What type of joint should be placed at the intersection of a new slab and an old slab during a remodel? Specifically, I have a "U" shaped house that had a room addition added about 10 yrs after built. The room slab was added to the rear porch slab with some type of butt joint. What should have been done? v/r Jerry
An expansion joint.
Dave
I would definitely put in some expansion material. I would add rebar drilled into the center of the old slab with a rotohammer and place a #5 rebar into the old 6 inches and extending 6 inches into the new slab. Do this at least every 12 -18 inches.
I am ASSUMING this is slab on grade and nothing to do with structural concrete. At least with the cold joint you should never have to worry about the slabs heaving. I have had good luck with this in the past when I extended the parking slab outside my home.
Ah, I'm no expert but I'm pretty sure you do *NOT* want to tie the two slabs together in any way. An expansion joint allows the two slabs to float independently, and avoids cracking. Old timers use a paper felt material to pack between the slabs, but I've also seen various caulking/sealing materials as well.
Dave
Thanks for the replies. The reason I asked is the joint is not "level" so to speak. I have Burber carpet down over the joint now and can't really pick it up to see what is under there. (I can but don't really want to..yet) There doesn't appear to be any problems with the joint, but I was just wondering what was going on down there because I can feel it when I step in the right place on the carpet. Thanks again. v/r Jerry
What happens to the structure when one of the slabs rises or falls a couple of inches?
You better rethink this one.
PJ
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