How to Build a Raised Garden Bed

Benefits of Raised Beds

Better drainage and soil control. Fewer weeds than open ground. Warmer soil (extends the growing season). Easier to work — less bending and kneeling. Better yields from concentrated growing space. Can grow vegetables even on poor or contaminated soil.

Choosing the Right Materials

Untreated hardwood (oak, larch, sweet chestnut): most attractive and long-lasting (15–20 years), costs £30–£60 per plank. Pressure-treated pine: affordable (£15–£25 per plank), lasts 10–15 years. Avoid railway sleepers unless specified as non-creosote treated. Reclaimed scaffolding boards: economical and attractive.

Dimensions

Height: 20–30cm for flowers and shallow-rooted vegetables. 40–60cm for root vegetables, fruit, and maximum growing conditions. Width: maximum 1.2m so you can reach the centre from both sides. Length: any length — 2.4m is a useful standard matching timber lengths.

Building the Frame

Cut timber to length. For corners, use 75x75mm corner posts driven 30–40cm into the ground, or bolt planks together using L-shaped metal brackets. Stack two or three courses of planks for deeper beds, staggering the joints for strength. Predrill to prevent splitting.

Preparing the Base

Place cardboard over the ground inside the bed to suppress weeds — it breaks down within a year. No need to dig unless you have compacted clay soil, in which case fork it over to improve drainage.

Filling With Soil

Use a mix of: 60% quality topsoil, 30% garden compost or well-rotted manure, 10% horticultural grit or perlite for drainage. Fill to within 5cm of the top. This mix costs approximately £50–£100 for a 2.4x1.2m bed.