Traditional Screed or Flowing Screed? Getting Floors Level and Sound

A screed carries the floor finish, hides the services and sets the level. The two common types behave very differently on site and fail in different ways.

A screed is the layer between the structural slab and the floor finish. It levels out the structure, provides the falls where they are needed, covers pipework and conduits and gives the finish something sound to bond to. The practical choice is between a traditional sand and cement screed laid and compacted by hand, and a flowing screed poured as a liquid and allowed to find its own level. Both are used in the Kingdom and the decision affects programme, flatness and risk.

Traditional sand and cement screed at a glance

A semi dry mix laid, compacted and ruled off by hand to levels established by dots and screeds. It is familiar to every contractor, cheap in material, can be laid to falls, and can be built up to substantial thickness. Its quality depends almost entirely on the gang: the mix, the compaction, the levelling discipline and the curing all vary with who is laying it.

Flowing or self levelling screed at a glance

A pumpable liquid screed, commonly cement or calcium sulphate based, poured to a set level and allowed to flow out. It produces a flat surface quickly over large areas with little labour, reduces the risk of poor compaction, and suits thin build ups. It needs a sealed, prepared substrate, careful day joint planning, and attention to drying before finishes are laid.

Achievable flatness

Traditional sand and cement screed: Depends on the gang and the set out, so it varies from excellent to poor within the same building.

Flowing or self levelling screed: Consistently flat because the material levels itself, which removes most of the human variation.

Ability to form falls

Traditional sand and cement screed: Falls are straightforward, since the material is laid and ruled to whatever profile is marked.

Flowing or self levelling screed: Difficult, because the material flows level, so falls usually need to be in the structure or formed separately.

Labour and speed

Traditional sand and cement screed: Labour intensive and slow per square metre, which makes large areas expensive in time.

Flowing or self levelling screed: Fast over large areas with a small crew, though it needs pump access and preparation.

Risk of poor compaction

Traditional sand and cement screed: A real risk, and poorly compacted areas sound hollow, break up under load and fail under tiles.

Flowing or self levelling screed: Largely eliminated, since there is no compaction step to get wrong.

Preparation required

Traditional sand and cement screed: Needs a clean substrate and, for bonded screeds, a bonding treatment and a sound surface.

Flowing or self levelling screed: Needs the substrate sealed and all edges and penetrations closed, because a liquid finds every gap.

Drying before finishes

Traditional sand and cement screed: Drying time depends on thickness and conditions, and finishes laid too early trap moisture.

Flowing or self levelling screed: Drying is critical and some binder types are moisture sensitive, so the finish and adhesive must be compatible.

Cracking behaviour

Traditional sand and cement screed: Cracks from shrinkage, poor curing or restraint, and needs joints at the perimeter and over structural joints.

Flowing or self levelling screed: Shrinks less in some formulations but still needs perimeter isolation and joints over movement joints.

When traditional sand and cement screed wins

• Floors that need falls, such as bathrooms, balconies and plant rooms.
• Thick build ups where a large depth has to be made up over the structure.
• Projects with no access for pumped delivery or limited specialist availability.
• Situations where small areas are laid progressively rather than a whole floor at once.

When flowing or self levelling screed wins

• Large flat areas where speed and flatness matter more than falls.
• Thin build ups over a structurally sound and accurately cast slab.
• Floors receiving large format tiles or stone that demand tight flatness.
• Projects where consistency across many identical units is important.

How to decide

Use a traditional screed where you need falls, where the build up is thick, or where pumping is impractical, and then put the effort into the mix, the set out and the curing because those are what decide whether it survives. Use a flowing screed over large, flat, level areas, especially where large format tiles or stone will follow and flatness tolerance is tight, and where the substrate can be properly sealed. In a villa both often appear in the same building: a flowing screed across bedrooms and living areas, and traditional screeds in the wet rooms and on the balconies where falls are required. Whichever is used, the perimeter isolation and the joints over structural movement joints are not optional.

The evidence is measured, not visual. For flatness, ask for a survey against the specified tolerance using the correct straight edge length, recorded room by room, because a floor that is out of tolerance costs the tiling and joinery trades real money and that cost usually lands as a variation. For soundness, tap the whole area and map any hollow zones before a finish is laid. For moisture, require a recorded measurement before the floor covering goes down, using the method that the covering manufacturer accepts, since an adhesive or a timber floor laid over a damp screed is a failure that appears months later. Keep the records, because the next time a floor finish debonds the first question will be what the screed moisture was.

Domira builds and supervises projects across Saudi Arabia, and this is the level of detail its site teams work at. Send the drawings or the site, and Domira will tell you what the specification has to say before anyone prices it.