Cement screed or self-levelling compound: what each does and what to check before quoting
An uneven commercial floor may need a new floor build-up, a smoothing layer, or repairs before either can be installed. Traditional cement screeds and self-levelling underlayments often serve different purposes, but product ranges overlap. Start with the floor condition, required height and final covering, then check the product proposed.
Two different jobs
A traditional screed commonly forms the floor build-up and base for a covering. A self-levelling underlayment commonly smooths a prepared floor before the covering. These are starting descriptions, not universal definitions: some flowing screeds and levelling systems allow greater depths than thin smoothing products.
Check the named product, permitted thickness, substrate and intended use. Self-levelling does not mean no tools or skill are needed: spreading and finishing follow the manufacturer’s instructions. It does not repair a structural defect in the slab.
Omni publishes cement screed flooring as a service. Ask the team to assess the floor and confirm which scope it can quote; this guide does not promise every levelling system is offered.
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Side-by-side comparison
Use this table to frame the conversation, not to decide alone. The right answer depends on the floor, the finish and the building rules. Where a figure matters, it comes from the manufacturer's data sheet for the product actually proposed.
| Question | Cement screed | Self-levelling compound |
|---|---|---|
| Main purpose | Sets the floor to its design height and forms the base for the specified flooring | Smooths and levels a sound, rigid floor before the final covering |
| Build-up | A laid layer, which can be bonded to the slab, separated from it, or floating on insulation | A flowing smoothing layer; permitted depth and build-up vary by product |
| Can it correct a big height difference? | That is a typical job for screed, subject to the design height and the thickness the system allows | Each product has its own limits, so check the data sheet for the one proposed |
| Condition of the floor underneath | Slab must be assessed, cleaned and prepared for the chosen type of screed | Floor must be sound, clean and primed as the manufacturer requires |
| Final finish | Can be a base for tiles, vinyl and other flooring, or finished as a visible floor if properly sealed | Usually a smooth base under the final covering; some products are not wearing surfaces |
| Main risks | Shrinkage cracking, curling and flooring laid before the screed is ready | Poor adhesion on a dirty or unprimed base, moisture from below, cracks and movement joints carried through |
What the floor underneath has to be like
Manufacturer instructions set the requirements for a sound, stable and clean substrate, compatible primer and any bond test. Mapei’s underlayment guide explains why old adhesives, coatings and weak layers need checking. Read the current instructions for the named product rather than applying one manufacturer’s rules to all systems.
An existing screed or covering is not automatically a suitable base. Ask what remains, what must be removed, and how moisture and adhesion will be checked. Identify suspect old materials before disturbing them; a foreign manufacturer’s age threshold is not a Singapore clearance rule.
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Moisture: test it, do not guess
Confirm the moisture-testing method and acceptance limit for both the preparation product and final covering. A dry-looking surface or fixed number of days does not by itself show readiness.
Mapei’s screed guidance discusses curing, shrinkage and residual moisture. Ask who checks readiness and what happens if results are outside the permitted limit. Thickness and site conditions affect the programme.
Cracks and movement joints
Ask how cracks will be assessed and treated, and how movement joints will continue through the new layers. Mapei’s guidance warns that levelling does not eliminate slab movement and movement joints must not simply be bridged.
If structural movement is suspected, obtain advice from building management and a suitably qualified professional before deciding on flooring. A cosmetic topping does not establish that a slab is safe.
Finish and use: not every product is a wearing surface
Some levelling products are underlayments that must be covered; others are designed as wearing surfaces. Indoor, outdoor, wet-area and loading requirements vary. Check the current sheet for the exact product.
The Sika documents illustrate differences in product purpose and traffic limits. If screed will remain visible, ask whether sealing or another finish is included, as Omni’s screed page advises. Loading bays and wet areas need their own assessment.
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What to put on the quotation
Send the same brief to each contractor and ask for the points below in writing. A line that is missing is a question to ask, not something to assume is included.
- Which product is proposed (cement screed type or named levelling compound), with the data sheet.
- Floor area, existing floor level and the finished level wanted, so the thickness is based on the site and not a guess.
- Whether the screed is bonded to the slab, separated from it or floating, and why.
- How the existing floor will be prepared: removal of old coverings and adhesive, cleaning, priming and any bond test.
- How moisture will be tested, against which limit, and who signs off that the floor is ready for the finish.
- What is done about existing cracks and movement joints.
- Who removes the old flooring and debris, and who handles disposal.
- What finish is included and what the floor can be used for until it is ready.
- Whether any approval, landlord consent or building rule applies before screed or levelling works start.
Check your lease for reinstatement requirements
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When a site assessment comes before a quote
Request a site assessment where levels vary significantly, cracks or hollow areas are visible, old coverings remain, damp staining is present, or the finish is moisture-sensitive. Photographs can support an initial enquiry, but unresolved conditions should remain explicit assumptions.
Also ask for an assessment if the unit is under a lease with reinstatement terms. The landlord may require the floor returned to a stated condition, and a new layer can change door clearances, thresholds and levels at the unit boundary. Check the lease, and where a rule is unclear, ask your landlord or Qualified Person before you commit.
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Send Omni Contractors your floor details
For a screed quotation, send the area, photographs of the floor and cracks, existing covering if known, planned finish and any lease requirements. Ask which preparation, removal and finishing works Omni can include after assessment.
If you are not sure whether a floor needs screed or only levelling, say so. That is a normal first question, and it is better to ask it before the finish is bought.
Sources
Read for this guide. Statements and figures in manufacturer documents apply to that manufacturer's products and systems, not to every screed or levelling compound.
Mapei Reference Guide RGF0214: Surface-Preparation Requirements for Self-Leveling Underlayments, read 16 October 2026. Supports the substrate, priming, bond test, moisture testing, cracks, joints and interior-use statements for Mapei products.
Mapei Technical Notebook: Installation of Heated Screeds and Substrates for Laying Floors (09/13), read 16 October 2026. Supports the definition of a screed, the bonded, unbonded and floating types, and the points on curing, shrinkage cracking and residual moisture.
Sika brochure: Sikafloor Level Underlayment, read 16 October 2026. Supports the description of self-levelling compounds as thinner in consistency than cement screeds and filling uneven areas before the final covering.
Sika Levelling Compound product data sheet, May 2018, version 01.01, read 16 October 2026. Supports the example of a product limited to indoor use, light commercial and foot traffic only. This is one product only.
Is self-levelling compound a replacement for cement screed?
Not automatically. Traditional screed commonly provides floor build-up and a base; a self-levelling underlayment commonly smooths a prepared base. Product ranges and permitted depths overlap. Choose from the floor condition and instructions for the named system.
Can I lay a self-levelling compound over my existing floor?
Only if the manufacturer's data sheet for that product allows it for your floor type and the floor is sound, clean, primed and tested. Mapei's guide, for example, lists coverings its products must not be laid over. Ask the contractor to name the product and show the data sheet.
How long must I wait before laying the final floor?
It depends on the product, the thickness, site conditions and the flooring. There is no single number. The waiting time should come from the product data sheet and the flooring manufacturer's moisture requirement, confirmed by a moisture test on your floor.
Will the new layer hide cracks in my existing floor?
Not reliably. Manufacturer guidance says existing cracks should be assessed and repaired first, that expansion and movement joints must be carried through, and that moisture coming up through cracks is not covered. Ask the contractor what will be done at each crack and joint.
Can screed or levelling compound be left as the finished floor?
Sometimes, depending on the product. Omni's cement screed page says screed can be the visible floor if properly finished or sealed. Some levelling compounds are rated for foot traffic only and are meant to be covered. Check the data sheet and ask what finish is included.
What should I send Omni Contractors for a screed quotation?
Send the area, photos including cracks, existing covering, planned finish and lease requirements. Ask Omni which scope it can quote after a site assessment.
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- Floor plan or unit size
- Photos of each room and the ceiling
- Lease reinstatement clause or handover checklist
- Handover or move in date
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