Pointing mortar: cement, dosage and use

Joints are the weak lines of any structure: water gets in through them, frost works on them, dirt settles in them. The short answer: masonry pointing mortar is dosed like standard mortar, about 350 kg of CPJ 45 per m³ of fine 0/2 sand, while tile joints call for formulated grouts — industrial products DAM does not manufacture, exactly like tile adhesive.

Masonry joints

On a block or brick wall, the joint does three jobs: distribute loads between units, lock the bedding and bar water. A raked-back, under-dosed or poorly compacted joint lets standing water settle in the interstice, then migrate inside. The quality gesture: mortar at 350 kg/m³ of sand, applied to a clean, slightly damp interstice, well pressed with the pointing iron, then struck clean — with no smears left on the wall to hold water.

Tile joints: a different trade

A tile joint is not ordinary cement mortar: it is a formulated product (binder, fillers, additives) classified CG — cementitious grout — under European standard EN 13888, with improved grades and reduced-absorption versions for wet rooms. Tile format dictates joint width; wet areas (showers, kitchens) call for humidity-suitable grouts. As with tile adhesive, DAM does not manufacture grouts: we produce the CPJ 45/55 cement that goes into their formulation.

The mistakes that let water in

• Mixing too fluid to go faster: the mortar slumps, the joint ends up hollow and porous.
• Pointing in full sun: fast drying cracks the joint surface before set.
• Skipping the cleaning of interstices: dust kills adhesion and creates leak paths.
• Filling partially: a shallow joint crumbles at the tile edge.

For masonry joints and all your mortars, CPJ 45 ships in bags, big bags or bulk — free personalized quote.