Patio jointing compound vs mortar: which is better?

Mortar pointing

Sand and cement pointing is pressed into the joints and finished by hand. It sets hard and rigid, holds up well to jet washing and suits wider joints in natural stone. Its weakness is that rigidity: if the patio flexes even slightly, the mortar has no give, and hairline cracks appear along the joints.

It also takes care to apply cleanly, because mortar smeared on the face of the slabs can stain them, especially pale sandstone.

Brush in patio jointing

Brush in compounds are swept into the joints and set over time. They are quicker to apply, less likely to stain the slab face when used correctly, and allow a little movement. They work particularly well with porcelain, where tight, consistent joints are part of the look.

They do need the right conditions. Most need the joints to be a minimum depth and the weather to suit, and the patio usually needs keeping clear while they cure.

Why patio pointing cracks

• The base underneath has settled, so the slabs move
• Joints were filled too shallow and could not hold
• The mortar mix was weak or dried out too quickly
• Frost has worked into joints that were already failing
• Heavy jet washing has eroded the joint over years

Repointing a patio

If the slabs are solid and level and only the joints have failed, repointing is worthwhile. The old pointing is raked out to a good depth, the joints cleaned, and new mortar or compound applied. It tidies the patio, stops weeds and keeps water out of the bed.

If the slabs rock or have dipped, repointing alone will crack again. Those slabs need lifting and relaying on a rebuilt bed first. Lifting, relaying and repointing old paving is work we do regularly, from small areas to whole patios.

Which we would use

We match the jointing to the slab and the joint. Porcelain and narrow, uniform joints often suit a brush in compound. Wider joints in riven sandstone often suit traditional mortar. We will explain the choice on the quote so there are no surprises.