Decking help

Discussion in 'Landscaping and Outdoors' started by hollyb96, Jan 29, 2021.

  1. hollyb96

    hollyb96 Member

    Hi, im building a deck for my neighbour. When i built our deck i did it the proper way and honestly it could survive an earthquake but my neighbour doesnt have a lot of money to spend and she said she's fine spending less money and only having it last a few years rather than spending more and having it last longer. The decking is being build over a current patio. I'm removing the slabs on top to expose the dirt underneath on the raised patio and then i was going to put down landscaping fabric and chips for drainage. I was going to use the brick wall of the patio for support of one of the beams. My original plan was to use galvanised post bases to raise it off of the wall for drainage but to save money and because its pressure treated i was thinking about scrapping that idea and just having it straight on the wall. My neighbour then wants the decking longer and past the old patio wall so i was going to do deep concrete footing and post bases but to save money im now trying to find out the minimum dimensions i could do the concrete footings to save money, any advice? Lastly the rest of the decking will just sit on top of the chips, not ideal and ive told her that but if shes able to get a few years without it being bouncy that will do. I could use the slabs on the right side to support it maybe rather than just chips? Don't want to attach decking to breeze block wall or outhouse wall because they're really old and crumbling themselves without having decking attached, if i attach decking it will probably pull the whole thing down. Any advice will be appreciated! Thanks!:)
     

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  2. AnotherTopJob

    AnotherTopJob Screwfix Select

    I would rest the deck legs straight on the old patio slabs, assuming they're stable.
    For the legs that need to to sit beyond the patio, sunken concrete blocks work well, with the height just above ground level to keep rainwater off.
     
  3. Severntrent

    Severntrent Screwfix Select

    If you are trying to reduce costs keep size of timbers to a minimum, can't see the logic in not using existing patio slabs as the support surface
     
  4. hollyb96

    hollyb96 Member

    so you're saying dont remove any slabs and rather than the joists laying flat on the slabs to add legs to the whole thing and the legs will sit directly on top of slabs?
     
  5. hollyb96

    hollyb96 Member

    and for the concrete footing, i cant buy premade blocks because nowhere close buy makes them and its going to cost £200 for shipping so if i was to dig footings myself, what is the shortest depth i could go while still making it structurally secure? thanks for your help:)
     
  6. Severntrent

    Severntrent Screwfix Select

    Yes, how high above the slabs will the joists be, what size joists are you proposing to use.

    Depends on the ground but just removing topsoil and putting a paving slab down should be man enough to support the end of the decking, depends how many supports you are putting under the joist which depends on size of joists used, What area is the decking and where do you propose to put support legs.
     
  7. hollyb96

    hollyb96 Member

    My new plan was going to be, remove some of the slabs in the centre and add gravel there for drainage. Leave some of the slabs for support and just lay the joists directly on them and directly on the patio wall too. Add legs to extended part at each corner and dig holes 30cm deep for concrete footings. The patio wall is only about 40cm high and im going to use 2x4 joists. Ive attached plan for decking plan. Thanks:)
     

    Attached Files:

  8. AnotherTopJob

    AnotherTopJob Screwfix Select

    Sounds fine. Not sure of the size but with 4x2 framing it might be sufficient just to have the centre resting on the patio slabs.
    30cm sounds good for footings.
     
  9. hollyb96

    hollyb96 Member

    The whole deck will be 284x408cm, the overhang is about 80cm. My only worry about not removing any paving is the drainage. I thought it would probably be better with some gravel?
     
  10. AnotherTopJob

    AnotherTopJob Screwfix Select

    A good idea to allow some extra drainage. The main thing with decks is to allow airflow under the structure and avoid any part of it to sit in standing water or soil.
     
  11. Severntrent

    Severntrent Screwfix Select

    Running the figures and assuming floor loading is the same as for a domestic dwelling, using Class c16 joists spaced at 400mmcentres and Service condition 3 (exposed to external elements) your joists will each need a central support or a support every 2nd joist carrying a support joist to the underside of your main joists. Lesser loading and using C24 changes things.
     
    chillimonster likes this.
  12. hollyb96

    hollyb96 Member

    I got it wrong. I thought the overhang would be 80cm but it will actually be 180cm. After looking online it seems like this will still be fine in terms of enough support for the deck.

    Are you saying rather than digging down for concrete footings i can just put down patio and have legs go directly on top of that?
     
  13. Severntrent

    Severntrent Screwfix Select

    Yes something like this IMGP1146.JPG
     
  14. hollyb96

    hollyb96 Member

    Yeh thats what i thought you meant. Structurally do you think that would be ok? I know the post would probably rot quicker this way than if i used galvanised post bases but it would be easy to replace them in the future if i needed to. Doing it this way would save a lot of hassle too. Thanks for your help:)
     
  15. Severntrent

    Severntrent Screwfix Select

    The photo was taken 10 years ago and the decking is still standing, well it was last summer but will after wait till lockdown is over to confirm
     
  16. hollyb96

    hollyb96 Member

    Thats good! Definitely think im going to do it that way. Did you put end grain protector on the cut ends?
     
  17. Severntrent

    Severntrent Screwfix Select

    No but timber was already treated and any cut ends placed away from ground
     
  18. hollyb96

    hollyb96 Member

    started preparing the ground today. Thanks so much for all your help and advice:)
     

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