A Guide to Fitting Underlay

You’ve invested in underlay to make the most of your fabulous new flooring. We would recommend you use a professional flooring fitter to lay both your underlay and new flooring. However, if you’d like to lay it yourself, we’ve put together a guide to help including hints and tips from our experts.


What to expect from this expert guide

We’ll cover each stage of the installation process:

1. How to measure a room

2. Types of underlay

3. Preparing the floor for carpet underlay

4. Fitting underlay for carpet

5. Fitting underlay for laminate flooring

6. Fitting underlay for engineered wood flooring


How to measure a room accurately

Fail to prepare? Prepare to fail. Preparation is everything when it comes to flooring and the most important thing to have is the correct room measurements.

Draw a simple diagram of the rooms that you’re fitting the underlay in - you don’t have to be an artist, just make sure the measurements are accurate.

For square or rectangular rooms, simply multiply the width by the height. (For example, a room that is 5m x 2m, you will need 10m² of underlay).

Ensure you add an extra 50-100mm to each edge.

If your room has recesses or chimney breasts, you still need to measure the complete surface area without these as the underlay will be cut around them. If this is not easy to work out, measure each individual area and write the measurement in the relevant space on the diagram. Then these areas can be added together to get the total area of the room.

Always measure twice (or even three times) to make sure your measurements are correct.

Remember to measure to the back of any door frames or room trims.

To work out the coverage for steps, measure the height and depth of each step which will give you the length before multiplying by the width. This will give you the area of each step.


Types of Underlay

Carpet Underlay

Carpet underlay makes your carpet feel even softer and more luxurious. Underlay absorbs any wear and tear so it doesn’t show on the surface, giving it longevity and maintaining its appearance for a longer time.

Laminate Underlay

Laminate underlay serves to add extra comfort to your laminate flooring as well as reducing the flexing that can occur without it when it’s walked on. It also helps to reduce footstep noise on the hard surface, and retains heat to make your home warmer as it’s a great insulator.


Wood Flooring Underlay

Just like underlay for laminate, wood flooring underlay can keep your engineered wood flooring looking stunning for longer and reduce your energy bills by retaining heat. It doesn’t just keep your home warm, it also cuts down on noise from footsteps and protects your flooring from moisture damage..


Underfloor Heating

If you have underfloor heating, you will need to use a specific underfloor heating underlay with it. These specialist products let air circulate and their low tog rating lets heat penetrate through the floor.


Preparing the floor for carpet underlay

Firstly, before you do anything, make sure the floor is clean and there are no nails or staples that could be left over if it’s previously been carpeted. Sweep or vacuum the floor to get rid of any dust and grit or anything lying on the surface that could cause bumps.


Tools you might need:

Utility knife

Underlay tape

Staple gun


Spray adhesive


Fitting Underlay for carpet

It’s important to use a high quality underlay as this will give your carpet a much longer life. It’s a good idea to also use floor lining paper as this stops the underlay from sticking and protects your carpet from dirt and dust.

Roll out the lining paper and fix with a hammer tacker or heavy staple gun. Fix around the edges by spraying with adhesive ensuring the rows overlap slightly.

Lay the underlay loosely, rubber side down. Use the knife to trim, so it’s level with the gripper rods.

Sit rows of underlay together but don’t overlap them. Use carpet tape to join them.

If you have doorways and recesses, cut the underlay into and around these spaces. It’s OK but not ideal, to add an extra piece if you need to but make sure it remains flat.

Ensuring you keep the underlay straight and gap-free, staple it along its edges inside the gripper. Use adhesive if you are laying carpet onto a concrete floor.

Use tape to stick along the full length of joins. Use the knife to trim off any excess underlay inside the grippers.


Fitting underlay for laminate flooring

There are various types of underlay for laminate flooring each with different advantages. Thicker options give more sound proofing, which could be a consideration if you are laying a floor in an upstairs room or flat.

Bear in mind that not all underlay types are suitable for wet areas such as kitchens and bathrooms.

Lay the underlay over the entire floor and trim to fit, cutting a 16mm gap around any pipes.

Lay lengths parallel and stick together along the length of the joins with masking tape.


Fitting underlay for engineered wood flooring

Again, bear in mind that not all underlays are suitable for wet areas such as kitchens and bathrooms but there are some types that come with a built-in damp-proof membrane.

Place the underlay at one end of the room and unroll from the wall.

Lay lengths parallel using scissors or a knife to trim and stick together with masking tape.

Continue in this way across the room. Although the edges need to meet, it’s important to ensure they don't overlap as this will create an uneven floor.

Leave a gap of 10mm around pipes.