Surface Preparation Guide
Good surface preparation is the single biggest factor in how long a floor coating lasts. In short: the substrate must be structurally sound, clean, dry enough for the chosen system, and mechanically profiled so the coating can key in. Contamination, laitance and moisture are the three most common reasons coatings fail early.
1. Assess the substrate first
Before any preparation starts, understand what you are working with. Check the concrete's age and strength, look for cracks, spalling, previous coatings, oil staining and signs of moisture. A slab that is crumbling, oil-soaked or actively wet needs those problems solved before a coating goes anywhere near it.
Look specifically for laitance — the weak, dusty layer of fine cement and water that rises to a freshly finished slab. It looks like sound concrete but has almost no strength. Coat over it and the coating will lift, taking the laitance with it.
2. Clean and degrease
Remove dirt, dust and — critically — oil, grease and other contaminants. Oil that has soaked into concrete can wick back up through a fresh coating and destroy the bond. Degrease heavily contaminated areas and verify they are clean before moving on; badly saturated concrete may need to be cut out.
3. Prepare mechanically
Mechanical preparation opens the surface, removes laitance and weak material, and creates the profile a coating keys into. The common methods:
- Diamond grinding — versatile, controllable, good for smoothing and removing thin coatings and laitance.
- Captive shot blasting — fast on large open floors, produces a consistent textured profile ideal for thicker systems.
- Scarifying / scabbling — aggressive removal of thick coatings or heavily damaged surfaces, usually followed by grinding to refine the profile.
The right profile depends on the coating: thin roller coats need a finer profile, thicker self-levelling and screed systems need a more open one. Always vacuum thoroughly afterwards — grinding dust left on the floor is just another contaminant.
4. Test for moisture
Moisture is a leading cause of coating failure in tropical Singapore conditions. Ground-bearing slabs without an effective damp-proof membrane can drive moisture up through a coating, causing blistering and adhesion loss. Carry out a moisture assessment appropriate to the slab, and choose a system that suits the reading — some Rayson primers tolerate damp substrates, but none tolerate standing water or active ingress without a considered approach.
5. Repair before you coat
Reinstate cracks, spalls, joints and surface defects before coating — a coating follows the shape of what is under it and will not bridge a hole or a moving crack. Use an appropriate repair mortar such as Rayson MortarBond EM90 or a thixotropic compound like Rayson PatchBond TX80 for vertical and overhead repairs, and allow repairs to cure before overcoating.
6. Prime, then proceed
With the surface sound, clean, profiled and repaired, prime with a Rayson primer matched to the substrate and its moisture condition. The primer seals porosity, binds the surface and creates the bond the rest of the system relies on. Only then apply the body coat and finish.
An acceptance-criteria mindset
Treat each stage as a checkpoint, not a box to tick: is the surface sound, clean, dry enough and correctly profiled before the next coat goes on? Catching a problem at preparation stage costs minutes. Catching it after the floor has failed costs the whole floor.
Frequently asked questions
Why is surface preparation so important?
A coating can only be as good as its bond to the surface. Most premature coating failures — peeling, blistering, delamination — trace back to preparation, not the product. Time spent on preparation is the cheapest insurance a floor gets.
Is acid etching a good way to prepare concrete?
Acid etching is generally discouraged for industrial coating work. It is hard to control, leaves residues that must be fully neutralised and rinsed, and does not remove contamination or weak laitance reliably. Mechanical preparation (grinding or shot blasting) gives a more consistent, sound profile.
How do I know if my slab is too damp to coat?
Carry out a moisture assessment before coating — relative humidity probes or calcium chloride tests are common methods. Different systems tolerate different moisture levels, and some Rayson primers accept damp (not wet) substrates. If readings are borderline or you have no damp-proof membrane, contact our technical team before specifying.
Can Rayson advise on preparation for my project?
Yes. Tell us the substrate, its age and condition, and the environment it serves, and we will advise on a suitable preparation and system. Contact us on +65 9821 9129 or [email protected].