What is included in a full K-Rend system?

A complete K-Rend silicone render system consists of five layers: HPX primer applied to the substrate, a basecoat (typically K-Rend Base Coat EWI at 4-5mm), fibreglass reinforcing mesh embedded in the basecoat, a second thin basecoat layer over the mesh, and then the silicone topcoat finish. You also need corner beads and stop beads around all openings and external corners.

How much K-Rend topcoat do I need per m²?

Coverage depends on the finish type and texture. Silicone Thin Coat uses approximately 2.5 kg/m² at 1.5mm thickness. TC30 (a coarser 3mm finish) uses around 4.5 kg/m². Scraped textures sit between at roughly 3.5 kg/m². These are manufacturer-stated rates — always add 10% for wastage.

Can I apply K-Rend over existing render?

K-Rend can be applied over sound existing render, but the surface must be clean, stable, and free from loose material. You should carry out adhesion tests first. If the existing render is painted, you may need to mechanically key the surface. K-Rend recommend using their HPX primer on all substrates before basecoat application.

How many stop beads do I need per window?

Each window or door opening requires stop beads on three sides — the head (top) and two jambs (sides). The sill is typically left bead-free with a drip detail. For a standard 1.2m × 1.2m window, that is approximately 3.6m of bead, which equals 2 standard 2.5m lengths. Our calculator accounts for this automatically.

What is the drying time between K-Rend coats?

The primer should dry for at least 12 hours before applying basecoat. The basecoat with embedded mesh needs a minimum of 24 hours curing (longer in cold or damp weather). The topcoat should only be applied to fully cured basecoat — K-Rend recommend at least 3-7 days depending on temperature and humidity. Never apply any coat if rain is forecast within 24 hours.

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K-Rend Render Calculator — Full Silicone System Materials

Calculate all materials for a complete K-Rend silicone render system including primer, basecoat, mesh, topcoat, and beads.

Total Wall Area

Net render area (subtract windows/doors)

Topcoat Finish

Determines topcoat consumption rate

External Corners

Number of external corner beads needed

Window/Door Openings

Each opening needs 3 stop beads (head + jambs)

Basecoat Price Per 25kg Bag (optional)

Enter your supplier price for basecoat

Topcoat Price Per 25kg Bag (optional)

Enter your supplier price for topcoat

How We Calculate This

This calculator estimates all materials required for a complete K-Rend silicone render system. It uses manufacturer-published consumption rates to calculate primer, basecoat, reinforcing mesh, and topcoat quantities for your measured wall area.

The formula

Material quantity = Wall area (m²) × Consumption rate (kg or L per m²) × Wastage factor

For example, 80 m² of wall area with Silicone Thin Coat at 2.5 kg/m² needs: 80 × 2.5 × 1.10 = 220 kg of topcoat (9 × 25kg bags). The basecoat at 5 kg/m² needs 80 × 5.0 × 1.10 = 440 kg (18 bags). Primer at 0.15 L/m² needs 80 × 0.15 × 1.10 = 13.2 L (1 × 15L tin).

Bead calculations

Corner beads are calculated by multiplying external corners by storey height (assumed 2.4m) and dividing by standard 2.5m bead lengths. Stop beads around openings assume 3 sides per opening (head + 2 jambs) at approximately 2.0m average per side, then dividing by bead length.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.