Decking: Concrete Posts or Embedded Slabs?

[construct]

Above is the area/shape I intend to cover with decking; the 10m length runs flush against my new fencing gravel boards, and the 0.5m length runs against shed brickwork, while the remaining sides are exposed. The decking itself will be as low to the ground as possible (obviously with clearance for the membrane and shingle etc.) and I'm currently torn between concreting many posts or embedding slabs onto the scraped back earth instead. There seems to be very divided opinions about what provides a taut deck, so I thought I'd see what people here think?

Obviously slabs would be more cost/time efficient but I'm not one for shortcuts, which is why I'm uncertain right now. has anyone here used slabs for a deck this size, and if so, has it worked out okay?

All comments welcome...

 

[freddiemercurystwin]

I've used slabs onto gravel straight on to the ground not moved for 12 years so far So a concrete base for the slabs will only be better. Gravity will hold it down and flat. All assuming your grounds OK.

 

[construct]

Decided to forge ahead with the slab option, I'm trying to find some way to butt/connect two joists end-on-end, but can't seem to find a product that would help, am I missing something?

I'd also welcome comments on how to join the joists to the 10m frame on the LHS, as I can't seem to find angled joist hangers either. I've been considering cutting angled blocks and screwing to them instead, but I'm open to ideas...

 

[Steve]

I wouldnt be joining two joists end on end, but if you need to (And the length of the run doesnt mean its going to lack sufficient support), you need to bolt another length of joist to one side, at least 2ft each side of the joint, with plenty of bolts. Obviously lengths depend on the strength required of the joint.

I hope you're not trying to do 7 metres in one span? You need intermediate support.

As for angled joints, I would cut the angle onto the end of the joist, then bolt through at an angle. No hangers required.

 

[construct]

Hi Steve

Thanks for your comments, I'm midway through now, and all joist connections are sitting on bedded slabs with 6x100 screws going through to another length of 4x2 on the side/front. The 7m span is made up of 2 x 3.6m lengths, resting on bedded slabs every 1.5m and it's all looking very, very solid.

The 10m run which is the side where the angled ends would rest, is flush with the gravel boards/fence posts, so there's no way of bolting anything, as there's no access to the back of the frame. I'm thinking of using 3 x 6x100 screws drilled through at an angle, backed up with slab sections underneath to provide additional support, but if there are other options i'd consider them.

I'm cutting the joists to length tomorrow, but not fixing them until the membrane is down...

 

[Steve]

Use 2 coach screws at each joint. pilot drill them. Shouldnt need additional support from below. Use a screw length that goes most of the way through both timbers.

 

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Phase 1 completed.

 

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Phase 2 almost finished...