Floor insulation

Gaps and draughts around skirting boards and floors are simple to fix yourself with a tube of sealant bought from any DIY store. Floorboards will rot without adequate ventilation, though, so don't block under-floor airbricks in your outside walls.

Older homes are more likely to have suspended timber floors. Timber floors can be insulated by lifting the floorboards and laying mineral wool insulation supported by netting between the joists.

Many homes – especially newer homes - will have a ground floor made of solid concrete. This can be insulated If it needs to be replaced, or can have rigid insulation laid on top.

You don't need to insulate the floors of upstairs rooms in your house if they're above heated spaces (like the living room). But you should think about insulating any floors that are above unheated spaces such as garages, as you could be losing a lot of heat through those.

How much could you save?

Insulating and draught-proofing your floor can be a cost-effective energy saving measure, especially if you are able to do some or all of the work yourself:

Insulating a concrete floor will save around the same as insulating a timber floor, but the cost will vary enormously depending on circumstances.

How to install floor insulation

Not all home insulation work has to be carried out by a professional: it may work out cheaper to do the smaller jobs yourself with materials from your local DIY store. Filling the gaps between the skirting boards and the floor boards costs about £20 if you do it yourself. Insulating underneath the floorboards on the ground floor will cost about £100 in materials if you want to do it yourself, and if your floorboards are easy to lift and in good condition. Remember to seal any gaps between and around the floorboards when you put them back.

It's even easier to insulate your timber floor if you have an unheated cellar or basement space underneath that you can get into. Check that the joists supporting the floorboards are in good condition and don't show any signs of wet or dry rot. If the joists are okay, you can fit insulation in between them and hold it in place with netting if needed. The basement's 'ceiling' should then have plasterboard fixed directly to the undersides of the joists, to provide fire resistance - and you can then fit more rigid insulation underneath that 'ceiling' to benefit from even more insulation. 

Rugs and carpets on the floor will also help your feet feel warmer - which might mean you don't feel the need to put the heating on as much. 

Professional floor insulation

For some jobs, you might need to get some professional help. If you don't feel confident lifting your floorboards yourself you can get a professional in to do this, fit the insulation and replace them afterwards. Costs will vary depending on how big your house is and how easy the floorboards are to lift and to replace, but as a rough guide costs might start at around £770 for a semi-detached house.

For solid concrete floors, make sure that if they ever need to be replaced, your builder puts in insulation - in fact, you have to insulate a floor when it is replaced in order to comply with Building Regulations. Solid floors are insulated using rigid insulation foam, which can be fitted either above or below the concrete. If the concrete is above the insulation it can sometimes store heat during the day which helps keep the room warm at night. On the other hand, if the insulation is above the concrete, the room will heat up more quickly in the morning.

If your concrete floor doesn't need to be replaced, it can still be insulated. Rigid insulation can be laid on top of the original concrete floor, then chipboard flooring put on top of that. This will raise the level of the floor, so you will need to make sure doors are trimmed shorter to make room for the insulation, and skirting boards and some electrical sockets might need to be moved.

Finding an installer

If you are looking for someone to come in and insulate your floor, then we would recommend that you look for an installer who is a member of the National Insulation Association.  (Visit the National Insulation Association website). 

If you are looking to insulate your floor as part of a bigger refurbishment job, then you will probably want to use your existing builder. If they are unfamiliar with floor insulation,  they can access advice on how to do this in our section for building industry professionals.

Complying with building regulations

If you are adding extra insulation to your floors, the work will need to comply with the relevant Building Regulations for where you live. Your installer will normally arrange this for you but if you are doing it yourself, it is your responsibility to comply.

If you live in England or Wales, the floor should achieve a U-value of 0.25 W/m2K or less, if possible. The U-value is a measure of how quickly heat will travel through the floor. To achieve this standard you will normally need at least 70mm of high-performance foam insulation, or 150mm of mineral wool, but this will vary depending on floor type, shape and size.

If you are replacing at least half of a floor then you have to insulate to these standards whether you planned to or not.

For further information, and for regulations in Northern Ireland and Scotland, we recommend that you contact your local Building Control Office before starting work. 

How do I tell what kind of floor I have?

If you have a basement or cellar beneath your house that you can get into safely, go and take a look. If the floor is a suspended wooden floor, you will probably be able to see wooden joists and the undersides of the floorboards. Also, if you have air bricks or ventilation bricks on the outside wall(s) of your house that are below floor level, you probably have a suspended timber floor. (If you do have these airbricks in your walls, don't block them up. They are needed to help ventilate the space under your floor and stop your floorboards from rotting.)

If you don't have access to the space underneath your house, you will need to lift a corner of the carpet and underlay and have a look. If you live in a flat (apart from the ground floor) then you will also need to lift the carpet to see what kind of floor you have. However, you don't need to insulate your floor if there is another flat beneath you.