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How to level a floor

Get your sub floor ready

Whether you go for vinyl, carpet or even ceramic tiles, changing your floor covering is a great way to give a room a new lease of life. But before you start work, make sure the surface beneath is in good condition and level. If it isn’t, any defects are likely to show through. This will spoil the look of your new floor and eventually cause it to wear unevenly. Luckily, there are some effective ways to deal with problem floors which we’ll share with you.

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Over time, traditional wooden floorboards can become uneven from warping or general wear and tear.

Covering existing floorboards with hardboard sheets provides a more even surface you can lay your new floor covering on.

Safety first

For your comfort and protection, it’s a good idea to wear knee pads when you’re working on the floor.

Top tips

To prevent hardboard sheets buckling as you nail them down, position nails in an expanding pyramid pattern, starting in the middle of one edge and gradually working across to the other side.

If you have any repairs to do like plumbing or wiring, now’s the time to do it.

If you need to smooth down any uneven areas, use a belt sander or orbital sander with coarse paper. Make sure you wear gloves, goggles and a mask.

Preparation

First, take a look at the existing floorboards to see what sort of condition it’s in. If there are any rotten floorboards, replace them. And if there are any loose or creaking floorboards, these will need to be screwed down before you lay the new floor.

Use a pipe and cable detector before you put the screws in. The boards may be loose because there’s a pipe or cable that’s preventing them from being fixed.

Any protruding nails or screw heads should also be punched or screwed below the surface.

Tools & materials for the job:

 

Start by watching our video guide below.

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Step 1

Choose 3 mm thick hardboard and condition them before they’re laid. This involves scrubbing water into the rough side of the sheet. The sheet should then be laid flat on top of one another in the room in which they’ll be used for 24 hours before you fit them so they can acclimatise. The rough sides should be laid facing each other.

Wetting the sheets causes them to expand slightly before they’re fixed. They’ll dry out and contract a little – this prevents bumps or uneven joints forming due to any expansion after they’re fixed.

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Step 2

Before you start laying the sheets, you need to check whether they should be laid rough side or smooth side up for your choice of floor covering. Normally, for self-adhesive and loose laid flooring, smooth side up is best, and for coverings that will be stuck down with adhesive it’s rough side up. Always check the floor covering and adhesive manufacturers’ guidance.

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Step 3

Start by laying the boards in the centre of the room so that the long side is at a 90° angle to the floorboards. Each sheet needs to be fixed at a maximum spacing of 150 mm in any direction, and nails at the edge of the sheet should not be more than 15 mm from the edge.

Top tip

Cut a piece of wooden batten to 150 mm to help get the right spacing between nails.

Nail along the long side first and then work diagonally towards the opposite corners in a pyramid pattern. Make sure all nail heads are either flush with the sheet or slightly below the surface of the sheet

Step 4

Position and fix the other sheets ensuring the joints are staggered like a brick wall. Try to maintain a stagger that is at least a quarter of a length of sheet. Use the off cut from the last sheet in the first row to start the second one. This prevents any waste and ensures the joints are staggered. Then just carry on like this until you’ve finished the floor, nailing the boards on the long side first and working diagonally towards the corners, maintaining a triangular shape as you go.

Top tip

Laying this hardboard will have increased the floor height. If the door opens into the room, you may have to remove the door and cut some off the bottom. If you need to do this, take into account the thickness of the new floor covering when you’re marking up the door.


If a lot of your floorboards are damaged, you’ll find it cheaper and easier to pull them all up and fit tongue-and-groove chipboard flooring panels. These will give you a firm foundation for your final floor covering.

Tools & materials for the job:

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Step 1

Start in the corner of the room. Lay the first panel so that its long side spans the joists and its end rests on a joist (if you need to cut it down, it’s best to do this on the skirting edge). Position the board about 9 mm from the wall to allow for any expansion. Then nail along the joists, beginning about 18 mm from the edge, using 50 mm ring-shanked nails spaced at 300 mm intervals. Remember to mark the location of any pipes or cables beneath the boards.

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Step 2

Check the fit of the next panel. If its tongued end doesn’t meet a joist, cut it back as necessary. Then apply PVA wood adhesive to the end tongue of the first panel, slot the end groove of the second over the tongue (aligning the long edges) and nail down the second panel. Wipe off any excess glue with a damp microfibre cloth.

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Step 3

If you’ve shortened the second panel to meet a joist, you’ll also need to cut off the grooved end of the next one so you can butt and glue them together over the joist. Cut the last board in the row to size, remembering to leave a 9 mm expansion gap at the wall. Lay the first panel of the second row against the last panel of the first so the joints are staggered.

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Step 4

Make sure the panels fit tightly by driving each into place with a grooved panel off cut. Continue to do this until you reach the far side of the room, staggering the joints and allowing an expansion gap at the wall. Then measure and cut the last row of boards to fit.


Tools & materials for the job:

Start by watching our video guides below, split into 2 parts to make it easy to follow.

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Step 1

First, dampen down the area using a spray bottle and give the floor a thorough sweep to get rid of any dirt and dust. By making the area damp beforehand it helps keep the dust down. Don’t be tempted to use a vacuum cleaner as it may get damaged by the concrete dust.

Check whether you need to make any repairs and look for any grease or oil on the surface. If there is, use a suitable degreasing product to clean it.

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Step 2

Most standard floor levelling compounds can be applied up to a maximum of 5 or 6 mm in thickness, but some products will allow you to apply them beyond this so always check the manufacturer’s instructions. If there are any holes or cracks that are deeper than the maximum thickness that the levelling compound can be applied to, they’ll need to be filled with a suitable concrete repair compound first.

Find out how deep the holes are by placing a spirit level across the floor and measure from the bottom of the level to the bottom of the dip. A steel rule is much better than a tape measure for this.

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Step 3

Seal the surface with a diluted PVA mix or suitable acrylic primer using an old paintbrush and give it time to dry.

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Step 4

Mix the compound following the manufacturer’s instructions and try do this outdoors if you can.

Top tip

Unless your door has a threshold, or you’ll be spreading the compound towards a feather edge, you’ll need to fix a temporary timber batten with nails to stop it spreading into the next room.

Step 5

Start in the corner furthest from the door and pour the compound onto the floor. Spread it to the thickness of about 3 mm with a plasterer’s trowel using long, sweeping strokes. Work quickly, but carefully. The compound will set in around 15 minutes, and you should be able to walk on your floor in a few hours - but check the instructions before you lay your new flooring.

Top tip

If your trowel marks are still visible after a couple of minutes, sprinkle water on them and smooth the compound again.


If you stagger your panel joints in adjacent rows, you can stop any annoying lumps and bumps from forming in the floor and showing through your floor covering.