Concrete Porch Addition

boman47k

I talked to a guy today about extenting my front porch out to the end of the house when I get the top extended. He seems to think he can pour up to and over the old the concrete. I wasn't sure this could be done but with binding agents and such, I am not sure. Comments?

tgeb

My initial thoughts are that it will crack along the perimeter of the existing.

Then I thought, if the new concrete is thick enough 4"+ and has rebar running through it, it just might last. But I would leave off the bonding agent so it is free to move over the old concrete.

The issue would be do you have enough room at the step down out of the house to do it this way.

If it is a thin layer "over-pour" of say 2", I'd say it is doomed to fail.

Let's see what others think.

__________________
Tom

www.gebcon.com

Tscarborough

Concrete over concrete is no problem, but as stated, it will probably fail at the change of thickness unless it is 4" or more. There are several ways to deal with it if it is thinner, but in no case should it be less than 2", or the new slab should abut and the old slab be re-finished with a material made for that purpose.

It it is 2", it should have control joint placed at the edge with slip dowels into the new. They will have to be small though, 5/16" smooth dowels for example.

More information = better answer.

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It ain't Rocket Science unless you are building rockets.

boman47k

I will try to get a pic up tomorrow to show what I am talking about.

But for now, I will try to explain a little more. The porch is now 8 X 12. It is to be extended to like 8 X 22. He is talking about entending it out by pouring about 3 to 4 inches over the existing porch ( up to the threshold at the door) on out to the 22' to the end of the house.
I also wonder if he can blend the front edge toward the street. I don't want two layers showing.

Years ago when this house was built, or when the proch was built, if it was built the way I think it was, the framing under the crete was not set right and it looks like the porch is bent toward part of the house.

I may end up ripping the old porch off, fill in and pour the thing myself.
Besides he was supposed to get back with some numbers this evening. Haven't heard from him.

macatawacab

3 to 4" will work. Especially since you are not in a freeze/thaw cycle area. to avoid the two layer, go past the old slab and form a drop edge on the new slab so you only have the new exposed.

boman47k

The odd thing about this is he is a neighbor and I have been meaning ti get with him on this porch as concrete is all I've ever known him to do. City projects, driveways, etc. So I saw him coming down the street and stopped him. I ask him if he was satying busy. Pretty moch sop for me to ask this. He said no. I said you are about as busy as you to be, aren't you. He is about ready to retire. He said nope, just aint nothin going on. I assume dhe would get back with some numbers.

I really think this should be the way I originally wanted it done. Out with the old, in with the new. I doubt there is 4" under the threshold.