Green roofs and living walls explained

Green roofs and living walls do several things at once: they insulate, they manage rainwater, they support wildlife, and they tend to make buildings last longer. They also look good. But they need to be designed and installed with care — particularly where structural loads and waterproofing are concerned. This guide covers the benefits honestly, the considerations clearly, and the accessible starting points in practical detail.

What green roofs and living walls are

A green roof is any roof that supports a layer of growing medium and plants. At the simplest end, this is a thin sedum mat on a flat shed roof — perhaps 80–120 mm of growing medium, planted with hardy succulents that need very little maintenance. At the more complex end, an intensive green roof might have 300 mm or more of substrate, capable of supporting shrubs or even small trees, essentially functioning as a garden above a building.

Between these two extremes sits the semi-intensive green roof — a middle ground with a greater variety of plants than a pure sedum roof but without the depth and weight of a full garden roof.

A living wall (also called a green wall or vertical garden) takes the same idea and turns it on its side. Plants grow on a vertical surface rather than a horizontal one. This can be as simple as a trellis with climbing plants — ivy, Virginia creeper, climbing roses, jasmine — trained up a fence or wall. At the more complex end, modular panel systems clip to a wall-mounted frame and hold individual plants in fabric pockets or rigid cells, sometimes with integrated drip irrigation.

Both approaches have been used on domestic and commercial buildings across many climates and both are growing in accessibility as more suppliers and installers enter the market.

The real benefits

Green roofs and living walls do several things simultaneously, which makes them particularly attractive in situations where space is limited and you want to achieve multiple goals at once.

• Insulation. A layer of growing medium and plants provides meaningful thermal insulation — slowing heat loss in winter and, crucially, reducing heat gain in summer. The plants also cool the air around them through transpiration (releasing water vapour), which can measurably reduce surface temperatures on the roof or wall compared to bare materials.
• Rainwater absorption and flood risk reduction. Growing medium absorbs rainfall and releases it slowly, rather than sending it immediately into drains and watercourses. In urban areas, where impermeable surfaces are common, this matters for managing flash floods and peak run-off. An extensive sedum roof can retain a significant portion of a rainfall event before releasing the rest gradually. If you collect rainwater, a green roof upstream of your gutters will reduce the volume reaching your tank but also reduce the peak flow.
• Biodiversity and pollinators. A sedum or wildflower roof creates habitat that is genuinely difficult to find in many urban and suburban areas. Pollinators — bees, hoverflies, butterflies — benefit from the nectar-rich plants, and certain invertebrates use the sheltered, rough growing medium as habitat. Our guide to making your garden wildlife friendly covers complementary ground-level measures.
• Extended roof life. The growing medium and plants protect the waterproof membrane beneath from ultraviolet light and temperature extremes — the two main causes of membrane degradation. A roof membrane under a green roof system typically lasts significantly longer than one left exposed to the elements.
• Acoustic insulation. The substrate and plants absorb sound, providing some reduction in noise — both from outside (rain noise, traffic) and from within the building below.
• Aesthetics and wellbeing. Research consistently finds that green space — including visible planting — has measurable positive effects on wellbeing. A living wall or green roof changes how a property looks and how it feels to be near it.

Honest considerations before you start

Green roofs and living walls are not complicated, but they do require proper planning — particularly around load and waterproofing.

• Waterproofing. The waterproofing layer beneath the growing medium must be robust and root-resistant. Standard felt or basic bitumen membranes are not sufficient on their own — roots will penetrate them over time. A proper root-barrier membrane or a purpose-made green roof waterproofing system is needed. For any occupied building or structure where a leak would cause damage, professional waterproofing installation is strongly recommended.
• Maintenance. An extensive sedum roof is low-maintenance, not zero-maintenance. It will need weeding once or twice a year (other species colonise the substrate over time), and some sedum species benefit from an occasional cut-back. Living walls typically need more regular attention — watering, pruning and occasional replanting of individual cells that die back.
• Cost. Materials for a DIY extensive green roof on a shed can be relatively modest — the main costs are the membrane, the drainage layer, the growing medium and the plants or seed. Professional installation on a larger structure adds design, labour and materials costs that vary significantly by country and complexity. Get multiple quotes if you are considering a professional installation.
• Slope. An extensive green roof works best on a roof with a gentle slope — typically up to around 20 degrees. Steeper slopes need special retention systems to keep the growing medium in place. Very flat roofs (no slope at all) need good drainage to avoid waterlogging. Check drainage carefully.
• Planning permission. In some jurisdictions, green roofs or large living walls on certain properties or in certain locations may require planning consent. Check with your local authority before starting, particularly for listed buildings, conservation areas or where the structure is visible from public land.

Easy entry points

If you want to start without committing to a large or expensive project, these approaches are accessible to most people with basic DIY skills.

• A sedum roof on a shed, bin store or cycle shelter. These structures are purpose-built for your garden, so you can design or commission them with green roof loading in mind from the outset. A flat or gently sloping roof is ideal. This is the most common and most practical entry point for a domestic green roof.
• A small living-wall planter on a fence or wall. Pocket-style planters — fabric or felt panels with pockets for individual plants — can be hung on any sturdy fence or wall with appropriate fixings. They need regular watering and work best in sheltered, partially shaded positions. Choose compact, hardy plants.
• Climbing plants on a trellis or wire frame. Training climbers up a wall or fence is the lowest-effort form of living wall. The trellis or wires should be fixed at a small distance from the wall surface to allow air circulation and prevent damp from being trapped against masonry. Self-clinging climbers (ivy, Virginia creeper) attach directly without support but require more careful management near roof edges and gutters.
• A balcony green screen. Modular trellis or mesh panels fixed to a balcony railing and planted with appropriate climbers create privacy, shelter from wind and insulation from sun — particularly useful on south-facing balconies in warmer months.

Suitable plants

Plant choice depends heavily on your climate, the aspect of the roof or wall, the depth of growing medium and how much maintenance you want to do.

For extensive green roofs (shallow substrate, minimal irrigation), sedums (stonecrops) are the most reliable choice across temperate climates. They are drought-tolerant, frost-hardy, need little soil depth, and many species flower attractively for pollinators. Wildflower seed mixes formulated for green roofs are also available and can create a more varied habitat, though they typically need a slightly deeper substrate and more establishment care than sedum alone.

For semi-intensive roofs with more substrate depth, you can expand to include ornamental grasses, low-growing herbs such as thyme and oregano (which also benefit pollinators), small perennials and even low shrubs. The plants need to be adapted to the exposed, free-draining conditions.

For living walls, plant choice depends on whether the wall is outdoors or indoors, and on light levels. For outdoor vertical planters in a temperate climate, compact ferns, small sedges, thymes, mosses, sempervivums (houseleeks) and certain ivies do well in partial shade. For sunnier positions, lavender, thyme and many herbs work. For indoor living walls, tropical foliage plants — pothos, philodendron, fittonia, peace lily — are commonly used.

For climbers on trellis, consider what you want from the plant: flower, fruit, foliage, speed of coverage or all-year interest. Clematis, climbing roses, wisteria, jasmine, honeysuckle and passion flower all provide seasonal interest and pollinator value. Evergreen climbers such as ivy or some Clematis species provide year-round coverage. Check that the root system and eventual size are compatible with your building — wisteria, for example, is vigorous and needs strong support.

How to build a simple sedum roof or living-wall planter

1. Assess the structure. For a green roof: confirm the roof can take the load (seek professional advice for any occupied building). For a living-wall planter: ensure the wall or fence can bear the weight of the planter when fully watered and planted.
2. Prepare and repair the existing surface. Any existing roof covering should be in sound condition before adding a green roof layer. For a new shed, the roof boards should be sound, level and properly secured. For a living wall, the wall or fence surface should be structurally sound and fixings should be suitable for the material (use stainless steel screws in timber; masonry fixings in brick or block).
3. Install waterproofing (green roofs). Lay a root-resistant waterproof membrane over the roof surface, lapping it up at the edges and sealing joints carefully. Proprietary green roof systems typically specify their own membrane. On a shed, a purpose-made EPDM rubber or modified bitumen sheet with root-barrier properties is suitable; follow the manufacturer's instructions precisely.
4. Install drainage layer (green roofs). Above the membrane, lay a drainage layer — typically a dimple-profile plastic sheet or a gravel layer — to allow excess water to escape rather than waterlogging the roots. This layer protects the membrane and keeps the growing medium aerated.
5. Add a filter layer. A geotextile filter fabric between the drainage layer and the growing medium prevents fine particles washing down into the drainage layer and blocking it.
6. Add growing medium. Use a purpose-formulated green roof substrate — typically a blend of crushed brick, pumice, grit and a small proportion of organic material. Standard garden compost is too dense, retains too much water and degrades over time in ways that cause the substrate to compact and settle. Aim for 75–100 mm depth for a basic sedum roof.
7. Plant or lay sedum matting. Pre-grown sedum mats (rolls or squares of sedum already established in a carrier layer) give instant coverage and are the fastest, lowest-risk option. Alternatively, plant individual sedum plugs at appropriate spacings and water in well. For living-wall pocket planters, fill each pocket with appropriate growing medium and plant one to three plants per pocket depending on size.
8. Edge retention (green roofs). Install edge-retention boards or a metal edging profile around the roof perimeter to keep the growing medium in place, particularly on any slope. Ensure gutters remain accessible and unblocked.
9. Water in and establish. Water new sedum mats or plugs well at installation and during any dry periods in the first season. Once established, extensive sedum roofs typically do not need irrigation. Living-wall planters need more consistent moisture management — install simple drip irrigation if you are planting a larger system.

DIY vs hiring a professional

A small sedum roof on a garden shed is a realistic DIY project for someone comfortable with basic construction work. The components are available from specialist suppliers, instructions are well-documented, and the scale is manageable. Mistakes are also more recoverable — if a shed roof leaks, the consequences are far less severe than a leak through a house roof.

For any green roof on a habitable building — a garage, extension, flat roof, or any structure people live or work under — professional involvement in at least the waterproofing and structural assessment stages is strongly recommended. The cost of a professional waterproofing installation is far lower than the cost of fixing a leak that has damaged timber, insulation or ceilings.

Large living-wall systems on building facades, particularly those with integrated irrigation and modular panels, are also best designed and installed by specialists. They involve significant weight, complex irrigation and sometimes electrical components. A small pocket planter on a fence is a DIY project; a full-height planted facade is not.

When choosing a contractor for any green roof or living wall project, ask for examples of completed projects, check that they are familiar with the specific system they are proposing, and ensure waterproofing warranties are clearly documented.

• Assess structural load capacity before any green roof installation — seek professional advice for occupied buildings.
• Use root-resistant waterproofing membranes; standard felt is not sufficient.
• Include a drainage layer and filter fabric between membrane and growing medium.
• Use purpose-formulated green roof substrate, not standard garden compost.
• Choose plants suited to your climate, aspect and substrate depth.
• Keep gutters and drainage outlets clear and accessible.
• Plan for basic annual maintenance — weeding and checking the membrane edges.
• Check planning requirements with your local authority before starting on any occupied building.