How To Use Self-Levelling Compound

Achieve a level floor effortlessly by applying a self-levelling compound, and let our guide walk you through the process.
Written By: David White | Updated:
How To Use Self Levelling Compound
David White/DIY Works

A self-levelling compound is often referred to as a floor screed, and it’s used to create an even floor surface on top of various uneven substrates. Whether you need to level out existing tiles, concrete, timber, or any other substrate, a self-levelling compound is the perfect solution. As long as there isn’t too much of a discrepancy, it’ll work on all types of uneven substrates.

In terms of checking how much a floor is out of level, you can use a golf ball. With the ball in hand, drop it on the floor in multiple spots to get an idea of where the floor is at its lowest.

Once you’ve found the lowest point, use a spirit level (at least 6 foot) and hold it up at the lower end of the level until the bubble is in the middle. You can then measure the gap between the floor and the raised end of the level.

Depending upon how uneven the floor is will determine which self-levelling compound you require. Most will provide a maximum depth of 5mm, but there are many different mixtures you can use to best suit your requirements. For our tutorial below, we used the Bostik Cempolay Ultra Strong formula, which was very easy to mix and use.

How Does It Work

A self-levelling compound uses gravity to self-level an uneven surface, and this is made possible by the inclusion of latex within the formula. The use of latex gives the mixture high flow characteristics and the flexibility to move without cracking. It also requires very little water, and once mixed up, it can simply be poured onto the uneven substrate. After pouring, you can then move it around to achieve the perfect finish for your floor.

What You’ll Need

  • Self-levelling compound
  • Scraper
  • Straight-edged timber
  • Trowel
  • Protective mask
  • Paddle mixer
  • Bucket
  • Water
  • Spiked roller

How To Lay Self-Levelling Compound


1. Prepare The Substrate

Before you begin, it’s always good practice to brush and vacuum any loose debris because it may prevent the compound from bonding with the surface. If any dirt and debris won’t budge, you may need to use a scraper to clear it.

2. Build Any Barriers (Optional)

Whether you want to stop the self-levelling compound from going into another room or anywhere that you need to access at a later date, you’ll need to build a barrier.

As you can see in the photo, this particular section of the floor was underneath a bath, and there were plumbing and electric cables that we needed access to at a later date.

In terms of building the barrier, you’ll want to use a straight-edged piece of timber and a suitable sealant to stop the self-levelling compound from passing through. The barrier itself doesn’t need to be incredibly sturdy because all it’s stopping is the flow of the self-levelling compound.

how to use self levelling compound over tiles

David White/DIY Works

3. Pour The Self Levelling Compound Into A Bucket

Once the substrate and any barriers have been prepared, you can proceed to mix up the self-levelling compound. To begin, find a suitable bucket and pour the compound of your choice into it. Depending upon the area you are levelling will determine how much of the compound you’ll need. There should be instructions on the bag stating the exact measurements you require.

As you can see in the image, there may be a kick-up of dust as you pour the self-levelling compound into the bucket. Therefore, we would recommend that you wear a protective mask for peace of mind.

how to screed a floor self levelling

David White/DIY Works

4. Add Water & Begin Mixing The Compound

With the self-levelling compound in the bucket, you can continue adding the required amount of water. Depending upon the mixture you use will determine the amount of water that’s required. For our particular mixture, the 20 kg bag required 3.8 litres of water.

To mix the water and compound, we used a paddle mixer, but you can use a cordless drill with the appropriate attachment if required. Before it’s ready to be poured, you’ll want to continue mixing it up until it’s lump-free and at the right consistency. After mixing, if you feel that it’s too lumpy, add more water, but if it’s too watery, you may need to add more of the compound.

how much self levelling compound do i need

David White/DIY Works

5. Pour The Compound Onto The Substrate

Once you are happy with the consistency of the mixture, you can pour it onto the substrate. Ideally, you want to pour it onto the farthermost part of the room and work backwards because this will avoid having to walk on top of it.

6. Mix & Pour More Mixture If Required

After pouring your first mixture of the self-levelling compound, you’ll then need to decide if you need any more to cover the entire floor. If you do, repeat steps 3, 4 and 5 to cover the entire floor. Alternatively, if you are working on large or deep areas, you can section off the area using lengths of timber.

As you can see in the image, the 20 kg bag didn’t cover the entire floor, and we ended up using 60 kg in total to cover the floor (result shown below).

how to lay self levelling compound

David White/DIY Works

7. Spread All Areas Using A Trowel

After you’ve covered the entire floor with the mixture, you’ll want to ensure it has reached all of the edges.

The best way to achieve this is to use a smooth-edged steel trowel to work the compound in sections (as shown in the image). After it has been spread and is nice and smooth, you can use a spiked roller to eliminate any air bubbles. Although there are many people who don’t do this step, it’s always advisable because if there is trapped air, it may cause issues once the compound has dried.

We used a budget spiked roller and all you need to do is run it through the compound for it to do its job.

how to self level a floor

David White/DIY Works

The End Result

Although there are lots of steps involved, using a self-levelling compound is a relatively easy task. As you can see in the image below, the end result is nice and smooth, and we successfully sectioned off areas where it wasn’t required.

how to screed a floor

David White/DIY Works

How Long Does Self-Levelling Compound Take To Dry

Once you’ve laid your self-levelling compound, it’s crucial that you give it enough time to cure and dry out completely. Ideally, you’ll want the room to have an air temperature of around 20°C and plenty of ventilation. You may even wish to use a suitable dehumidifier to remove excess moisture within the room.

In terms of how long the self-levelling compound takes to dry, it dries at approximately 24 hours per 1mm of thickness. Therefore, if the thickness of the compound is 5mm, it’ll take at least 5 days for the self-levelling compound to dry completely. However, in terms of being suitable for foot traffic, some compounds can be walked on as soon as 30 minutes, whereas others may take a few hours.

how long does self levelling compound take to dry

David White/DIY Works

Compatibility With Underfloor Heating

If you’ve installed underfloor heating and are looking to level the floor, it’s crucial that you check that the compound you use is compatible. The majority can be used, but it will specifically state on the bag if you can use it with underfloor heating. It’s important to note that you shouldn’t use underfloor heating as a method of speeding up the drying process because this may result in cracking of the floor.

Conclusion

Hopefully, our guide on how to use a self-levelling compound gives you the confidence to try it out yourself. However, if you need any further information, feel free to get in touch, and we will provide our assistance where possible.

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