How do you build a level deck on a sloping garden?
Keep the boards level and let the posts get longer downhill. Here's what changes and what doesn't.
You don't follow the slope. The frame stays level and the ground falls away under it, so each row of posts is cut to the ground where it stands. The house side stays low and the outer edge ends up higher.
The number of posts and footings doesn't change. Their lengths do, and so does the height that counts for safety. A deck that is 300 mm up at the house can be 900 mm up at the far edge, and that far edge is what decides whether you need a guard.
Steps get longer too. They come down from the level frame to lower ground, so you may need one or two more than you'd guess standing at the back door.
Check before you buy or dig
- Measure the fall with a string line and level from the house edge to the front edge, not by eye.
- Tall downhill posts usually need bracing. Ask your local rules or an engineer once posts get past about 1.2 m.
- In the UK and Ireland, a deck more than 300 mm above the ground at any point normally needs planning permission.
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Open a sloping deck in 3DA general answer, not a structural design. Local rules, ground and loads decide the final build.