Frequently Asked Questions

How many coats of Sikafloor 161 primer are needed before applying a self-levelling Sikafloor 264 epoxy floor coating on a new concrete industrial floor slab?

The number of Sikafloor 161 primer coats required on a new concrete industrial floor slab depends on the concrete substrate porosity and moisture content. For a standard mechanically prepared (shot-blasted to CSP 3) new concrete slab that is at least 28 days old and has moisture content below 4 per cent (CM method), one coat of Sikafloor 161 at 0.2 to 0.3 kg per m2 is typically sufficient. After the first primer coat cures (12 to 18 hours), inspect the surface: if the entire floor shows a uniform epoxy sheen with no matte, uncoated, or rapidly absorbed patches, the concrete is sufficiently sealed and the floor coating can be applied. If there are matte patches (areas where the primer soaked in completely and left no surface film), these areas have higher porosity and require a second coat of Sikafloor 161 at 0.15 to 0.20 kg per m2 applied only to the matte areas or across the full floor if more than 20 to 30 per cent of the floor shows this. On highly porous or old concrete slabs (above 28 MPa but with open surface from age, abrasion, or previous floor coating removal), apply two full coats of Sikafloor 161 to the entire floor regardless of the first-coat appearance. For new industrial floors placed with Sika ViscoCrete and proper curing and power-trowelled finishing, one coat of Sikafloor 161 is generally sufficient.

What minimum concrete strength and moisture content are required before Sikafloor 161 and a Sikafloor epoxy system can be applied?

Sikafloor 161 and epoxy floor coating systems have two primary substrate requirements that must both be met before application: minimum compressive strength and maximum moisture content. Minimum concrete strength: the concrete substrate must achieve a minimum compressive strength of 25 MPa (typically confirmed by coring or Schmidt hammer testing on the specific floor area) and a minimum pull-off tensile strength of 1.5 MPa (tested with a pull-off adhesion tester on 50 mm diameter dollies) before applying floor coating. These strength requirements ensure that the floor coating system does not delaminate by pulling the concrete surface off below the adhesive bond when the floor is loaded. For new warehouse and industrial floor slabs in India specified at M25 or M30, the concrete reaches the required compressive strength at 28 days but it is good practice to allow 56 days before coating application to allow continued strength gain and initial drying shrinkage to complete. Maximum moisture content: the concrete substrate must have a moisture content below 4 per cent (measured with a CM carbide moisture meter on a drilled concrete sample from 20 to 30 mm depth). This is the critical constraint in India during monsoon season (July to September) and for new ground-floor slabs on damp subgrade — applying epoxy floor coating over concrete with moisture content above 4 per cent traps moisture vapour below the coating, which can create osmotic pressure and cause blistering and delamination within 1 to 3 months of application. If moisture content exceeds 4 per cent, allow further drying time or apply Sikafloor Primer MB (moisture barrier primer) designed for higher moisture concrete substrates.

Can Sikafloor 161 and the Sikafloor epoxy coating system be applied on a concrete floor of a cold storage facility that operates at minus 18 degrees C?

Sikafloor 161 and Sikafloor epoxy coating systems can be applied on concrete floors intended for cold storage service at minus 18 degrees C, but the application must occur before the cold room is commissioned and cooled — not after. Sikafloor 161 requires a minimum substrate temperature of plus 10 degrees C and ambient temperature of plus 10 degrees C to cure properly. Application on cold substrates below 10 degrees C results in incomplete epoxy curing, surface tack that never fully disappears, and soft, under-strength floor coating that will fail rapidly under forklift traffic. The correct sequence for a cold storage floor coating project: complete the concrete slab and allow 28 to 56 days curing and drying (floor exposed to ambient temperature, not refrigerated). Shot-blast the floor to CSP 3. Verify moisture content is below 4 per cent using CM method. Apply Sikafloor 161 primer and Sikafloor 264 coating system at ambient temperature (ensure the floor is between 15 and 30 degrees C during application and for the full cure period). After the Sikafloor coating has achieved full cure (7 to 14 days at 20 degrees C), the cold room can be commissioned and cooled to minus 18 degrees C. The cured Sikafloor 264 epoxy is suitable for long-term service at minus 18 degrees C — epoxy coatings maintain their mechanical properties at low temperatures (they actually become slightly harder at subzero temperatures). Select the correct Sikafloor grade rated for cold storage service conditions — consult Space Arc Engineering for cold store floor coating specification.