Retaining Walls

Low retaining walls without mortar or curing time

Terrace a garden without a bricklayer. PolyBrick® blocks push-fit together on a properly prepared base, so low retaining walls go up in hours and stay put for decades.

Why PolyBrick works here

A retaining wall is the job most people put off. Masonry means mortar, mixing, curing and getting it right first time. Sleepers rot from the back where you cannot see them. Gabions need a mason's eye to look deliberate rather than industrial.

PolyBrick sidesteps most of it. Blocks interlock by pushing together, so there is no mortar, no mixing and no curing: the wall is finished when you stop building rather than three days later. Nothing rots, rusts, shrinks or warps, so the back face is as sound in year fifteen as the front.

What it still needs is a properly prepared foundation. A retaining wall of any kind concentrates load into a narrow strip of ground, so the trench, the compacted fill and the level of that first course carry everything above them. What that foundation should be depends on the height of the wall, the ground it sits on and what it is retaining, so establish it for your site before you start rather than assuming.

Where this works well

• Garden terracing and level changes
• Raised bed and border retention
• Driveway and path edge retention
• Sloping garden steps and platforms
• Low boundary and screen walls
• Planter and seating walls
• Bin and log store surrounds
• Allotment and community garden terracing

At a glance

Know the limits before you start

Worth being straight about this, because retaining walls are the one garden structure where getting it wrong has consequences beyond appearance.

A retaining wall holds back soil, and soil is heavy, especially when saturated. The taller the wall, the more force it carries, and the relationship is not linear: a wall twice the height carries considerably more than twice the load.

For low garden terracing, raised beds and edge retention, a properly built PolyBrick wall on a compacted base is well within its comfort zone. For anything taller, anything retaining a driveway or a structure, anything on a steep or unstable slope, or anything where failure would affect a neighbour, a building or a highway, take engineering advice and have the wall designed. That applies to any material, not just this one.

If you are unsure which side of that line your project sits on, tell us the height, the slope and what is above and below the wall, and we will give you an honest answer rather than a sale.

Drainage is what keeps a wall standing

Most retaining wall failures are water failures. Soil behind a wall holds rain, that water has weight and nowhere to go, and the pressure builds until something moves.

Build free drainage in from the start. Backfill directly behind the wall with clean angular stone rather than the soil you dug out, so water travels down through the stone instead of loading the back face. Where a wall is more than a couple of courses, run a perforated pipe at the base of that stone to take water away to somewhere sensible.

The advantage PolyBrick has here is that it does not care about the water. There is nothing to rot, rust or spall, and the joints are not mortar that can be washed out. Get the drainage right and the wall is genuinely maintenance free.