The short answer
A balcony or roof terrace has no soil for a base, so the priorities differ from a garden. Choose a non-infill (or low-infill) grass that holds its shape without heavy sand, keeping the weight low where there is a load limit. Pick a shorter, denser pile (around 20–30mm) that stays tidy and drains fast, and a fully permeable backing with plenty of drainage holes so rain runs straight through to the waterproof surface and away to the drain. The grass lays directly over the hard floor, sometimes on a thin underlay for comfort, and is held with tape or adhesive at the edges rather than pins, so the membrane is never pierced. Check the floor falls to a drain and that you are allowed to lay it.
Laying artificial grass on a balcony or roof terrace is very different to laying it on soil. Weight, drainage and fixing without damaging the waterproofing all come first. Here is how to choose and approach it.
Balcony grass
- Grass typeNon-infill / low-infill
- PileShort, dense ~20–30mm
- BackingFully permeable, many holes
- FixingTape/adhesive, not pins
- CheckFloor drainage and load limit
Why a balcony needs different grass
In a garden, artificial grass sits on an excavated, compacted aggregate base, usually weighted with kiln-dried sand. A balcony or roof terrace has none of that — just a hard, waterproofed floor — so the same approach does not apply. The grass instead lays over the existing surface, which changes what you need from it.
Weight is the first consideration. Roof terraces and balconies often have load limits, and adding several kilograms of sand per square metre may not be wanted or allowed. A non-infill grass, designed with a dense construction that holds its shape without sand, keeps the weight low. A shorter, denser pile around 20mm to 30mm also suits these spaces: it stays tidy, drains quickly and copes with the foot traffic an outdoor terrace sees.
| Factor | Garden lawn | Balcony / roof terrace |
|---|---|---|
| Base | Aggregate sub-base | Existing hard floor |
| Infill | Kiln-dried sand | Non-infill preferred |
| Pile | Medium 30–37mm | Shorter, denser 20–30mm |
| Fixing | Pins, sand ballast | Tape or adhesive, no piercing |
| Drainage | Through base | Through backing to drain |
| Key check | Ground prep | Load limit and waterproofing |
Indicative comparison; check building rules and tenancy terms.
Drainage and protecting the waterproofing
Drainage is critical because there is no soil to soak water away. Choose a grass with a fully permeable backing and plenty of drainage perforations so rain passes straight through to the floor below, which must itself fall slightly towards a drain or gutter. If the floor does not drain, water will sit under the grass, so confirm the surface sheds water before laying anything over it.
Protecting the waterproof membrane is the other priority. Never use ground pins or anything that pierces the floor on a balcony or roof terrace, as a single hole can let water into the structure below. Instead the grass is held at the perimeter with exterior double-sided tape or a suitable adhesive, or simply weighted and cut to fit snugly. A thin underlay or shock pad can be added for comfort and to even out small irregularities, provided it too lets water through.
Permissions, heat and practical checks
Before laying grass on a balcony or terrace, check you are allowed to. Leaseholders and renters often need landlord or freeholder permission, and adding weight or covering a communal-looking surface may be restricted. Confirm the load the floor can take, especially on an older balcony, and that any changes will not affect the building's waterproofing guarantee.
On comfort, a sunny, exposed terrace can make a grass surface hot in summer, so a lighter colour and the option to rinse it on hot days help. Keep the surface clear of leaves and debris so the drainage holes do not clog, and lift the grass periodically if needed to check the floor beneath stays dry and the drainage is working. With the right non-infill grass, good drainage and edge-only fixing, a balcony or roof terrace can carry a tidy, soft green surface without risk to the structure.
Measuring, cutting and finishing the edges
Because a balcony or terrace is usually a defined, often awkward shape, careful measuring and cutting make the difference between a neat result and a makeshift one. Measure the space accurately, allowing a little excess to trim back, and note any obstacles such as drainage outlets, planters, railings and door thresholds that the grass needs to fit around. Where possible, run the pile in a single direction towards the main viewpoint so the colour reads evenly, and avoid unnecessary joins; on a small terrace a single piece is often enough, which removes the trickiest part of the job.
Cutting is done from the back of the grass with a sharp blade, following the lines of the backing, so the fibres are not chopped unevenly. Around fixed features and the drainage outlet, cut carefully so water can still reach the drain rather than being sealed off. At the edges, the grass is trimmed to sit cleanly against the perimeter and held down with exterior-grade double-sided tape or adhesive, keeping the fixing to the surface only. A tidy, well-cut edge that follows the shape of the space is what makes a balcony lawn look intentional rather than improvised.
Once laid, upkeep on a terrace is light but worth keeping to. Brush the pile occasionally to keep it standing, rinse the surface to remove dust and pollution that settle on an exposed balcony, and clear leaves and debris so the drainage holes stay open. Every so often it is sensible to lift a corner and check the floor beneath is dry and the drainage is working, particularly after a long wet spell. With a suitable non-infill grass, good drainage, edge-only fixing and this simple routine, a balcony or roof terrace gains a soft, green, usable surface that transforms the space without putting the structure or its waterproofing at risk.
To sum up, the best artificial grass for a balcony or roof terrace is chosen for weight, drainage and safe fixing rather than for the qualities that suit a garden lawn. Favour a non-infill or low-infill grass to keep the load down, a shorter, denser pile around 20 to 30mm that stays tidy and drains fast, and a fully permeable backing with plenty of holes over a floor that already falls to a drain. Lay it over the existing surface, fix only at the edges with tape or adhesive so the membrane is never pierced, and confirm both the load limit and any permission you need before starting. Get those points right and a terrace can carry a soft green surface safely and for years.
Frequently asked questions
Can you lay artificial grass on a balcony?
Yes, provided the floor is waterproof and drains, you keep the weight low and you fix the grass without piercing the surface. A non-infill grass laid over the existing floor and held with tape or adhesive at the edges is the usual approach. Always check load limits and any permission you need first.
Do you need infill on a balcony or roof terrace?
Usually not. A non-infill grass is preferred so you avoid adding the weight of sand, which matters where there is a load limit, and so sand does not wash out through the drainage. Non-infill grass is designed to hold its shape without sand, making it well suited to balconies and terraces.
How does artificial grass drain on a roof terrace?
Through a fully permeable backing with drainage holes that let rain pass straight to the floor below, which must fall slightly towards a drain or gutter. There is no soil to soak water away, so both the grass backing and the existing floor drainage must work together. Keep the holes clear of debris.
Sources & further reading
Figures on this page are typical UK ranges drawn from published cost guides and are intended as guidance, not a quotation.