Replace a chimney cooker hood like-for-like on a solid brick or block wall

Swap a like-for-like chimney cooker hood safely, from isolating power to reconnecting ducting and testing extraction.

CH-01Prepare and check compatibilityNote the make, model and duct size of the old hood (usually 100mm or 150mm round, or a flat rectangular duct) so the new one lines up. Lay a dust sheet under the hood to catch screws and debris. Get your tools together: cordless drill, masonry bit, spirit level, screwdriver and a voltage tester. Check the new hood's fitting kit against the wall before you start - some brackets sit slightly differently to the old one.

1 each · Dust sheet

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CH-02Isolate the electricsTurn off the circuit that feeds the hood at the consumer unit - this could be a dedicated fused spur near the hood or a kitchen sockets circuit if it plugs in. Prove it's dead with your voltage tester before touching any wiring. If you're not sure which circuit it's on, turn off the whole consumer unit while you work. Never rely on the local on/off switch alone.

CH-03Remove the old hoodSupport the hood's weight before undoing the last fixing screws - it can be heavier than it looks, so get a second pair of hands if you can. Disconnect the flexible ducting from the hood's outlet, then open the terminal cover and disconnect the wiring, making a note of which wire went where. Cap the loose wire ends with a terminal block for safety. Lower the hood clear of the wall and set it aside.

1 each · Terminal connector block

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CH-04Check the ducting and outside ventLook at the existing ducting run from the wall through to outside. If it's a short, sound rigid or semi-rigid duct, it can usually be reused. If it's perished, crushed or full of grease, replace it. Check the external grille or vent cowl isn't blocked with debris or a bird's nest, and clean it out if it is.

1 1m length · Flexible aluminium ducting, 100mm or 150mm

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CH-05Mark up the new fixing heightCheck the new hood's manual for its minimum height above the hob - this matters most over a gas hob because of fire risk, and the figure can differ from the old hood. Typical figures are around 650mm above a gas hob and 550-600mm above an electric hob, but always use the number printed in your hood's manual. Use a spirit level to mark a level line, then mark the bracket hole positions from the fitting template.

1 each · Pencil and masking tape

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CH-06Drill and fix the bracket into the brick or blockCables and pipes can run almost anywhere, even up a chimney breast. Run a detector over the marked spots, but still treat every hole as a risk - detectors miss cables that are deep, in metal conduit, or outside the usual safe zones. Find your stopcock (usually under the kitchen sink) and check it turns before you start, so you can shut the water off fast if you hit a pipe; if there's any real doubt, isolate the relevant circuit at the consumer unit and turn off the stopcock before drilling. Drill an 8mm hole to match your plug and screw size (for example a 50mm screw needs roughly a 55mm-deep hole), insert the wall plugs, then drive the screws through the bracket until snug but not fully tight.

1 each · Masonry drill bit, 8mm

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4 each · Red wall plugs, 8mm

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4 each · Screws, 5 x 50mm

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CH-07Hang the new hood and check it's levelLift the hood onto the fixings, check it sits level with your spirit level, then tighten all the screws fully. Give the hood a firm tug to check it's secure before letting go. Don't fit the filters or connect anything else yet - it's easier to work with the front open.

CH-08Connect the ductingFit the ducting onto the hood's outlet spigot and secure it with a jubilee clip or foil tape - don't rely on tape alone on a long run. Route the duct with as few bends as possible, since sharp bends cut extraction performance. Support any long horizontal run so it doesn't sag and collect grease.

2 each · Jubilee clips

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1 roll · Aluminium foil tape

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CH-09Reconnect the electricsMatch the wires to your earlier notes and reconnect them at the terminal block inside the hood, using the same live, neutral and earth connections as before. This is a like-for-like swap using the existing circuit, so it isn't notifiable work under Part P of the Building Regulations. If you're adding a new circuit or moving the fused spur instead of reusing it, that work must follow Part P and either be notified to your local authority or carried out by a registered electrician.

RULES

KNOW THE RULES

Part P of the Building Regulations covers electrical work in dwellings. A straight like-for-like swap on the existing circuit isn't notifiable, but new circuits or moved connection points are.

CH-10Fit the filtersClip the metal grease filter mesh back into place under the hood. If it's a recirculating hood, fit a new carbon filter now rather than reusing an old one - carbon filters don't wash and lose their effect over time.

1 each · Carbon filter (if recirculating)

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CH-11Restore power and testTurn the circuit back on at the consumer unit. Switch the hood on at each fan speed and check the light works. Listen for any rattling or vibration from the ducting, which usually means a clip has slipped.

CH-12Check extraction and duct jointsWith the hood running on full speed, hold a piece of tissue near the outside vent to check air is actually moving. Check every duct joint by hand for air leaking out, and re-tape or re-clip any loose ones. Run it for a few minutes to make sure it settles down and stops rattling.

CH-13Tidy up and dispose of the old hoodSeal any gap around the duct where it passes through the wall with a bead of silicone sealant, inside and out, to stop draughts and grease staining the wall. Wipe down the new hood and worktop below, and clear away the dust sheet and offcuts. Take the old hood to a WEEE recycling point rather than the general bin - electrical appliances can't go in household waste.

1 tube · Silicone sealant

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