Replace a chimney cooker hood like-for-like on a metal stud wall

Isolate the power, work out your wall type, then fit a fixing strong enough for a heavy hood before reconnecting it.

RH-01Isolate the power and set up the jobSwitch the cooker hood off at its isolator switch, or at the consumer unit if there is no separate isolator. Prove the circuit is dead with a voltage tester before you touch any wiring. Clear the worktop below and lay a dust sheet to catch screws, dust and grease.

1 each · Voltage tester (non-contact or two-pole)

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1 each · Dust sheet

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RH-02Check for cables and pipes before you drillCables and pipes can run almost anywhere behind a kitchen wall, especially near an extractor or a socket for the hood. Run a detector over the area, but still treat every spot as live until you prove otherwise. Detectors miss deep cables, cables in metal conduit, and anything behind metal-backed board, and a metal stud frame will confuse a cheap detector further. Find your stopcock now (usually under the kitchen sink) and check it turns freely. If you have any doubt, isolate the relevant circuit at the consumer unit before drilling, and know how to shut the water off before cutting into anything that could carry water.

1 each · Cable and pipe detector

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1 each · Small magnet (for stud/screw checks)

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RH-03Work out what's behind the old hoodSolid brick or block feels hard and dense when you tap it, with no hollow sound. Dot-and-dab plasterboard sounds hollow but has a firm, uneven backing when you press it, with solid patches every 300-600mm where the adhesive dabs are. A timber stud wall sounds hollow, and a detector or magnet finds screw heads in a regular vertical line roughly 400-600mm apart; a small pilot hole brings out pale timber dust. A metal stud wall also sounds hollow, but a magnet sticks to the frame edges and a pilot hole brings out fine grey steel swarf instead of dust. Lath and plaster feels slightly springy and uneven, with narrow timber laths spaced a few centimetres apart under the plaster.

RH-04Disconnect and remove the old hoodUndo the ducting clip or tape at the back of the hood and slide the ducting free. Remove the grease filter, then disconnect the wiring at the terminal block – the circuit should already be dead from Step RH-01. Unscrew the hood from its wall bracket and lift it clear with help, as hoods are awkward and heavier than they look.

1 each · Pozidriver screwdriver

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RH-05Remove the old bracket and inspect the fixingsTake the old bracket off and look closely at what it was screwed into. If it was screwed straight into plasterboard or a bare metal stud with ordinary wood screws, that explains any wobble or past failure – plain screws strip straight through 0.5mm steel and pull out of plasterboard under vibration. Note the wall type from Step RH-03 so you fit the right replacement in the next step.

RH-06Fit the right fixing for your wall typeA cooker hood is heavy, vibrates when running, and gets pulled on when you remove the filter, so it needs a proper fixing whatever the wall. Solid brick or block: drill 10mm holes 60mm deep, fit red or brown masonry plugs, and use two coach screws or heavy-duty frame fixings at least 60mm long. Timber stud wall: drive wood screws at least 60mm long into the centre of the studs, not just the plasterboard, using pilot holes first. Metal stud wall: standard screws and plastic wall plugs will not hold a hood's weight – use self-drilling metal-stud anchors rated for the load, but a metal stud alone often is not enough for this weight with vibration, so fit a timber noggin or pattress between the studs first, or run longer fixings through to the masonry behind if there is any. Dot-and-dab plasterboard: use fixings long enough to pass through the dab and grip the masonry behind, typically 75-100mm, not just plugs in the plasterboard skin. Lath and plaster: locate a solid lath with a pilot hole and screw into it, or, if the wall is hollow-sounding throughout, fix through to the masonry or joists behind rather than relying on the laths alone.

4 each · Masonry plugs and coach screws (brick/block)

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4 each · Wood screws 60mm (timber stud)

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4 each · Self-drilling metal stud anchors

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1 each · Timber noggin 400mm length

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4 each · Long fixings for dot-and-dab (75-100mm)

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1 each · Drill with masonry and wood/metal bits

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RH-07Mount the new hood and check it is levelLift the new hood onto the bracket with help and secure it with the fixings from Step RH-06. Check it is level and square to the units above with a spirit level before fully tightening. Give the hood a firm downward tug to check it holds without any movement in the wall.

1 each · Spirit level

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RH-08Reconnect the ductingSlide the ducting back onto the hood outlet and secure it with a clip or foil tape, making sure the joint is airtight. Check the run to outside is not kinked, crushed or blocked, as this cuts extraction badly. Support any loose ducting so it does not sag onto the hood.

1 roll · Foil ducting tape

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RH-09Reconnect the electrics and testReconnect the wiring exactly as it came off, matching earth, neutral and live to the new hood's terminal block per its instructions. Switch the circuit back on at the isolator or consumer unit and test the lights and all fan speeds. If anything trips or feels wrong, switch off immediately and check the connections again.

RULES

KNOW THE RULES

Kitchens are a special location under Part P of the Building Regulations. Reconnecting a like-for-like hood on the existing circuit is not usually notifiable, but if you need to add a new circuit or fused spur, that work must be done or checked by a registered electrician.

RH-10Tidy up and check extractionRefit the grease filter and wipe down the hood and surrounding units. Run the hood on full speed and check you can feel air moving at the outside vent. Dispose of the old hood and packaging, and put any spare fixings aside for future use.

1 each · Degreasing kitchen cleaner

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