Laying concrete on concrete . . .

[Fogey]

Is it possible / sensible / advisable to lay a new concrete surface over an existing concrete surface? How should the old surface be prepared? What about minimum or maximum thicknesses for the new layer?

Any help / ideas / suggestions much appreciated.

Ta

Fogey

 

[Cabby89]

What are you trying to accomplish? What is currently wrong with the slab?

 

[iBang]

I would be interested in this as well. The carport I am currently turning into my garage was poorly laid in 5'x5' squares that are now all sorts of uneven and it would be very nice to be able to re-level the surface a little.

 

[subagon]

I would think you'd need at least 2" and the use of a concrete fiber admixture. Here's a couple of things I found via google that might help;

http://www.concretenetwork.com/concrete/fixing/overpouring.htm

http://www.psiconcretefibers.com/monofilament-fibers.html

 

[allinon72]

Mike Holmes did it on a huge garage floor. He was told 4" minimum with fiber strands.

 

[DuluthMN]

We just had a guy come out yesterday and this is what he said. Right now our floor heaves up right in the middle where the drain tile is, so naturally the water does not drain. So we need to have the area cut out and repoured so that it slopes to the center. He said he would do 4" on the outside and 2" on the middle and he felt it would not take long before it was cracking if poured over the old service.

Have your slab cut out and pour a new slab.

 

[Fogey]

Ok guys - thanks for the answers.
In answer to Cabby89's question the existing slab slopes from one side to the other. Basically I want to level it up - didn't really want the hassle of breaking up the existing slab though and looking for an easy way out!

 

[DuluthMN]

Ok guys - thanks for the answers.
In answer to Cabby89's question the existing slab slopes from one side to the other. Basically I want to level it up - didn't really want the hassle of breaking up the existing slab though and looking for an easy way out!

When it comes to concrete you will REGRET taking the easy way out! Famous last words...

 

[ng8264723]

Actually what woks well and be built up in layers is the leveler they sell at Home depot. It finished to a tought smooth surface. I have built it up 2 inches in areas to fix a slab

 

[thegarageguy]

you don't need to pour 4 inches over an existing slab. There are acrylic modified self leveling concrete that are specifically formulated for this type of application and are applied from 1/4 inch to an 2 inches thick if needed. They are 5000 to 6500 psi fast curing poured floors. Used them for years and work well.

 

[admranger]

What's causing the settling and what is going to prevent it from continue to move?

I'm in agreement with DuluthMN here.

 

[Fogey]

What's causing the settling and what is going to prevent it from continue to move?

I'm in agreement with DuluthMN here.

It isn't settling and hasn't moved it was just poorly laid (as part of the driveway) when the house was originally built 30 years ago

 

[pauls340]

Fogey, there's a product out there called Mg-Krete that gets to over 11,000psi at any mix (wet or dryer) and it will bond to any clean dry concrete. I've seen it placed from 36" thick (airport runway light pods) to zero but your situation is not possible to make it look new, without any cracks, for more than a week or two. Your existing floor is considered your substrate and like the 5x5 squares, Mother Nature will win and any movement will recrack your topcoat. I have tested over two dozen products over seven years and MN always wins. I have a similar situation in one of my garages.
20'x22' and to get it removed and replaced was $2600 three years ago. Probably less now cause of the industry...SE Michigan. Get some quotes and let us know.

 

[pauls340]

Also, that darker rectangle towards the back of my car in my avitar is a product used on waste water treatment concrete. A thin coat of that can be wrapped around your finger without breaking but if there's a shear crack, which is what cracks in garages or on driveways are, it tears. Also, I just did a 3" to 5" thick Mg-Krete job in a hazard material plant and all the prep work was to scarify the 1200 sq foot slab. Finished it at noon Saturday, Monday morning a 100,000# backhoe went back to work.

 

[Dan in Pasadena]

you don't need to pour 4 inches over an existing slab. There are acrylic modified self leveling concrete that are specifically formulated for this type of application and are applied from 1/4 inch to an 2 inches thick if needed. They are 5000 to 6500 psi fast curing poured floors. Used them for years and work well.

Garageguy, What brand have you used/do you recommend?

 

[thegarageguy]

I work with Mapei, Ardex, CMP and Duraamen. I do have a preference but it's mainly due to availability and cost. If it's spec'd on a job I use it. They all work well.

 

[central1ny]

I work with Mapei, Ardex, CMP and Duraamen. I do have a preference but it's mainly due to availability and cost. If it's spec'd on a job I use it. They all work well.

Where do you buy any of these?