Signs your patio needs re-pointing
Walk the patio after rain and look for:
- Gaps and hollows where filler has washed or blown out.
- Cracked or crumbling mortar that lifts out with a screwdriver.
- Weeds and moss rooted in the joints. The RHS notes that weeds in paving take hold where joints have opened up and collected soil.
- Dark wet lines that stay damp long after the slabs have dried, a sign water is getting under the patio.
- Sand washed onto the surface after rain, common with old sand-filled joints.
Re-point or relay?
Before choosing a filler, check the bedding. Stand on each slab and rock gently from edge to edge, then tap it with the handle of a hammer.
- Firm and solid sound: the bed is fine. Re-pointing is worth doing.
- Rocks, dips or sounds hollow: the slab has lost its bed. New pointing around a loose slab cracks within months. That slab needs lifting, re-bedding on a full mortar bed and then pointing.
- Large areas sinking: the sub-base has failed, which on Middlesbrough's glacial till and lake clays usually means the base was too thin or water has been getting in. Relaying is the lasting fix.
We check this on every visit before pricing anything, because pointing over a failed bed only hides the problem.
The three main options
Sand and cement mortar
The traditional choice. A semi-dry or wet mix is pressed into the joints and finished with a pointing iron to give a slightly recessed, rounded joint that sheds water.
- Good for: sandstone and concrete slabs with joints of about 10mm or more; matching an older patio.
- Watch out for: cement staining on porous sandstone if it is not cleaned off straight away; cracking if the base moves. Cement is also hazardous to handle: the HSE warns that wet cement can cause serious burns and dermatitis, so gloves and eye protection matter.
Brush-in jointing compound
Ready-mixed compounds, often resin-based, are swept into damp joints and harden over a day or two.
- Good for: porcelain and sandstone, joints of a consistent width, and anyone who wants a neat finish without cement staining.
- Watch out for: most need a minimum joint depth and width, often around 20mm deep, and they do not bond well to old mortar left in the joint. Some are permeable and let water through to the bed, which is helpful on free-draining ground but less so on clay. Weather matters: most should not be laid in heavy rain or near freezing.
Slurry grout
A pourable cementitious grout is worked across the surface and into the joints, then the surface is cleaned off.
- Good for: porcelain, where the dense surface cleans off easily, and narrow joints.
- Watch out for: not suitable for porous stone, which can stain, and it needs careful timing when cleaning the surface.
How we re-point a patio
- Rake out the old filler to a consistent depth, removing loose mortar, sand, soil and roots.
- Clean and prepare the joints and slab edges. For brush-in compounds the joints are wetted; for mortar on sandstone, slab edges may be protected.
- Fill and finish with the chosen material, compacted fully to the base of the joint.
- Clean down the surface the same day so no residue is left to stain.
- Protect the work from heavy rain and frost while it cures.
Re-pointing needs a dry spell and temperatures safely above freezing. That makes late spring to early autumn the usual window in Middlesbrough.
Making new pointing last
- Avoid aggressive jet washing. A narrow high-pressure jet strips joints quickly, especially brush-in compounds. Our patio cleaning guide covers safer methods.
- Deal with water. If water stands on the patio or runs towards the house, fix the fall or add drainage, or the new joints will fail like the old ones.
- Keep leaves off. Rotting leaves trap moisture and seed weeds.
- Check before winter. Small gaps let water in, and freeze–thaw then widens them.
Permeable joints and the front garden
If the paving is in a front garden, think about where the water goes. The government's guidance on permeable surfacing explains that front gardens over five square metres need permission if paved with an impermeable surface that drains onto the road. Permeable jointing on a suitable base is one way to let rain soak through. Our planning permission guide explains the rule.
Questions people ask
What is the best filler for patio joints?
It depends on the slabs and joints. Mortar suits sandstone and wide joints, brush-in compounds suit porcelain and sandstone with deeper joints, and slurry grout suits porcelain.
Is wet or dry mix better for pointing?
A wet or semi-wet mortar gives a stronger, more complete joint than dry brushed-in sand and cement, which often fails to bond and crumbles.
Can I point over the old mortar?
Not successfully. Fillers need clean joints of the right depth to bond; a thin skim over old mortar cracks away.
How long does patio pointing last?
That depends on the base, drainage and cleaning. Good pointing on a sound, well-drained patio lasts many years; on a moving base it fails quickly.
Sources: HSE: cement, health risks in construction; GOV.UK: guidance on the permeable surfacing of front gardens; RHS: weeds on hard surfaces; BGS Geology Viewer.