How to level a subfloor

A subfloor is the surface that you will lay your natural stone tiles or wooden flooring onto. Firstly, identify what the subfloor is made of. Select a levelling compound that is suitable for application to your subfloor type – Mira X-Plan is a good all-round product, suitable for most surfaces. Ensure the subfloor is free from contamination (eg: glue, bitumen, plastic tiles etc), thoroughly clean off dust and dirt then prime with Ardex P51 primer (or Ardex P82 resin primer if wood) at a ratio of 3 parts water to 1 part primer, then allow to dry completely. Using a spirit level, find the highest point of the floor. If you are sure there are no pipes or cables below the surface, you can then tap in small masonry nails or wood pins at around 1 square metre intervals from the high spot so that the heads are at the same level as this spot. Take care not to tread or kneel on these – circle them with a coloured marker pen in order to avoid this. If you are not confident in nailing into the subfloor, use self-adhesive pads or “Sticky-Fixers” in layers.

Once complete, mix the levelling compound according to the instructions on the bag. Starting at the furthest point from the door, pour onto the floor and use a flat trowel to spread it, making sure the levelling compound just covers the top of the nails. Work back towards the door and place a batten in the doorway if needed to finish up to. Allow to dry as per manufacturers’ recommendation before laying floorcovering.