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concrete mix for garden wall foundation

Hi all,
I was wondering what the correct mix for a concrete foundation is. I read somewhere the mix is one of cement, 3 of sand and 6 of gravel. When I asked in the yard they told be that the gravel and sand is already mixed, so does that mean the mix should be 9 of that and one of cement?
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Comments

  • molerat
    molerat Posts: 33,492 Forumite
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    edited 14 October 2021 at 5:32PM
    Should be 6 parts all in ballast (or 2 sand 4 gravel) to 1 cement which is the standard C20 general use mix.  9 to 1 will be far too weak.
  • Agree with molerat 6 ballast to 1 cement. If you can get it my local wickes & travis Perkins are always running out. how high is the wall going to be as this affects depth of footings
  • It will be about 1M high in bricks. I've never done bricklaying before, this will be a steep learning curve. Will the mortar be 1 of cement and 6 of sand as well?
  • grumbler
    grumbler Posts: 58,629 Forumite
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    edited 14 October 2021 at 8:24PM
    woody7777 said:
    Hi all,
    I was wondering what the correct mix for a concrete foundation is. I read somewhere the mix is one of cement, 3 of sand and 6 of gravel. When I asked in the yard they told be that the gravel and sand is already mixed, so does that mean the mix should be 9 of that and one of cement?
    If you mix 3 volumes of sand with 6 volumes of gravel you'll get 6 (yes, six) volumes of mix.
    IIRC, they say 1 part of cement +2 parts of sand + 3 parts of gravel for concrete. This, IMO makes 1 part cement + 3 parts ready mix.

    For bricklaying I use 1+5. And I'd build a full-brick (not half-brick) wall even if it's lower than 1m.

  • stuart45
    stuart45 Posts: 4,585 Forumite
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    You could add some plasticizer to the mix to make it more workable for brickwork. Leave it mixing for a bit longer to get a bit more air into the mix.
  • grumbler said:
    woody7777 said:
    Hi all,
    I was wondering what the correct mix for a concrete foundation is. I read somewhere the mix is one of cement, 3 of sand and 6 of gravel. When I asked in the yard they told be that the gravel and sand is already mixed, so does that mean the mix should be 9 of that and one of cement?
    If you mix 3 volumes of sand with 6 volumes of gravel you'll get 6 (yes, six) volumes of mix.
    IIRC, they say 1 part of cement +2 parts of sand + 3 parts of gravel for concrete. This, IMO makes 1 part cement + 3 parts ready mix.

    For bricklaying I use 1+5. And I'd build a full-brick (not half-brick) wall even if it's lower than 1m.

    So concrete should be 1 of cement and 3 of ballast?
  • For a mortar mix I have allways used 4 sand to 1 cement. A good idea is to get a small container and use this to do the measuring of quantity.
  • stuart45
    stuart45 Posts: 4,585 Forumite
    Sixth Anniversary 1,000 Posts Name Dropper
    There isn't one mortar mix that covers all masonry. This is the NHBC guide for new builds. 6.1.14 Mortar - NHBC Standards 2021 NHBC Standards 2021 (nhbc-standards.co.uk)
    Then there's lime mortar. Rule of thumb for mortar is to be weaker than the masonry units.
    Same for concrete. There are lots of different mixes for different jobs. 10 or 8 to 1 lean mix for cavity fill, 6/1 for standard strip foundations, 4/1 for lintels etc. 
    Some foundations require sulphate resistant cement. Other mixes can have various additives. 
    However for a standard garden wall you could go with 6/1 for the foundation. Brickwork either 4 or 5  to 1 with plaz.
  • grumbler
    grumbler Posts: 58,629 Forumite
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    edited 15 October 2021 at 8:07PM
    woody7777 said:
    grumbler said:
    woody7777 said:
    Hi all,
    I was wondering what the correct mix for a concrete foundation is. I read somewhere the mix is one of cement, 3 of sand and 6 of gravel. When I asked in the yard they told be that the gravel and sand is already mixed, so does that mean the mix should be 9 of that and one of cement?
    If you mix 3 volumes of sand with 6 volumes of gravel you'll get 6 (yes, six) volumes of mix.
    IIRC, they say 1 part of cement +2 parts of sand + 3 parts of gravel for concrete. This, IMO makes 1 part cement + 3 parts ready mix.

    For bricklaying I use 1+5. And I'd build a full-brick (not half-brick) wall even if it's lower than 1m.

    So concrete should be 1 of cement and 3 of ballast?
    That's how I did this.
    However, here they say 1:2 ½:3 ½ or 1:5 (ballast mix), i.e. apparently 2 ½+3 ½=5 .

  • Thank you for the link grumbler. I read on it that hardcore should be placed under the concrete for a better job. 
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