Replace a chimney cooker hood like-for-like on a lath and plaster wall

Turn off the power, remove the old cooker hood, then fit and wire the replacement securely on your kitchen wall.

CH-01Isolate the power and get set upSwitch off the cooker hood's circuit at the consumer unit, then prove it's dead at the isolator or connector block with a voltage tester. Lay dust sheets and clear the worktop below. If your hood plugs into a fused spur, switch that off too and remove the fuse if you can.

1 each · Voltage tester

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1 each · Dust sheet

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CH-02Remove the old hoodUnscrew the hood from its bracket and lower it clear. Pull the ducting free from the spigot and disconnect the wiring at the connector block, noting which wire went where. Unscrew the old bracket only if the new hood needs a different fixing pattern.

CH-03Check the new hood is a true like-for-like fitCompare the fixing hole centres, duct spigot size and cable entry point against the old unit. Buy a reducer or adapter now if the new duct size is different. Doing this before drilling saves you re-drilling later.

1 each · Duct reducer/adapter (if needed)

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CH-04Work out what's behind the lath and plasterMost chimney breasts are solid brick or block behind the laths, so a test hole feels hard and brings out brick dust. A stud partition wall feels hollow between the timber uprights and a detector picks up a line of screw or nail heads along the studs; a pilot hole here brings out timber dust. Metal studs and dot-and-dab almost never sit behind original lath and plaster, so treat a wide metal reading with suspicion and check with a small pilot hole before trusting it.

1 each · Cable and pipe detector

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CH-05Mark up and drill your fixing holesCables and pipes can run almost anywhere behind a wall, so scan first with your detector, then still assume something is there until you prove otherwise as you drill. Know where your stopcock is (usually under the kitchen sink) and check it turns, so you can shut the water off fast if you hit a pipe. If you have any doubt at all, isolate the circuit at the consumer unit before drilling.

1 each · Masonry drill bit (for brick/block)

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1 each · Wood drill bit (for timber stud)

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CH-06Fit the fixings for your wall typeOn a solid brick or block chimney breast, drill through the plaster and laths into the masonry, using a fixing long enough to bridge the air gap behind the laths — typically a 60mm to 70mm screw with an 8mm Rawlplug, so at least 40mm goes into solid masonry. On a timber stud partition, drive a wood screw into the centre of the stud, using a pilot hole first so the lath doesn't split. Never rely on the laths themselves to hold the weight; the fixing must reach solid timber or masonry behind them.

4 each · Rawlplugs 8mm x 60mm

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4 each · Masonry screws 60-70mm

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4 each · Wood screws 50mm

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CH-07Hang the bracket and check it's levelScrew the new bracket or mounting plate into your marked fixings and check it's level with a spirit level before fully tightening. Give it a firm tug to check it's solid before hanging the hood on it.

CH-08Hang the hood and connect the ductingLift the hood onto the bracket and secure it with the retaining screws supplied. Push the ducting onto the spigot and secure it with a jubilee clip or foil tape, sloping it slightly downward toward the outside wall so condensation drains out rather than back into the hood.

1 each · Jubilee clip

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1 each · Foil ducting tape

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CH-09Reconnect the electricsMatch the wires to the connector block exactly as they were on the old hood, then restore power at the consumer unit and switch on to test. A like-for-like swap using the existing isolator or fused spur is not notifiable work under Part P. If you add any new wiring, a new circuit, or a new fused connection unit, that counts as notifiable electrical work under Building Regulations and must be certified by a registered electrician or signed off by building control.

RULES

1 each · Connector block

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KNOW THE RULES

Part P of the Building Regulations covers electrical work in the home. Simple like-for-like replacement using existing wiring and an existing isolator is not notifiable, but new circuits or new fixed wiring are, and must be certified.

CH-10Test extraction and seal upRun the hood on full speed and check air is pulling through properly and the ducting isn't leaking or rattling. Seal any gap around the duct where it passes through the wall with mastic to stop draughts and grease build-up.

1 each · General purpose sealant/mastic

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CH-11Tidy upVacuum up any plaster or brick dust from the work area and wipe down the worktop and hob below. Dispose of the old hood at your local recycling centre, as it can't go in general household waste.

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