Concrete base for garden office

[Mad Professor]

Hi All.

I am looking at starting a new project within the next few weeks, and I am looking for any help and advise that you can give me before I get started.

At this point in time all I am trying to achieve is a nice strong 10x10 foot concrete base for a wooden garden office.

This will be my first time working with cement to make a concrete base.
I must admit that the more I research this subject the more conflicting information I find, such as needing / not needing sub-base, rebar, fibermesh, thickness, etc.
As such I need your help and advise with regards to what materials will be required, type of cement, sand, etc.

(1) Hire a local builder to carry out the required work, but what will I learn from this.
(2) Order concrete to be delivered, unfortunately the logistics of this would end up blocking the road.
(3) Using bags of premix cement. lots of bags and not cheap.
(4) Order delivery of cement, sand, aggregates, etc. will still end up blocking the road but nowhere near as long as option 2.

Most of what I have read so far seems to recommend at a minimum of a 4" (100mm) concrete base.
When I phoned local places about concrete being delivered a few of them recommend that I went for C20, whatever that means.

So if we are using the size of 10' x 10' x 4" (3.048m x 3.048m x 100mm) that's 33.33 cubic feet (0.93 cubic meters). some number rounding, but approx.

My local builders merchants are, B&Q / TradePoint, Sydenhams, Travis Perkins, and Jewson.

I do have access to power and hand tools, such a plate compactor, electric cement mixer, spades, shovels, wheels barrows, floats, etc, etc.

I welcome any advise.
Thanks in advance.

 

[StephenOak]

You are more likely to get help if you post in the appropriate section. The Moderators can move this for you. Click on 'Report' to ask for that.

 

[mrrusty]

Why a concrete base for a wooden garden office - there are choices? If it's a wooden building the top of the base needs to be clear of the ground to stop the timbers rotting - so the base needs to be a bit above ground level. It also needs to be sized so the cladding can overhang the top surface of the base so water doesn't track in to the building. If you do want to use concrete, for a 10x10, just shutter it using some 6x2 (or 6x1 at a pinch) and hopefully get a barrowmix company to barrow the concrete in. To secure the formwork roadpins are great if you can find someone local who sells them https://streetsolutionsuk.co.uk/pro...IE5PX35sEv5OLvc3EAFQGE6-YtHBFe2hoC-J0QAvD_BwE Won't take long for that size!! 4" of concrete is enough IMHO for this job, but you do need to wack down some MOT under it as a sub-base. https://imixconcrete.co.uk/news/how-to-lay-a-concrete-shed-base-guide/ If you don't want to use concrete you could look at a grid base filled with aggregate https://www.ibran.com/products/plas...u-8Fi0MYC807mVrJD2xhW13MV4MxSEqhoCLpkQAvD_BwE

or easypads (which I used recently for a 6.5m x 3.6m timber frame garden room) https://easypads.co.uk/?gad_source=...adU20UgGu7LwsvnolZg86puUn3oHd75xoCldMQAvD_BwE

 

[23vc]

2 bulk bags of ballast, however many bags of cement (calculators online for it) and a mixer positioned so it can tip each load directly in place. Keep the mixer going and just do load after load. That size should be comfortably doable within a couple of hours. You get into a flow and it’s easy enough.
Concrete on dpm on sand blinding on compacted hardcore. Steel mesh optional, more needed if something like a tree nearby

 

[yorksbuilder]

Read these 2 links

Plain Concrete Hardstandings

Notes on the construction of concrete pavements, slabs, hardstandings and concrete bases for sheds, garages, etc.

www.pavingexpert.com

Reinforcement for Concrete

The use of steel and fibre reinforcement for concrete slabs

www.pavingexpert.com

Hope they help you.

I'd recommend getting a mix to order service, where the truck mixes only what you need on site, often they will help barrow the concrete to your office slab base location as well

 

[Mad Professor]

Thank you for your replies.

I've looked at online calculators, but seem to get different numbers all based on 0.93 cubic meters, and using 25Kg bags of cement, I've had as little as 8 and as high as 15.

Regarding the sub-base layer, can I use gravel / stones that have been removed from the garden or would it be best to just order in some MOT Type 1?
I ask as I currently have approximately 4 tonnes that have so far been removed from the soil.

 

[mrrusty]

can I use gravel / stones that have been removed from the garden

Most likely not. MOT is a mix of sharp edged aggregate from about 40mm down to fines. MOT, once wacked becomes extremely solid and stable. Round stones don't - think how you sink on a shingle beach.

 

[big-all]

as an aside
its worth considering a building off say 8x12ft or other oblong sizes as sheet material short and long spans need different timber sizes for the different spans
in other words a square building is least efficient at using materials as you have 1 fixed size rather than a compromise off plus a few mm on this and minus a few mm here allowing best use off sheet material and best use off timber as shorter spans need smaller section so more headroom