Render mortar: dosage, cement and application

Render is a building's skin: it shields the masonry from rain, wind and salt, and it sets the final look of the facade. The short answer: a render mortar based on CPJ 45 is dosed at roughly 350 kg of cement per m³ of 0/2-0/4 sand for the body coat, while decorative render gets by on about 300 kg/m³. In southern Morocco, where salty air attacks facades, render quality is not a cosmetic detail — it is the building's first line of defence.

Three jobs, one mortar

Protect, first: render blocks rainwater and slows the salts that corrode rebar and masonry. Accommodate, second: a well-formulated render follows the substrate's micro-movements without crazing. Dress, last: grain, tint and finish — sponged, floated or rough-travelled — give the building its character. A mortar that fails the first job fails all three.

Composition and dosage

Classic render mortar is CPJ 45 cement, 0/2-0/4 sand and water — about 1 volume of cement to 3-4 volumes of sand. The reference dosage for the body coat is 350 kg of cement per m³ of sand; decorative finishing render usually drops to 300 kg/m³. On materials, washed sand trades at roughly 80-120 DH/T and CPJ 45 cement is quoted personally — ask for your quote to price a site-mixed render mortar, labour excluded. Ready-mixed render in bags (4-6 DH/kg) simplifies small areas.

Straight cement or bastard mortar?

Pure cement mortar is strong but stiff: on mixed substrates or in intense sun it can crack. Bastard mortar — cement and lime — gains flexibility and more even colour, at the cost of some strength: a sound choice for renovating old masonry and traditional finishes. Our cement-vs-lime comparison details how the two binders complement each other.

Applying render in hot, coastal weather

In Dakhla, where heat, wind and salt combine, a handful of simple precautions separate render that ages well from render that flakes off in three winters:

• Dampen the substrate before applying — without soaking it: the wall must not rob the mortar of its water.
• Work the cool hours, on shaded elevations, never in a wind that skins the surface before set.
• Protect fresh render from direct sun for the first hours, then let it harden slowly.
• Detail the weak points: window sills, drips and junctions are where water gets in first.

For binder volumes and site planning, CPJ 45 is available on quote within 24 h, delivered in Dakhla City.