Extractor Fan Installation & Repair in North West London

Why does the bathroom still go mouldy when there is a fan?

Usually because the fan runs but moves very little air out of the room. Hold a single sheet of toilet tissue against the grille while the fan runs. A working fan holds it flat. If the tissue flutters or falls, the problem is almost always behind the grille, not the motor. The common causes, roughly in the order we find them:

• The duct ends in the loft, or has come off its outlet, so wet air condenses on the joists and rafters
• A long flexible duct has sagged into a dip where water collects and blocks the airflow
• The backdraught shutter, on the fan or at the outside grille, is stuck shut with dirt or paint
• The fan is too small for the room, often a basic 100mm unit that moves less on a long duct run
• No air can get in to replace what is extracted, because the door has no gap underneath
• The isolator is switched off, or the overrun timer is set to a few seconds
• A humidistat is set so high it never triggers in normal use

Extractor fan not working: what to check before you call

First check the isolator, a small switch usually outside the bathroom door or above it. Tenants and decorators often switch it off and forget. Then check the fused spur, if there is one, and whether the fan is wired to come on with the light. A fan that only starts after the light goes off is on a delayed timer, not broken. If the fan hums but the blades do not turn, or it rattles and squeals, the bearings are worn.

On a cheap axial fan, replacing the whole unit usually costs less than repairing it. If the fan spins but the tissue test fails, the fault is in the duct or the outside shutter. A new fan will not fix that, and we tell you so before fitting one. A fan with scorch marks, a melted grille or a burning smell should be isolated and left off until it has been looked at.

Timer, humidistat or continuous: which suits a rental?

In a let property, a continuous low-speed fan that boosts when the room is used is often the best choice, because it keeps working however the tenant behaves. These fans run quietly all the time and step up to a higher rate on the light switch or on humidity. There is nothing to switch off and no timer to turn down. A standard intermittent fan with an overrun timer is fine where the occupants use it. Approved Document F expects any automatic control, such as a humidistat, to have a manual override. It also says the installer should check that run-on timers are set to at least 15 minutes.

A humidistat suits a bathroom. A separate WC has an odour problem rather than a moisture one, and the guidance advises against relying on humidity control there. The continuous rates in the guidance differ from the intermittent ones: 8 litres per second at the high rate for a bathroom and 13 for a kitchen. The sum of all the continuous fans must still meet the whole-house rate for the number of bedrooms. We size these on the survey rather than guessing.

Bathroom zones, isolators and Part P

Where the fan goes in the bathroom decides how it must be wired. Inside the special location around a bath or shower, any addition or alteration to a circuit is notifiable building work under Part P. Approved Document P defines that space as running up to 2.25 metres from the floor, or the shower head if higher, and 0.6 metres out from the bath or tray edge, or 1.2 metres from the shower head where there is no tray. A fan directly over the bath or shower sits in zone 1. NICEIC's householder guidance says equipment in zones 1 and 2 must be rated at least IPX4, the splash-proof grade.

Over a shower, we often fit a low-voltage SELV fan. Its transformer sits outside the zones, usually in the loft or above the ceiling, so only extra-low voltage reaches the wet area. The isolator also goes outside the zones, where it can be reached safely for cleaning. Replacing an existing extractor fan on its existing cable does not need notifying to building control. That is paragraph 3.32 of Approved Document F. A new fan feed in the zones, or a new circuit, does. We tell you before we start which applies, and notifiable work is certified and notified to Building Control.

Getting the air outside: ducting that works

The duct matters as much as the fan. We use rigid round or flat-channel duct wherever it can go, because flexible hose stretched across a loft loses much of the fan's performance. The run is kept short, with as few bends as the building allows, and it falls slightly towards the outside so condensation drains away from the fan rather than back into it. Where the duct crosses a cold loft we insulate it, or the moisture condenses inside the pipe before it reaches the outlet. The 2026 edition of Approved Document F, which takes effect on 24 March 2027, asks for the air flow to be measured on a new fan in an existing home with more than 2 metres of duct or more than one 90 degree offset.

That is a useful test of any installer's quote now. The outlet is a wall grille, a soffit vent or a roof terminal, depending on the room. In a leasehold flat, check your lease before a new hole goes through an external wall. That wall is often the freeholder's, so their consent may be needed.

Kitchen extraction and recirculating cooker hoods

A recirculating cooker hood filters grease and smells but returns the moisture to the room. Approved Document F is explicit that a recirculating hood on its own is not a means of ventilation. Steam from a pan of pasta still ends up on the window and behind the units. The options are a cooker hood ducted outside, which the guidance accepts at 30 litres per second where it spans at least the full width of the cooker, or a wall or window fan rated at 60 litres per second.

In many rental kitchens, the practical fix is a properly sized wall fan on an overrun, wired so it runs whenever the kitchen light is on. Where a ducted hood can reach an outside wall, we can wire and duct it. Fitting the kitchen units themselves is not something we take on.

Positive input ventilation (PIV): when it helps

A PIV unit is a fan, usually in the loft, that pushes a gentle, constant supply of filtered air into the house. The slight positive pressure moves damp indoor air out through the gaps and vents the house already has. Wall-mounted versions exist for flats with no loft. It needs a permanent electrical supply, and we install it as a ventilation unit like any other fan. It tends to help in a house with condensation on windows and in bedrooms throughout, rather than one problem room.

It does not replace the extract fans in the bathroom and kitchen, where the moisture is made. It will not fix water coming in from outside, a leak or rising damp. If the mould sits in one corner or only on an outside wall, we look at the wet rooms and the cause before suggesting a unit for the whole house.

Condensation, mould and a landlord's legal duty

Damp and mould growth is one of the hazards councils assess under the Housing Health and Safety Rating System (HHSRS). Under the Housing Act 2004, a rented home must be free of Category 1 hazards. The Homes (Fitness for Human Habitation) Act 2018 adds that it must be free of damp and mould so serious that the home is not reasonably suitable to live in. Government guidance on damp and mould (updated 1 April 2026) says it is unreasonable to blame mould on tenants' lifestyle choices. It tells landlords to service, repair, replace or install ventilation where it is inadequate, and to re-inspect at least six weeks after the work.

Since 22 June 2026, councils can fine landlords up to £7,000 under the Renters' Rights Act where a serious (Category 1) hazard is found. Awaab's Law sets fixed repair deadlines for damp and mould. It has applied to social landlords since 27 October 2025. For private landlords, it is only a proposal: the government's consultation runs from 8 October to 18 December 2026, and no start date has been set. A working, correctly ducted fan in every wet room is the cheapest evidence that the ventilation side has been dealt with.

What affects the price of an extractor fan?

The duct route more than the fan. Swapping a fan on an existing outlet and cable is a short job. A new outlet through a solid wall needs core drilling. A new fan in an internal bathroom may need a duct run across the loft and out through a soffit or roof tile, and running it across a top-floor flat ceiling takes longer again. The type of fan also counts: a basic timer unit, a quiet continuous model and a SELV unit with a remote transformer are priced differently.

So is a PIV unit, which depends on loft access and where the supply can come from. Making good the ceiling or wall afterwards, and whether the job is notifiable, are the other variables. A photo of the room and the outside wall usually lets us give a fixed price without a visit.

Certificates and defined jobs are a fixed price confirmed before we attend; repairs are charged by the hour, with the rate and an estimate confirmed before we attend.

Extractor fans across North West London

We fit and repair fans across Harrow, Kenton, Stanmore and Edgware, and in Wembley, Kingsbury, Queensbury, Pinner, Wealdstone, Rayners Lane, Mill Hill, Burnt Oak and the nearby areas. Many of the interwar semis here have a bathroom on an outside wall, so a straight-through wall fan is simple. Later loft conversions and en-suites are another matter: they often have no window, and a duct must cross the loft.

Some purpose-built blocks have internal bathrooms vented through a shared riser, and that riser belongs to the block, not the flat. Demand peaks once the heating goes on in October, when windows stay shut and condensation shows up within weeks. Booking before then avoids the queue.

Electricians by area: Electrical work in Harrow, Electrical work in Kenton, Electrical work in Stanmore, Electrical work in Edgware, Electrical work in Bushey, Electrical work in Colindale, Electrical work in Hendon, Electrical work in Mill Hill, Electrical work in Northolt, Electrical work in Northwood, Electrical work in Pinner, Electrical work in Ruislip and Electrical work in Wembley.

What we will not do

We do not carry out damp investigations or surveys. If the walls are wet from a leak, rising damp or water coming in through the brickwork, a fan will not fix it. We will tell you if that is what we see, and refer you to a damp specialist or surveyor. We do not treat or remove mould growth beyond cleaning around our own work.

Our decorators can wash down and repaint once the cause is fixed. We do not alter shared ventilation risers in blocks of flats without the freeholder's agreement, and we do not do roofing beyond fitting a vent terminal.

Why people trust us

• Work by registered electricians, certified, and notified to Building Control where the job requires it
• A walk-in office on Kenton Lane, not a serviced address
• The fault found and the options explained before we go further
• A time slot rather than a morning-or-afternoon window
• Work photographed before and after, and reported
• We tell you when you do not need something we sell

We are building a review profile under this name and would rather show you none than borrow someone else's. Ask us for references from landlords and we will put you in touch.

Official sources

• GOV.UK: Approved Document F, Ventilation, Volume 1 dwellings (2021 edition, and 2026 edition taking effect 24 March 2027)
• GOV.UK: Approved Document P, Electrical safety (2013 edition)
• NICEIC: Bathrooms and electrics, householder guidance
• GOV.UK (OHID): Understanding and addressing the health risks of damp and mould in the home (updated 1 April 2026)
• GOV.UK: Awaab's Law, guidance for social landlords
• GOV.UK (MHCLG): Clampdown on dangerous homes to protect more tenants and families (8 October 2026)

Last reviewed October 2026 by EliteShires Property Services.