Repair guide
How to reattach a natural-stone coping to a concrete garden wall
MS polymer bonds stone to concrete and stays flexible through frost, but a coping stone is heavy and exposed, so the bed has to shed water and the stone must be properly supported while it cures.
The short answer
Clean and dry both faces, apply MS polymer in beads that run front to back rather than along the wall, and bed the coping down onto it. Beads running the width of the wall let any water that gets in drain out rather than sit in a sealed pocket and freeze. Support the stone so it cannot slide while curing and keep the wall dry for 48 hours.
- Difficulty
- Difficult
- Time needed
- 1 hour work, 24 to 48 hours cure
- What you need
- MS polymer adhesive and a heavy duty caulking gun, bolster and hammer for removing old mortar, stiff brush, 80 grit abrasive, spirit level, packers, gloves, safety boots
A coping stone does the most important job on a garden wall: it keeps water out of the top. So the fixing has to do two things, hold the stone and manage water, and the second is where most repairs go wrong. Bed a coping in a solid unbroken layer and any water that finds its way past the front edge has nowhere to go. It sits there, freezes, and lifts the stone off again.
Running the adhesive in beads across the wall, front to back, gives drainage channels. It is the same reasoning behind bedding a plaque on vertical beads.
Stone itself varies enormously. Limestone and sandstone are porous and dusty and need brushing thoroughly. Granite and slate are dense and smooth and need abrading where they will be bonded. All of them hold water for far longer than they look, which is why dry weather and a day of drying matter more than the choice of product.
Weight is the last point. Coping stones are heavy enough to hurt someone. Adhesive alone is normal practice for a domestic wall, but the stone must be stable on its bed before you leave it, and on a wall by a path or a play area, a stainless dowel into the wall is a sensible addition.
Step by step
- Lift the coping stone off and set it somewhere safe. They are heavier than they look, so get help.
- Scrape all old mortar and adhesive off both the wall top and the underside of the stone.
- Brush both surfaces hard with a stiff brush and remove all dust.
- Abrade the underside of a dense stone such as granite or slate with 80 grit. Porous stone just needs brushing.
- Let both dry for at least 24 hours of dry weather.
- Apply MS polymer adhesive in beads running front to back across the wall, about 100mm apart, keeping 20mm in from the front and back edges.
- Lower the stone into place, press it down and slide it a few millimetres to bed it, then check it is level and correctly overhanging.
- Wedge or prop it so it cannot slide, leave it 24 hours, and keep it dry for 48.
What to avoid
Do not bed the stone solid. Trapped water freezes and lifts the coping.
Do not use cement mortar on its own for a repair like this unless you are rebedding the whole run. A patch of rigid mortar between two flexible joints cracks first.
Do not work on a damp wall or in cold weather. Below about 5 degrees most adhesives will not cure properly.
Coping stones are heavy and drop onto feet. Wear boots, get help with the lift, and never work on a wall that is leaning or unstable. On a wall next to a path, pavement or play area, add a stainless dowel as well as adhesive. Check the wall itself is sound before repairing the top of it.
The full bonding guide
Everything about gluing Concrete to Natural stone
Last reviewed 13 September 2026.