Will a C16 deck joist (about 2“ by 5”) span 3m (about 15 feet)

deckingjoists

I'd like to add a decking to my garden, dimensions are 5m width x 3m depth.
Am planning to have 3m joists laid vertically (about 50cm apart) and 5m decking boards horizontally
As the soil is not very stable I was wondering whether about 10 C16 joists (2 inches x 5 inches), with bearers on both ends (3m apart), would work, could anyone confirm?

Thanks

Best Answer

Are you asking whether a 2x5" joist will span 15 feet (3m)? No. It'll be a trampoline. (Or yes, but it'll be a trampoline.) Here are your options as I see them:

  1. Go with your original plan and lay it on the soil. Then you'll have critical intermediate support even with loose soil. Worst-case scenario it settles into the soil and ends up lower then it started, or becomes uneven in the case of non-uniform soil.

  2. Lay a sleeper at the midpoint to cut the joist span in half. In this case I'd remove 4-6" of soil under each of the three sleepers and replace with crushed rock.

  3. (Preferred method): Remove 4-6" of soil and replace it with crushed rock laid over heavy landscape fabric. Then set your joists right on the rock.

Related Topic