Systems
Liquid Screed Beneath Resin Floor Coatings
Resin coatings demand a fully dry, mechanically prepared screed surface, since any residual moisture or laitance beneath a coating can cause adhesion failure or blistering.
Specifying a screed ahead of a resin finish?
We'll plan the screed programme with your resin applicator's moisture and preparation requirements in mind — call 07791 510849.
Or call our landline on 01392 237700
Resin flooring is an unforgiving finish when it comes to what's beneath it. Unlike a floating floor covering with some tolerance for minor imperfections, a resin coating is bonded directly to the screed surface, so moisture content, laitance, surface profile and flatness all have a direct bearing on whether the coating adheres and performs as intended.
The most critical single factor is moisture — resin coatings are generally applied once the screed has reached a moisture level appropriate for the specific coating system, confirmed by appropriate testing such as relative humidity (RH) probes or a calcium carbide (CM) test, rather than by estimation or a fixed number of drying weeks.
Surface preparation ahead of coating — usually mechanical, such as diamond grinding or shot-blasting to remove laitance and open the surface — is just as important as the moisture reading, since a resin coating applied over weak or contaminated laitance will bond to the laitance, not the sound screed beneath it.
Moisture testing before coating
Because resin is impermeable once cured, applying it over a screed that hasn't reached suitable dryness for that specific coating traps moisture beneath the film, which commonly shows up later as blistering, delamination or discolouration. Testing — typically RH probes inserted into the screed, or a calcium carbide test — gives an objective reading rather than relying on elapsed time alone.
Timeframes for reaching a suitable moisture level depend on depth, ventilation, temperature and the screed type, so testing at the appropriate point in the programme is far more reliable than assuming a fixed number of weeks will always be sufficient.
Surface preparation for coating adhesion
Laitance — the weak layer that can form at the surface of a curing screed — needs to be mechanically removed before any resin is applied, typically by diamond grinding or shot-blasting, since coatings applied directly over laitance are bonding to a layer that can itself detach from the sound screed below.
Flatness requirements are often tighter under a thin resin coating than under a floor covering with more inherent tolerance, so the SR class targeted at the screeding stage should reflect the intended resin finish from the outset.
Screed Under Resin Coatings — the points that decide it
- Resin coatings require confirmed moisture readings appropriate to the specific coating, via RH or CM testing
- Laitance must be mechanically removed before coating, regardless of how dry the screed reads
- Surface flatness (SR class) requirements are typically tighter under thin resin finishes
- Any surface contamination — curing compounds, dust, oils — can cause coating adhesion failure
- Coordination between the screed installer and resin applicator on timing avoids wasted programme time
- Some resin systems have specific primer or damp-proof membrane requirements over screed
- Testing should follow the resin manufacturer's specified method, not a generic assumption
Specifying a screed ahead of a resin finish?
We'll plan the screed programme with your resin applicator's moisture and preparation requirements in mind — call 07791 510849.
Or call our landline on 01392 237700
Other pages that answer this properly
Screed Under Resin Coatings — your questions
In short
Resin coatings demand a fully dry, mechanically prepared screed surface, since any residual moisture or laitance beneath a coating can cause adhesion failure or blistering.
Specifying a screed ahead of a resin finish?
We'll plan the screed programme with your resin applicator's moisture and preparation requirements in mind — call 07791 510849.