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Old 11-17-2011, 08:10 AM
18 posts, read 241,782 times
Reputation: 47


Hi friends,

I am about to have my concrete patio built in my backyard. Nothing fancy, it's just a regular 4 inches thick 3/8 rebar, 3000PSI concrete patio floor. The size is about 20x35. The 35 feet width is going to be the side right alone the house. The contractor was asking me if I want to attach the concrete to my existing house foundation. They will drill the steel rebar into my house foundation and put an expansion joint on the top to prevent the slab to move in the future. I see the benefit of attaching it to the foundation but I am afraid it will crack my house foundation couple years down the road. it also voids my house warranty. The house is pretty new, it was built in 2009.

What do you guys think? Should I tell him to attach it to the house foundation or not? Please help!!
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Old 11-17-2011, 08:20 AM
18,039 posts, read 25,052,276 times
Reputation: 16721
I don't know the answer, but I was afraid that it would void my foundation warranty.
The problem is that a few months later the slab started moving up to about 1/2" and all kind of bugs made that place their house.

I had to fill it up with sand and then use some silicon product to fill it up.
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Old 11-17-2011, 08:36 AM
Location: Ohio
668 posts, read 2,177,447 times
Reputation: 832
No, dont attach the slab to the house.

Unless you put down a foundation, the slab will rise and fall with 'frost freeze'.. And, it 'will' crack your foundation.

Now you know why they would void your house warranty

The Rebar will not expand, it will simply start a crack in the walls, and since its concrete, it has nothing else to do, but rip itself out when the pad 'lifts', and put a crack all down the wall...
But, thats my opinion

I wish you well...

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Old 11-17-2011, 09:35 AM
1,211 posts, read 3,537,642 times
Reputation: 1592
You absolutely DO NOT want them to tie a concrete patio to your slab. There are a number of reasons why, but none of them have anything with "frost freeze" like the previous poster suggested.

If you are not building a covered patio addition onto your home, that would consist of a framed structure that is integrated into the frame of the home, there is no need to tie them together. In fact, if you were adding a covered patio, the slab portion would need to be properly engineered and integrated into the house slab. It's a lot more complicated than simply drilling and adding rebar dowels. You have a post-tension slab, more than likely, and there is an extremely high probability that whichever clown was operating the hammer drill would eventually hit, knick, or otherwise damage the stressed cable that runs the width of your slab. At that point you would have significant problems ($$$) and a slab repair to disclose when, and if, you were to ever sell the home.

The most important thing for your contractor to do, is to properly place treated,or preferably, redwood expansion joints on 10' centers, minimum, both directions ( 20' x 35' ). The 35' foot length that is adjacent to the house slab, must be separated by what is called 'black joint'. Don't allow them to use a wood expansion joint along the slab. If they balk at that, find another concrete finisher. That fact that he asked you if you wanted that patio tied to that slab in the first place is troublesome.

Last edited by RCH99; 11-17-2011 at 09:43 AM..
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Old 11-17-2011, 12:25 PM
18,039 posts, read 25,052,276 times
Reputation: 16721
That was my thought when I told them not to attach it to my foundation.
I told them:
"I don't care if that slab slides 3ft from the house, the only thing I care is the foundation of the house"
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Old 11-17-2011, 04:28 PM
Location: Westbury
3,283 posts, read 6,012,785 times
Reputation: 2950
that is weird that they would ask you. most simple concrete patios are not tied in for that very reason
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Old 11-18-2011, 01:02 PM
660 posts, read 1,607,164 times
Reputation: 323
he's probably a little confused. i've seen existing paving connected to new paving with smooth dowel with expansion cap. but yeah i agree it's best to use isolation joint and not connect them in this case.

unless you plan on adding structure on your patio and connecting that structure to your house. then you may need to worry about differential settlement of your foundations if they are not connected.
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Old 11-29-2011, 09:37 AM
Location: Wylie, TX
2 posts, read 76,799 times
Reputation: 13
If done properly, it's good to have it attached to the house. It shouldn't cause a problem; that's what they do at the garage/ driveway. If you ever put a patio cover over a detached slab, you may have issues if you want to attach the cover to your house. It likely won't crack your foundation if done improperly but it will crack the patio slab. The edge where it's attached needs to be at least 8" thick with the dowel about 4" down and a rebar across the dowels. Obviously you transition back to the normal slab depth.
Regardless of whether you attach it or not, you need to seal the joint with a GOOD rubberized sealant, not the fiber EJ stuff they put in.
But if it voids your warrantee, you may want to take that into consideration.
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Old 11-29-2011, 12:05 PM
Location: Sugar Land
2,465 posts, read 5,760,052 times
Reputation: 2733
My pool deck is attached to my house fundation and is perfectly fine. You just need to do it the right way with the right components.
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Old 11-29-2011, 12:34 PM
660 posts, read 1,607,164 times
Reputation: 323
i'm probably beating a dead horse lol

"Match the new driveway level with the existing garage slab and sidewalk. An isolation joint is needed where the drive is to meet these existing pavements. Typically ¼" to ½" thick premolded joint material is used to make this joint."

Last edited by Brom; 11-29-2011 at 12:49 PM..
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