What is monocouche render and how is it different from sand and cement?

Monocouche (meaning 'one coat' in French) is a factory-mixed render applied in a single 15-25mm coat, compared to traditional sand and cement which requires 2-3 coats. Monocouche render comes pre-coloured in a wide range of colours, so no painting is needed. It is more expensive per m² than sand and cement but saves significant labour time. Popular UK brands include K Rend, Weber and Parex.

How many bags of K Rend do I need per m²?

K Rend Silicone TC30 covers approximately 1.0-1.2 m² per 25kg bag at the standard 20mm application thickness. This means you need roughly 1 bag per m² of wall. At 15mm thickness, coverage increases to about 1.3-1.5 m² per bag. Always add 10% wastage for cutting, corners and normal application losses. Similar rates apply to Weber Monocouche and Parex Monorex.

Do I need mesh with monocouche render?

Reinforcing mesh (160g/m² alkali-resistant glass fibre) is recommended at all junctions between different substrates (e.g. block to concrete, or over EWI joints), around window and door openings, and in areas prone to cracking. Many specifiers now require mesh over the entire wall area for belt-and-braces protection. The mesh is embedded into the first pass of render. Allow 15% extra for overlaps (minimum 100mm overlap at joints).

What beads and accessories do I need for monocouche render?

Essential accessories include: bellcast/drip beads along the base of all rendered walls (to prevent water tracking underneath), corner beads on all external corners (for protection and a clean edge), and stop beads where the render terminates (around windows, doors, and at abutments). All beads should be stainless steel or PVC for longevity. A primer coat (e.g. K Rend HP12) is applied to the substrate before rendering to control suction.

How long does monocouche render take to dry?

Monocouche render should not be applied in temperatures below 5°C or above 30°C, or in direct strong sunlight. Initial set takes 4-8 hours, after which the surface can be scraped back to create a textured finish. Full curing takes approximately 28 days. The render should be protected from rain for the first 24-48 hours. Do not apply if frost is forecast within 24 hours.

Monocouche Render Calculator — K Rend, Weber & Parex

Calculate monocouche render bags, mesh, bellcast beads, corner beads, stop beads and primer for K Rend, Weber and Parex render systems.

Wall & Render Details

Total Wall Area

Gross external wall area to be rendered

Wall Base Length (optional)

Total length along base of walls, for bellcast beads

Render System

Select the render system for your calculation

Application Thickness

20mm is standard for most substrates

Openings & Features

Number of Windows

Each deducts 1.2 m²

Number of Doors

Each deducts 1.8 m²

External Corners

For corner bead calculation

Additional Stop Ends

Where render meets another material (not windows/doors)

Options

Include reinforcing mesh

160g/m² alkali-resistant mesh with 100mm overlaps

Include primer

Substrate primer (e.g. K Rend HP12) at ~5.5 m²/litre

Include wastage allowance

Adds 10% extra for mixing and application losses

Wastage Percentage

10% is standard for monocouche render

Price Per Bag (optional)

Price per 25kg bag for cost estimate

How We Calculate This

This calculator estimates all materials needed for a monocouche render system including render bags, reinforcing mesh, beads and primer. It supports K Rend Silicone TC30, Weber Monocouche and Parex Monorex GF — all of which have similar coverage rates.

How it calculates

Net wall area = Gross wall area − (Windows × 1.2 m²) − (Doors × 1.8 m²)

Render bags = Net area ÷ Coverage rate × Wastage factor. At 20mm thickness, all three render systems cover approximately 1.0-1.2 m² per 25kg bag. Thinner application (15mm) increases coverage proportionally.

Coverage rates (per 25kg bag)

At 15mm: ~1.3-1.5 m² per bag
At 20mm: ~1.0-1.2 m² per bag (standard)
At 25mm: ~0.8-0.9 m² per bag

Accessories

Mesh: 160g/m² alkali-resistant, factor of 1.15 for 100mm overlaps
Bellcast beads: Along the base of all rendered walls (2.5m lengths)
Corner beads: On all external corners, full building height (2.5m lengths)
Stop beads: Around windows, doors and render terminations (2.5m lengths)
Primer: ~5.5 m²/litre, applied to substrate before rendering

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Verify with your supplier.