it is getting pretty thick for the inlet spigot and also for the holesaw depth to cope with going from one direction.
Suggest you drill a pilot all the way through the ceiling from either top or bottom in case you need to tackle from a different direction. Be prepared.
Came out cleanly for me no problems and no damage.
Hope it helps.
It would help if downlights were being installed, but as the OP is cutting for an extraction fan (misread), maybe not so much. But some of the information is still applicable, cutting into lathe & plaster is a pain in the harris when wanting to recess units into them, whether it is a light or a fan.
If access from above is not available, then more than likely the solution is to cut a larger section of the ceiling out, ideally catching joist for support and replacing with a suitable depth of plasterboard and skimming over.
If access can be made from above, bedding a plyboard section above or even a plasterboard section with dry-wall adhesive will be very helpful in offering some additional strength to the ceiling to take the cut, but if it were for downlights, then you have the added problem that not all downlight fixing spring clips work on fabric depths exceeding 20mm.
Chain drill the circle and carefully remove the plaster from the centre of the chain drilled hole.
Carefully drill out the remaining wood from the lathes or use other tools to break the land between the chain drilled holes and remove the lathes that would have bridged the hole in plaster.
Insert and fix a baton either side of the hole so that all the cut lathes are tied together, ideally through the plaster.
Carefully drill out the remaining wood from the lathes or use other tools to break the land between the chain drilled holes and remove the lathes that would have bridged the hole in plaster.
Insert and fix a baton either side of the hole so that all the cut lathes are tied together, ideally through the plaster.
Have you ever actually tried to do this? Was it a success?
I just end up with a pile of ceiling on the floor - any time that I try and do anything with lath and plaster.
I just end up with a pile of ceiling on the floor - any time that I try and do anything with lath and plaster.
As long as you take it steady you can cut holes in lath and plaster no probs. I've found a half blunt hole saw to be better than a brand new sharp one. Keep the drill running at full speed and press on to the ceiling as gently as possible letting the drill do the work. Do not try and force it. I've done it hundreds of times with out a problem.
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