Raised decking plan

9 Sep 2005
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United Kingdom
I’m building some raised decking on my garden to host a summer house. My garden has a slope so the decking does need to be raised. The summer house is quite large (5m x 4.5m) and will be heavy so I want to ensure I build a suitably heavy duty base.

For the decking “stilts”, I’ll use 4”x4” fence posts postcrete'd approx. 18” into the ground and I’ll use 6”x2” timber for the frame and noggins. I’ll screw the frame to the posts.

On top, I’ll use standard decking boards, again screwed to the frame.

Below, I’ve knocked up a mock-up of the frame and fence post locations. Was hoping to get some feedback on this – is the frame, noggins and posts in the right places? too many noggins and posts or not enough? Will it take any strength away if I use 6”x2” for the frame and 4”x2” for the noggins?

I want to ensure it’s going to last many years but at the same time don’t want to do stuff that’s not necessary.

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6" x 2" will span 8ft (2.4m). All timber should be "regularised and treated". Also you should consider whether or not you need planning permission, particularly in regards to height of decking, its size in relation to garden size and proximity to boundary. more info will be available in the "Planning and building regulations" section of this forum.
That looks like a lot of posts. Have a look at span tables.

Consider installing the posts like this rather than taking all the weight on bolts (or worse, screws):

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I'm not sure about this design. I think you are going to have two problems further down the line.

1. The wood that goes into the postcrete will rot and wick up moisture within 10-15 years, at that point it will collapse. That's why people use these metal fittings, if they are using wood. You just set them on concrete pads.


2. Although less serious, the bearers/joists that the decking is on look ok, but I would prefer to make the four outer edges more hefty than 6" x 2". 2" seems a bit flimsy.

Have you considered using landscaping and/or brickwork for the structure instead of posts? It won't rot and will be very strong.

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