Finishing a garden room with bespoke metal planters

Why metal rather than timber

Timber planters sitting against timber cladding compete with the building and rot from the inside within five to eight years. Steel does neither. Corten weathers to a deep russet that flatters cedar and thermally-modified timber, while powder-coated aluminium or mild steel in a dark anthracite disappears behind the planting and picks up the frame colour of bifold doors.

Metal also lets you go tall and narrow without the walls bowing, which matters when you are screening a boundary in a small garden.

Getting the proportions right

Scale the planters to the building, not to the plants. A 3m glazed elevation reads well with a single long trough rather than three small pots. As a starting point:

• Along a glazed elevation: 300–400mm high, 400mm deep, run the full width
• Either side of the door: matched pair, 600–900mm high cubes
• Boundary screening: 800–1000mm high, 500mm deep, planted with bamboo or pleached hornbeam
• On decking: check the point load — a filled 1m trough is around 300–400kg

Drainage, liners and frost

Specify drainage holes and feet so water leaves the base and air circulates underneath — standing water rots roots and stains decking. Ask for an internal liner or a drainage layer of scoria so soil is not in permanent contact with the base. Steel conducts cold, so for anything you want to overwinter, insulate the inner face or keep to hardy planting: hebe, pittosporum, ferns, grasses and multi-stem amelanchier all cope well.

Where to get them made

Off-the-shelf sizes rarely match a garden room elevation, so a made-to-measure run is usually the better buy. We regularly specify pieces from Bespoke Metal Planters, who fabricate Corten and powder-coated planters to exact dimensions in the UK — useful when you need a trough cut around a step, a corner return, or a matched set in the same finish as your door frames.

Planning the planters before the base goes in

Decide planter positions before groundwork starts. Anything sitting on paving or decking needs a level, load-bearing area beneath it, and if you want irrigation you will thank yourself for laying the pipework in the same trench as the armoured electrical cable rather than lifting slabs afterwards.