Which screed should you choose for your project? The five questions that actually decide, a decision table by situation, and the minimum thicknesses required in Belgium under TV 189.
There is no best screed in the abstract. The choice turns on five site parameters: the presence of underfloor heating, the height available, exposure to water, the time before the floor covering goes down, and the loads to be carried. Answer those five questions and the type of screed almost always follows by itself.
The essentials in three points
The type of screed is not an aesthetic choice nor a contractor's preference. It is the consequence of physical constraints. Here are the five questions, to be asked in this order, because each of them eliminates options.
If so, the thermal conductivity of the screed becomes the first criterion. A flow screed encases the pipes without air pockets and transfers heat faster than a screed levelled with a rail, which always traps some air around the circuits.
Anhydrite is the reference on this point. It also allows a reduced thickness above the pipes, which lowers inertia and shortens the time to reach temperature. Our guide to screeds with underfloor heating sets out the commissioning protocol.
This is the question that blocks the most renovation projects. The available height is measured between the existing substrate and the finished level imposed by door thresholds, skirtings and junctions with adjoining rooms.
Into it must fit the insulation, the screed and the floor covering. When the total exceeds the clear height, it is no longer comfort that decides but geometry. Below 6 cm available, the options narrow sharply.
Bathroom, utility room, garage, cellar, terrace: in all these situations anhydrite is ruled out. Calcium sulphate degrades under prolonged moisture, it loses cohesion and the screed breaks up.
This is not a precaution but a material contra-indication. For these rooms the question reduces to a choice between a traditional screed and a cement-based flow screed.
A screed is not ready when it is hard, it is ready when it is dry. These are two different things, and that misunderstanding causes more failures of bonded floor coverings than anything else.
An anhydrite screed of 5 cm can take several weeks to reach an acceptable residual moisture level, measured by the carbide method. If the programme does not allow for that, this type of screed is ruled out, whatever its qualities elsewhere. The subject is covered in detail in our article on drying times before tiling or wood flooring.
An ordinary dwelling presents no difficulty. A garage where a car is driven, a workshop with machinery, a storage area: these uses demand greater mechanical strength, obtained through more thickness, reinforcement or fibres.
The European standard EN 13813, applied in Belgium as NBN EN 13813, classifies screed mortars by compressive and flexural strength. It is that class which should appear on the quotation, not simply the word screed.
This table gives the type of screed that imposes itself in the configurations most common in Belgium. It does not replace an assessment on site, but it rules out the wrong paths.
| Site situation | Recommended screed | Minimum thickness | Point to watch |
|---|---|---|---|
| Underfloor heating, new build, large area | Anhydrite | Sufficient cover above the pipes | Long drying, sanding of laitance mandatory |
| Underfloor heating in a wet room | Cement-based flow screed | 5 cm floating | Thermally less effective than anhydrite |
| Renovation, under 6 cm available | Flow screed or dry screed | 3 cm bonded | Check the permissible load of the existing floor |
| Bathroom, utility room, cellar | Traditional or cement flow screed | 5 cm floating, 3 cm bonded | Anhydrite ruled out without exception |
| Terrace, garage, open shelter | Traditional cement screed | Above the indoor minimums | Fall mandatory, anhydrite ruled out |
| Garage, workshop, vehicle loads | Reinforced, mesh or fibres | Above the usual minimums | The strength class must appear on the quotation |
| Tight programme before floor covering | Traditional or cement flow screed | 5 cm floating | Anhydrite is the slowest to dry |
The traditional screed is a mix of sand, cement and water, levelled with a rail. It remains the most versatile choice: it tolerates moisture, it carries heavy loads, it can be laid outdoors and it dries faster than anhydrite.
Its two limitations are well known. Its flatness depends entirely on the skill of the team, and its shrinkage on drying calls for movement joints. For detail on its composition and uses, see our article on the traditional screed.
The anhydrite screed is a flow screed based on calcium sulphate. It self-levels, giving a flatness that hand levelling does not reach, and its near-zero shrinkage allows large areas without joints.
It imposes three constraints in exchange: long drying, sanding of the surface laitance before the floor covering goes down, and a strict prohibition in wet rooms. The full comparison is in traditional screed versus anhydrite flow screed, and the technical definition in the anhydrite screed entry.
The cement-based flow screed combines the self-levelling of a flow screed with the water resistance of cement. It is the answer to situations where you would want anhydrite but the room forbids it.
It performs less well than anhydrite with underfloor heating and calls for slightly more thickness, but it remains a sound compromise in a bathroom or utility room that demands high flatness. See the flow screed entry.
The reinforced screed takes the basis of a traditional screed and adds steel mesh or fibres. The reinforcement does not make the screed indestructible; it distributes stresses and limits the opening of shrinkage cracks.
It is justified in three cases: heavy loads, large continuous areas, and underfloor heating, where temperature variation works the screed continuously. The detail is in traditional, reinforced or flow screed.
The dry screed is not poured. It is made of boards laid over a bed of granulate, which removes all added water and therefore all drying. It is walkable immediately.
It is the solution for timber floors that cannot carry the weight of a wet screed, and for sites where the floor covering must follow straight away. Its load resistance is lower and it does not suit wet rooms. See dry screed: definition and advantages.
Choosing anhydrite without checking the programme. This is the most frequent error. The site is ready, the tiler is available, the screed is not. Residual moisture is not negotiable and forcing the installation ends in debonding or blistering.
Deciding the type of screed after ordering the insulation. The logical order is the reverse: the type of screed and its minimum thickness govern how much insulation can still be fitted beneath.
Accepting a price per square metre with no defined scope. A screed quotation may include or exclude substrate preparation, the edge strip, the membrane, the insulation, the sanding and removal of waste. Our article on the price of a screed per m2 in Belgium sets out the items to check before comparing two offers.
The five questions above rule out incompatible options. They do not replace checking the substrate, the real height and the existing moisture level, which is done on site.
If you are still hesitating between two types, describe the configuration to us: substrate, available height, presence of underfloor heating, intended floor covering and programme. We will tell you which solution fits and what it implies. Discover our screed laying service or request technical advice.
Last updated: September 2026. Sources: Buildwise (formerly CSTC/WTCB), Technical Note 189, Screeds for floor coverings, part 1, materials, performance, acceptance; TV 193, Screeds, part 2, installation; standard NBN EN 13813 on screed materials.
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