Ceiling hole too big for new extractor fan

20 Aug 2019
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United Kingdom
The previous homeowner has taken their extractor fan and I've bought a replacement.

The hole in the ceiling is now too big - see picture.

How would I go about fixing this or best getting a professional plasterer in?



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is that an extractor fan? Or a cooker hood with chimney?

What size is the duct, above, that you have connected to?

Is there a room above that ceiling?
Its a chimney of a cooker hood.
The hole is in a recess that holds an RSJ, there is a room above yes.
The white piping - duct? That fits in the chimney.
I'm guessing a strip of plasterboard, slightly longer than the hole glued to the otheride of the original plasterboard and then plastered?
wouldn't it be better to board and plaster the whole hole, then make a new circular hole just for the vent? And change vent for metal too (I have plastic, daft builder didn't buy metal!)
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The chimney needs to extend into the hole though - the reason being due to the RSJ recess which has removed head height from the ceiling.
If it was me, I would cut a square "collar" of plasterboard that would fit closely to the ceiling and fit round the chimney or duct. Painted to match the ceiling I think it would look neat. You may not keep that hood for ever.

However I might have shortened the chimney by adjustment or by cutting so it didn't need to penetrate the ceiling.

I don't know how you'd fireproof the hole to prevent smoke or flame erntering the void and setting fire to the room above. Plaster ceilings are quite a good fire barrier, if they don't have holes in them. If there is an RSJ it must have fire protection as it will soften and give way when hot.
fwiw, i agree with johnD and jonbey suggestions:
ref. coming at it from the room above - remove a floorboard
and jonbey's blank the hole and then re-hole .
OP, i dont understand your objection "reason" about the RSJ and head height? the metal chimney is supposed to stop at the plasterboard.

as mentioned, definitely replace the Pvc flex duct - they retain moisture and food particles and are a v. bad fire risk.
replace best with Alu semi-rigid ducting or similar rigid ducting.

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