Backfill for raised patio / step on concrete slab

Discussion in 'Landscaping and Outdoors' started by Mmi, Apr 26, 2021.

  1. Mmi

    Mmi New Member

    Hi everyone

    I have a bit of a wonky mini raised patio / wrap around step, by the front door, which has been built on a solid concrete slab.

    Im planning on removing all existing patio and laying about two courses of concrete blocks on the perimeter of the slab to get a consistent level and then backfill it all. Then lay new slabs on a wet bed.

    Im just wondering what I should use to backfill the space. Thinking of getting a jumbo bag of mot type 1 to fill it in? I also have some old bricks from a small wall that came down, can I use those? or what about just dirt and other garden waste material?

    Here's a quick drawing to try an show what I mean


  2. stevie22

    stevie22 Screwfix Select

    Don't use dirt.

    If you've got some old bricks you could just use a bit of weak mortar and bed them rather than try too break them up and compact
  3. Mmi

    Mmi New Member

    Thanks. I wont have enough bricks to do the whole area, so would filling the rest in with type 1 still be best option?
  4. stevie22

    stevie22 Screwfix Select

    Yes, but rather than proper type 1 try to get crushed concrete or even crushed brick as this will be cheaper and better for your purpose. You can compact it ok by hand for small areas but it's hard work. It wants to be damp to compact properly.
  5. Strevs P

    Strevs P New Member

    4 golden rules for a hardcore infill.............
    1) ensure retaning walls are strong enough
    2) ensure materials being compacted are small enough
    3) ensure material being compacted is slightly damp
    4) use a compacting machine........even if you try and do a small area by hand, you'll tire out before everything is down as far as it could be.

    Cost of hiring ranges but at around £30 for a weekend for a small one, much easier.
    Mmi likes this.
  6. Mmi

    Mmi New Member

    ah thanks for the tip, i didnt know that was a thing! I see what I can find for that

    Another thought I had, since it is only a small area, could I just use the concrete blocks for the whole area, avoiding the need for in filling? mortar them all down to create a level platform and then put the paving on that?

    Lastly, are the concrete blocks ok for this job, which ever way I go, or should I be using engineering bricks instead?

  7. Strevs P

    Strevs P New Member

    As long as you avoid the cheap Aerated ones it will be fine. Personally I'd use Engineering for the boundary and standard for the infill
  8. Mmi

    Mmi New Member

    Thats good to know. I guess it just comes down to price? a perimeter of bricks and infill with crushed stuff, or build the whole level using bricks.

    The slab itself is at a bit of a slope, is it ok to make up the differences with extra mortar between the bricks? I know I could cut the bricks if needed but not sure if the difference is enough, the cut pieces would be tiny
  9. Strevs P

    Strevs P New Member

    It's okay to make up to a different level with changes of mortar thickness as long as:-
    Thickness of mortar doens't get over thick
    It's not put in on a wedge shape to correct vertical alignment
    Mmi likes this.

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