Ultimate Guide To Floor Levelling Compound

Spreading out levelling compound.

Ultimate Guide To Floor Levelling Compound

What is a Self-Levelling Compound?

A levelling compound is a self-levelling liquid used to level out uneven subfloors. It is a fast-drying and easy-to-use product that can be applied over a variety of interior subfloor types, including concrete, tiles, timber and plywood. Self-Levelling compound is typically used to prepare subfloors for the installation of floating floors, such as laminate, hybrid, timber, and bamboo flooring and other floor coverings as they require a very flat and even subfloor.

Benefits of levelling compound:

  1. Simply & Effective: Easy to use as it lets gravity do the work by pulling the compound into a flat and smooth surface.
  2. Rapid Hardening: Most levelling compounds hard set in only 6 – 12 hours. This means you can walk and let other trades work whilst it cures, saving you time!
  3. Flexible Application: Levelling compound is very versatile and can be used over almost every type of subfloor whether concrete or timber.

How To Determine Whether My Subfloor Needs Levelling

Hard flooring is great, however, their worst enemy is an uneven subfloor. Unlevel subfloors can cause a myriad of problems including bouncing underfoot, creaking noises, and in severe cases – damage to the floorboards themselves! Subfloor unevenness can be caused by a number of factors, such as poor construction, settling, or moisture damage. Luckily, modern technology brings self-levelling concrete into the picture. These are designed to level out the subfloor by coating the surface which will set into a new flat and even subfloor.

A subfloor is considered uneven if it has any variations in height greater than around 2 – 4 mm over a distance of 2m which really isn’t a lot if you think about it.  You can check whether your subfloor is suitable or not by using a spirit level. We recommend a two-metre-long spirit level as it replicates your typical floorboard length. Check the height of subfloor bumps and dips with a ruler as you slide the spirit level across the subfloor. Be sure to rotate and check from different angles.

Spirit level on subfloor

Can Levelling Compound Be Used On Any Surface Other Than Concrete Slabs?

Yes, they can be used on almost every surface. What varies is the application method, depending on whether the subfloor is a concrete slab or wooden base. A properly sealed concrete slabs only require a primer before a self-leveller can be poured over, whereas a wood substrate needs waterproofing and sealing as well.

Self-levelling compound cannot be applied over existing floating floors. We highly recommend removing and disposing of any existing floor coverings in advance.

The following subfloors don’t always require waterproofing (may require sealing):

  • Concrete Slab
  • Ceramic, Porcelain and Travertine Tiles
  • Aerated Concrete e.g Hebel Flooring

These wood-based subfloors ALWAYS require waterproofing and sealing (non exhaustive list):

  • Solid Timber Flooring
  • Wooden Sheets i.e Plywood, Masonite, Particleboard
  • Yellow/Blue/Red Tongue Flooring
  • Cork Flooring (May be more suitable to remove if there is concrete beneath)

Exceptions which may not be suitable for levelling:

  • Magnesite Subfloor – This may contain asbestos, hence FloorVenue recommends contacting a professional magnesite removalist company. Especially if it has cracks and bounces underfoot.

How To Use Self-Levelling Compound On Uneven Concrete Slab

Note: Self-levelling compound is not the only way to level a subfloor. If you wish to discover more methods, check out our comprehensive guide on how to deal with an uneven subfloor.

Step 1: Clean & prepare the subfloor

The subfloor must be clean, dry, and free of any dust and debris before applying a self-levelling compound. Any cracks or holes in the subfloor should be repaired or sealed using a suitable filler.

Step 2: Prime the subfloor (Wooden Subfloors Require Waterproofing and Sealing As Well)

A primer is applied to the subfloor to help the self-levelling compound adhere properly. The primer should be allowed to dry completely before applying the self-levelling compound. Rookies will often skip the priming process which results in the levelling compound cracking after drying.

If you have a wooden subfloor, it is important to seal all gaps/holes with sealant or a membrane and apply a waterproof primer on top. This is because wood absorbs moisture which can cause warping or buckling problems down the line if not prepared properly.

Step 3: Mix the self-levelling compound

The self-levelling compound is mixed with water (or another suitable solvent) according to the manufacturer’s instructions. It is important to mix the compound thoroughly until it has a very smooth consistency and is free of lumps. This can be done easily with an industrial mixer which looks like an oversized egg beater.

Step 4: Pour the self-levelling compound

The self-levelling compound is poured onto the subfloor from the farthest corner of the room and worked towards the door. This needs to be done carefully with the goal of having even distribution across the surface. The compound should be spread out evenly using a trowel or roller if necessary.

Note that most levelling compounds have a minimum required thickness of 3mm to maintain structural integrity. Too thin, and it may crack once dried!

Pouring self-levelling compound onto concrete slab.

Step 5: De-gas the self-levelling compound

Once the self-levelling compound has been poured, it is important to de-gas it to remove any air bubbles. This can be done using a spiked roller or a de-gassing brush. This will otherwise result in air pockets, which means the new substrate won’t be stable once dry.

Spiked roller to de-gas the levelling concrete.

Step 6: Allow the self-levelling compound to dry

The self-levelling compound should be allowed to dry completely before installing the floating floor. The drying time will vary depending on the thickness of the compound and the ambient temperature. The more airflow and open windows (unless it rains), the quicker the levelling compound will dry. There should be less than 10% moisture reading before installation unless you are laying waterproof hybrid flooring with a plastic moisture barrier.

Where To Buy Levelling Compound

If you are looking for a high-quality self-levelling compound, look no further than FloorVenue. We stock a range of self-levelling compounds that are specifically designed for the installation of floating floors. It is easy to use, fast-drying, and produces a smooth and level surface for any subfloor.

FloorVenue stocks floor levelling compounds specialised for both internal and external use. Whether it’s an uneven concrete slab or wooden particle board, we have a suitable compound for you.

Does FloorVenue Offer Subfloor Levelling Services?

If you wish to let the experts do it, our specialists at FloorVenue have decades of experience in preparing all types of subfloors for floating floor installation. We can level all types of subfloors including concrete and wood. That way you can have all your flooring needs sorted with one company. Don’t hesitate to reach out if you wish for a free quote!

Frequently Asked Questions

Self-levelling compound generally takes 6 – 12 hours to hard set. However, this will vary depending on the brand. We recommend giving around 7 days for enough moisture to leave before installing any non-waterproof flooring. To speed up the drying process, we recommend opening the windows and putting down a fan.

Yes, you will always need to apply the suitable primer to any surface before pouring down self-levelling compound. Ensure the primer is completely dry and covers the full surface of the subfloor where applicable.

If your subfloor is very uneven, it may be necessary to apply a second coat of levelling compound to properly get rid of bumps and dips. This is because every layer has a maximum thickness of around 18 – 20mm before it loses structural stability. Although its not very common, this can be done provided the first layer is completely dry.

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