Slab advice- New workshop

Hi,

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

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 :cool:

Joel

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.

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

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Originally Posted by 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.

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

It says F72 mesh :D

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

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.

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.

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

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

Thanks Pulse

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.

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.

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Originally Posted by 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.

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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

Looks like the duck's nuts ;)

Two more very basic questions, sorry :o 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

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

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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.

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

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Yes.

JDub

I put in a 3 inch pvc pipe with the sweeping bends that has been suggested before and also you may need to know they need to be in at a depth of 600 mm. I ran two 15 amp lines from the metre box to the shed and all worked well.

Pete

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Originally Posted by Doughboy

JDub

I put in a 3 inch pvc pipe with the sweeping bends that has been suggested before and also you may need to know they need to be in at a depth of 600 mm. I ran two 15 amp lines from the metre box to the shed and all worked well.

Pete

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Can you run them above ground in conduit along a brick wall to the metre box? If not Im stuffed :o

You'll have to check with the sparky but I think you're OK. The 600mm thing is just if you are burying them, to make them harder to dig up. Mine aren't that deep where they first come out from under the shed slab but we have poured a kerb slab over the top to protect them until the point they go into the trench.

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Originally Posted by JDub

Can you run them above ground in conduit along a brick wall to the metre box? If not Im stuffed :o

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I had to bury my conduit 600mm underground from the main to the submain in the shed. No prob for me as I'm on sand.

Another thing too, this from personal experience. Check the shed dimensions very carefully before you do your formwork. In small print on my plan for a 9m x 7.5m kit shed it said "Nominal Size" and I didn't discover that until the slab was poured and I found the shed was only 8.725 metres long. had to get a special weatherproof flashing made up. It was lucky I decided to go overspec with the slab (150mm thick rather than the spec 100mm) as the end portal wall is not over the piers (which weren't in the specs either and are 800mm deep x 500 x 500).
Good luck with it. In retrospect though I should have got the experts to erect it.

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Originally Posted by Shedhand

In retrospect though I should have got the experts to erect it.

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Really? I was reading your old Shed WIP thread last week and you said it fit perfectly on the slab?. Did you encounter any other major issues besides the slab dimensions?

Myself and my BIL are doing the slab but Im undeceided whether to erect it myself or not.... see this thread:

http://www.woodworkforums.ubeaut.com...ad.php?t=39564

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Originally Posted by JDub

Really? I was reading your old Shed WIP thread last week and you said it fit perfectly on the slab?. Did you encounter any other major issues besides the slab dimensions?

Myself and my BIL are doing the slab but Im undeceided whether to erect it myself or not.... see this thread:

http://www.woodworkforums.ubeaut.com...ad.php?t=39564

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Idid fit perfectly exept for the 275mm apron on one end which as it turns out was a good thing because I can bolt a timber rack to it.
If all you're saving is 1200 bucks then get the pro's in. It'll save you a lot of needless worry if you're at anal about it. The quicker its up the quicker you can be in it making things to brag about here,,,:D

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If all you're saving is 1200 bucks

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Jeez I wish I could be that blase about $1,200 :eek: