Anhydrite Screed vs Cement Screed: Which Fits?

A screed choice made at the start of a build can affect every trade that follows. The decision between anhydrite screed vs cement screed influences programme dates, underfloor heating performance, floor-covering preparation and how the finished floor stands up to its environment.

Neither material is automatically the better option. Anhydrite and cementitious liquid screeds both produce level, high-quality floors when specified and installed correctly. The right choice depends on the floor build-up, room use, drying allowance, floor finish and site conditions.

Anhydrite Screed vs Cement Screed: The Core Difference

Anhydrite screed is a calcium sulphate-based, flowing screed. It is commonly supplied as a liquid and pumped into place, where it flows around pipework and across the floor area to create a smooth, flat surface. Its low shrinkage is one reason it is widely used on larger areas and underfloor heating projects.

Cement screed uses cement as its binder. Modern cementitious liquid screeds are also pump-applied and self-compacting, so they should not be confused with traditional semi-dry sand and cement screed. They can provide a highly level finish while offering different drying and moisture-handling characteristics.

The practical distinction is this: anhydrite is often selected for its excellent flow, consistency and performance over underfloor heating, while cementitious screed is often favoured where faster drying, external moisture risk or wet-area suitability is a priority.

Performance Over Underfloor Heating

Both screed types work well with water-based underfloor heating when the system is designed as a complete floor build-up. A screed needs to fully encapsulate the pipes, transfer heat evenly and protect the installation from point loading.

Anhydrite has long been a popular choice for underfloor heating because it flows closely around the pipework with minimal voids. This close contact supports efficient heat transfer and a uniform floor temperature. Its low-shrinkage properties can also allow large bays with fewer joints, subject to the design and manufacturer guidance.

Cementitious liquid screed also offers strong thermal performance. It is particularly useful where the project needs a faster route to commissioning the heating system and preparing for the final finish. The exact thermal response will depend on screed depth, insulation, pipe spacing, flow temperature and the chosen floor covering - not the screed alone.

For either system, pipework must be securely fixed, pressure-tested before the pour and protected during subsequent work. Heating should only be commissioned in line with the screed manufacturer’s stated curing and heat-up procedure. Turning underfloor heating on too early or increasing temperatures too quickly can damage a floor that was otherwise correctly installed.

Drying Time Is Not the Same as Curing Time

Drying is where many projects lose time. A screed may be firm enough to walk on relatively soon after installation, but that does not mean it is ready for tiles, timber, vinyl or carpet.

Anhydrite screed needs controlled drying and adequate ventilation. Its drying rate is affected by thickness, temperature, humidity and site conditions. Natural drying can take longer than clients expect, particularly during colder or wetter months. Dehumidification and carefully managed underfloor heating can assist, but only where the product guidance permits it.

Cementitious liquid screeds are often specified where a shorter drying programme is required. Some proprietary formulations are designed to reach low moisture levels more quickly than standard screeds. That can be valuable on developments, extensions and refurbishments where follow-on trades have fixed dates.

However, faster-drying does not mean no testing. Before any floor finish is laid, the screed must be checked using an appropriate moisture test and assessed against the flooring manufacturer’s requirements. Guessing from the calendar, surface colour or how hard the floor feels is a common cause of adhesive failure and damaged finishes.

Moisture Resistance and Room Use

Cementitious screed is generally the more suitable option where there is a greater risk of moisture exposure. Bathrooms, wet rooms, utility areas and spaces with uncertain drying conditions may favour a cement-based system, particularly where the final waterproofing and floor-finish specification requires it.

Anhydrite screed should not be exposed to prolonged moisture or used where it may remain wet. It can still be used successfully in many residential rooms, including kitchens and bathrooms, but the floor build-up must be properly planned. This includes suitable waterproofing, compatible adhesives and clear control of moisture before finishes are installed.

This is not simply a choice between “dry rooms” and “wet rooms”. A well-designed bathroom floor may be appropriate for either screed, while an apparently dry ground-floor renovation with residual moisture in the slab may need a more cautious specification. The substrate, damp-proofing arrangement and proposed finish all matter.

Surface Preparation Before Floor Coverings

Anhydrite screed forms a fine surface layer known as laitance as it dries. This layer must normally be removed by mechanical sanding once the screed is sufficiently dry, followed by thorough vacuuming. Skipping this stage can compromise the bond between screed, primer, adhesive and final floor covering.

Cementitious screeds do not have the same calcium sulphate laitance requirement, although they still need proper inspection and preparation. Surface contamination, weak material, curing compounds, dust and unevenness must be dealt with before flooring starts.

The adhesive system is equally important. Calcium sulphate screeds require compatible primers and adhesives, especially beneath tiles and resilient finishes. A flooring contractor should know exactly which screed has been installed, its measured moisture condition and the preparation already completed. That handover detail prevents costly assumptions later in the programme.

Thickness, Joints and Floor Build-Up

Required screed thickness is determined by the product, loading, substrate and whether underfloor heating is present. It is not safe to choose a thickness from a generic rule of thumb. Some systems are designed for thinner applications, while others need greater cover over heating pipes or additional depth to meet loading requirements.

Anhydrite can be advantageous across large, open domestic and commercial floor areas because of its flow and low shrinkage. Cementitious liquid screed can be equally practical where the build-up is tight or the programme calls for earlier drying. In both cases, movement joints in the building must be respected, and perimeter edging is required to allow for movement.

The screed should be considered alongside insulation compressive strength, membrane details, door thresholds, stairs, finished floor levels and the planned floor covering. A few millimetres missed at design stage can create problems at kitchen plinths, patio doors or bathroom transitions.

Which Screed Is Right for Your Project?

Anhydrite is often a strong fit for a new-build home, large extension or development with underfloor heating, a stable programme and a need for a very flat finish. It is particularly effective where its flowing nature can speed installation across substantial areas.

Cementitious liquid screed is often the better fit where drying time is tight, the room has a higher moisture risk or the flooring specification calls for a cement-based substrate. It can also be the sensible choice for phased works where programme control is critical.

The best decision should be based on the complete specification, rather than one headline benefit. Consider the following together:

• the required finished floor level and available screed depth;

• underfloor heating design, pipe coverage and commissioning date;

• drying conditions and the date flooring is due to be laid;

• room use, moisture exposure and waterproofing details;

• the final floor finish, adhesive and manufacturer requirements.

Getting the Specification Right Before the Pour

A liquid screed installation is quick once pumping starts, but the preparation cannot be rushed. The substrate should be checked, insulation boards tightly fitted, edge strips installed, membranes detailed correctly and heating pipes securely fixed. Site access, pump location and the order of work also need to be agreed in advance.

For builders and developers, coordinating screed and underfloor heating through one specialist helps avoid gaps between trades. For homeowners and self-build clients, it provides a clearer route from floor build-up design to a level surface ready for finishing. Precision Screed assesses these details before installation so the selected system suits the project rather than forcing the project to suit the material.

Before placing an order, confirm the final floor finish, the available drying window and the environment each room will face. That conversation is far easier before the screed is poured than after a flooring contractor finds an incompatible substrate or a moisture reading that holds the project back.