Coach Screws for Decking Posts

Discussion in 'Carpenters' Talk' started by Coldingham, Aug 8, 2016.

  1. Coldingham

    Coldingham New Member

    I want to add a handrail to a Decking base that was done a year ago and was looking to attach notched deck posts with coach bolts, however after removing the top deck boards I think it will be difficult to use the coach bolts due to the way the deck has been constructed (not a particularly great job). After doing a search on Screwfix I came across Turbo Coach Screws 10 x 160mm and was wondering if they would be suitable to attach the notched posts. The base is approx 2ft above the ground at the highest point and sits on a slabbed patio.

    Any advice would be appreciated.
     
  2. KIAB

    KIAB Super Member

    Got some photo's.

    Turbo Coach Screws are great, most likely would be suitable, but it would intresting to see how the way deck has been constructed.
     
  3. Coldingham

    Coldingham New Member

    Hi KIAB, thanks for the quick reply. I don't have any photo's as I put the deck boards back down but the the issue is basically that it appears that the fitter made the original deck slightly too short so he has attached an additional length of 2 x 4 to the end of the deck base to make it longer. Deck board has been put on top & down the side Covering this. I don't think I would be able to get a coach bolt through the notched post, the 2x 4, normal deck structure & the supporting post in order to make a secure fixing. I could be wrong though.
     
  4. KIAB

    KIAB Super Member

    In the old days, a coach bolt were used for a more secure fixing, but saying that,but I've used those Turbo Coach Screws to sister some joists together, they pulled up tight & gave a very firm joint, it's highly unlikely you would never ever pull one out.
     
  5. Phil the Paver

    Phil the Paver Screwfix Select

    Coach screws are fine providing you are fixing them to something solid.

    From your description its hard to tell what you are fixing too.
     
    KIAB likes this.
  6. mr moose

    mr moose Screwfix Select

    I think the screws might be a little short, also I would try and get some additional support under the 2x4 so the second screw(if just using 2 on each post) can go lower down.
     
  7. dwlondon

    dwlondon Active Member

    Sounds like some undoing to effect a decent result. So take off the end finish and expose the frame. You could notch out the 4x2 and set in the posts and replace the end sections to cover it all.
     
  8. Jeepers, Cold.

    Not enough info, man.

    If you cannot provide a photo, then any chance of a simple pencil sketch showing the 'layers'?

    As said above, these coach screws are great - easy to use. I'd drill pilot/almost clearance holes in the deck posts themselves, and they'll screw themselves nicely in to the deck base behind. Provided there's enough meat there for them.

    There's longer/heftier ones too, of course: http://www.screwfix.com/p/turbocoach-coach-screws-yellow-zinc-plated-12-x-200mm-25-pack/3645g

    Also as said above, there's a couple of issues to consider - the first being whether the bolts are long enough (only you know this) but the other is the leverage that will be placed on the bolts.

    Ie - if you were to fit just one bolt, then it's pretty obvious the leverage form the deck post/hand rail on that bolt will be excessive, so you'd need to fit at least two, one above t'other and as far apart from eachother as practical.

    If this can't be done, there's another solution which it to fit longer deck posts as Moose suggests, and continue them below the deck board level perhaps up to a foot extra. Then you make triangular braces (like a gallows support, but upside down) to go from the underside of the decking to near the bottom end of the post - that will brace it strongly and prevent any outward pushing of the hand rail.

    Also consider putting flat washers on the bolts to help prevent them digging in to the timber post.
     
    mr moose likes this.
  9. KIAB

    KIAB Super Member

    Use square plate washers, gives a larger area, than a flat washer.
     
  10. Pollowick

    Pollowick Screwfix Select

    mr moose and KIAB like this.
  11. KIAB

    KIAB Super Member

  12. Yeah, but my round ones are bigger than your square ones... :p
     
    KIAB likes this.
  13. Mr Rusty

    Mr Rusty Screwfix Select

    Coach screws are good, and you're most likely going to get a good fixing, but rail posts may have a huge leverage on the first fixing. An alternative to coachbolts might be to get a very long drill and use a length of stud bar all the way through. You'd only need one per upright to contain the leverage forces and the coach screws could provide the rest of the fixing.
     

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