Latest Discussions : Basement & Foundation


06:02PM | 12/26/02
Member Since: 12/25/02
2 lifetime posts
I'm about to rebuild an existing shop that was built 20+ yrs ago on a concrete slab. I would like to pour a slab on top of the existing slab.

Is it feasable to pour a slab on top of an existing slab? If so, how deep should it be to prevent cracking (the existing slab has very few cracks - none major), it will have vechicles on it occassionally? Also, should I drill into the existing slab and insert rebar to connect the old to the new?


01:46PM | 12/27/02
No need to drill into the old slab. It would only weaken it unnecessarily. Being the old slab is in pretty good condition you can pour directly over the old slab with 4”-5” of new concrete. Use a 6x6 10x10 welded reinforcing wire in the new concrete to help prevent cracking. Overlap any seams by at least 6” and make sure it is pulled up into the fresh concrete as it is being poured. An alternative to the wire is to have fiber reinforcement added at the concrete plant to help prevent cracking.



04:51AM | 12/30/02
Member Since: 12/25/02
2 lifetime posts
Is there any prep work that needs to be done to the existing slab so that the new slab will "stick" to it?

robert Fieder

05:08AM | 12/30/02
Member Since: 12/28/02
8 lifetime posts
Yes you should consult with your local cemant supplier and ask hem what latex binder glue you should use. All you do is apply it 1/2 hour to 1 hour before you pour.

Keith Martin

06:38AM | 01/17/03
Member Since: 01/15/03
20 lifetime posts
There are several alternatives to topping a slab. You can add some toppings as thin as 1/4". An important point that you should know is that regardless of the topping, Any cracks that are in the current slab will telegraph through the new one. the prep work to stop this from happening is a lot of work for the results that you get.

Latex binders are okay for the most part, If it were mine, for the money I would use an alphiatic resin binder. It will provide more open time and provides a higher bond strength. It is a step between ,latex and epoxy.
If your reason for adding the slab is to get rid of cracks or other appearance issues. I would suggest a traffic bearing urethane overlay.

good Luck,



03:52PM | 02/23/03
Member Since: 02/22/03
23 lifetime posts
You can even go so easily as a self leveling overlay material such as Mapei or Super Flow-crete.
Use a bonding agent such as P-100 as early as a day before. Much easier than pouring and finishing. You can seal it with a high solids epoxy and it will be better and harder than new concrete. If you are worried about slip-resistance, you can add a product called "Shark Grip" to the epoxy and even in water, it won't slip.

[This message has been edited by klmal (edited February 23, 2003).]


09:57PM | 05/25/18
I just had a slab pored and the guy did a bad job it’s not level how would be the best way to level it out ?


02:12PM | 04/03/20
A room addition was done - a new slab was por on top of exsiting slab. Now the new slab is sliding of the old slab, Both slides are over 20 years old. How do I stop top slab from sliding off

Thank You

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