Self Levelling Compound For Underfloor Heating
19/02/2025Can You Use Self Levelling Compound on Underfloor Heating?
Yes, there are many self levelling compounds available if you’re laying a floor with an underfloor heating system. Also known as self levelling screed or cement, it is used by professional tilers, floor fitters and eager DIYers.
No matter the size of the area you’re flooring, adding a self levelling compound to your underfloor heating helps keep your heating system in place while creating a flat, even surface for flooring to be installed on top of.
What Type of Self Levelling Compound is Best for Underfloor Heating?
When using a self levelling compound on underfloor heating, it’s important to choose an SLC designed for your type of heating system, whether that’s loose cables or pipe heating, heating mats or electric underfloor heating.
A liquid levelling compound such as Level it Super30 Rapid Setting or Tilemaster Adhesives Pro Flow is ideal as the mixture easily flows around your heating system, leaving no gaps and helping the heat transfer evenly. We also recommend looking for a flexible compound that can withstand temperature changes within the pipes.
How To Lay Self Levelling Compound on Underfloor Heating
Prepare the floor
Underfloor heating and self levelling compounds can be installed on any type of flooring. However, the critical part is ensuring your floor prep is done correctly. Remove any old flooring and sweep, hoover, and clean the area of any dust or debris. Next, check and repair any dents or cracks. For non-structural cracks, you can use the Ardex P 10 SR Rapid Hardening Crack Repair Resin Kit – it’s easy to use and no mixing equipment is required.
Prime your floor
Primer works like a bonding agent, helping the SLC stick to the floor effectively and create a smooth surface for your self levelling compound. Mapei Eco Prim Grip Plus is a go-to primer for many customers – ready to use, requires zero mixing and can be used on internal and external floors. Your chosen self levelling compound may have a recommended primer – check the manufacturer's instructions and follow the steps. If you’re unsure which primer is best for your type of underfloor heating and SLC, our team are happy to help.
Edge Framework
Allow the primer to fully dry before installing a framework around the edge of your floor. This will help protect connecting walls and help map out where your underfloor heating system will sit. An edge also ensures your self levelling compound stays in the desired area and prevents any leakages.
Fit Your Membrane
Wet or liquid levelling compounds are the preferred option for underfloor heating. Due to its fluidity, you’ll also need a decoupling membrane to separate the subfloor from your flooring material. This will help prevent movement in your flooring due to temperature fluctuations.
Lay Your Heating System
Depending on your type of underfloor heating, follow the manufacturer’s instructions to correctly space, lay and attach your pipes to the flow manifold. Before applying your SLC, test the pressure. Start by closing the manifold isolation valve and opening the circuits. Connect a test pump and raise the pressure. You’ll be able to spot any pressure loss and rejig your pipes to resolve the issue.
Application
When it comes to applying self levelling compound over an underfloor heating system, we always recommend following the manufacturer's instructions for the best results. However, the process usually follows these steps:
Mixing Self Levelling Compound
First, check you have all the correct self levelling tools for the job. Add your self levelling compound and water/latex (this may vary depending on the type of SLC you’ve chosen) into a bucket. Mix thoroughly with paddle mixer until smooth and lump-free.
Start To Pour
The depth of self levelling compound will depend on your flooring project and the type of underfloor heating. As a rule of thumb, you want a minimum thickness of 10mm - 20mm. Again, we suggest checking the instructions recommended by your heating system’s manufacturer. However, you essentially want to ensure all of your pipes are fully and evenly covered.
As you pour the floor levelling screed, use a flooring trowel to spread evenly and create a smooth surface, moving the self levelling compound to the very edge of your framework. Be mindful of your trowel and press gently to avoid damaging the cables or pipes beneath.
Inspect
Use a spirit level to check for any slopes or uneven areas. You can mix additional SLC and use a trowel to raise these low areas. Not all SLCs can be used for multiple layers, so be sure to check this before and whether primer needs to be applied between the layers.
Drying Process
Check the recommended drying time of your SLC product. This usually takes between 2-24 hours for the levelling compound to fully dry and harden. Once the recommended time has passed, and you are happy to do so, remove the framework.
Test your heating
Only when the SLC is completely dry should you test your underfloor heating. Start with a low temperature to monitor its performance, and raise the temperature slowly over a few days.
Self Levelling Compound For Underfloor Heating FAQs
How Long Does Self Levelling Compound Take To Dry?
Each self levelling compound will have a different recommended drying time. This can span anywhere between 2-24 hours. For best results, always follow the manufacturer's instructions.
What Is The Best Latex SLC?
We have a great blog which covers this in detail, read about the best latex self levelling compounds here.
How To Mix Self-Levelling Compounds?
Mixing self-levelling compounds differs with each brand and type. For best results, follow manufacturer instructions. In general, once all water/latex is added, you add two-thirds of the powder, then the remaining third once fully mixed, as this will aid in a smooth mixture. We wouldn't recommend adding extra water/latex as this can compromise the mixture, especially with latex, as this is designed as a 1 bag - 1 bottle mix.
How Thick Should I Lay Self-Leveling Compound?
This is dependent on the type and brand of self levelling compound. For example, the Mapei Ultraplan Maxi 3230 Ultra Fast Drying Self Levelling Compound is ideal for thicknesses from 3 to 30mm. Whereas the BAL Level Max All In One Leveller is suitable to 2 - 80mm – one of the largest in the market, so it is very dependent, but to find the perfect self levelling compound feel free to contact our team on 01604 859800.
How Long Until You Can Walk On Self Levelling Compound?
Again, this is very dependable on the type and brand of self levelling compound. The Kerakoll Keralevel Eco LR Rapid Repair Mortar can handle foot traffic after 2 hours, whereas the Tilemaster Fine Flow 3000 Free Flowing Heavy Duty Self Levelling Compound can handle light foot traffic after 3 hours.
Can You Use A Self Levelling Compound Outside?
Yes, if the self levelling compound is suitable for both internal and external environments, it can be used outside. For example, the Ardex A46 Multi-Purpose Concrete Repair Mortar can be used outside to repair damaged concrete, building ramps and levelling a patio. Here are some popular examples of external self levelling compound options:
Read more: Work In Cold Weather: Can You Tile Outside In Cold Weather?
Can You Put Self Levelling Compound On Tiles?
Yes, you can pour self levelling compound on existing tiles. Ensure the surface is prepped and primed before laying it.
What Tools Do I Need To Lay Self Levelling Compounds over Underfloor Heating?
To effectively lay your levelling mixture, you’ll need specific self levelling compound tools. These include a mixing bucket, a mixer/mixing paddle, and a flooring trowel.
Flooring Trowels
Flooring trowels are used to help distribute self levelling compound over subfloor and are great for directing SLC in the right direction.
Floor Preparation Tools
Floor preparation tools are used to prep your floor for laying self levelling compound, ensuring you get the best finish possible.
Mixing Buckets & Tubs
Having a clean mixing tub or bucket is important when mixing self levelling compounds. It ensures debris doesn't get trapped in the mixture, resulting in a bumpy/uneven finish.
Popular Self Levelling Compounds for Underfloor Heating Systems
At Pro Tiler Tools, we stock a wide range of self-levelling compound products to aid your underfloor heating projects.
Self Levelling Compound for Underfloor Heating | Walkable In | Internal Or Exterior | Thickness | Coverage | |
 | 90 minutes | Internal | 2 - 15mm | Approximately 5m² at 3mm Thick Per Unit | |
 | 90 minutes | Internal | 2 - 30mm | Approximately 4m² at 3mm Thick Per Unit | |
 | 30 minutes | Internal | 3 - 60mm | 1.481 kg/m2 per mm of thickness | |
Ultra Tile Fix ProLevel Two Flexible Two Part Self Levelling Compound |  | 2.5 hours | Internal | 2 - 15mm | Approximately 6m² at 2mm Thick Per Unit |
 | 4-6 hours | Internal | 3 - 40mm. | Approximately 6m² at 3mm Thick per Unit |
Ultra Floor Self Levelling Compounds
Ultra Floor offers a premium range of Level it Self Levelling Compounds ideal for all types of underfloor heating systems. Its moisture-tolerant formula offers a mix of levelling products from the mid-strength of Level It Two to the high-strength Level It Smooth for a high-performing and extremely smooth finish.
BAL Self Levelling Compounds
BAL self-levelling compounds are another popular choice, as they have been formulated to create a smooth, flat and level surface quickly and efficiently. BAL’s fast set range can be walked on only after 30 minutes and tiled on after 45 minutes! Perfect for those working on a time crunch.
Kerakoll Self Levelling Compound
Kerakoll Self Levelling Compounds are a popular choice for homeowners, DIYers and professional developers. Known for its flexibility and exceptional quality, there are a couple of options ideal for underfloor heating, including Kerakoll Proflow and Kerakoll Levelflex.
Ultra Tile Self Levelling Compound
Ultra Tile self levelling compounds support any sized renovation project. From ensuites and entrance halls to commercial offices and open-plan spaces, you’re guaranteed a flawless finish. With rapid setting, exceptional strength and flexibility, it can withstand high traffic with long-lasting results.
Mapei Self Levelling Compounds
Mapei self levelling compounds are known for their quality and performance. One of their most popular SLCs is Mapei Topcem Fast Set Hydraulic Screed Binder, perfect for high-traffic areas, fast drying, external and internal use, and suitable for underfloor heating!
At Pro Tiler Tools, we have everything you need to successfully lay self levelling compound over your underfloor heating systems. Our team have the expertise to guide you in the right direction as to the best products to suit your needs. To speak with our team, contact us at 01604 859800 or email us at [email protected].