Everything you need to know about self-levelling compounds — types, application, depths, curing times, and how to choose the right product for your floor
A complete 2026 guide to self-levelling compounds. Covers what they are, how they work, cement-based vs. gypsum-based types, substrate preparation, priming, mixing, pouring depths from 1 mm to 50 mm+, curing timelines, typical uses over concrete and timber substrates, and common problems and solutions for Australian residential and commercial floor applications.
Self-levelling compounds are one of the most versatile and widely used floor preparation products in Australian construction — essential for achieving flat, smooth floors before tiling, timber, vinyl, and other floor finishes in 2026
A self-levelling compound (SLC) — also called self-levelling screed, floor leveller, or self-smoothing compound — is a cementitious or gypsum-based pourable material that, when mixed with water and applied to a prepared floor substrate, flows under gravity to seek its own level and create a smooth, flat surface. Unlike traditional sand and cement screeds that must be mechanically compacted and hand-trowelled, self-levelling compounds use superplasticisers and carefully engineered particle size distributions to achieve a fluid consistency that self-smooths and self-levels with minimal physical effort from the applicator. The result is a flat, dense, hard-wearing substrate suitable for the direct application of ceramic tiles, porcelain tiles, natural stone, engineered timber, LVT/LVP, carpet, and other floor finishes.
Self-levelling compounds are used wherever an existing floor substrate is uneven, damaged, or has an inadequate surface profile for the intended floor finish. Common applications in Australia include: correcting uneven concrete slabs with dips, ridges, or surface blemishes; levelling timber floors (bearers and joists, particleboard, plywood) before tiling or hard flooring; creating falls to floor wastes in wet areas; filling and levelling old vinyl, terrazzo, or tiled floors before new finishes are applied over them; and providing a smooth, clean substrate in new construction where the base concrete has been poured with inadequate surface tolerance. In underfloor heating applications, specific self-levelling compounds are used to encapsulate heating pipes and cables in a thermally conductive screed layer.
The Australian self-levelling compound market in 2026 is served by major manufacturers including Ardex, Mapei, Laticrete, Weber (Saint-Gobain), Bostik, Sika, and Dunlop (Selleys). Products are available from trade suppliers, tile shops, and hardware retailers including Bunnings and Total Tools. For residential applications, DIY-suitable products are available in 20 kg bags; large commercial applications are typically handled by specialist floor-laying contractors using high-volume continuous mixing and pumping equipment. All Australian self-levelling compounds should be used strictly in accordance with the manufacturer's Technical Data Sheet (TDS) — application temperatures, mixing ratios, priming requirements, and depth limitations vary significantly between products.
The correct application sequence for self-levelling compounds in residential and commercial floor preparation
Check the substrate for structural integrity — SLC cannot bridge cracks or compensate for structural movement. Grind or scarify high spots, ridges, and adhesive residue to a flat profile. Remove all loose material, dust, oil, grease, paint, curing compound, and laitance by grinding, shot-blasting, or scabbling. Vacuum thoroughly. Check substrate moisture — most cement-based SLCs require substrate moisture content below 5% (75% RH); check the TDS for the specific product. Repair cracks wider than 0.5 mm with an appropriate crack filler and allow to cure before applying SLC.
Before priming or pouring, fix self-adhesive compressible foam strip (typically 5–10 mm foam, 50 mm wide) around the perimeter of the area, against all walls, columns, doorframes, and fixed penetrations. This foam isolates the SLC layer from rigid abutments, accommodating minor thermal and moisture movement and preventing edge cracking and drumming. Do not omit this step — perimeter foam is required by most SLC manufacturers for warranty compliance and is standard best practice on all applications.
Priming is mandatory for virtually all self-levelling compound applications. The primer seals the substrate, controls suction (prevents the substrate absorbing water from the SLC too rapidly, causing weak surface layers and premature stiffening), and improves adhesion between the SLC and the substrate. Use the primer specified by the SLC manufacturer — mixing brands is not recommended and may void product warranty. Apply by brush or roller evenly and allow to reach the correct tack condition before pouring. On highly porous substrates (aerated autoclaved concrete, porous screed, old timber boards), two coats of primer may be required. On non-porous substrates (glazed tiles, terrazzo), a bonding primer or epoxy primer may be needed.
Before mixing, establish the target finished floor level using a laser level or spirit level. Install depth gauge pins (screw-in plastic pins, timber scraps, or purpose-made levelling clips) at the required height intervals — typically every 1–1.5 m across the area. These pins act as pouring guides to confirm correct depth during application. For areas with deliberate falls to floor waste (wet areas), set your datum points at calculated heights to achieve the required fall gradient — typically 1:100 (10 mm per metre) for wet areas to comply with AS 3740.
Add the specified quantity of clean, cold potable water to a clean mixing bucket first, then add the SLC powder. Mix with a slow-speed drill (300–400 RPM) fitted with a mixing paddle for 2–3 minutes to a smooth, lump-free, pourable consistency. Do not add extra water beyond the manufacturer's specified water ratio — excess water causes surface crazing, reduced strength, and increased shrinkage. Do not re-temper (add more water to a mix that has begun to stiffen) — discard and prepare a fresh mix. Large-area commercial applications use continuous mixing pumps that meter water and powder automatically for consistent mix quality.
Pour the mixed SLC onto the primed substrate and spread with a gauge rake or notched spreader set to the required depth. Work quickly — most SLC products have a pot life (open time) of only 15–25 minutes at 20°C; in warm Australian conditions above 25°C, pot life shortens to 10–15 minutes. Work systematically from the furthest point back towards the exit. Immediately after spreading, spike-roll the compound with a spiked roller (pin roller) to release entrapped air bubbles and ensure full surface coverage at the required depth. Do not overwork — SLCs are formulated to self-level and excessive manipulation degrades the surface.
Protect the freshly poured SLC from foot traffic, draughts, direct sunlight, and rapid temperature changes during the initial curing period. Most cement-based SLCs can be walked on in 2–4 hours but require 24 hours before tile adhesive is applied and 48–72 hours before installation of heavy floor finishes or traffic. Gypsum-based anhydrite screeds require 3–7 days drying per 10 mm thickness and must achieve the manufacturer's specified residual moisture content before any floor finish is applied. Do not use heat guns or forced drying to accelerate — this causes surface crazing, delamination, and debonding of subsequently applied floor finishes.
Tiles, timber, LVT, carpet, vinyl — installed after SLC has fully cured
Smooth, flat, hard surface — the focus of this guide
Controls suction, improves adhesion, seals substrate — mandatory step
Existing floor — must be clean, sound, dry, and structurally adequate
Perimeter expansion foam strip (not shown) isolates the SLC from all walls and fixed elements around the entire perimeter
Bar heights are proportional to depth — always confirm maximum single-pour depth with the specific product TDS; some products require pea gravel extension or multiple pours for depths above 20 mm
Self-levelling compounds available in Australia in 2026 fall into two primary binder categories — cement-based and gypsum-based (anhydrite) — with significant performance, application, and suitability differences between the two. Within each category, products are further differentiated by their intended depth range, substrate suitability (concrete, timber, existing tiles), intended final use (underfloor heating, direct tile bed, floating floor), and their strength and flexibility characteristics. Selecting the correct product type for the specific substrate, depth, floor finish, and exposure conditions is the most critical decision in any SLC application. Using the wrong product — particularly using a gypsum-based SLC in a wet area, or applying a cement-based SLC over an incompatible timber substrate without a flexible primer — is a leading cause of SLC failure in Australian floors.
Cement-based SLCs use Portland cement or calcium aluminate cement (CAC) blended with fine aggregates, superplasticisers, and polymer additives as their binder system. They are suitable for use in wet areas, exterior applications (covered), and anywhere moisture resistance is required. Cement-based SLCs are compatible with all floor finishes including ceramic, porcelain, and natural stone tiles, timber, LVT, and carpet. They achieve compressive strengths of 20–40 MPa at 28 days and are moisture-stable once cured — they do not re-soften if wetted. In Australia, cement-based SLCs are the standard product for bathrooms, laundries, commercial kitchens, and any application subject to intermittent wetting or high humidity. Products include Ardex K360, Mapei Ultraplan Maxi, and Weber floor 4310.
Gypsum-based SLCs (calcium sulfate or anhydrite binder) flow exceptionally well at low water-cement ratios, producing extremely flat, smooth surfaces with very low shrinkage and minimal cracking. They achieve high compressive strengths (25–40 MPa) and are ideal for underfloor heating systems where their thermal conductivity and heat distribution are superior to cement-based products. However, gypsum-based SLCs are not suitable for wet areas, exterior use, or anywhere subject to persistent moisture — calcium sulfate is water-soluble and will soften and fail if repeatedly wetted. In Australia, anhydrite screeds are primarily used in commercial buildings for underfloor heating and large-area flat floor applications in dry, climate-controlled interior environments. A critical requirement is achieving ≤ 0.5% CM moisture content (≤ 75% RH) before applying impermeable floor finishes such as tiles or LVT — a drying period of several weeks is typically required for deeper pours.
Polymer-modified SLCs incorporate acrylic or vinyl acetate co-polymer redispersible powders or liquid polymer admixtures into the cement-based binder. This modification increases flexibility, improves adhesion to difficult substrates (timber, vinyl, tiles), reduces crack propagation, and improves impact resistance. Flexible SLCs are the preferred product for use over timber substrates (plywood, particleboard, hardwood) where minor movement occurs, and over existing resilient floor coverings (vinyl tiles, cushion-backed sheet vinyl) that cannot be fully removed. In Australia, products such as Ardex K16, Mapei Novoplan Easy, and Dunlop 15 Floor Leveller Plus are widely used flexible SLC products. Flexible SLCs are slightly less hard (lower compressive strength) than standard cement-based products but provide far superior adhesion and durability over movement-prone substrates.
Self-levelling compounds used to encapsulate underfloor heating systems (electric heating cables or mats, hydronic pipe) must meet specific requirements: high thermal conductivity (to efficiently transfer heat from the element to the floor finish above), low shrinkage (to avoid cracking over heating cables), compatibility with the heating element materials, and adequate compressive strength to support floor loading. In Australia, gypsum-based anhydrite screeds are preferred for hydronic underfloor heating in commercial settings due to their superior thermal mass and flow. For electric underfloor heating under tiles, cement-based SLCs with a thermal conductivity of ≥ 1.2 W/m·K are specified. The SLC must be cured for the full manufacturer-specified period before the underfloor heating system is commissioned — typically 7 days minimum, with temperature ramping protocols required to prevent thermal shock cracking.
Fast-setting SLCs use calcium aluminate cement (CAC), calcium sulfoaluminate cement (CSA), or blended rapid-hardening binder systems to achieve walkable surfaces within 30–90 minutes and tile-ready surfaces within 2–4 hours. These products are essential for commercial refurbishment projects where floor downtime must be minimised — retail centres, hospitals, aged care facilities, and offices where areas cannot be closed for 24+ hours. In Australia, products such as Ardex K22, Mapei Ultraplan Easy, and Laticrete NXT Level Plus are widely used rapid-setting SLCs. Key precautions: rapid-setting SLCs have very short pot lives (5–15 minutes), require experienced applicators familiar with time-critical placing and spreading, and must be used in cooler conditions — ambient temperatures above 30°C (common in Australian summers) further shorten working times to dangerous levels without product cooling strategies.
Standard self-levelling compounds have maximum single-pour depths of typically 10–25 mm before aggregate extension or multiple pours are required. For deeper applications (25–80 mm), specialist deep-fill SLCs or structural concrete topping compounds are used. These products are typically extended with 6–10 mm pea gravel or coarse aggregate on-site to reduce cost and control heat of hydration in deeper pours. They are used for infilling service trenches, building up levels where slabs have been ground down, levelling stepped slabs, and creating structural toppings over existing concrete substrates where a bonded overlay approach is preferred over a full slab pour. In Australia, Ardex Pandomo, Mapei Topcem, and Weber floor 4320 are examples of deep-fill SLC products; their application requires specialist experience and appropriate substrate preparation including mechanical keying and bonding agents.
Timeline is indicative for a standard 5–10 mm cement-based SLC at 20°C — rapid-setting products achieve tile-ready in 2–4 hrs; gypsum screeds require significantly longer drying time before sealed finishes. Always confirm with product TDS.
Calculating the correct quantity of self-levelling compound required for a project is straightforward once the area and average depth are established. Coverage rates for standard SLC products are typically expressed as kg per m² per mm of depth — most cement-based SLCs have a coverage rate of approximately 1.5–1.7 kg/m²/mm. This means a 20 kg bag at 5 mm depth covers approximately 12.5–13.5 m², while the same bag at 10 mm depth covers approximately 6–6.5 m². Always order 10–15% additional material to account for waste, overpour, substrate absorption, and the need to complete each area in a continuous pour without running out mid-application. Running out and stopping mid-area creates a pour joint (a visible line in the surface) that is very difficult to eliminate.
| SLC Type | Depth Range | Walk-on Time | Tile-Ready | Wet Area Suitable | Best For |
|---|---|---|---|---|---|
| Standard Cement-Based | 2–25 mm | 2–4 hours | 24 hours | Yes | General concrete levelling, tile prep, commercial floors |
| Rapid-Setting (CAC/CSA) | 2–20 mm | 30–90 min | 2–4 hours | Yes | Fast-track refurbishment, retail, hospitals, minimal downtime |
| Flexible / Polymer-Modified | 1–10 mm | 2–3 hours | 24 hours | Yes | Timber floors, existing vinyl, particleboard, movement-prone substrates |
| Gypsum / Anhydrite Screed | 25–80 mm | 12–24 hours | 3–7 days/10mm | No — dry areas only | Underfloor heating, large-area flat floors, commercial interiors |
| Deep-Fill (Aggregate Extended) | 25–80 mm | 4–8 hours | 48–72 hours | Yes (cement-based) | Infilling trenches, large level differences, structural topping |
| Skim / Finishing Compound | 0.5–5 mm | 1–2 hours | 4–8 hours | Yes | Final surface smoothing, feathering out, imperfection filling |
| Underfloor Heating SLC | 3–30 mm over element | 24 hours | 48 hours (then commission heating) | Check TDS | Encapsulating electric mats/cables and hydronic heating pipes |
The substrate — the existing floor onto which the SLC is applied — determines the choice of product, primer, surface preparation method, and maximum application depth. The most common Australian substrates for SLC application are concrete slabs (by far the most frequent), timber floors (plywood, particleboard, tongue and groove hardwood), and existing floor coverings (vinyl tiles, ceramic tiles, terrazzo). Each substrate has specific requirements that must be followed. Applying SLC over an inadequately prepared or unsuitable substrate — particularly over unsecured timber or moisture-affected surfaces — is the leading cause of SLC failure in Australian residential and commercial floor projects.
Self-levelling compound failures in Australian floor projects are almost always caused by one of three root causes: inadequate substrate preparation, incorrect product selection, or deviating from the manufacturer's mixing and application instructions. Understanding the failure modes and their causes helps practitioners avoid repeating errors and diagnose existing problems correctly. When SLC fails, the floor finish above it (tiles, timber, vinyl) almost always also fails — creating expensive and disruptive remediation works. The following are the most frequently encountered SLC problems in Australian construction in 2026, with their typical causes and remediation approaches.
Ardex is one of Australia's leading SLC manufacturers. Their website provides Technical Data Sheets, application guides, substrate preparation guides, and product selectors for their full range of self-levelling compounds including K360, K16, K22, and Pandomo deep-fill systems.
Visit Ardex Australia →Mapei produces a comprehensive range of self-levelling compounds for the Australian market — including Ultraplan Maxi, Ultraplan Easy, Novoplan Easy, and Topcem deep-fill. Their technical support team provides specification assistance for complex substrate and depth requirements.
Visit Mapei Australia →AS 3740 (Waterproofing of Domestic Wet Areas) is the key Australian Standard governing the construction of wet areas including bathrooms and laundries — relevant to any SLC application in wet areas, specifying waterproofing requirements that must be applied over the cured SLC substrate.
Visit Standards Australia →