Author Topic: Concrete slab question -done  (Read 1128 times)

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Offline #jonesy

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Concrete slab question -done
« on: December 20, 2018, 11:35:54 AM »
I am going to pour a concrete slab to butt up to the garage floor

It is about 4m X 2 m and about 4" thick.
And will be pinned to the existing slab, and using reo mesh.

Do I put expansion roll around the retaining wall and the brick wall at the other end?(not in photo)

Should I put plastic underneath before pouring?

The existing slab edge has a big chunk out of it, and a few small ones. Will the new concrete hold as a repair patch?

Any tips for screeding it level as I only have one side to work from?
« Last Edit: April 13, 2019, 06:30:06 PM by #jonesy »
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Offline whitedg

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Re: Concrete slab question
« Reply #1 on: December 20, 2018, 12:44:34 PM »
We added to our garage by adding a slab at the back. It was tied in to the existing slab by drilling into the existing slab and banging in some DBar (with Chemset in the hole).

We then had to add a termite barrier and a foam expansion all the way around, including up against the existing slab. Plastic was also laid underneath it to keep it all watertight.

For levelling, use a screed and a spirit level on top, or you can add some timber to the right levels, screed to that, and remove before it fully sets and mix up a small batch to fill in the void where the timber was. You can do this on the edges and even up the middle if the slab is big enough. Don't forget to add the cut or groove for the cracks (can't remember the proper term for this).

Good luck

whitedg

Offline BaseCamp

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Re: Concrete slab question
« Reply #2 on: December 20, 2018, 01:33:31 PM »
130mtrs of concrete going in tomorrow morning...   I'll post up some pics of the prep...

But it looks like:-
Thick plastic underlay
Sand/crusher dust under
Foam expansion around the retaining walls
Termimesh around the penetrations
(and in your case) - dowels (reo rods) from existing slab onto the mesh..

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Online austastar

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Re: Concrete slab question
« Reply #3 on: December 20, 2018, 03:55:13 PM »


130mtrs of concrete
??
Führernbunker?
Cheers


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Offline GBC

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Re: Concrete slab question
« Reply #4 on: December 20, 2018, 06:59:44 PM »
I am going to pour a concrete slab to butt up to the garage floor

It is about 4m X 2 m and about 4" thick.
And will be pinned to the existing slab, and using reo mesh.

Do I put expansion roll around the retaining wall and the brick wall at the other end?(not in photo)

Yep

Should I put plastic underneath before pouring?

Yep - prevents the slab getting damp in the future

The existing slab edge has a big chunk out of it, and a few small ones. Will the new concrete hold as a repair patch?

Only if you cut the edges square and at least 75 mm deep. Otherwise it will pop out. Better off using repair mortar later.

Any tips for screeding it level as I only have one side to work from?

It will self level with a vibrator. Pin the walls with a few nails at the heights you want prior. Start pouring in a far corner and work your way out with the screed. Bullfloat from the existing slab and then you can steel it with a heli if needed. It is the sort of job that needs a couple of blokes who know their business to get right because there isn’t a lot of room for fixing it later.

Offline SJindustries

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Re: Concrete slab question
« Reply #5 on: December 21, 2018, 06:23:19 AM »
Don’t forget the reo chairs.
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Offline MarkGU

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Re: Concrete slab question
« Reply #6 on: December 21, 2018, 06:25:28 AM »
Don’t forget the reo chairs.
unlike Speewa chairs . 8)
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Offline SJindustries

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Re: Concrete slab question
« Reply #7 on: December 21, 2018, 06:29:16 AM »
unlike Speewa chairs . 8)
:cup: :cup: :cup:
I wonder if he’ll get a chair from Santa this year. He’s not as young as he use to be nowadays  >:D
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Offline speewa158

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Re: Concrete slab question
« Reply #8 on: December 21, 2018, 06:35:10 AM »
l was going to be rude to for that comment buuuuuuut l cant remember what l was going to  Ummmmm     Merry Xmas to All  :cup:                        :cheers:
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Offline Niley

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Re: Concrete slab question
« Reply #9 on: December 21, 2018, 07:47:52 AM »
Jonesy

Try and tidy the existing slab edge up as much as you can, ie vertical joint. It's only a smal slab so put dowel bars in @ 400mm spacing and 150mm epoxy into slab, about 300 into new pour. Double up on the retaining wall EJ to about 25mm as retaining walls move. Also notice a small infill near a post, if you can leave pour this until 7 days after pouring the main section you will avoid this section cracking down the track. Put a 12mm bar diagonally to the internal corner on that post to resist tension and cracking coming from the corner.

When you put the mesh down make sure you have wire of the mesh along the edge of the joint.

Hope this helps

Cheers

Neil
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Offline #jonesy

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Re: Concrete slab question
« Reply #10 on: December 21, 2018, 08:29:19 AM »
Thanks for the tips. The area will be a storage area for bikes and other stuff so I was willing to have a go at it myself, which is bigger than any I've done before
The ground and behind the wall are bone dry and never has moisture, except when the water heater was leaking.

Still have to cleanup the ground and I'll try and tidy the edge a bit better.

Jonesy
. Also notice a small infill near a post, if you can leave pour this until 7 days after pouring the main section you will avoid this section cracking down the track. Put a 12mm bar diagonally to the internal corner on that post to resist tension and cracking coming from the corner.

Neil not sure if I properly understand what you mean about the diagonal reo.  Do you mean like the yellow line i put on the photo. I was also going to cut across the new slab from the post to the wall as a joint.
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Offline BaseCamp

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Re: Concrete slab question
« Reply #11 on: December 21, 2018, 12:05:30 PM »
??
Führernbunker?
Cheers


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haha...   it only took a bit over 3 truck loads of 32mpa - so no, unfortunately not....

But had the job not involved 4 weeks worth of rock breaking; and the removal of 500 cubic metres of dirt and rock....   I would have been tempted to plough on and put in a "bunker" as well ....    (but enough was enough)....

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Offline GBC

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Re: Concrete slab question
« Reply #12 on: December 22, 2018, 11:01:40 AM »
Thanks for the tips. The area will be a storage area for bikes and other stuff so I was willing to have a go at it myself, which is bigger than any I've done before
The ground and behind the wall are bone dry and never has moisture, except when the water heater was leaking.

Still have to cleanup the ground and I'll try and tidy the edge a bit better.

Neil not sure if I properly understand what you mean about the diagonal reo.  Do you mean like the yellow line i put on the photo. I was also going to cut across the new slab from the post to the wall as a joint.

Just in case he’s gone for Xmas, yes you’ve drawn it correctly. Keep at least 50mm back from the post. You can do 2 or three 100mm apart - it won’t hurt. Wrap the post with 10mm Abel flex as well. If it is on its own footing, standard practise is to expose the top of the footing and install a few crank bars up into the slab as well and tie the two slabs together.
This thing is getting engineered now 👍.
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Offline Niley

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Re: Concrete slab question
« Reply #13 on: December 22, 2018, 12:17:06 PM »
Jonesy,

GBC has you doing it right.

Cheers

Neil
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Offline #jonesy

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Re: Concrete slab question
« Reply #14 on: December 22, 2018, 10:12:23 PM »
Thanks guys. Still might take me a few months at the rate it's taken this far.
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Offline #jonesy

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Re: Concrete slab question
« Reply #15 on: April 13, 2019, 04:12:50 PM »
Finally found the time to do the job. Just need to do the last patch around the post.
Followed all the tips, recut the slab edge. 
The only thing I didn't do was put plastic under the slab.  My thinking is if I get moisture under there I have some serious problems and would like to know if water is getting in. It has always been bone dry, except when the water heater was slowly leaking and seeping under the house.

First half looked great, the second part I went for the "rustic" look.  Started to set before we could finish mixing and levelling.  Ready mix wasn't an option as we have a very steep driveway and tight access in to that corner.

The workbench and rubber matting will hide it.
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