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Floor insulation

By Ellie Simmonds

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Draught proof and insulate your floor to cut your energy bills. We’ll help you pick the best floor insulation for your floor and find a good installer.

Floor insulation can help you keep your home warm, cut back on draughts and cut your energy bills.

Floors at ground level can feel pretty cold and should be insulated if possible. The floors of upstairs rooms do not usually need to be insulated if the room or space underneath is heated. But if your room is above an unheated space, such as a garage, you could benefit from floor insulation.

Want to go even further to make your toes toasty? Get an underfloor heating system.

How much does floor insulation cost? 

We've worked with the Royal Institution of Chartered Surveyors*, which publishes average building work and repair costs, to bring you the average cost for floor insulation. 

We've also split these so you can look at the average costs for a terraced, semi-detached and detached house. Do bear in mind that costs will vary, depending on where you live in the country. 

Only logged-in Which? members can view our recommendations in the table below. If you're not yet a member, you can get instant access by joining Which?.

House type Price from Price to
Terraced Subscriber only content Subscriber only content
Semi-detached Subscriber only content Subscriber only content
Detached Subscriber only content Subscriber only content
Table notes: This includes, floor insulation to existing suspended ground floor, 150mm thick rockwool insulation slab, re-fitting the floor boards using existing boarding, making good on completion.

Floor insulation savings

If you have already installed loft insulation and wall insulation and are keen to save even more on your heating bills, then the next insulation job is your floor. As much as 15% of the heat in a room can be lost through uninsulated ground floors. 

Properly insulating your floor will not only warm your feet, it will also help you to save money. Insulating your floor and skirting boards can save as much as £65 a year and, if you can install it yourself, pay for itself in around two years through savings on your heating bills.

Your insulation options depend on the type of floor you’ve got: 

  • suspended floors (typically with floorboards) 
  • solid floors, such as concrete 
  • tiled floors

Costs vary depending on how big your house is, how easy your floorboards are to lift and put back into place, and, whether you can access the space beneath a suspended floor.

Floorboard insulation (suspended floors)

Suspended floors are where the floorboards rest over joists. They are likely to lose more heat as they are, in effect, suspended above a void.

The easiest and least disruptive way to insulate floorboards is from underneath, if you have access via a cellar or basement. Here you are insulating the crawlspace (void) below the floorboards. When insulating from below, the insulation is secured with netting draped between and stapled to the floor joists.

If the floor is not accessible from underneath, you will need to deal with it from the top. This is more disruptive as it involves lifting the floorboards in order to fit insulation between the joists – a job that requires clearing out furniture and is therefore best combined with other messy tasks, such as decorating. 

Insulating from the top is more disruptive, as you need to lift floorboards.

You’ll need to lift the floorboards so that the insulating material, such as mineral-wool rolls, can be laid between the joists. Insulation can be made of various materials, including sheep’s wool, hemp and recycled plastic bottles, or rigid insulation boards. 

Insulating floorboards can be done as a DIY job or using a professional installer. If you want to do it yourself, materials can normally be purchased from larger DIY stores.

Floorboards will rot without adequate ventilation, though, so don’t block underfloor airbricks in your outside walls.

Solid-floor insulation

Solid floors, such as concrete or screed, should, in principle, lose less heat than suspended floors. But they can still be insulated by laying a new layer of rigid insulation on top. This would usually be covered by chipboard plus your desired floor covering. The insulation can be placed directly above the existing concrete or screed in the form of a ‘floating’ floor.

This method will raise the floor level, so skirting boards and, potentially, some electrical sockets will need to be refitted and doors will need to be trimmed.

It's advisable to lay a damp-proof membrane beneath the insulation.

Laying a continuous damp-proof membrane beneath the insulation is advisable, taking care to overlap with any damp-proof course in the external walls. Damp-proof membranes can come flat or in rolls that look a bit like a big bin liner roll. They can be purchased from larger DIY stores.

It is possible to insulate a solid floor yourself, though it’s a bit trickier than dealing with suspended floors and you might require an electrician if you need to move electrical sockets. If you want the help of a professional, you can use Which? Trusted Trader to find a trustworthy, local electrician.

Skirting board insulation

Heat can also escape from the gap between your floor and your skirting boards. Filling that gap with a tube of sealant is a cheap, quick and easy solution. Sealant is available from DIY shops and costs just a few pounds.

Insulating tiled floors

Tiled floors can be extremely cold, as the material conducts heat very well. There is little you can do to improve the energy efficiency of a tiled floor, as they are so rigid and are usually laid on a concrete base.

As with wooden floors, tiled floors can benefit from checking for leaks. The skirting boards should be checked, as should the grouting between the tiles.

Insulating with rugs and carpets

Rugs on the floor will also help your feet to feel warmer and block off draughts, but they won’t solve all the problems. 

Carpeted floors are usually the warmest floor type. The nature of carpet makes it a good insulator in itself. However, a thick, insulating layer of underlay underneath the carpet will further improve its insulating qualities.

Finding an installer

You can find a trustworthy, local installer using Which? Trusted Traders

If you fit floor installation yourself, make sure you comply with building regulations for the minimum energy-efficiency values. You can use the website Planning Portal to check building regulations for where you live.

RICS cost calculations

*To arrive at the average prices above, RICS uses cost data from its Building Cost Information Service (BCIS) database, where costs are collated from a variety of sources and analysed. 

Material costs are based on the best trade prices from a range of suppliers across the UK, which are then benchmarked to reveal the best national average. Labour rates are based on the current Building and Allied Trades Joint Industrial Council wage agreement. Prices correct September 2019.

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