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What to put over old concrete

832 Views 8 Replies 5 Participants Last post by  zetmandu
Brand new member here and just beginning to learn things about concrete and have a question.
I have an old large concrete patio about 14x60 that while not in terrible shape for its age (poured in 1964) it does have some cracks and some holes about about 6-8" wide and maybe an inch deep. I really dont want to have his dug up and a brand new pad poured even though the little bit I have learned about concrete recently tells me thats the best fix.
Ive also read that just pouring a new 4-6" of concrete over the old isnt the fix as it will eventually just have issue in the same locations I do now. So what Im thinking is to put something over the top of the current slab, like waterproof plywood to separate the old from the new and basically build a box 4" deep up form this plywood and have new poured.

Is this something that would work or am I just wishful thinking?
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First there is no "waterproof" plywood, so you would be dealing with rotting wood between the slabs eventually, sooner than later. One of our concrete guys will be along soon, but I believe an isolation barrier laid down prior to the second pour would help keep the cracking from telegraphing through.
Hi, Sorry. I should have noted that as pressure treated plywood although I dont know if the end result would be much different.
your best bet's replacing the existing however you could have an unbonded overlay placed,,, make necessary reprs 1st tho,,, then place a base of 15# roofing felt, form up the overlay thickness, & place the new overlay
CAUTION: install proper jnt pattern at the right time to avoid random cracking & any reflective cracking from the old conc
Thanks for the reply and advice. Ive looked at the unbonded overlay and thats a real possibility. As for making the necessary repairs first, can that be done with something like an the thin set floor leveler stuff ive used indoors before doing placing some tiles but rated for exterior?
No, as you stated, that is for indoor applications. And it is very lite weight concrete. I would be asking why did it crack? Fix that issue. I mean you can use that stuff, but then I have to ask. How many times do you want to work on this pad before breaking down and replacing it? You can use the original concrete as fill for the new. Just break it up small. There are many things that you can use and do. But it will never be the same as removing and pouring new. Pouring new will be a lot less money in the long run.
Thanks for the advice Handy Andy. I guess the biggest reason I am against ripping up the old concrete is accessibility for trucks and other larger equipment that it take to get that done. Hilly narrow driveway and due to fencing etc Im afraid of the additional headaches that may result from all of that.

Im also not really tied into going back over the old concrete with new as Im not totally against just putting new decking boards over the top of it and making it a wooden patio floor. If I went this route however I still want to somehow seal off where the dips are in the old concrete so they dont become mosquito breeding pools. Could I put some type of water proofing substance over the old to prevent this? and then just add my wood planking?
So how many of these " dips/holes " are there to repair ? Are there 5 or 10 or 50 ? It would seem to me if the number is fairly low and you have to determine what fairly low is to you that they could be repaired with a variety of patching/top coat products . If it were me and IF the concrete is in good shape overall ( your words ) I would consider a DIY repair . I would pressure wash if possible to get it clean .

Identify all the dips/holes you want to repair and brush on a concrete bonding agent , generally it is white milky in color . Follow directions from the bonding agent and the top coat manufacturer and go to town filling and leveling the depressions . Will it be perfect ? Nope . Will it last ? I would think it would especially if you are planning on covering with a wood deck . Keep in mind I am just a DIYer and others that have chimed in may/are more knowledgeable than me .
Thanks again for the info.
I would guess maybe 6-8 of these low spots would need patching. Ranging in size from basketball size to twice that size. So if i did decide to go ahead and just make this a wooden patio deck instead of concrete then I would not be as much concerned about the looks of the patch but more about it just not continuing to get worse (bigger) and eventually possibly causing water seepage into the basement down the road.
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