Slab advice- New workshop

[JDub]

Hi,

Im putting in a new workshop (wooooo hooooooo!) and will be organising the slab etc myself.

It is a kit form colorbond (fairdinkum) shed that requires a slab 6 x 3.5m

Plans specify 100 thick with 6 x 300x300x400 footings (no thickened edges).

Workshop is in the backyard, on clay subbase (hard as rock ATM) and will have no vehicle traffic at all.

Now, my BIL is a concreter but when I say concreter, he is a concrete finisher for a large company and has little to nothing to do with the formwork, steel and actual concrete ordering.

So I need to get all the appropriate gear and he will be there on the day to do the actual finishing.

I have the plastic for under the slab, can get the formwork....

What type of mesh do I need to get?
What mix of concrete / slump? Sorry for the basic questions, never concreted (besides small pre mix bag stuff) before.

(will be poured in summer)

Thanks for spoon feeding me LOL

Joel

[Wood Butcher]

JDub,
I'm suprised that no specs for the mesh have been specified on the plans for the buildng approval. There is normally a minimum spec for the concrete too.

[ausdesign]

I would say SL72 mesh - 20mPa & 40mm slump but don't quote me.

[JDub]

JDub,
I'm suprised that no specs for the mesh have been specified on the plans for the buildng approval. There is normally a minimum spec for the concrete too.

You are right, on closer inspection (bloody small print)

It says F72 mesh

Concrete (part I dont fully understand in bold):
Concrete shall have a min 28 day strength of 20MPa for exposure A1 and B1, 25MPa for exposure A2 and B2 and 32 MPa for exposure C. Cement to be Type A. Max aggregate size 20mm Slump to be 80mm +-15

[Tommy]

It might be a good idea to check out the cost difference between 20 and 32mpa concrete .With only 2.4-2.6 cubic meters the difference would be about $35 .32mpa is harder and makes a stronger slab..Money well spent IMHO.

[ausdesign]

F72 is now called SL72
The A1 etc etc relates to the exposure of the concrete i.e. whether covered, dry etc or outside getting wet feet. I've never heard of it referred to in a residential context.
It sounds to me that the 6 (I think it was ) pad footings are what is being referred to as far as the concrete strength.
The slab to my mind would be classified as an 'infill slab' & have no structural relationship to the shed itself.

[JDub]

Can someone please explain 'slump' to me? I assume it refers to how runny/wet the concrete is?

[Pulse]

Hey Jdub, the slump determines how workable it is. It is a standard size tapered cone that is filled with samples of concrete, The cone is then removed and the amount by which the heap "slumps" compared to the height of the cone is the "slump". Full details are on www.concrete.net.au

Cheers
Pulse

[JDub]

Thanks Pulse

[JDub]

Right, Ive got all the conrete stuff sorted....

Now, I know this is being discussed ATM in another thread in this forum..... but:

It is worth putting down 30-50mm of roadbase under the slab? (cant go much more than this due to step heights/footpath etc)
The shed has no vechile access but it is on a clay.

[silentC]

We put roadbase under ours.

We also formed a rebate in the edge of the slab so that the tin comes down the side and laps over the edge of the slab. Keeps out the vermin and the rain. It's about 50mm deep and 20mm wide. Just nail a batten around the inside of the formwork. Make the formwork 40mm wider and longer than the finished size of the shed frame, excluding the tin.

[JDub]

We put roadbase under ours.

We also formed a rebate in the edge of the slab so that the tin comes down the side and laps over the edge of the slab. Keeps out the vermin and the rain. It's about 50mm deep and 20mm wide. Just nail a batten around the inside of the formwork. Make the formwork 40mm wider and longer than the finished size of the shed frame, excluding the tin.

Yep have actually ordered a product called vermaseal which does the same job, plastic moulding that sits on the edge of the slab that covers bottom of the sheeting: Here is a link (diff shed company but same product).
http://www.shedproducts.com/prod2-vermaseal.html
and
http://www.huntersheds.com.au/vermaseal.html

[silentC]

Looks like the duck's nuts

[JDub]

Two more very basic questions, sorry but Id rather look like a goose than get it wrong....

1) what size electrical conduit bend should I put in the slab to run the power through? What is the standard?

2) should I line the footing holes with black plastic as well?

Cheers

[silentC]

what size electrical conduit bend should I put in the slab to run the power through? What is the standard?

I don't know what is standard but I put a 1" sweeping bend in and it wasn't anywhere near enough for all the wires that I wanted to bring in. I'd suggest you put in at least 3 or 4.

should I line the footing holes with black plastic as well?

Yes.