Designing decking for sloped gardens
A sloping garden is decked either by terracing it into two or three levels or by lifting one platform on posts. Terracing usually costs less, feels better to use, and needs less balustrade. Whichever route, drainage and retaining come before boards, and steep plots typically add 30 to 60 per cent to a flat-garden price.
First measure the fall
Everything follows one number: the drop from the house threshold to the far end of the garden. Under about 300mm and you can level the frame and pack the posts, and it stays a flat deck job. Between 300mm and roughly 900mm and terracing into two levels is normally the best answer. Beyond that, you are designing a structure, with retaining, deeper footings and guarding all in play. A laser level or even a string line and tape gets you the figure in ten minutes, and it is the first thing a good contractor asks about.
Terrace, or lift on posts
Lifting a single platform level with the back door gives you one big usable space, but on a serious slope the far end can end up 1.5m in the air, which means substantial posts, bracing, balustrade all round, and a dead void underneath. Terracing steps the deck down the slope in two or three levels linked by short flights, which keeps each level close to the ground, cuts the balustrade metres, and gives you separate zones: dining by the doors, seating lower down, planting where the ground finally gets away. It reads better and it usually costs less.
Retaining and drainage do the real work
Cut into a slope and the soil behind the cut has to be held: sleeper walls, gabions or a block retaining wall, all of which need drainage behind them so water pressure does not push them out. Teesside's boulder clay is the aggravating factor, because it holds water rather than letting it through, so land drainage and a route for water to escape matter more here than on free-draining sand. The essentials: never dam the natural flow with a solid retaining wall and no outlet; keep a generous gap and cross-ventilation under the deck; and get water off the boards and away from the house rather than trapping it against a wall.
Steep plots, the Teesside version
The showcase cases sit on the coast and under the escarpment. Saltburn's cliff-side gardens off Marine Parade and the streets running down to the beach fall hard and fast, sit in a conservation area, and get salt wind straight off the North Sea, so posts are set in generous concrete, every fixing is stainless, and permitted development limits are checked before anything is designed. The lanes behind Staithes and Runswick are steeper again, with access that means every bag of ballast arrives by hand. Inland, the plots on the Guisborough and Great Ayton side of the Cleveland Hills fall away from the house with heavy clay under thin topsoil, so footings go deeper than you would expect and drainage is designed rather than assumed.
Costs and sequencing
Expect a sloped garden to add 30 to 60 per cent over the same area laid flat, most of it in footings, retaining and steps rather than boards. Raised and multi-level rates run £150 to £220 per square metre, plus £60 to £120 per linear metre of balustrade and £250 to £700 per flight of steps. Where a slope is being reshaped wholesale, decking is usually sequenced with landscaping so retaining, drainage and paving levels are set before the frame goes down, which avoids paying twice to move the same soil.
See raised and multi-level decking for the structural specification, balustrades and steps for the guarding, and the Saltburn and Guisborough pages for local detail.