Decking supports

Discussion in 'Carpenters' Talk' started by Jab64000, Mar 23, 2021.

  1. Jab64000

    Jab64000 New Member

    Hi, I wondered if I could ask a basic question about decking supports. My daughter had some decking built ( it’s quite high at some points because it goes to their back door so just under 2m)
    The joiner was very experienced and the decking looks good, but when I had a look underneath I felt it could do with some extra uprights. The uprights the joiner had fitted in some places seemed very loose to me and were barely touching the bricks that he had used on the ground as supports. In addition he had screwed these uprights using only a couple of screws into the joists. I fitted a few extra uprights but instead of screwing through and into the joists I fitted them a tight but not too tight under the joists and onto a flat piece of decking as a footing. Is there a reason that the joiner would have screwed them rather than making them rigid underneath the joists? I get it that as you load the decking the weight would push down and the uprights “should” then start to make full contact with the footings. Although I was concerned that the supports would only be as strong as the 2 screws that were taking all the extra strain. Is there a correct way to fit these supports? I did consider bolting the upright to the joist(12mm stainless bolts) would that be an adequate way of connecting them? Any advice welcomed
  2. Jord86

    Jord86 Screwfix Select

    Depends on span, distance between supports, and the joiners inclination on a Friday afternoon. It's very difficult to ascertain things without any photos, but one thing for sure is that 12mm bolts are a ridiculous overkill for a simple deck. Why didn't you ask the joiner?
  3. Jab64000

    Jab64000 New Member

    it’s a bid decking it’s 4x5m and a couple of metres high. Supports are distanced approx 1.5m but it was built on uneven ground. The reason I didn’t ask the joiner is because I wasn’t there- it is my daughters house, but they do tend to have a lot of people to parties etc so it could easily see 20 or more people on it at a time.
  4. Truckcab79

    Truckcab79 Active Member

    From your description it sounds like the deck is only supported when it flexes enough to push down on the uprights. That’s obviously not correct. Would be very interested to see pictures. 2m in the air is a hell of a height. Surely there are supporting posts fixed into the ground which are supporting the structure?
  5. Jab64000

    Jab64000 New Member

    I have attached some pictures( I should have done that to start with) the supports underneath also include the extra 6 supports I have put in. I was a bit concerned with the way that the support was connected to the joists by just 2 screws, my preference would be to see it directly under the joist so that it is in compression ( with a screw either side to hold it in place?

    Attached Files:

  6. AnotherTopJob

    AnotherTopJob Screwfix Select

    Replacing the screws with bolts won't hurt, screws aren't really adequate.
    Having some L shaped brackets at the bottom of the supports is probably a good idea.
    Not likely to be a problem unless you have intolerant neighbours, but planning permission is required for a deck of this height.
  7. Jab64000

    Jab64000 New Member

    Thanks for your advice. For the extra supports I put in I have screwed the foot plates to the concrete. ( instead of l shaped brackets) the decking was a replacement and Planning permission / building warrant was requested for that original decking
  8. AnotherTopJob

    AnotherTopJob Screwfix Select

    Looks like a neat job, the gaps are pretty wide on the boards though.
  9. Hager the Horrible

    Hager the Horrible Active Member

    Looks neat from above but I would not be happy with that support structure. I'm not a joiner but have done 3 or 4 decks over the years with 1 or 2 easily as high as that. I built 6x2 frames with joists at 400mm centres (plus noggins) to carry the boards and supported them on 4x4 fence posts set 400mm into the ground (concrete finsished above gl and floated to shed water away from post base). There was one post that had an existing concrete path underneath it so I used a bolt down shoe on that one...
    I would not have considered simply resting the supports onto loose or uneven ground that could washout or compact. I see you have glass panels fitted and the fixings on these can be very sensitive to movement so you may encounter issues if your deck settles or moves.

    Your photos look just like the supports under decks that get put up around static caravans. We have a caravan with one of those done by others and it has moved and settled quite a bit over the last few years. Luckily it does not have glass panels in so no disasters yet but it is not great.
  10. Jab64000

    Jab64000 New Member

    Thanks for your advice, I am not a joiner either (I am a Mechanical engineer), but I did feel the supports were a bit inadequate, saying that the decking is attached to the wall of the house so that should be taking the majority of the weight close to the house. I think I will put a few extra supports in the centre by digging a few fence posts into the ground and attaching them with some bolts just to be one the safe side. - thanks again.
  11. Truckcab79

    Truckcab79 Active Member

    Looks neatly finished but I wouldn’t be at all happy with that structure. Far too high to be rested like that. Should be on much more substantial posts concreted into the ground. I’d personally be building it rested on double bearers sandwiched either side of said posts and at that height would want to see some diagonal bracing to stop it wanting to pivot over.

    Screws are not the correct way to fix either. Should be using Timberlock / Timberdeck structural fixings or bolted through.

    Probably never going to fall over but it’s not right.
    Your fence post ‘upgrade’ will do the job and give you peace of mind.
  12. Hans_25

    Hans_25 Screwfix Select

    The support for the decking looks completely inadequate, especially with the glass panels which will crack if moved.

    If it were mine, and with the potential for a lot of weight on it, I'd be getting some 6x2 and making a cross-braced spine wall/support underneath and probably adding support around the outside too.

    Its the kind of thing you see on TV programs, looks great but doubt it will last.
  13. stevie22

    stevie22 Screwfix Select

    As others have said looks good but.....

    Screws or bolts you're still relying on shear in the post connection: a rebate to directly support the beams would be so much better.
    Hans_25 likes this.

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