mineral / Cementitious / Concrete/Masonry
Screed/Render System
Cement-based leveling and finishing system for floors and walls
Atlas code
MIN-CEM-SCR-001
At-a-glance signals
Cement-based leveling and finishing system for floors and walls
Overview
Executive summary
Cement-based levelling and finishing systems applied to floors (screed) and walls (render) to provide smooth, durable, and weather-resistant surfaces. Floor screeds are sand-cement mixes (typically 1:3 to 1:5 by volume) applied at 15-75 mm thickness over concrete substrates to level floors before final finishes such as tiles, vinyl, or timber flooring. Wall renders are cement-sand-lime mixes (typically 1:1:6 to 1:0.5:4.5) applied in 2-3 coats at 10-20 mm total thickness to masonry or concrete substrates to provide a weatherproof, aesthetically finished exterior or interior surface. Products range from traditional site-mixed sand-cement screeds to factory-premixed polymer-modified renders, self-levelling compounds, and insulated render systems (EPS/XPS backed). Compliant with AS 3958.1 (ceramic tiling substrates), AS 2311 (painting of buildings), and NCC requirements for external wall finishes. Cement render is exempt from NCC fire hazard property requirements under NCC Specification C1.10 alongside plaster, concrete, and ceramic tile.
Best when…
- Versatile finishing system suitable for both floors (screed) and walls (render) across all building types.
- Non-combustible material exempt from NCC fire hazard property requirements under Specification C1.10.
- Wide range of textures, colours, and finishes available from smooth to heavily textured coatings.
- Relatively low material cost compared to alternative wall finishes and floor levelling systems.
- Long service life (20-50+ years) when properly applied to suitable substrates with appropriate maintenance.
Top advantages
- 01 Versatile finishing system suitable for both floors (screed) and walls (render) across all building types.
- 02 Non-combustible material exempt from NCC fire hazard property requirements under Specification C1.10.
- 03 Wide range of textures, colours, and finishes available from smooth to heavily textured coatings.
- 04 Relatively low material cost compared to alternative wall finishes and floor levelling systems.
- 05 Long service life (20-50+ years) when properly applied to suitable substrates with appropriate maintenance.
Top limitations
- 01 Susceptible to cracking from shrinkage, substrate movement, and thermal cycling without proper joint detailing and reinforcement.
- 02 Requires skilled application for consistent thickness, flatness, and surface quality — poor workmanship is a common cause of failure.
- 03 Traditional sand-cement screeds require extended curing times (28 days minimum) before final floor finishes can be applied.
- 04 Exterior cement renders are moisture-sensitive — water ingress behind render causes delamination and substrate damage.
- 05 Limited flexibility — rigid cement-based renders cannot accommodate significant structural movement without cracking.
Technical
Physical ·9
- Density
- 1800-2200 kg/m3 Standard sand-cement screed/render. Lightweight screeds with perlite or vermiculite 600-1400 kg/m3. Self-levelling compounds ~1800-2000 kg/m3.
- Specific gravity
- 1.8-2.2 Standard sand-cement mix. Derived from density.
- Porosity
- 15-25 % Highly variable depending on water-cement ratio, compaction, and mix design. Polymer-modified renders have lower porosity.
- Water absorption
- 5-15 % Traditional cement render is porous and absorbs water. Polymer-modified and acrylic renders have significantly lower absorption (2-5%). Waterproofing additives further reduce absorption.
- Hardness
- 3-5 Mohs Varies with cement content and aggregate type. Typical cured sand-cement mortar.
- UV resistance
- good Plain cement render is UV stable. Pigments may fade over time. Acrylic render coatings have good UV resistance when properly formulated.
- Chemical resistance
- moderate Moderate resistance. Vulnerable to acid rain, sulphate attack, and chloride environments. Polymer-modified renders improve chemical resistance.
- pH tolerance
- 6-13 pH Cement-based materials are naturally alkaline (pH 12-13). Resistant to alkaline conditions; vulnerable to acid attack below pH 5.
- Surface roughness
- 10-5000 um Highly variable by finish type. Steel-trowelled smooth ~10-50 um. Float finish ~100-500 um. Textured render ~500-5000 um.
Mechanical ·7
- Tensile strength
- 0.5-2.0 MPa Tensile strength of cement mortar. Low tensile strength is the primary cause of shrinkage cracking.
- Compressive strength
- 1-30 MPa Sand-cement screeds: commonly 1-5 MPa (highly variable with mixing quality). Proprietary screeds: 15-30 MPa. Cement render: 5-15 MPa depending on mix. Per ARDEX Australia TB159 and Screedflow technical data.
- Flexural strength
- 1.0-5.0 MPa Varies significantly with mix design. Standard 1:3 cement:sand screed ~1-3 MPa. Polymer-modified screeds ~5-8 MPa. Per ARDEX Australia technical data.
- Shear strength
- 1.0-3.0 MPa Bond shear strength to substrate is critical — typically 0.3-0.5 MPa for cement render to masonry. Internal shear strength of mortar ~1-3 MPa.
- Poisson's ratio
- 0.15-0.25 Typical value for cement mortar. Per engineering references.
- Impact resistance
- moderate Moderate. Thin renders (10-20 mm) are vulnerable to impact damage, particularly at corners and edges. Screeds are more robust due to greater thickness.
- Creep resistance
- moderate Cement mortar exhibits some creep under sustained load, similar to concrete but with higher variability due to mix inconsistency.
Sustainability & Health
Embodied carbon & energy ·7
- Embodied carbon
- 0.12-0.22 kg CO2-eq/kg Varies with cement content. Standard 1:3 cement:sand mortar ~0.12-0.22 kg CO2-eq/kg. Lime-cement blends lower. Per ICE database v2.0 mortar model. Higher cement content = higher embodied carbon.
- Carbon footprint
- 5-15 kg CO2-eq/m2 For 20 mm render coat at ~2000 kg/m3 density = 40 kg/m2 mortar. At 0.15 kg CO2-eq/kg = ~6 kg CO2-eq/m2. For 50 mm screed = ~15 kg CO2-eq/m2.
- Embodied energy
- 1.0-1.5 MJ/kg Per ICE database v2.0. Standard cement mortar. Varies with cement content and aggregate source.
- Water footprint
- 100-200 L/kg Water for mixing (water-cement ratio 0.4-0.6) plus water for curing. Factory-premixed products include manufacturing water.
- Recycled content
- 0-20 % Standard cement mortar has low recycled content. Supplementary cementitious materials (fly ash, slag) can replace 20-40% of cement. Recycled sand can partially replace natural sand. Not yet common in Australian render products.
- Renewable content
- 0 % Cement mortar is entirely inorganic with no renewable content.
- Circular score
- 4 /10 Cement render/screed is difficult to separate from substrates for recycling. Demolished render becomes construction waste, potentially crushed for fill material. Low circular economy performance.
Compliance & Fire
Fire performance ·6
- Combustibility class
- Non-combustible (NCC exempt) Cement render is exempt from NCC fire hazard property requirements under Specification C1.10 (now Specification 7). Listed alongside plaster, concrete, terrazzo, and ceramic tile.
- Fire resistance level
- System dependent (contributes to wall FRL) FRL (minutes) Render itself does not have an independent FRL rating — it contributes to the fire resistance of the overall wall system. A 20 mm cement render layer on masonry or concrete adds to the insulation and integrity rating of the wall assembly. Some proprietary fire-rated render systems are tested to AS 1530.4.
- Ignition temp
- Not applicable degC Cement mortar does not ignite — inorganic non-combustible material.
- Flame spread index
- 0 Zero — cement mortar is non-combustible.
- Smoke dev. index
- 0 Zero — cement mortar produces no smoke.
- Heat release rate
- 0 kW/m2 Non-combustible material — zero heat release.
Cost & Lifecycle
Capex & lead time ·6
- Material cost (range)
- 5-40 AUD/m2 Material only. Sand-cement render: $5-15/m2. Acrylic render system: $15-35/m2. Floor screed: $10-25/m2 (25-50 mm thickness). Self-levelling compound: $20-40/m2. 2024-2025 pricing.
- Material cost (per unit)
- 8-15 AUD/m2 Mid-range external cement render system (3-coat sand-cement-lime), material only.
- Lead time
- 1-5 days Materials readily available ex-stock from building suppliers. Premixed render products from Dulux AcraTex, Rockcote, Boral etc. available within 1-5 days.
- Lifecycle cost
- 100-250 AUD/m2 30-year analysis for external render including initial application, two repaints, and minor crack repairs. Floor screeds: initial cost only as they last the building life.
- Annual maintenance
- 1.00-5.00 AUD/m2/year External render: periodic repainting and crack repair. Floor screed under finishes: nil ongoing maintenance.
- Market availability
- excellent Widely available across all Australian states and regions. Basic materials (cement, sand, lime) available from all building suppliers. Proprietary render products available from major paint and building product manufacturers.
Service life & durability ·3
- Expected lifespan
- 20-50+ years Well-applied cement render on suitable substrate with appropriate maintenance. Acrylic renders may need recoating every 15-20 years. Floor screeds last the life of the building if properly laid.
- Maintenance interval
- 5-10 years External renders: inspect for cracking annually, repaint every 7-15 years, repair cracks promptly to prevent water ingress. Floor screeds: no maintenance required under floor finishes.
- Warranty period
- 5-15 years Proprietary render system warranties (e.g. Dulux AcraTex, Rockcote). Traditional sand-cement render has no standard warranty — quality depends on application.
Layer D
Where it's used
External wall rendering
Floor screeding
Internal wall finishing
Insulated render systems (EIFS)
Self-levelling floor compounds