I've done a bit of searching and found conflicting answers: do I need reinformenent in my concrete slab?

I am planning on putting down a 12ft by 8ft concrete slab for a shed (just for garden storage, no machinary or vehicles will be using it), with a 3x3ft bit on the side for a coal bunker. The concrete will be around 4inches thick, mixed using a standard mixer on site.

Do I need to put in concrete reinforcement in this?

Some say "yes" some say "no". Some say "might as well put it in" others say "it can cause issues in a small slab, so don't do it".

A I understand it, putting some metal in, as long as it is fully surrounded by concrete, it would help rather than cause any issue. But if I put some in, and there's any way for water to get in, the metal will rust, expand and break my slab apart before its time. The soil is pretty firm clay, but it is on quite a slope.

  • Hand mix(bags) concrete or from a mixer truck? It should help with hand mixed, it would be an option only for truck mixed.
    – crip659
    Jul 17, 2023 at 12:20

1 Answer 1


Reenforcement makes concrete perform better.

The primary issue with a 4" thick slab is that providing steel with 2" of concrete cover (which prevents corrosion) is difficult (must be precisely in the middle), or impossible if it's only "around" 4" thick. In more severe exposures (such as salt water areas) as much as 3" of cover may be required.

An easy alternative is reenforcing fibers added to the mix, which do not rust. They should be available at your concrete materials supplier.

  • I was going to put those fibers in anyway - they were so cheap it seemed silly not to.
    – Puffafish
    Jul 17, 2023 at 12:41
  • 1
    Where steel is applicable, it is also quite cheap compared to the cost of the concrete. Yet people often don't use either steel or fibers, and once it's poured it's too late to change your mind.
    – Ecnerwal
    Jul 17, 2023 at 12:46
  • For a shed, use the fibers and relax. It should be plenty strong unless you are using it as a blacksmith shop.
    – RMDman
    Jul 17, 2023 at 13:23
  • Fun fact: asbestos is the perfect fiber for reinforcing concrete.
    – RonJohn
    Jul 17, 2023 at 21:02

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