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Don Farr
06-09-2003, 11:00 AM
My house is almost three years old. In the back yard next to the house is a 18' X 36' patio with flag stone on top. Or at least there was. The flag stone started cracking and the grout was coming up in chunks.

After getting several opinions ( and much complaining from SWMBO) I decided to tear it out. Most of the flagstone came up fairly easy, but the jack hammer on the slab is getting the best of me and my helpers.

My question is if we just tear it out to the large crack that appears what was causing most of the problem, would I be successful tying in the new part with the old? If so, how do I do that?

One opinion is to drill into the side of the existing slab and insert rebar. I don't know, that's why I like woodworking.:confused:

Ken Garlock
06-09-2003, 1:24 PM
Hi Don. My first question regarding your problem is do you have a home warranty and if so does it cover the patio. But, if you do and it does, you may have voided it by taking on the repair yourself. Just a thought/question.

Since you are planning on removing the part of the patio slab which is cracked away from the remainder, you will need to put some good size re-bar into the good part of the slab, at least #4 (each number is the number of 1/8 inches in the diameter of the re-bar, hence #4 is 1/2 in.) And you need to put it in deep, I would go deeper than the slab is thick. This means drilling a horizontal hole every 12 inches(my guess) which is 4 plus inches deep. These re-bar stubs extending the same depth into the new concrete will help keep the slab strong where the new joins the old. A good rotary hammer will do a good job. (A rotary hammer is not a "hammer drill.") Also, I would put in #3 re-bar as a grid where the new concrete is to be placed, put it up off the ground on the little plastic cones made for that purpose. I would also put a bed of good clean sand down before I poured the concrete. Make sure the re-bar is up in the concrete and not slipped down to the ground.

The above is approximately what our concrete contractor did to extend our patio from the main house slab when we built last year.

That is what I would do, but others may have better solutions.
My opinions are worth what you paid for them....

Don Farr
06-09-2003, 3:07 PM
Thanks Ken for the reply,
That's pretty much what I had planned to do, I just wasn't sure .
You confirmed it for me.

I didn't know that there was a difference between a hammer drill and a rotary hammer.Glad you pointed that out before I made the trip to the rental center.

Do you see any need for anything in the hole with the rebar? I guess I am thinking of adhesive or something?

Oh! I forgot your first question. The builder is long gone and bankrupt. I have only standard homeowners insurance. No help there.

Ken Garlock
06-09-2003, 4:00 PM
Don, now you are asking me to remember something that happened several months ago, and I have slept on it :) As I recall, they just put the re-bar in the hole without any added goo.

The rotary hammer is built first as a hammer and second as a drill, IMO. It is a heavier duty machine. However, it does take a special drill bit with an "SDS" shank which goes in the chuck. A simple quarter turn locks the bit in place. The bad part is that the drill are kinda expensive, in the $10 to $40 range depending on the diameter and shank length. I bought a Milwaukee rotary hammer as a factory refurb and it works like a champ- 5/8" hole thru 4" of concrete in less than a minute.

Don't spare the re-bar....

Lee Schierer
06-10-2003, 9:49 AM
If you are replacing the patio, with concrete. The key to keeping a slab from cracking is drainage. Particularly if you live in an area where the ground freezes. Water or even really damp soil under concrete will cause it to heave. If it heaves, it will crack. A good base with proper drainage will prolong the life of the slab.

Bob Boake
06-17-2003, 11:00 AM
I joined two slabs as you are doing and put some epoxy in the holes pror to inserting rebar. I Think I had seen it done before but I don't know where. The process was such a monumental pain that it seemed like it was best to take every measure possible.

Don Farr
06-17-2003, 1:07 PM
Thanks for the tip Bob, but I have already drilled the holes and hammered in the rebar. It really did seem to fit tight. I don't think I could pull it back out now.

You are correct about it being a royal pain in the b___! This has turned into to much work for this old man. I am trying to find a contactor to take it over and complete the job.

Plus I am getting a lot of heat from SWMBO. She can't get out the back door that leads to the pool and it is prime pool time in good ole Georgia.