Concrete base for shed....how to...

[Steve Campbell]

I've binned my old 6*4 garden shed for a new 8*8 "log cabin" ... so I need to extend the concrete base (it's ~45cms longer & 1.4m wider to accommodate new cabin + a slight change of position) .. not a huge area to concrete ... so doing it myself...first time to "play" with concrete. Cabin is just that, no heavy traffic...just everyday garden use.

I've dug out and "shuttered" (19mm * 100mm boards) into 3 sections, making sure they are level, and dug out and leveled the bottom of each section.

My neighbor has an electric cement mixer I can borrow...and I have the time next weekend. I'd like to limit the amount of concrete to "enough" to ease my back and I also think 100mm of concrete is OTT for effectively a "pretty" garden shed. Looking forward to giving it a go and extending my DIY skills :-).

Was planning to use this stuff to both "line" the base and make the concrete.
http://www.wickes.co.uk/Wickes-Ballast-Major-Bag/p...
Questions :
1) How much "dry" ballast and how much concrete to fill the 100mm depth ? 25mm ballast / 75mm concrete ? 50/50 ? What would you do and why ? Less concrete = less work...but I want the base to be sound and last. If it's 100mm concrete...so be it.
2) If I use the above material, what proportions for the concrete ? 1 cement to 5 of these ? Anyone used this Wickes material for concrete ?
3) Any tips / pointers or "obvious" pitfalls in doing the job ? Have done some internet research but some pointers for a complete novice at this from the professionals would be good.

Thanks in advance !! Hope my back stands up to it.... my day job is desk bound most of the time :-)
Steve

[Steve Campbell]

Clayey....been heavy digging...even for 100mm :-)

[Steve Campbell]

There is already a 7' * 5' slab so I'm just extending it...& I thought 0.5m3 was minimum order which would be too much?

Thanks for comments...keep them coming !

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Edited by Steve Campbell on Tuesday 29th July 07:46

[Steve Campbell]

Exactly why I'm going DIY as by my calculations at a 6:1 mix I need about 18 bags of ballast + 3 of cement...total cost < £50

OK it'll take more time, but it's something I've not done before so actually looking forward to giving it a go....and even if I make a bit of a hash of it, it's only for a garden shed and I'll do the back bit first so you can't see it :-)

[Steve Campbell]

TA14.....would be good if you can check my calcs then.

Original size was what I "thought" it was (typing from work)...I've now measured accurately and the area needed filling is 3.7m2...so at 100mm that would be a max of 0.37m3. The Wickes web site says each ballast bag will give 0.35m2 at 50mm depth for course concrete...so by those numbers..I reckon a max 21 bags ballast (+ concrete at 6:1 ratio). Is my man maths right ?

I'm in South Bucks

Edited by Steve Campbell on Wednesday 30th July 09:39

[Steve Campbell]

Thanks for all comments, base was done 2 weeks ago, shed.built yesterday, painted today.

Also had a bit of fun.....

https://m.youtube.com/watch?v=0EPRzbuPp2k