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What is a suspended floor?

A suspended floor is a ground floor held up off the soil on joists or beams, with an open, ventilated space underneath, rather than laid straight onto concrete. Many are timber boards on wooden joists, kept dry by airbricks in the outside walls.

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How is a suspended floor built?

A suspended floor is held up rather than laid on the ground. In many older houses that means timber joists spanning between walls, with floorboards or sheets of chipboard nailed on top. Under the joists there is a void, a gap of open space over the soil or a thin layer of concrete.

Some newer homes have suspended floors made of concrete beams with blocks between them, instead of timber. They work on the same idea of keeping the living space up off the ground, but they are built and repaired differently.

This page is mostly about suspended timber floors, because those are the ones people most often ask about when a board bounces, squeaks or smells musty.

QuoteZila starts in Cheshire, with Crewe, Nantwich and Sandbach first, and anyone in the UK can post a job.

Why do airbricks matter so much?

The void under a timber floor needs air moving through it. Airbricks, the small perforated bricks low down in the outside walls, let that air in and out. Without them, damp from the ground builds up under the floor and the timber suffers.

The Planning Portal puts it plainly: don't block under-floor airbricks in your outside walls, because floorboards will rot without adequate ventilation [S1].

Check yours from time to time. Look for airbricks covered by a raised flowerbed, a new path, a patio laid too high, a pile of logs or a sheet of plastic. If the ground outside has risen up to an airbrick, or an extension now covers one, ask a builder how air will get to that part of the void.

What are the signs of a problem?

  • Bounce or dip. A floor that sags when you walk across it can mean loose boards, a weak joist, or a joist end that has rotted where it sits in the wall.
  • Squeaks. Usually boards rubbing on nails or on each other. Annoying, rarely serious on its own.
  • Musty smell or damp patches. A sign the void is not drying out. Blocked airbricks, a leaking pipe under the floor or high ground outside are common causes to check.
  • Soft or crumbly wood. Rot or insect damage. Our woodworm treatment guide covers what a specialist will look at.
  • Gaps and draughts. Gaps between boards, and between the floor and the skirting, let cold air up from the void.

Joists hold the floor up, so a sagging floor or a rotten joist is structural work. Do not cut, notch or remove joists yourself. Ask a builder or joiner to look, and ask whether building control needs to be involved. GOV.UK: find your local council for building control. QuoteZila is not affiliated with this organisation. GOV.UK explains when building regulations approval is needed.

Can a suspended floor be insulated?

Yes. The Planning Portal says timber floors can be insulated by lifting the floorboards and laying mineral wool insulation supported by netting between the joists [S1]. The same page says gaps between floorboards and skirting boards can be filled with a tube sealant to stop draughts [S1].

The rules matter if the job gets bigger. The Planning Portal says renovating more than 25 per cent of a solid or suspended floor, involving the replacement of a timber floor deck, would have to meet the standards required by the building regulations Approved Documents [S2]. If you are lifting a large part of the floor anyway, ask the builder what that means for your job.

Whoever insulates the floor must keep the void ventilated. Insulation should sit between and under the boards, not stuffed against the airbricks.

Who should you call?

  • Bouncing, sagging or rotten joists: joiners, carpenters or builders, depending on how much needs replacing.
  • Musty smells and damp under the floor: our damp proofing page covers specialists who look at ventilation and moisture.
  • Squeaky or loose boards only: floorboard repair costs explains what changes that smaller job.

The Planning Portal says planning permission is not generally needed to replace a floor, but that people in listed buildings should contact their local planning authority [S3]. Citizens Advice suggests getting written quotes from at least 3 different traders before you decide on one [S4].

Jobs you might post

These are examples, not taken from real job posts.

  • "Lounge floor bounces near the bay window. Suspended timber floor. Please inspect and quote for any joist or board repairs."
  • "Musty smell in the back room and one airbrick is behind a raised flowerbed. Please look at the ventilation under the floor."
  • "We want to insulate under the floorboards in two downstairs rooms. Please quote, including lifting and relaying the boards."

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Honest status: QuoteZila is new. We're starting in Cheshire, beginning with Crewe, Nantwich and Sandbach, and growing area by area. Anyone in the UK can still post a job or register a business. How fast you get quotes depends on how many local businesses have joined near you. Businesses can register and receive jobs straight away. We don't check insurance, qualifications or registrations, so please check these yourself before you hire.

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Questions about suspended floors

How can I tell if my ground floor is suspended?

Look for airbricks low down on the outside walls, just above ground level. Indoors, a floor that sounds hollow and is made of boards nailed to joists is usually suspended. Lifting a single board, or looking through a hatch, shows the space underneath. A fitter or joiner can confirm it in a few minutes.

Can I block the airbricks to stop draughts?

No. The Planning Portal warns not to block under-floor airbricks in your outside walls, because floorboards will rot without adequate ventilation. Stop draughts at the gaps between boards and skirting instead, and keep the airbricks clear outside.

Can laminate or engineered wood go on a suspended floor?

Often, yes, once loose boards are fixed and the floor is firm. Ask the fitter which underlay suits a timber floor, and make sure nothing they lay seals off the ventilation the void depends on.

Do I need permission to replace a suspended floor?

The Planning Portal says planning permission is not generally required to replace a floor, but if you live in a listed building you should contact your local planning authority. Building regulations can apply when a large part of the floor is renewed, so ask the builder whether that applies to your job.

Does QuoteZila check builders and joiners?

No. We don't check insurance, qualifications or registrations, so please check these yourself before you hire. You can report a quote or a business from your job page.

This page is general information, not professional or legal advice. QuoteZila does not check Gas Safe, WaterSafe, NFRC, NICEIC or other registrations against the register on your behalf: look them up yourself.

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Sources

  1. QZ1: QuoteZila product fact. QuoteZila home and FAQ copy.
  2. QZ2: QuoteZila product fact. QuoteZila FAQ How does getting quotes work.
  3. S1: Floor insulation (energy saving), Planning Portal. Accessed 2026-11-01. https://www.planningportal.co.uk/permission/common-projects/energy-saving/floor-insulation/
  4. S2: Building Regulations: floor insulation, Planning Portal. Accessed 2026-11-01. https://www.planningportal.co.uk/permission/common-projects/insulation/building-regulations-floor-insulation
  5. S3: Ceilings and floors: planning permission, Planning Portal. Accessed 2026-11-01. https://www.planningportal.co.uk/permission/common-projects/ceilings-and-floors/planning-permission/
  6. S4: Before you get building work done, Citizens Advice. Accessed 2026-11-01. https://www.citizensadvice.org.uk/consumer/getting-home-improvements-done/before-you-get-building-work-done/