Floor Insulation Guide

Are you looking for information about floor insulation? Well, you've come to the right place.

In this guide, we will go over everything you need to know about floor insulation, including the different types of floor insulation, the pros and cons of installing it, the price of installing floor insulation, and the questions to ask when looking for a floor insulation specialist.

What Is Floor Insulation?

Insulating a floor involves installing a type of insulating material beneath the floorboards. This then reduces the amount of heat that is lost through the floor. In a typical uninsulated home it's thought that around 10 to 20% of heat is lost through the floor. Insulation also helps to prevent draughts from coming through the floorboards.

Installing floor insulation can help to reduce your energy bills as you won't need to spend as much to heat your property to make up for the lost heat through the floor. Insulation is most commonly installed at the same time as installing a new floor. However, it is possible to install new insulation to existing floors.

Types of Floor Insulation

There are several different types of floor insulation. Below is a list of the different types and the pros and cons of each type:

Insulation Boards

Expanded polystyrene sheets (EPS sheets) are a popular choice for floor insulation, and while you generally need a greater thickness than PIR, they are a lightweight option that's easy to fit.

Insulation boards must be laid on an even base, and they are pressure-resistant. This means that the floor is less likely to crack or collapse.

Pros

• ✔ Easy to install.
• ✔ Pressure-resistant.

Cons

• ✖ Must be installed to even ground.
• ✖ Thicker board required to achieve same benefit as PIR.

Polyurethane Spray

Polyurethane spray has one of the best lambda values of all of the different floor insulation types. It has a very good seal, and it easily fills gaps and irregularities.

Unfortunately, it's not possible to install this type of insulation yourself. With this in mind, this type of insulation tends to be more expensive than others.

The main advantages of this type of insulation are the very fast installation times and the choice of different floor insulation thicknesses.

Pros

• ✔ One of the best lambda values of all floor insulation types.
• ✔ Fast installation.
• ✔ Choice of floor insulation thickness.

Cons

• ✖ It can't be done as a DIY job.
• ✖ Expensive compared to other floor insulation types.

Insulating Screed

Insulation screed or insulation concrete is made up of a combination of cement and insulating materials. This insulation material usually consists of polystyrene granules that have a diameter of around 3 to 6mm.

The insulating screed must always be installed with some other form of insulation to get a good insulation value.

Pros

• ✔ Easy to install.
• ✔ Choice of floor insulation thickness.

Cons

• ✖ It needs to be installed with another insulator for good insulation value.

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What Are the Pros and Cons of Floor Insulation?

There are several pros and cons to installing floor insulation at your home. The list below highlights the main advantages and disadvantages of floor insulation.

Pros

Save on Energy Bills

When you get floor insulation installed, you can prevent some heat from leaving the room through the gaps in the floorboards.

This means that your room will stay warm for longer, and you won't need to keep your heating on for as long or as high to maintain your desired room temperature. This means that you can save money on your energy bills.

Keep the Home Warmer

Since less heat is lost, you can keep your home much warmer by installing floor insulation. Floor insulation stops heat from leaving the room and keeps more heat inside the room, similar to how ceiling and wall insulation works.

Cons

Costs

As with any addition to the home, installing floor insulation does come with some upfront costs. You will need to pay to have insulation installed under your floors.

However, you will save money on your energy bills and over time, this will make your initial investment worth it.

Disruptions During Installation

Most people will get their floor insulation installed at the same time as a new floor for the least amount of disruption.

However, if you are looking to add insulation to an existing floor, this may be disruptive as you'll have to pull up the flooring before the installation and then re-install your floor once the insulation has been put in.

How Much Does It Cost to Install Floor Insulation?

The cost of insulating a floor will depend a lot on the type of insulation that you use.

The costs may vary depending on the type of floor insulation, the size of the room, and the type of floor you have. The cost for this type of home improvement is quite reasonable compared to some other home improvement jobs.

Floor insulation requires an upfront investment. However, it will usually pay for itself within a few years.

How to Insulate a Floor

Installing floor insulation can sometimes be done as a DIY job, especially where you have good access and the work is straightforward. However, many people prefer to hire professionals, as the insulation must still meet building regulations and be installed safely around ventilation, wiring, and pipes.

You can request multiple quotes from local floor insulators using MyJobQuote. It's fast, free, and there's no obligation to go ahead.

Installing with New Flooring

If your insulation is being installed at the same time as your floor, this makes the job considerably easier. If you have your insulation installed when your home is built, you may have the option to get cheaper insulation installed.

Insulating Existing Flooring

If you are installing insulation after your flooring has already been built and installed, then there will be fewer options available, and the whole process is likely to be more expensive and take much longer to complete.

This is because the floor will need to be taken up before you can install the insulation, and then the flooring will need to be replaced and finished. The job may become more difficult if the floor is solid and needs to be raised or if any other work is necessary.

How to Lay Floor Insulation

Below is the typical installation process for installing different types of floor insulation:

Insulation Boards

• Determine U-Value Requirements — When fitting flooring insulation, the U-value needs to be taken into account. This determines how much insulation should be installed.
• Prepare the Floors — The floors will need to be prepared as needed. The type of preparation needed will usually depend on the material of the floor. All flooring should be pulled up, and any dust and debris should be cleared away before you start the installation.
• Install a Damp-Proof Membrane — Before installing the insulation a damp-proof membrane (DPM) needs to be laid on the floor so it connects with the DPM in the walls, with all joints lapped and taped.
• Lay in Staggered Design — Lay your insulation boards on the DPM so they are tightly butted together and in a staggered design to strengthen the integrity of the floor.
• Seal the Joints — Use waterproof tape to seal the joints between each of the boards.
• Alternative Insulation Methods — If you are using a different insulation method, complete this installation according to the manufacturer's instructions.
• Lay the Upper Layer — Before screeding, lay a polythene sheet over the boards to protect them, making sure all joints overlap by at least 150mm and are taped. You can now screed on top of the boards, with a minimum depth of 65mm for sand and cement screed, and any other screed as per the manufacturer's instructions.

Suspended Floors

• Remove Floor Covering — Lift the floorboards and remove any existing floor covering. Inspect the floor joists for signs of damp, rot, or damage.
• Ensure Proper Underfloor Ventilation — Make sure there is adequate underfloor ventilation and the air bricks aren't blocked by the insulation, so you reduce the risk of moisture problems that could rot floor timbers.
• Fit Breathable Membrane — Fit a breathable membrane over the joists to create pockets where the insulation will sit. Secure this in place using battens fixed to the floor joist sides.
• Fit the Insulation — Install glass mineral wool, sheep wool, or loose fill insulation between the floor joists. Note that the membrane is typically not required when using Celotex or polystyrene insulation.
• Replace the Floorboards — Lay a vapour-permeable membrane over the insulation before the floorboards are replaced.

Concrete Floors

• Remove Floor Covering — Remove the current floor covering. While insulation can be added on top of an existing concrete floor, replacing the floor provides an ideal opportunity to install insulation beneath it.
• Lay Damp-Proof Membrane — Place a damp-proof membrane over the concrete surface.
• Lay Rigid Insulation Boards — Position rigid insulation boards (such as Celotex) on top of the damp-proof membrane.
• Place Timber Sheet Material — Lay chipboard flooring or comparable timber sheet material over the insulation boards.
• Re-Lay Floor Covering — Replace the floor covering. Be aware that adding insulation to an existing floor raises its level, which may require adjustments to doors, skirting boards, stairs, and electrical outlets.

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How Long Does It Take to Insulate a Floor?

The time it takes to insulate your floor will depend on several factors, including the room's size, the type of insulation that is being installed, the type of flooring in the room, and the number of contractors working on the job.

On average, it will take around 2 to 5 days to add floor insulation to an average-sized room. This includes removing the existing floor, installing the insulation, sealing everything, and re-installing the top flooring.

The fastest insulation method is the installation of insulating boards. These boards are the easiest type of insulation to install and, therefore, can be completed in the fastest time. When installing this type of insulation, you may be able to complete the work within a day if the room is small.

Building Regulations & Planning Permission for Floor Insulation

If you are the homeowner, it is your responsibility to ensure that all building work complies with building regulations. This applies when installing floor insulation. You won't usually need to worry about planning permission for this type of work.

You must also take steps to minimise any risks of fire, and where a floor is replaced or more than 50% is renovated, take all practicable steps to achieve the minimum U-value with your insulation to meet building regulations. In England, this is 0.25 W/m²K or lower for a renovated floor and 0.18 W/m²K or lower for a replacement floor. In Wales and Northern Ireland it's 0.25 W/m²K, and in Scotland it's 0.18 W/m²K.

Replacing a floor or renovating more than 50% of one requires approval from building control. With no relevant competent person scheme your installer cannot self-certify, so you are legally responsible for compliance and certification by the council's building control or a registered building control approver. You should check with them if you are unsure.

Floor Insulation Repairs

Below is a list of common underfloor insulation repairs and how to carry out the work:

Moisture Repairs

Insulation can affect the air and moisture beneath your floor, and issues like blocked air bricks, gaps in the insulation, or vapour barriers used instead of breathable membranes can all lead to trapped moisture.

This can lead to rotting. In this case, you will need to replace the rotting timbers as these can be dangerous and may lead to mould, which is bad for your health.

Once you've changed them, make sure the underlying moisture problem is addressed and the underfloor space is properly ventilated and air bricks are kept clear. If you have damp or rotten joists you might want to seek professional advice before insulating the floor again.

Uneven Insulation

In some cases, if the insulation hasn't been installed correctly, you could end up with bumps or dips in the flooring where the insulation has moved or compressed. If this is the case, you may need to lift the affected areas of flooring and add or move insulation materials as needed.

Questions to Ask When Hiring a Floor Insulation Specialist

You may need to consider several things when finding the right contractor to install your underfloor insulation for you. Below is a list of common questions that you should ask when looking for the right contractor for the job:

• Does the contractor have any qualifications that relate directly to installing floor insulation?
• What equipment will the contractor be using to complete the job? Will they be using the correct type of equipment? Do you need to provide any equipment?
• Does the contractor possess any form of insurance for the work? You should look for contractors who have insurance that covers property damage, personal injuries, and a work guarantee.
• How much experience does the contractor have in installing floor insulation? Can they provide any testimonials or evidence of previous work? Can they provide photos of previous work?
• Does the contractor offer any guarantees with their work? How long does the guarantee last? What issues are covered under the guarantee? Will the contractor fix any issues that arise?

FAQs