Help with pouring concrete for a Steel Tech shed

Hi!

Are you sure you have the volume of concrete right? A 3x3m shed would need a base of around 3.1m by 3.1m and a depth of about 15cm. That works out at 1.44m³, not 0.45m³?

As for mixing this onsite, that's a huge ask for somebody with zero experience, especially if you are doing it alone, as you'll need to float out the base as you mix fresh-batch and the process is likely to result in the batches fully setting before you get to the mid-point of the shed base. With pre-mixed concrete you at least should have all of the product poured into the formwork around the same time, allowing you to float it off properly and obtain a good surface finish.

So please have a think about this and how you want to play it, I'd be going for the pre-mixed route if I was you.

In that case, no. I did the same job on a 4x3m shed with a mixer. It took me about 3 hours and worked out fine. I did it with sand and cement though, no ballast (804 granular) as it's too large for a 45mm depth. Gravel should be ok as long as it's small.

The trick I did - and it may not be everybody's cup of tea - was to pre-lay a 30cm wide 'path' down the center of the shed at exactly 45mm high so that I broke the shed-floor into two halves. I was then able to stand on that path and use a float stick to level off the new concrete against the path and the side of the shed.

What are you using for shuttering if you are doing it within the shed?

Also, are you guys talking about dry premix or ready-mix concrete delivered?

You could probably barrow in readymix easily enough from a delivery, assuming you dont have good road access to the shed. (just get a barrow with 2 front wheels, much easier to handle!)

I think I left it 48hrs before standing on it. It's fully supported by the base, so as long as you keep off the edges you should be fine.

I'd guess that the Chadwick's bag is ok, not sure in that respect. There is some info here though:

I dampened down the freshly laid concrete for about 3 days or so as it was warm and windy.

Ah picture frame base and you are filling in the middle, gotcha.

In that case the 30NM strength is for the picture frame part, you wont need that for the base unless you are planning on storing lead barrels in there :)

Yeah, assuming its going on top of well compacted 804/hardcore this will be fine, you could even do it in 2/3 sections to give yourself a break, will make finishing easier and will function as expansion joints to control cracking.

Note that if you do this you will need a shuttering board the length (or width!) of the space and some way of fixing it, but a 4/5 blocks should should hold it as its only 45mm.

FYI: My shed was laid on a full concrete slab and not a picture-frame base as per that link above. Whacking down the aggregate is obviously critical, but the float method used in that video above would be fine too.

Yeah, sounds right. Read about how you measure a slump and you'll get used to looking at the mix then to see if it's roughly right. You can easily gauge it off a trowel then to suit your needs. Don't use a metal float to finish off the surface unless you specifically want an almost perfectly flat finish as I think it shows up the imperfections more. The wooden float finish is enough for me.

Looks great - what did the materials plus mixer rental cost you? I'm looking into a 5 x 6m steeltech shed (so more than 3 times as big) and I'm considering whether to do something similar myself or just pay someone to do it

I don't know if they do 0.45m3 loads though.