Best way to support 150x150mm x 3m posts for Pergola

Discussion in 'Landscaping and Outdoors' started by Matt J, Apr 28, 2020.

  1. Matt J

    Matt J Member

    Hi everyone,

    Just signed up and this is my first post. I've taken on a renovation so suspect I'll be posting a lot on the future!

    I hoping someone can give me their thoughts on the best way to support my pergola posts.

    I am building a pergola (and deck and bbq etc) over a concrete slab. There are 4 posts, 2 of which sit on the slab and I will be securing them with 150x150mm bolt down post supports and through bolts to anchor them to the slab.

    But the other two sit over a small run of mud alongside the slab. Pics here -

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]



    I guess I have three options that will vary based on cost and practicality.

    1) To fill the entire are with concrete which in total is 0.72m3 so that's a lot to fill, and then use the post bolt downs.
    2) To section off two areas where the post will sit (as apposed to the entire space) and fill those bits with concrete and use the post bolt downs.
    3) to buy longer 3.6 m posts, and sink 1.2m into the ground with a concrete base but that would mean trying to source 3.6m or higher 150x150mm posts which are very difficult to get hold of at the mo and I have 4 pc 150x150mm x 3m posts arriving tomorrow.

    Any thoughts on what is best to do would be much appreciated :)

    Matt.
     
  2. wiggy

    wiggy Screwfix Select

    Bring the posts in to sit on the concrete. I cant see them getting in the way of anything.
    You can shoot your beam past the post if you want.
     
  3. Kas228

    Kas228 Screwfix Select

    Option 2. Dig out 2 areas slightly bigger than posts where posts will locate, fill with concrete to correct level. Leave to set and away you go.
     
  4. Matt J

    Matt J Member

    Thanks wiggy. I can’t move the posts unfortunately; you can’t see sit in those pics but the outdoor kitchen relies on them being off to the left. Pretty annoying!
     
    wiggy likes this.
  5. Matt J

    Matt J Member

    Great thanks @Kas228 Is there a recommended depth / area that I should be making these two areas? I honestly haven’t a clue! At a stab in the dark I’d just go 200mm down and say 450x450mm leaving 150mm around all edges of the 150mm post essentially?
     
  6. Matt J

    Matt J Member

    Is it that obvious ‍ha!
     
  7. Kas228

    Kas228 Screwfix Select

    use your own judgement based upon the amount of weight on each support, personally i would go a bit deeper than 200 mm, say 300 mm,
     
    Matt J likes this.
  8. Matt J

    Matt J Member

    Excellent thanks @Kas228
     
  9. CharlMil

    CharlMil Member

    Use postcrete. All instructions are on the bag (or google first). Just dig your hole to required depth for height of the post, 100mm shingle for drainage, Post in, Postcrete in, water in, give it a mix, support so it’s level and plumb. Done
     
    Matt J likes this.
  10. Kas228

    Kas228 Screwfix Select

    Think the OP was saying that he couldn't get longer posts at present hence the concrete base option.
     
    Matt J likes this.
  11. CharlMil

    CharlMil Member

    oh yes, I missed that bit!

    OP, what is your final floor going to look like? Are you decking or paving or leaving as is?

    This will determine the best choice and advice you receive
     
    Matt J likes this.
  12. Matt J

    Matt J Member

    @CharlMil It will be decking with the pergola posts going through the deck to the floor. I'm going to box in the posts on the subframe too for a little extra support...
     
  13. CharlMil

    CharlMil Member

    Sounds good! I would just make a concrete slab big enough for each post then rather than concrete the whole lot as it won’t be seen.
     
    Matt J likes this.
  14. Matt J

    Matt J Member

    @CharlMil Awesome thanks mate! very helpful
     
  15. CharlMil

    CharlMil Member

    you’re more than welcome mate! Please send us pics of your progress and finished project! Love to see it
     
    Matt J likes this.
  16. Matt J

    Matt J Member

    Will do mate! Laid the concrete today. Subframe tomorrow!
     
  17. CharlMil

    CharlMil Member


    Nice how did it go?

    Making more progress than me lol!

    The Mrs keeps changing her bloody mind so I prep an area for shed base then it keeps moving round the garden!!
     
  18. Matt J

    Matt J Member

    Ha! Went down fine. Wildly underestimated the amount I needed but luckily I had a mixer to hand. Did around 9/10 loads. Did the first on a spot board then thought better of it!
     

Share This Page