Screeding FAQ: Every Question About Floor Screeding Answered

This page answers the most frequently asked questions about floor screeding in the UK. Every answer is written by screeding.com — BS 8204 certified screeding contractors with over a decade of experience installing liquid screed, sand and cement screed, and resin flooring on residential and commercial projects across the UK.

What is floor screeding?

Floor screeding is the process of applying a smooth, level layer of material over a structural floor base to create a flat, even surface suitable for floor finishes such as tiles, engineered timber, vinyl, LVT, or resin. Screed is typically applied at depths of 25mm to 75mm depending on the type and application. The most common screed types used in the UK are liquid anhydrite screed and sand and cement screed.

What is the difference between screed and concrete?

Concrete is a structural material used to form the base slab of a building. Screed is a finishing layer applied on top of the concrete to create a smooth, flat surface for floor finishes. Concrete contains coarse aggregate and is designed for structural load-bearing. Screed uses finer aggregate, is laid thinner, and is designed for flatness and surface finish rather than structural strength.

How much does screeding cost per m² in the UK?

Screeding costs in the UK typically range from £15 to £28 per m² depending on screed type, depth, and area. Liquid anhydrite screed costs approximately £15–25 per m² for residential projects at standard depths. Sand and cement screed costs approximately £18–28 per m². Fast-drying screed attracts a premium of 20–40% over standard liquid screed. Larger commercial areas attract lower per-m² rates due to the efficiency of pump installation.

How long does liquid screed take to dry?

Liquid anhydrite screed dries at approximately 1mm per day up to 40mm depth, then more slowly beyond that. A 35mm liquid screed will typically take 35–40 days to be ready for floor finishes under normal UK conditions (15–20°C). Fast-drying liquid screed formulations can reduce this to 7–14 days at the same depth. Drying time is affected by depth, temperature, ventilation, and whether underfloor heating is present.

How long does sand and cement screed take to dry?

Sand and cement screed dries at approximately 1mm per day throughout the full depth. A 50mm unbonded screed will take approximately 50 days. A 75mm floating screed will take approximately 75 days under normal UK conditions. Always moisture-test before laying floor finishes — the screed may feel dry to the touch long before it has released sufficient moisture for sensitive floor coverings.

What is the best screed for underfloor heating?

Liquid anhydrite screed is the industry-recommended choice for underfloor heating in the UK. It flows around and under UFH pipes, eliminating air voids that reduce heat transfer. Its thermal conductivity is higher than sand and cement, meaning the system responds faster and runs more efficiently. It can be laid at 25mm above the pipe — significantly thinner than the 65–75mm required for sand and cement floating screed — reducing floor build-up and preserving ceiling height.

What is SR1 and SR2 surface regularity?

SR1 and SR2 are surface regularity classifications defined by BS 8204. SR1 is the higher standard, requiring a maximum 3mm deviation measured under a 2m straightedge. SR2 allows a maximum 5mm deviation. SR1 is required for direct-stick floor finishes including LVT, engineered timber, and resin floors. Liquid screed achieves SR1 as standard. Sand and cement screed typically achieves SR2 and requires additional grinding to reach SR1.

What is BS 8204?

BS 8204 is the British Standard governing the specification, design, and installation of screeds in the UK. It covers all screed types including sand and cement, anhydrite, and pumpable self-smoothing screeds. It sets minimum depths, mix specifications, substrate preparation requirements, and surface regularity standards. Compliance with BS 8204 is typically a contractual requirement on commercial projects, and a BS 8204 compliance certificate is issued by the screeding contractor on completion.

What is laitance and does it need to be removed?

Laitance is a weak, powdery layer that forms on the surface of cement-based and anhydrite screeds as they dry. It consists of fine cement particles and mineral salts drawn to the surface by rising water. Laitance must be removed before any adhesive-fixed floor finish is applied — tiles, LVT, engineered timber, resin — otherwise adhesive failure will occur. It is removed by light sanding or diamond grinding. On anhydrite screed, laitance removal is mandatory before priming and bonding any floor finish.

How soon can you walk on fresh screed?

Liquid screed can typically be walked on with soft-soled boots after 24–48 hours under normal UK conditions. Sand and cement screed also achieves light foot traffic after 24–48 hours. Neither type should have wheeled traffic or materials dragged across them for at least 7 days. Full structural cure takes 28 days for both types, though drying for floor finishes takes considerably longer depending on depth.

What screed depth do I need?

Screed depth depends on the type and application. Liquid screed: 25mm minimum over UFH pipes, 30–35mm for floating applications without UFH. Sand and cement bonded screed: 25–40mm. Sand and cement unbonded screed: 50mm minimum. Sand and cement floating screed over insulation or UFH: 65–75mm minimum. These depths are set by BS 8204 and must not be reduced without specialist advice.

What is anhydrite screed?

Anhydrite screed is a type of liquid screed that uses calcium sulphate (anhydrite) as its binder rather than Portland cement. It is self-levelling, pumpable, and achieves SR1 surface regularity as standard. Anhydrite screed is the most widely used liquid screed type in the UK, sold under brand names including Gyvlon and Cemfloor. It requires laitance removal and specialist priming before floor finishes are applied, and must be commissioned before UFH systems are activated.

Have a question not answered here? Ask our AI Screed Advisor, available 24/7 on the screeding.com homepage — or ring us directly on 07500 005328.