Best option for decking footings???

Discussion in 'Landscaping and Outdoors' started by jimmy86, Jun 5, 2020.

  1. jimmy86

    jimmy86 New Member

    Hi All,



    I am planning on building a ground level deck, where the deck boards will be level with the surrounding turf. I am struggling to decide on a plan for the footings and was hoping you might have some suggestions.

    The decking frame will be formed of 150 x 47 mm treated timber. Joists will be at 400mm centres with noggins every 1.2m. I will be adding a weed membrane.

    I plan on digging out approx 230mm of soil to sink the deck into, this will be enough for the frame, boards and some form of footings. There seems to be conflicting advice on the best option for footings. Will patio slabs bedded on gravel be sufficient? Or would I be better using posts and postcrete? The deck will be 6m x 4m so would mean a lot of hole digging if going for the posts option! What do you advise.

    The deck will part of a play area for kids and also where the inflatable hot tub is stood in the nice weather (approx 1300kg, 2m diameter).


    Any advice would be greatly appreciated as this is my first attempt at decking.

    Thanks,
    Jimmy
     
  2. wiggy

    wiggy Screwfix Select

    Go for it.
     
    jimmy86 likes this.
  3. jimmy86

    jimmy86 New Member

    Thanks Wiggy!

    Any guidance on thickness of the slab or will some 35mm thick 450x450mm slabs I have from a previous projest be sufficeint?

    Another quick question....joist hangers? Are they required or is it acceptable to fix each joist using 100 or 150mm timbascrews?

    Thanks
     
  4. wiggy

    wiggy Screwfix Select

    Either or on the fixings.
    The more ground clearance the better, just use whatever you have.
     
    jimmy86 likes this.
  5. jimmy86

    jimmy86 New Member

    Thank you. I'll give it a go.

    Fingers crossed it goes to plan.

    Let me know if you have any other tips.

    Cheers
     
  6. Severntrent

    Severntrent Screwfix Select

  7. wiggy

    wiggy Screwfix Select

    I would border it with a channel of pebbles or stone and have a slightly larger deck gap than normal to help with ventilation, maybe 6 or 8mm you could give the frame a good dose of creosote also.
    These things aren't crucial but they help.
     
    jimmy86 likes this.
  8. jimmy86

    jimmy86 New Member

    Thanks ServernTrent. Are those slabs on a sub base of any kind?
     
  9. Severntrent

    Severntrent Screwfix Select

    IMGP1146.JPG Just a 25/50mm bed of sharp sand to get them all the same level. Attached better photo
     
    jimmy86 likes this.
  10. jimmy86

    jimmy86 New Member

    Thanks.

    Did you have slope on the slabs to provide a fall for water or was the fall altered when fixing the frame to the posts?

    How essential is the fall when the decking is nowhere near the house?
     
  11. Severntrent

    Severntrent Screwfix Select

    Didn't bother with a fall, if its throwing it down I'm inside and it all disappears eventually IMHO
     
  12. jimmy86

    jimmy86 New Member

    Just thinking about this some more. Why does a patio need a hardcore base then mortar bed to fix slabs yet decking just needs the slabs with no real sub base?
     
  13. Severntrent

    Severntrent Screwfix Select

    Decking tends to be a structural entity in its own right and tends to redistributes any mismatch of forces and movements around as a whole with the decking keeping things in alignment, slabs are discrete elements and therefore it is important that the subase is of a standard strength all over as movements of just a couple of mill we be easily noticed. Worst case of a single post settleing can be easily sorted with a plastic packer under the post
     
    jimmy86 likes this.
  14. jimmy86

    jimmy86 New Member

    Thanks. That makes sense now.
     
  15. jimmy86

    jimmy86 New Member

    Hi,

    Making good progress with the garden project with the help of the advice above.

    I have some dense concrete blocks left from a previous project so planning to use these to sit the frame on. These will be levelled on some type 1 as I have some of that left too.

    Do people reckon it's worth putting some DPM between the block and the frame?

    Cheers,
    Jimmy
     
  16. Severntrent

    Severntrent Screwfix Select

    Won't do any harm but going back to my photo I wouldn't bother
     
    jimmy86 likes this.
  17. jimmy86

    jimmy86 New Member

    Thanks
     
  18. jimmy86

    jimmy86 New Member

    Hi All,

    So framing is complete and boards all cut to length and ready to fit.

    Was hoping to get the boards fixed today. The boards seem to have dried out reasonably but the joists are still a little damp. I have held off screwing the boards down as there has been torrential rain the last few days. My question is will it be OK to fix the boards while things are still a bit damp or would I be better holding off until things have dried out a bit more? Conscious there is more rain on the way over the coming days.

    (all framing is treated C24 6 x 2).

    Thanks,
    Jimmy
     
  19. I-Man

    I-Man Screwfix Select

    just be wary of the fact that once dried out, your boards may decide they don't want to be straight and have decided to fulfill their lifelong desire of impersonating a banana!

    (had a nightmare with my last batch of treated timber, straight but damp when bought, left to dry out and ended up shaped like boomerangs :( )
     
  20. chillimonster

    chillimonster Screwfix Select

    I wish I had Severntrent's soothing voice on a tannoy as I tackled today's garden
    back gate replacement with the leaning posts and cat poo booby traps.
    Yes, I am unwinding with a bottle of chardonnay.
     
    jimmy86 likes this.

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