cement slab

Old 03-31-02, 08:06 AM
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Angry cement slab

I have an existing cement slab and am wanting to extend area. Is there a way for me to do this without creating a seam?
Any help is greatly appreciated
Old 03-31-02, 10:27 PM
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You can try to feather the new slab edge onto the old, but really a seam is preferable. The new slab will move independently of the old slab, even with rebar drilled into the old to join them. A crack Will develope. A seam will hide the new crack and in the long run be much less unsightly.
If you want to totally get rid of the seam, there are new polymer concrete overlays which you can put over the old and new slab, a bit more costly and maybe beyond a DIYers abilbity, but check out decosup.com for some good examples and decorativeconcrete.net for a professional forum to discuss the options.
Hope this helps, have fun with the project,
Old 04-01-02, 12:09 AM
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Thank You,

That is what I figured. Should I use an expansion joint, wood, or what in between?
Old 02-21-08, 03:56 PM
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More info here

Try this website, very infomative
Old 02-21-08, 04:29 PM
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cement slab

You cannot hide the joint, so make look like it was planned.

1. Drill holes in the existing slab and extend them into the new slab.

2. Compact the base under the new slab to minimize any settlement.

3. To make the joint match, grind the corner of the existing slab to match the edging tool you will use on the new slab.

4. After about a month calk the joint between the slabs with a high quality caulk, using a backer rod to allow you to force the caulk in and adherse to both sides.

The color of the two slabs will not match, but give it a few months to determine if you want to do something to make the match better.

Old 02-24-08, 10:31 PM
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jrr, listen to dick,,,

not the other 2,,, they both rec'd the same source,,, dcforum's run by decosup

never used it but guess its a decent enough mtl,,, have had some 'conversations' w/decosup's pres/owner.

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