New Concrete On Top of Old

3084 Views 20 Replies 9 Participants Last post by stadry, Jan 5, 2013

St. A

Discussion Starter · Dec 29, 2012

I touched on this topic in another thread, but thought this title would get right to the point. I'd like level an existing concrete foundation which was graded rather steeply at 7 1/2'' over an 18' run. I'm looking at doing this in two locations- one under the house (carport), one on a concrete parking area. I'm thinking of cleaning the old concrete, drilling some holes in it, adding rebar to help reduce any shifting, and then call in a truck for the pour. It looks like it would be about three yards in each location. How does this manner of leveling sound? Thanks- Aaron

1 - 20 of 21 Posts

woodworkbykirk

· #2 · Dec 29, 2012

if you have done your calculation right on the volume you should be fine.. just be sure to strike a level line with a laser level so to have something to finish to

stadry

· #3 · Dec 29, 2012

would you touch on this a bit more 'cause i just got in :laughing: someone poured a footer that's 7 1/2" LOW on 1 end 18' from the correct elevation ? ? ?

obviously having the conc contractor come back isn't an option ? then again, i he hadn't noticed the forms had fallen OR didn't use a level, why would you want him back,,, 'cleaning the old concrete' may involve scarifying or using a bushing tool, mortar for a bonding compound to prevent old conc from sucking moisture out of the new, vertical rebar 2' o/c + horizontal #4 bar tied to the vertical bar,,, anyway, that's my story & i'm stickin' to it :yes:

Bondo

· #4 · Dec 29, 2012

St. A said:
I touched on this topic in another thread, but thought this title would get right to the point. I'd like level an existing concrete foundation which was graded rather steeply at 7 1/2'' over an 18' run. I'm looking at doing this in two locations- one under the house (carport), one on a concrete parking area. I'm thinking of cleaning the old concrete, drilling some holes in it, adding rebar to help reduce any shifting, and then call in a truck for the pour. It looks like it would be about three yards in each location. How does this manner of leveling sound? Thanks- Aaron

Ayuh,.... 'n you shoulda stuck with that thread,...

You've only answered a few of the questions asked of you, There....
Now yer runnin' another thread, 'n Nobody has a clue as to what yer talkin' 'bout....

If ya run 1 thread 'bout the project phase, All the relevant info is where it can be referenced...
New thread,... No reference,.... equals Confusion....

Btw,... I asked ya another question in yer 1st thread....

St. A

Discussion Starter · #5 · Dec 29, 2012

There's no contractor to call as the work was done years ago before I owned the house. But in any case, there is no fault, the concrete was graded, presumably for drainage away from the house. I just want to level part of it so I can build something on top of the level foundation. Thanks- Aaron

PS- Spanked about starting a second thread. Wasn't trying to break any rules of etiquette here. I was just trying to help by simplifying the question. On other forums where I am an active member, I know users often search for subjects by title and I thought clearing up mine would aid in other people's searches. Sorry for any confusion I may have caused. Thanks for your help- Aaron

stadry

· #6 · Dec 29, 2012

is this a buried wall OR slab ? maybe a picture's a good idea :laughing:

forget those other forums - ALL the good guys are here :thumbsup:

md2lgyk

· #7 · Dec 29, 2012

St. A said:
I just want to level part of it so I can build something on top of the level foundation.

What is it you want to build? Your slab isn't a "foundation" and likely has no footers.

Bondo

· #8 · Dec 29, 2012

md2lgyk said:
What is it you want to build? Your slab isn't a "foundation" and likely has no footers.

Ayuh,... Click on the links in post #4 to find his Other thread, with all the Information...:whistling2:

Canarywood1

· #9 · Dec 29, 2012

St. A said:
I touched on this topic in another thread, but thought this title would get right to the point. I'd like level an existing concrete foundation which was graded rather steeply at 7 1/2'' over an 18' run. I'm looking at doing this in two locations- one under the house (carport), one on a concrete parking area. I'm thinking of cleaning the old concrete, drilling some holes in it, adding rebar to help reduce any shifting, and then call in a truck for the pour. It looks like it would be about three yards in each location. How does this manner of leveling sound? Thanks- Aaron

Not a good idea to go from "0" to 7 1/2 inches,the "0" end should be at least 3 inches thick,and a good bonding agent applied for 3-4 feet.

St. A

Discussion Starter · #10 · Dec 29, 2012

Canarywood- Thanks for your reply. Is the feather edge always a bad idea? If it is an issue of traffic/ weather, would thinset/ tile over the top mitigate the degradation problem or is it another issue like brittleness in the thin feateredge? Thanks again, Aaron

Canarywood1

· #11 · Dec 29, 2012

St. A said:
Canarywood- Thanks for your reply. Is the feather edge always a bad idea? If it is an issue of traffic/ weather, would thinset/ tile over the top mitigate the degradation problem or is it another issue like brittleness in the thin feateredge? Thanks again, Aaron

Feathering to "0" is always a bad idea,and thinset and tile would not mitigate the degradation problem,i've never seen it work in my 35 years in the business.

St. A

Discussion Starter · #12 · Dec 29, 2012

Thanks Canarywood. I sure appreciate the information. I asked another similar question in another section of the forum- basically using sleepers over vapor barrier over concrete to attempt the same thing- a level floor for a living area. If you have the time, I'd be curious if you'd ever seen this or another solution to this problem. -Aaron

http://www.diychatroom.com/f19/small-wood-shop-grade-165832/#post1081792

sixeightten

· #13 · Dec 29, 2012

St. A said:
Thanks Canarywood. I sure appreciate the information. I asked another similar question in another section of the forum- basically using sleepers over vapor barrier over concrete to attempt the same thing- a level floor for a living area. If you have the time, I'd be curious if you'd ever seen this or another solution to this problem. -Aaron

http://www.diychatroom.com/f19/small-wood-shop-grade-165832/#post1081792

We have done that before. Cheaper than the concrete also. I didn't read the other thread so I am just going by what you have here.

Canarywood1

· #14 · Dec 29, 2012

St. A said:
Thanks Canarywood. I sure appreciate the information. I asked another similar question in another section of the forum- basically using sleepers over vapor barrier over concrete to attempt the same thing- a level floor for a living area. If you have the time, I'd be curious if you'd ever seen this or another solution to this problem. -Aaron

That would be a much better and a lot cheaper solution to your problem,just be sure to use PT sleepers.

St. A

Discussion Starter · #15 · Dec 29, 2012

Last question and then that's it (until the next time :laughing

: Should I anchor the sleepers to the concrete? If so, with what? Thanks again all. -Aaron

Canarywood1

· #16 · Dec 29, 2012

St. A said:
Last question and then that's it (until the next time :laughing: Should I anchor the sleepers to the concrete? If so, with what? Thanks again all. -Aaron

Any construction adhesive will work,and it's an easy way to anchor them.

kwikfishron

· #17 · Dec 30, 2012 (Edited)

If you're going to pour a slab you should bust out and remove about a third to a half of what you have now on the high side. As mentioned 7 1/2 to zero is a bad plan.

St. A

Discussion Starter · #18 · Dec 30, 2012

I have decided to go with the sleeper method, at least on the interior project. My intention was to do concrete, vapor barrier barrier, sleeper, ply sub-floor. A construction adhesive would just adhere my sleeper to the vapor barrier and not to the concrete. Would you put the vapor barrier elsewhere?

Canarywood1

· #19 · Dec 30, 2012

St. A said:
I have decided to go with the sleeper method, at least on the interior project. My intention was to do concrete, vapor barrier barrier, sleeper, ply sub-floor. A construction adhesive would just adhere my sleeper to the vapor barrier and not to the concrete. Would you put the vapor barrier elsewhere?

In that case a ramset would work,or maybe tapcons.

Guywithskills

· #20 · Jan 5, 2013

I have done lots of pours over old concrete for a variety of reasons. Tried lots of "quick solutions." My experience says, if you pour over old, the cracks and joints will mirror up no matter what you do. That is guaranteed. You will not bond to it. It is all we could do to bond to Cool Decking around a pool that was already rough, TSP washed and acid washed.
If the old slab is without cracks and decent shape, pour the new one, match the expansion joints up exactly by marking so they can be seen to follow after the new poor place 15lb roofing felt over old slab. If old slab has cracks, we bust it up with an 8lb sledge hammer into 8" pieces approximately, actually not that hard. Takes an hour for a 10' x 20' slab. If it is especially hard, use a pry bar and just leverage the slab up a couple of inches and start at the far end and break your way to the lever. This works very well and Ive seen lots of guys in the trade use this. We were not the only ones. Dont pull it up, you are just breaking it up and leaving in place. Then lay 15lb felt over and pour your new slab. You do not want it binding to the old and you can put your expansion/cut joints where you please. This will give a good result. In the early days of my concrete life in the 70s, we tried probably all the short cuts. The real labor is in breaking up the old. Like I said, maybe an hour of sledge hammer. If out of shape and fortunate enough to not have to do such hard labor, bring a buddy and trade off. Charge him $20 for the work out...

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