s Self-Levelling Compound Waterproof?

Is Self-Levelling Compound Waterproof?

It is important to know that a self-levelling compound is not guaranteed to be waterproof. It all depends on the type of self-levelling compound you use and what it is mixed with.

Self-levelling compound comes in many different types each with different waterproofing properties. A lot, depends on what the self-levelling compound cement is mixed with.


You can only use specialist external self-levelling compounds outside. Most self-levelling compounds should be used internally as an underlayment. It is the floor covering on top that is normally waterproof and protects the self-levelling compound.
Exterior Use
Bostik Cempolay Self-Levelling Compound, Water & Frost Resistant, 25kg

Suitable for garage floors

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Self-levelling compound that is mixed with water has the same waterproofing qualities as cement or concrete.

If you are trying to work out how much self-levelling compound you will need for a project. Check out this handy Self-Levelling compound calculator it takes the work out of working it out!

All self-levelling compounds that are mixed with water and are porous so will absorb water if they get saturated. Despite being slightly porous, external self-levelling compounds will allow water to bead off them if they are used outside.

Self Levelling Compound Bags
Self Levelling Compound Mixed with latex (Left) Mixed with Water (Right)

If you think of self-levelling compound like a very fine cement, suspended in a solution of (water or latex) it can help you to understand its properties.

Is Latex Self-Levelling cement waterproof?

Self-levelling compound cement that you mix with water will be porous. So it is possible for it to absorb water. However, It is still less porous than conventional cement or concrete, as it is made from smaller particles making it denser and harder for water to penetrate it.

Self-levelling compound that you mix with a tub of latex, will be impermeable to water. Latex is a naturally occurring rubber and as we all know rubber is waterproof, hence why rubber is often used as a flat roof covering.

If you want your self-levelling compound to be unaffected by water and you are using it in an area that could be at risk of damp. I would recommend using a self-levelling compound that is mixed with a tub of latex – such as the one below. Arditex NA is unaffected by moisture and can be applied directly to damp-proof membranes or damp concrete.

See the Arditex NA DATA SHEET

Suitable for all subfloors
Ardex - Arditex NA Powder & Latex (24.5kg)

No need to Prime

Easy to spread due to Latex

Finds its own natural level

Pre-mixed ratio

1 Bag = 1 Tub = 1 Bucket

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02/24/2024 11:18 am GMT

If you are using a self-levelling compound externally or on a garage floor, I would recommend using Bostik Cempolay Ultra Strong. It is Ideal for resurfacing internal and external areas such as garages.

See the Bostik Cempolay Ultra Strong DATA SHEET

All in all, Self-levelling compounds are waterproof to varying degrees. Another way of saying it would be that self-levelling compounds have different degrees of porosity.

Latex mixed Self Levelling compound like Ardex NA is virtually waterproof. Due to the high latex content. The high latex content also makes it suitable for areas where there may be movement.

External self-levelling compounds like Bostik Cempolay Ultra Strong although not fully impermeable to water are perfectly fine to be used outside. They have great waterproofing qualities despite being mixed with water. The very fine cement used set to form an almost impermeable barrier to water.

It is also important to note that, just because something is capable of absorbing a little bit of water it does not mean that there is a problem. You would rarely need a Self-Levelling Compound to be 100% waterproof anyway!

Self-Levelling Compound Queries

Sam Wood

Wood by name, wood by nature. I am a fully qualified, time-served, award-winning joiner with an NVQ Level 3 in Carpentry and Joinery as well as an HNC in Construction. Beyond my joinery qualifications, I have also earned a degree in building surveying. I believe these qualifications make me perfectly positioned to provide expert advice on many different areas of DIY as well as share all of the tips I have picked up in over a decade working on building sites!

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