concrete foundations for garden steps

[Stephen]

Hello,

My garage is on a slope and there were steps made from timber decking but they have seen better days. I was going to make a small flight of steps with bricks and paving slabs. The steps would be about 800mm wide and 600mm high (that's in total, not per step). I was hoping to make the riser two bricks high and have three steps.

I know I need to pour a concrete foundation beneath the bricks but I am unsure how deep. I have found various web sites via google and they all give different answers. I find answers from 100mm to 200mm. I have to say I have never found anything that substantial under garden walls or garden steps but perhaps they haven't been built properly!

What does the group think?

Thanks, Stephen.

[Tim Watts]

One one hand things have been built on compacted earth and survived. In other cases, things done so will move a bit and may crack.

Me: I'd dig it out to 12", ram 6-8" hardcore in then add 3-4" of concrete - not even all over unless you feel like it, but around the base line of the bricks.

That should be incredibly solid.

[The Natural Philosopher]

depends on what the soil is like. Clay moves a lot, sand washes away

Plenty of people will lay slabs on a mixof hardcore and sand with no concrete at all.

You need a foundation for two purpose - first is to provide a rigid base to stop what's built on it cracking - if you reinforce concrete, that really works - the other reason is to prevent it sinking onto the soil. For that just hardcore works

[Bill Wright]

Do the cans of paint fall off the ends of the shelves?

It isn't a motorway is it? So just use your common. Dig down until you find decent solid undisturbed ground. Mix the concrete as dry as you can because that makes it stronger. Don't step the concrete leaving a neck because that's where it will crack. Lay the concrete as a sloping ramp and build on that (another reason for mixing it fairly dry), filling the gaps in the first course with concrete used as mortar and bits of brick. Further courses should be normal mortar. Make the surface of the concrete very rough. Make the concrete a bit wider than the structure it supports. If it moves you want it to move in one piece, not crack half way up. I'd consider putting some steel bars in it. The cheapest way of getting these is to buy some 10mm threaded bar from a proper fixings shop (not B & Q etc). Use rough stone (not rounded pebbles) to fill the gap between the sloping concrete and the flags, with an inch of coarse sand on top for the flags to bed down into. Put a slight forward fall on each flag so water runs off. Each flag (step) should overhang an inch or so to provide some nosing.

Bill

[Peter Parry]

is usually the most reliable reference.

[Stephen]

Thanks everyone for the help. In the end I put about 4 inches of concrete in. By the time I had mixed 200kg, my back wasn't in the mood to do any more!

I did think that next time I should use a cement mixer but even then you have to shovel the stuff in.