Cost of Insulating Flooring
A guide of the process of hiring a tradesman to insulate your floor, including the costs of labour and materials.
This article will detail the main ways in which you can insulate a floor in a house or office premises, to either make it more temperature controlled or to remove the possibility of noise. It will look that the pros and cons of each method and detail the amount of work and the costs involved.
Many older houses have a ventilation space under the ground floor to prevent damp rising up from the ground, but this also means that cold air is constantly blowing around the space beneath your feet. This means that you have a constant flow of cooled air blowing around under your living space and sending chilly draughts up between the boards and under your skirting boards.
The only way to effectively deal with this is to fit an insulating material in this space, effectively cutting off the flow of cold air.
Floor insulation costs
This depends upon the type of insulation used and your floor type. The cost will have two elements; the cost of the insulation material, which can vary considerably, and the cost required to actually install it. As a guide, most jobs end up costing between £85 and £110 per square metre.
What laying floor insulation entails
The fitting of insulation can be done either at the initial build of the property or as a retrofit later. If it is being done as part of the building sequence, then the whole task is considerably easier, and you have the option of installing a more cost-effective insulation. If your insulation is being retrofitted, then there are less options open to you and the whole process is likely to become more expensive since time must be taken gaining access to the floor before you can even do anything about upgrading the insulation. This will add significant time and cost to the project.
Insulating floors is often considerably more difficult than insulating other areas of your home. The ground floor beneath a house is usually warmer than the air above it, and so it would usually be lower on your list of insulation priorities than walls and roofs. However, it makes sense to consider retrofitting, particularly if you have a suspended timber floor, simply to prevent cold air from being able to circulate and come up through the floor.
Generally, the job will entail taking up the current floor, adding the insulating element, replacing the floor, and making good anything that is required. However, the job may become more complex if the flooring is solid and either has to be raised or some other remedial action needs to be taken. When fitting floor insulation, you need to be aware of the U value, which determines how much insulation you should have. Building Regulations/Standards set the U-value requirements. These depend on the location of the project. The U-value is the levels of thermal insulation required when carrying out building work, either for new builds or refurbishment projects. be it England, Scotland or Wales, the type of building and whether it is domestic or non-domestic, and the application, such as the floor, wall or roof. The U values are usually expressed in terms of W/m²·K.
Where is best to install floor insulation?
Insulation is best carried out on so called floating floras as there is a space beneath into which insulating elements can be fitted. You can retrofit floor insulation on top of a solid concrete base, but this will of course have an impact on floor height build-up as the layer of insulation is added. Furthermore, this will require major work, and it’s really only worth digging out the floor if you’re undertaking a major renovation within the property.
Other tasks to tackle
If you are raising floorboards, it is also a good time to inspect the joists and general condition of the floor before you apply the insulation. Any rot should be removed and replaced.
General advice when installing floor insulation
Most modern homes have a solid floor, typically constructed of:
- Concrete slab
- Concrete planks
- Block and beam
In this case, the insulation material needs to be laid on the substrate and covered with a screed to seal it in. There will need to be a damp-proof membrane under the insulation and possibly a second membrane on top, depending on the type of screed used. In this case, a rigid foam insulation is usual, and it is possible to get away with only a thin layer (>25mm) to notice a large increase in warmth. Once the insulation is in place, the top flooring can be re-laid, understanding that it will now be at least 25mm higher.
Here is a list of commonly asked questions in regards to having floor insulation installed.
Q What is the minimum depth liquid screed can be applied over insulation?
Liquid screed can be applied over insulation as either thermal or acoustic at a depth of 40mm in domestic applications and 40mm in commercial applications. If used in combination with underfloor heating the minimum cover required over the pipe is 30mm, as outlined in BSEN 13813:2002
Q Will spray foam insulation rot my floor timbers?
No. Generally, open celled foam is breathable, when applied to any surface it allows any moisture present to dry out through evaporation, this is important as timber and masonry surfaces need to breathe to ensure that no damp or rot problems are caused. However, if your timbers are already damp or have some form of rot or woodworm they should be treated and dried first.
Q How long does it take to install spray foam?
Foam expands around 100 times in 4 -12 seconds after being applied. With proper ventilation, you can use the room 24 hours or less after installing. The majority of homeowners installs can be completed within a day.
Q How do I cut insulation boards to size?
They can be cut with a sharp knife or a fine-toothed saw. As a responsible company, we recommend that users take a sensible approach to the cutting of boards with strict regard for health, safety and environmental standards. Eye protection should be worn when cutting boards. Cutting with power tools generates dust so should be kept to a minimum. Operations which produce dust should be carried out in well ventilated conditions and where possible an appropriate dust mask should be worn.