Hello all. I've been reading this forum and overusing Google, and I think I've come up with a decking plan that makes sense, but would really appreciate a sanity-check of the design, please, to make sure I've not missed anything obvious. I've mocked it all up in Sketchup, both to check construction but also to help with quantity estimating.
Here's an overview picture, to show the context. Essentially, it's a ground-level deck that extends 3m from the back of the house, and spans the 7.5m back of the house. The two cut-outs towards the left are for a waste pipe (under the window) and rainwater downpipe (end of house).
Starting at the waste pipe, there's a 5" sewer pipe running almost at the surface of the ground, right along the back of the house. I'm therefore intending to create a wall-plate to act as the first joist (given that the boards are running away from the house), which will be a 4x2 bolted every 500mm or so, just below the DPC and with 10mm spacers.
Once past the waste pipe, I'll dig down enough to give a couple of inches clearance underneath the frame.
The frame itself is all 4x2, and I've designed it on the assumption of 4.2m lengths. The 4x2s around the rim have supporting 4x4 posts 1m apart, and are fixed to the wall-plate by a hanger (in the middle) and by an angle-bracket (on the right).
The 4x2 joists have 400mm centres, and are attached by hangers to the outer rim and the middle spine, and by screws to the angled "beam" on the left. They're further supported every 1m by 4x4 posts. There are also noggins with approx 600mm centres to strengthen the frame.
The decking boards will run away from the house with a slight fall (I figured maybe 10mm over 3m??), and the grass just beyond them will be leveled up to be at the same level (with a small gap to prevent the wet grass rotting the timber).
Any and all advice welcome. I've never done this before, so there's every chance I've missed something obvious.
Thank you very much, in advance, for any help you can offer.
Here's an overview picture, to show the context. Essentially, it's a ground-level deck that extends 3m from the back of the house, and spans the 7.5m back of the house. The two cut-outs towards the left are for a waste pipe (under the window) and rainwater downpipe (end of house).
Starting at the waste pipe, there's a 5" sewer pipe running almost at the surface of the ground, right along the back of the house. I'm therefore intending to create a wall-plate to act as the first joist (given that the boards are running away from the house), which will be a 4x2 bolted every 500mm or so, just below the DPC and with 10mm spacers.
Once past the waste pipe, I'll dig down enough to give a couple of inches clearance underneath the frame.
The frame itself is all 4x2, and I've designed it on the assumption of 4.2m lengths. The 4x2s around the rim have supporting 4x4 posts 1m apart, and are fixed to the wall-plate by a hanger (in the middle) and by an angle-bracket (on the right).
The 4x2 joists have 400mm centres, and are attached by hangers to the outer rim and the middle spine, and by screws to the angled "beam" on the left. They're further supported every 1m by 4x4 posts. There are also noggins with approx 600mm centres to strengthen the frame.
The decking boards will run away from the house with a slight fall (I figured maybe 10mm over 3m??), and the grass just beyond them will be leveled up to be at the same level (with a small gap to prevent the wet grass rotting the timber).
Any and all advice welcome. I've never done this before, so there's every chance I've missed something obvious.
Thank you very much, in advance, for any help you can offer.
