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Tying New Concrete to an Existing Foundation - Yes or No?
Posted on 6/24/14 at 11:35 am
Posted on 6/24/14 at 11:35 am
We will be pouring a back patio slab (about 20'x30'x6") in the next few months that will butt up to our existing home's foundation. It will eventually be covered, but not at this time. I've been told that we should tie the new pour to the home foundation using rebar, but I've also read conflicting arguments that anchoring the new slab to the foundation with the rebar could cause cracking to the slab or to the home's foundation. I'm not familiar with any of this and I was wondering if I could get some advice? 

Posted on 6/24/14 at 11:38 am to ForeverLSU02
I didn't do it to mine and have had no issues.
Come to think of it .. My patio doesn't have a crack in it ...and It 8 years old
Come to think of it .. My patio doesn't have a crack in it ...and It 8 years old
Posted on 6/24/14 at 11:38 am to ForeverLSU02
you might need to dowel into it or you have two different concrete slabs abutting each other. Let a professional construction guy make the decision and he can be on the hook for it. It likely won't be an issue unless your property subsides majorly. Just make sure its got the proper joints.
This post was edited on 6/24/14 at 11:40 am
Posted on 6/24/14 at 11:40 am to Geauxld Finger
quote:I'm assuming you're talking about expansion joints?
Just make sure its got the proper joints
Posted on 6/24/14 at 11:41 am to ForeverLSU02
Need more information. Is the existing home on piles? Is it a post tension slab? Why are you going 6" thick? What's the future plans?
Posted on 6/24/14 at 11:42 am to ForeverLSU02
quote:
I'm assuming you're talking about expansion joints?
This and my patio is not tied in.
Posted on 6/24/14 at 11:44 am to BSG
quote:I have no idea
Is the existing home on piles? Is it a post tension slab?

I bought the home 3 years ago. How do I find this out?
quote:Nothing too crazy. I'd like to cover it in the future and put some patio furniture to relax and have people over. Should I not do 6"?
Why are you going 6" thick? What's the future plans?
Posted on 6/24/14 at 11:44 am to ForeverLSU02
Are you using Quickcrete?
Posted on 6/24/14 at 11:45 am to Traffic Circle
quote:Nah, I was going to get it poured
Are you using Quickcrete?
Posted on 6/24/14 at 11:48 am to ForeverLSU02
quote:
I'm assuming you're talking about expansion joints?
expansion yes, also i'm not sure you need 6" thick concrete if you aren't driving a car or anything on it.
Posted on 6/24/14 at 11:48 am to ForeverLSU02
most drive ways are four inches thick, i hope you arent having friends over that are big enough to require 6" of concrete. 4" should be more than enough.
i dont think you should tie in because the new pad will settle, no matter how much you get the grade packed. when it settles even if its 1/2" you put alot of stress on the existing foundation if you are tied into it.
i dont think you should tie in because the new pad will settle, no matter how much you get the grade packed. when it settles even if its 1/2" you put alot of stress on the existing foundation if you are tied into it.
Posted on 6/24/14 at 11:49 am to Geauxld Finger
quote:Ok. That answers my next question. So would you go 4"?
also i'm not sure you need 6" thick concrete if you aren't driving a car or anything on it.
Posted on 6/24/14 at 11:50 am to Happygilmore
quote:Thanks
dms4720

BTW, I do have some large friends

Posted on 6/24/14 at 11:52 am to ForeverLSU02
I wouldn't tie it to the existing foundation. I'd imagine that the little bit of settlement that would occur near the sill is negligible/tolerable. You could do a thickened turndown along the existing to help with differential movement.
If anything, tying the slab to existing foundation will restrain it during the curing process and lead to more unsightly temperature/shrinkage cracks.
If anything, tying the slab to existing foundation will restrain it during the curing process and lead to more unsightly temperature/shrinkage cracks.
Posted on 6/24/14 at 11:53 am to ForeverLSU02
I wouldn't tie in into the existing slab. If the newly placed patio settles and is tied into existing slab, all that is going to happen are cracks within the new slab. Just make sure to have a sufficient foundation for the new slab to reduce settlement.
Posted on 6/24/14 at 11:54 am to BSG
quote:
Is the existing home on piles?
If the OP is in Albany, I can't imagine it being on piles unless you're building in swampy area.
Livingston Parish generally has really good soil.
Posted on 6/24/14 at 11:57 am to ForeverLSU02
quote:
So would you go 4"?
Because its the easiest quickest way to do the form work. Just lay a 2X4 on the ground with the 3 1/2" side vertical and boom instant form. Do remove the grass first.
And I'm about 99.9% (unless it is off the ground) sure your house isn't on piles. Don't tie your new slab into the house foundation. The two slabs will settle differently and cause cracks in your new patio.
Posted on 6/24/14 at 11:57 am to Happygilmore
quote:
i dont think you should tie in because the new pad will settle, no matter how much you get the grade packed. when it settles even if its 1/2" you put alot of stress on the existing foundation if you are tied into it.
He's not going to overstress the existing foundation by tying a patio slab to it. This isn't the issue.
Posted on 6/24/14 at 11:59 am to ForeverLSU02
quote:
Nothing too crazy. I'd like to cover it in the future and put some patio furniture to relax and have people over. Should I not do 6"?
How do you plan on reinforcing the slab? And how do you plan on covering it in the future?
Posted on 6/24/14 at 12:00 pm to urinetrouble
quote:
reinforcing the slab
don't use anything more than wire mesh
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