Levelling up – how to prepare the sub floor when installing Rigid LVT

Steve Ball, Technical Services Manager for Malmo™, highlights the importance of sub floor preparation when installing floorcoverings such as Rigid luxury vinyl tile (LVT). Here are his top tips…

Luxury Vinyl Tile (LVT) continues to be the number one flooring choice in 2021 due to its ability to deliver high design, easy installation and low maintenance. Rigid or ‘click’ LVT is particularly popular as it is faster and easier to fit than a stickdown product, however understanding the importance of site preparation prior to installation is paramount.

The quality of the finished floor will only be as good as the sub floor over which it has been laid and this deserves as much attention as its elegant surface finish. All flooring finishes require a clean, sound, level surface that is sufficiently strong and stable. Successful preparation of the sub floor will ensure the longevity of the installation and a satisfied end user long term.

Rigid LVT installation offers several benefits to installers; in most instances the need for a thick plywood underlayment is avoided and installers can traverse existing tiling and concrete sub floors. Fitters won’t go far wrong by following the manufacturers’ installation instructions, but it is vital that they take the time to consider the following when preparing the sub floor.

Levelling works

The sub floor should be thoroughly inspected before the flooring is installed in line with BS 8201: 2011 and BS 8204 -1:2003 standards. The sub floor should be a maximum of 3mm from flat over a 2m span and if it exceeds this, then remedial levelling works should be undertaken before fitting the floorcovering. This can take the form of rectifying uneven tiling, applying a floor levelling compound to the sub floor to level in any hollows or over-boarding with 6mm flooring grade plywood.

It is important not to overlook this step as any necessary remedial works can significantly impact on project costs and timescales.

Drying time for new concrete slabs or screeds

Another element that should not be rushed is the correct drying out time for a new concrete slab or screed. Depending on the site conditions and thickness, some concrete slabs could take a year to attain equilibrium. It is important for installers to ask themselves the following questions before they even think about applying the floorcovering; When was the slab poured? Are site conditions prime for the drying out of the slab? Is the building weathertight? Have wet trades completed their work? These questions should all be considered before applying a floorcovering.

The rule of thumb is to allow one day per mm of thickness, up to the first 40mm of thickness. Above this, the thickness may require twice as long to dry out. Some modified screeds can accelerate the drying process, but installers should closely follow the chosen manufacturers guidelines. If in any doubt DO NOT fit the flooring.

Check the moisture content

Before installing a floorcovering, including Rigid LVT with its waterproof core, the moisture content of the concrete sub floor should be thoroughly checked. The concrete sub floor must have a moisture content by volume of below 3% or a relative humidity of 75% or less. If moisture content exceeds these measurements, the issue should be rectified before fitting the floor. Hygrometer testing is still the most accurate way to determine the dryness of an installation.

Installing Rigid LVT over existing sub floors


  • Fully inspect wooden floors and secure or replace any loose or worn boards.
  • Ensure there are no protruding nail or screw heads.
  • Thoroughly inspect for wood rotting, fungi or insect damage and remedy accordingly.
  • There should be no gaps between floorboards, they should be 2mm maximum.
  • If necessary, overlay with flooring grade plywood sheets (minimum 6mm thickness) and screw down, allowing a minimum 6mm perimeter expansion gap.


  • Thoroughly inspect ensuring any loose tiles are fixed or removed.
  • Check the flooring is completely level i.e. under 3mm over a 2m area.
  • Rigid LVT is designed not to slump into the grout lines left by tiling, so it avoids the need for a plywood underlayment and keeps room height loss and the trimming of doors to a minimum.

Existing vinyl tiles

  • Careful inspection is recommended as early types of LVT contain asbestos. If in doubt, get the site professionally assessed.
  • Make sure all vinyl tiles are soundly fixed in place before proceeding with installation.
  • Any form of soft vinyl or textile type flooring must be removed before installing a Rigid LVT floor.

Products with a built-in underlay such as our Malmo™ Rigid click LVT can simplify and speed up the installation process, as long as it is laid onto a suitably level flat sub floor surface, providing immediate and long-lasting results.

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