Objective – raised beds for less than £10 per sq m
Having moved to a new home late 2016, these two raised beds and greenhouse were my main gardening project in 2017-2018. The design is mine, inspired by circular water and oil tanks which rely on tension in the outer skin to contain the liquid, rather than flexure of the sides.
Whilst potentially expensive to construct, a raised bed (with boards containing the soil) has a number of advantages over a traditional cultivated bed:
- Tidy and space efficient, with the soil contained by the sides
- Soil improvement can be focussed and achievable
- Less digging, as there is no need to walk on the soil
- Improved drainage,warming up faster in the Spring
- Improved yields
- Less bending over, depending on the height
However, creating beds of sufficient size for vegetable or fruit growing can be cost prohibitive, with kits in recycled plastic costing £50-£75 per sq m or more.
The material used is a recycled plastic used in agriculture called Stokbord, cut into strips and bolted together with stainless steel bolts. The completed construction will be highly durable and should last for many years.
Some statistics on materials:
- Outer ring fabricated from six 20cm x 244cm strips of 12mm Stokbord (one 2.44m x 1.22m sheet) and 48 No M10 x 45 stainless steel bolts (each with two 30mm washers); 12 No 6mm Stokbord cover splices 40cm x 20cm
- Inner ring fabricated from three 15cm x 244cm strips of 6mm Stokbord and 12 No M6 x 25 stainless steel bolts
- Tub in centre fabricated from spare material from 6mm Stokbord and 4 No M6 x 25 stainless steel bolts
Dimensions of raised bed
- Outer ring diameter 4.66m
- Inner ring diameter 2.14m
- Raised bed annulus width 1.26m
- Raised bed area 13.5 sq m
- Stokbord 12mm sheet 2.44m x 1.22m £55
- Stokbord 6mm sheet 2.44m x 1.22m £30
- Stainless steel bolts A2 grade £33
- Total cost £118
- Cost per sq m £8.80
So after a lot of turf stripping and double digging, here’s the first raised bed completed in 2017:
Greenhouse and Raised Bed 1
The following year, a second raised bed was added, this one slightly taller and smaller in diameter:
Raised Bed 2 in 2018
Now in 2020 with lots of compost added, the soil continues to improve and the beds have become very productive.