7 min read

Laying Artificial Grass Over Concrete and Patios

Laying artificial grass onto concrete is a genuinely good solution for tired patios, old garage bases, balconies and small courtyards, and it saves the cost and mess of breaking a slab out. It also fails badly if the drainage underneath is not sorted first, so the survey matters more here than on a soil garden.

First question: where does the water go?

Concrete is not permeable, so any rain landing on the grass must run across the slab to somewhere it can escape. Pour a bucket of water on the slab and watch. If it drains to a gully, a border or off an edge, you are in business. If it puddles in the middle, the water will sit under the grass and the lawn will smell and grow algae.

Where a slab holds water we either core drill drainage points through it into a stone filled void, cut a channel to a drain, or build a shallow fall using a self levelling screed. Occasionally the honest answer is to break the concrete out.

Preparing the surface

The slab needs to be clean, structurally sound and reasonably smooth. Grind off high spots, patch spalled areas and fill any hollows, because every imperfection telegraphs through the grass and shows in low sunlight.

Kill off moss and algae and let the surface dry thoroughly before anything is bonded to it.

Underlay: foam shockpad or straight onto the slab

A perforated foam shockpad is strongly recommended over hard surfaces. It softens the feel underfoot, which is the main complaint people have about grass on concrete, evens out minor imperfections and creates a small drainage plane between grass and slab.

For children's play areas over concrete, a thicker shockpad is a sensible addition. Choose a perforated pad so water can still get through.

Fixing the grass down

You cannot use pins on concrete, so the grass is bonded. We fix the perimeter with an exterior grade grab adhesive or a bonded batten, and seam joins with jointing tape and adhesive rather than tape alone.

Leave a small expansion allowance at the edges. Synthetic grass moves with temperature, and a lawn fitted tight in cold weather can ripple in a heatwave.

Infill on hard surfaces

Sand infill still helps: it weighs the grass down, which matters when there are no pins holding it, and keeps the pile upright. Use less than on a soil base if drainage across the slab is marginal.

Where this works best

Old concrete garage bases, side returns, roof terraces and balconies, courtyard gardens, and patios that are structurally fine but ugly. It is quick, clean and there is almost no waste to remove, which usually makes it cheaper than a full excavation.

Got a slab you would rather cover than remove

Send a photo of the area with a note on where water currently runs and we will tell you whether it can be grassed over as it stands.

Ask about your patio View Artificial Grass 07535 661664

Frequently asked questions

Can artificial grass be laid straight onto concrete without underlay?

It can, but it feels hard and shows every bump in the slab. A perforated foam pad transforms the comfort and hides minor defects for a small extra cost.

Will water get trapped between the grass and the slab?

Only if the slab holds water. Where the fall is wrong we drill drainage points or channel water to an outlet before laying anything.

Do I need to remove the old patio slabs first?

Not usually. Sound, well bedded paving makes a decent base once it has been levelled and cleaned, though badly rocking slabs need lifting and re bedding.

Is grass on concrete suitable for a balcony?

Yes, it is one of the neatest uses for it. Weight, drainage outlets and any building or lease restrictions need checking first.

Is it cheaper than laying on soil?

Often yes, because there is no excavation, no aggregate and no spoil to take away, though drainage work on a poorly falling slab can offset that.