How to prepare a floor before laminate, LVT or engineered wood
A new floor is only as good as the one underneath it. Before you order, clear the room, check the floor is dry, sound and flat, and fix the low spots. Then measure for the boards and underlay. The flooring maker's fitting guide sets how flat and dry the floor must be, so read it before you start.
Clear the room and lift the old floor
Take everything out, including the old flooring, gripper rods, staples and nails. Take the skirting off if you plan to fit the new floor under it, or keep it and plan for beading along the edge. Scrape off old adhesive and lumps so the floor is clean and smooth.
If the old floor is tiles or sheet vinyl laid many years ago, don't break, sand or scrape them until you know what's in them and the adhesive under them. If you're unsure, ask a specialist to check them first.
Check what the floor is made of
The prep depends on the subfloor:
- Concrete or sand and cement screed. Check it's dry, sound and flat, and that there's no dusty or crumbling surface.
- Timber boards or chipboard. Check for loose or squeaky boards and screw them down. Punch nail heads below the surface and replace any soft or damaged boards.
- Existing tiles. Some flooring can go over sound, flat tiles. Check the maker's fitting guide.
Check it's dry
A new screed or concrete floor holds a lot of water and needs time to dry before a floor finish goes down. The screed drying time calculator gives a rule-of-thumb timeline. For a 65 mm sand and cement screed it works out 90 days: 40 days for the first 40 mm and 50 days for the next 25 mm. Cold, damp or unventilated rooms take longer.
That's a guide, not a measurement. Before you lay anything, test the moisture with a hygrometer or the method your flooring maker asks for. On concrete, check whether the maker asks for a damp-proof membrane, either built into the underlay or laid separately.
Check it's flat
Lay a long straightedge across the floor in several directions and look for gaps under it. Mark the high spots and the dips. Grind or plane down the high spots, and fill the low spots.
The flatness each product needs differs, and click-fit floors can be fussy about it. Check the fitting guide for the tolerance and how it's measured.
Level the low spots
For a concrete or screed floor, a self-levelling compound fills dips and gives a smooth surface. Prime the floor first if the bag asks for it. The self-levelling compound calculator works out the bags from the area, the average depth and the consumption on the bag. For a 4 × 2.5 m room at 3 mm, with a product using 1.6 kg/m² per mm, that comes to 48 kg, or 3 bags at 20 kg.
If the depth varies, enter the thinnest and thickest points and the calculator uses the average. Check the maximum depth on the bag: deeper dips may need a different product or more than one layer.
On a timber floor, check the levelling product's instructions first: some aren't made for timber, or need the boards overlaid with ply.
Measure and order the flooring
Once the floor is ready, measure the room and work out the boards and underlay. Our guide to measuring a room for flooring covers doorways, alcoves and awkward shapes. The flooring calculator adds the waste allowance and rounds up to whole packs. For a 5 × 3 m room with packs of 2.22 m², it works out:
- 15 m² + 5% waste = 15.75 m²
- 15.75 ÷ 2.22 = 7.09, so 8 packs (17.76 m², with 2.01 m² left over)
- 2 rolls of underlay at 15 m² a roll
Check the underlay suits the floor type and the subfloor: our guide to underlay explains the options. If you're still choosing the floor, see laminate vs LVT vs engineered wood.
Before the boards go down
- The old floor, gripper rods, nails and adhesive lumps are gone.
- Loose boards are fixed and soft boards replaced.
- The floor is dry, and you've measured the moisture rather than counting days.
- High spots are ground down and low spots filled.
- The damp-proof membrane and underlay suit the floor and the subfloor.
- The boards have had the time in the room that the maker's guide asks for.
- You've left the expansion gap the maker asks for at the walls, and you know how you'll cover it.