Surface preparation
Deciding how to treat laitance before floor coverings
A decision-focused guide to choosing an appropriate laitance treatment approach, rather than a single removal method.
Laitance, the weak surface layer that can form on some screeds, needs to be addressed before certain floor coverings are installed, but the right approach depends on several factors rather than one default method. What works for one flooring type or screed can be entirely unnecessary, or insufficient, for another.
This is about the decision-making process — what to consider and when — rather than a step-by-step removal procedure. The aim is to help a client or main contractor ask the right questions of both the screed installer and the flooring installer before assuming a particular treatment is required.
Because laitance treatment sits at the boundary between two trades, clear communication between the screed installer and whoever is installing the final floor covering is usually what determines whether the right decision is made at the right time.
Laitance treatment decisions — the points that decide it
- Whether laitance treatment is needed at all depends partly on the screed type and the flooring adhesive or covering being used.
- Timing matters: treating laitance too early, before the screed has adequately dried, can be less effective or counterproductive.
- Mechanical sanding is one common approach, chosen partly based on area size and practicality on site.
- The flooring installer's own requirements should be checked, since some coverings and adhesives are more sensitive to laitance than others.
- Dust control during treatment is a practical consideration, particularly in occupied buildings.
- A decision not to treat laitance should be based on the flooring manufacturer's guidance for the specific product, not assumed.
- The extent of laitance can vary across a single floor, so a visual and tactile check of the whole area is more reliable than spot inspection.
- Responsibility for laitance treatment — screed installer, flooring installer or a specialist preparation contractor — should be agreed and stated clearly.
- Programme allowance should be made for treatment and any subsequent cleaning or priming before flooring work begins.
Why the decision depends on the flooring, not just the screed
Some floor coverings and adhesive systems are largely unaffected by a thin laitance layer, while others require a fully sound, laitance-free surface for reliable bonding. This is why the flooring specification, not the screed alone, often drives the decision.
It is worth checking this early rather than assuming a default approach, since specifying and carrying out unnecessary treatment wastes time and cost, while missing a genuinely required treatment risks a flooring adhesion failure later.
Getting the timing right
Treating laitance is generally more effective once the screed has reached an appropriate stage of drying, and coordinating this with the flooring installer's programme avoids either delaying unnecessarily or treating the surface before it's ready.
Treating a surface too early, while it is still releasing significant moisture, can be less effective and may need repeating once the floor has dried further, so timing is usually agreed alongside the wider drying programme rather than fixed independently.
Choosing between treatment methods
Mechanical sanding is a common approach for larger areas, removing the weak surface layer to expose sound material beneath, while other preparation methods may be more appropriate depending on area size, access and the surface condition found.
The chosen method should be practical for the site conditions, including dust extraction and containment where the work is happening in an occupied or partially finished building.
Agreeing responsibility and programme allowance
Because laitance treatment sits between the screed and flooring trades, it is worth explicitly agreeing who is responsible for carrying it out and confirming it has been done to the required standard before flooring work is booked in.
Allowing time in the programme for treatment, any resulting dust or debris to be cleared, and where relevant a priming step, avoids a last-minute scramble if treatment is found to be necessary once the flooring installer inspects the floor.
Deciding whether your floor needs laitance treatment?
Tell us your screed type and intended flooring and we'll advise on a sensible approach.
Or call our landline on 01392 237700
In short
A decision-focused guide to choosing an appropriate laitance treatment approach, rather than a single removal method.
Laitance treatment decisions — your questions
Deciding whether your floor needs laitance treatment?
Tell us your screed type and intended flooring and we'll advise on a sensible approach.