Decking advice please

Discussion in 'In the Garden' started by Steveb21, 21 May 2017.

  1. Steveb21

    Steveb21

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    Hello all,

    Not sure if this is the correct place to post this, please correct me if it needs to be moved.

    I am planning to build a deck in line with my outdoor pool.

    Deck size will be:

    5.4m x 6.0m
    17.7ft x 19.6ft

    I can get hold of either 5.4m or 6.0m deck boards so i have a choice on which way i lay my deck, both options will be no waste/cutting of boards.

    I am considering laying the deck boards vertically and using the 5.4m boards.

    Plan is to dig footings for posts (under frost line)
    Fill with concrete and attach a post bracket (in wet concrete or attach via bolts)
    Lay beams (using 2 joists nailed together)
    Install joists
    Lay decking boards


    Questions:
    For an area 32.4m square how many footings should be required? I think i can get away with 3x3 = 9 , or should i do 4x4 = 12

    Thinking of using a post bracket fitting on top of the footing and then attaching deck post. Is this a good method? Something like this... http://www.toolstation.com/shop/p29...roduct=29420&gclid=CPiUzZ2DgdQCFUg8GwodQSUPLw

    This is a pic of the are in question..
    [​IMG]
    [​IMG]
     
    Last edited: 21 May 2017
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  3. Chud

    Chud

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    OK a couple of things...

    5.4m boards may work out a little bit cheaper - some suppliers will charge a bit more (per linear metre) for longer lengths over your 2.4m standard length - it'll probably be negligible between 5.4 and 6 though!

    Secondly, either way will be a looong board so I would advise using a smooth topped deck board - if you fit it grooved side up then any water that gets into the grooves is effectively going to be trapped. To be honest I think I read that originally the grooves in decking were there to assist with ventilation to the frame so were supposed to be fitted downwards but someone at some point thought they'd be good for grip (they're not btw).

    I would also suggest giving the deck a coat of osmo anti-slip - it'll help prevent slips and aid it in shedding water.
     
  4. Steveb21

    Steveb21

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    Many thanks for your reply.

    Would 4x4 posts and 2x8 joist be sufficient ? I will double up a joist to use as beams.

    I am thinking of either 9 or 12 posts. 4 covering 6.0m and 3 covering 5.4m side.

    Looking at the first picture above the deck will run from the fence side down to where the steps are ( i will install a gate in front of the steps after)
     
    Last edited: 24 May 2017
  5. mattwood22

    mattwood22

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    I recently helped a friend with some decking and found the timber merchant very helpful in deciding how many posts / joists / beams. I'm sure someone knowledgeable will be along in here as well though.

    Is there any reason you aren't putting your posts straight into the concrete? I did it this way for my fence, and the timber merchant agreed it was the better way although they did sell various other options.

    Additional tools that will make your life easier...

    1. Post hole digger - something like this for quicker digging and less concrete

    http://m.ebay.co.uk/itm/Heavy-Duty-...%3A418a863415c0a86c0cb618daffff99f7%7Ciid%3A3

    2. Fence post level. Couple of quid from toolstation

    Good luck and let us know how you get on!
     
  6. motorbiking

    motorbiking

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    agree with a deck stain paint it really improves the finish and waterproofing.

    i'd lay your support posts at 1.2m intervals or less and use 2 x 5 or 6 beams spaced 600mm or less.

    if you don't have one buy a post shovel as it makes digging the holes so easy.

    I'd use screws not nails
     
  7. Steveb21

    Steveb21

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    Morning all,

    Is there any reason you aren't putting your posts straight into the concrete? Basically i was thinking that if the timber never touches soil it will prolong the life span of it? Also if a post ever needs changing it would be easier as it will just mean removing a few bolts and attached a new one. I am also a little worried incase i set the post incorrectly in the concrete!

    I have already got hold of a post hole digger and and post level - heard good things about both of these.

    i'd lay your support posts at 1.2m intervals or less and use 2 x 5 or 6 beams spaced 600mm or less.
    Laying at 1.2m intervals is approx. around 20 posts, just seems a lot but hey ive never laid a deck before. 5x4 (6.0m x 5.4m) posts = 20 Excuse my lack of knowledge however when you say space beams 600mm or less what do you mean by this?

    A few other questions:

    If i lay the boards vertically i will not be able to get a flush finish in the line with the pool height (as i will need to angle the deck for rain water to drain off). Should i decide to switch the boards and lay horizontally ? I can get 6.0 length boards for that. (I am trying to minimize any cutting).


    Should i attach a ledger board against the pool wall? I'm a little confused on how this works, if i dig posts in the ground near the pool wall the beams will sit on top and then the joists however the edge of the deck (which meets the pool) will have no support directly underneath.


    Something like: [​IMG]



    [​IMG]



    Do the joists need to sit in the beams or on top of them?


     
    Last edited: 26 May 2017
  8. motorbiking

    motorbiking

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    [​IMG]


    Support legs spaced approx 1.2M apart avoids the need for support beams/sub frame - if you want them further apart then you probably need bigger/more support beams - you could probably do 1.8m easily enough - it depends on height etc.
    joists are spaced 600mm apart, so you have a support post screwed to a joist, 600mm a joist, another 600mm (from centres) next support post.

    With a post spade its 10-15 mins a hole tops.

    I'm in the process of breaking up a deck I did `18 years ago and the posts are just standard pressure treated wood and haven't rotted at all.

    In the picture you posted - there's no way I'd have a bbq or party on that. Though the beam looks about 8" or more. Also if its more than 30cm from ground level - you need planning permission/building control
     
    Last edited: 26 May 2017
  9. Steveb21

    Steveb21

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    Thanks for that example, it is pretty much what i am trying to achieve.

    '' Support legs spaced approx 1.2M apart avoids the need for support beams/sub frame''

    Sorry, but how will the joists be supported if there are no support beams? Am i correct in thinking that as the legs space is 1.2m apart the joists will attach to the posts without beam support underneath?

    My plan is/was to:

    6.0m x 5.4m Deck area

    Install posts x 20 - will use 4x4 for this.
    Attach beams (1 on each side of posts) - will use 2x6 joist for this.
    Attach subframe on top of the beams
    Attach joists
    Attach noggin
    Attach deck posts
    Attach deck boards


    The height off the ground will be minimum from one end and 2ft from the other.
     
    Last edited: 26 May 2017
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  11. motorbiking

    motorbiking

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    Every other joist will be attached to a leg and the decking with noggins will be stiff enough, If you have space under you can use any spare joists as support beams as needed.
     
  12. Steveb21

    Steveb21

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    Many thanks that makes sense.

    I have been attempting to remove the tree stump which has led me to think, even after getting it out the roots are shooting all over the place, digging 20 post holes is going to be a fair effort.

    If I attach a doubled up joist and bolt it to the pool wall, could I then get away with fewer posts? My deck will max 2ft off the ground - even less the other end.

    Something like the attached pic... (it only has 3 posts.)
     

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    Last edited: 29 May 2017
  13. motorbiking

    motorbiking

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    Personally I wouldn't go drilling holes in your pool for the sake of a few post holes. Depending on the length of joists you are buying you'll need the posts 2.7 and 3m apart, depending which way you run them. So you should be fine with 125 - 150mm supports.

    As long as you add noggins to stop the joists from twisting or flexing under load it should be OK.

    [​IMG]
    Tree roots = Mattock - approx £15 from toolstation.
     
    Last edited: 30 May 2017
  14. Steveb21

    Steveb21

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    True about drilling into the pool wall - will avoid that.

    If i dig 9 post holes and lay 3 beams (2x5, 2x6 or 2x8?) vertically (x2 5.4m joists bolted together on either side of post) at a spacing of 3m apart

    Sit 3m (2x5, 2x6 or 2x8?) joists in between and add noggins as you mentioned for extra support.


    ps.... i have been using a axe to try and cut through the roots. Will get hold of a mattock.
     
    Last edited: 30 May 2017
  15. motorbiking

    motorbiking

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    150mm so 2 x 6 - If you can get 6M lengths just overlap them rather than cutting them down - you'd need 20.. If you can get 4.8M lengths then you need 22 and another 6 post holes would make the perfect set up. Another 3 for noggins, but you could get away with 2 x 4 or 2 x 5 for those. My quick calcs suggest 4.8M is £100 cheaper drawing.jpg
     
  16. Steveb21

    Steveb21

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    Finally got that tree stump out!

    Quick couple of questions:

    How deep does the post hole need to be?
    I take it the post holes around the edge and corner of the deck are not to be placed right on the edge/corner? They need to sit a little in so i can install any rails later. Is this correct? I had planned to start my corner post holes 10" in from both the corner sides.

    or, could i use my 4x4 post and keep the height to use as a rail post? or is this not recommended?
     
  17. motorbiking

    motorbiking

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    down to solid ground. but about 450mm is good. i.e. depth of a normal spade.

    set your posts back enough for you to fix edge boards flush with deck.
     
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