Subfloor Requirements

The Core Rules for a Suitable Subfloor

An uneven, damp or unstable subfloor is one of the most common causes of flooring issues, including movement, creaking, gaps, lifting boards and premature wear. Before any installation begins, the site conditions must be checked carefully and corrected where necessary.

Whether you are installing engineered wood, parquet, laminate or LVT, the subfloor must provide a clean, dry, level and structurally sound base. Skipping this stage can affect both the final appearance and the long-term performance of the floor.

• Cleanliness: The surface must be swept clean and free from paint, plaster, adhesive, wax, oil and dust build-up.
• Dryness: There must be no rising damp or trapped moisture. A suitable damp-proof membrane may be required depending on the base.
• Flatness: High spots must be ground down and low spots corrected with a suitable levelling compound.
• Strength: The base must be firm enough to support the finished floor without flexing or breaking down.
• Compatibility: The chosen underlay, adhesive or installation method must suit both the product and the subfloor type.

Concrete and Screed Subfloors

Concrete and screed bases must be fully cured before installation. In new-build properties, a drying period of at least 60 days is commonly required, although thicker slabs, poor ventilation or cool site conditions may increase the time needed.

Moisture levels should always be tested rather than guessed. A subfloor may appear dry on the surface while still holding excessive moisture internally. Installing flooring too early can lead to swelling, cupping, adhesive failure or long-term damage.

• Use a recognised moisture test before fitting any wood, laminate or LVT flooring.
• Apply a damp-proof membrane where required by product instructions or site conditions.
• Repair cracks, holes and weak sections before laying underlay or adhesive.
• Check thresholds and finished floor heights before starting the build-up.

Timber, Plywood and Floorboard Subfloors

Timber-based subfloors must be structurally secure and firmly fixed to the joists to reduce movement and unwanted sound. Loose boards, bounce, vibration and squeaks should be corrected before installation.

Because wood is a natural material, moisture balance is especially important. The subfloor and the flooring product should be appropriately acclimatised and within compatible moisture ranges before fitting begins.

• We often recommend an additional plywood layer to create a flatter, more consistent surface.
• Check moisture content before installation, especially in older buildings.
• Ensure good ventilation beneath suspended timber floors.
• Replace damaged or weak sections before laying the finished floor.
• Fix loose boards securely to reduce creaks and movement.

Pre-Installation Checklist

Before installation starts, it is good practice to complete a simple site review. This helps identify issues early and reduces the risk of callbacks, delays or warranty problems.

Professional Tips for Better Results

A great floor is not only about choosing the right product — it is also about respecting the structure beneath it. Professional preparation creates a quieter, flatter and more durable installation.

• Always resolve moisture concerns before ordering or fitting the floor.
• Do not rely on visual checks alone — test, measure and document site conditions.
• Allow materials to acclimatise in the room environment where required.
• Choose installation products that are approved for the floor type and subfloor condition.
• Never install over an unstable or contaminated base just to save time.