Ok to pour new concrete over old concrete slab? (1 Viewer)

[skycriesmary]

I'm attempting to level out my concrete floor in garage, to renovate for new living space. There is about a 3" difference between high point and low point. I have the option of pouring over the old concrete and feathering out, and having the ceiling height be about 6' 9", or taking out the existing slab, and starting over, and building up to 7".

I've heard conflicting information whether or not old concrete and new concrete will bond, and if the concrete that feathered out less than 3" on top will crack.

The difference between pouring over or starting from scratch is about $700.

Anybody in the profession, or with experience care to lend an opinion?

 

[jon_mx]

I would definitely take out the old slab and start over. It costs a little more, but there will be no issues. Pouring a slab over a slab seems a bit shaky.

ETA: having a 6'9" ceiling height in garage seems odd. Is this a pretty old house?

 

[whiskey7]

I would definitely take out the old slab and start over. It costs a little more, but there will be no issues. Pouring a slab over a slab seems a bit shaky.

+1

Do it right, IMO.

 

[randall146]

Can't help, but what's the price quote for tearing it up and repouring? What size garage?

 

[ChiefD]

Tear it out and start over.

 

[cstu]

http://indecorativeconcrete.com/?page_id=1268

[SIZE=small] For this to be feasible, the contractor needs to pour at least 2 inches thick, use smaller aggregate, and incorporate reinforcement such as welded wire mesh or fiber mixed into the concrete. Steel rebar is also a good idea if the slab is thick enough to allow it. To clarify the point, this article deals with pouring concrete over concrete, not applying a thin polymer-modified stampable overlay, which is another option. For more on thin overlays, please click here. [/SIZE]

 

[LarryAllen'sJockstrap]

We poured over the existing slab when we got a stamped concrete patio out back. No problems to date, but different situation.

ETA - our patio was raised by 3-4 inches and they did use the wire mesh in the new slab. Not sure about rebar.

 

[El Floppo]

dot

 

[Cliff Clavin]

Rent a jackhammer and get a good workout in to be safe.

 

[MikeIke]

I would definitely take out the old slab and start over. It costs a little more, but there will be no issues. Pouring a slab over a slab seems a bit shaky.

+1Do it right, IMO.

Agreed. Better to start fresh with what you know is a good foundation. That extra $700 may pay for itself many times over in the future.

 

[jon_mx]

Thinking about this. You already have a 3" slope. At your high point you will need at least 3" of concrete, then at your low point you would have 7" of new concrete plus the original 4" slab. Seems like you could gain 7" of head room for your ceiling by starting fresh.

 

[Long Ball Larry]

Did that roof collapse yet?

 

[NutterButter]

Rent a jackhammer and get a good workout in to be safe day laborer.

A lot easier.

 

[skycriesmary]

Can't help, but what's the price quote for tearing it up and repouring? What size garage?

The total square feet is 330, the quote including demo and removal of old material, and putting in a new 4" slab is $2,650.

 

[skycriesmary]

Did that roof collapse yet?

Har, Har...No, got city approval w/out a structural engineer, and will be using a engineered beam, and a couple of 2x8's.

 

[skycriesmary]

I would definitely take out the old slab and start over. It costs a little more, but there will be no issues. Pouring a slab over a slab seems a bit shaky.

+1

Do it right, IMO.

Yeah, I'm getting it torn out, and will see what kind of clearing height I can get once the old is ripped out.

 

[Arizona Ron]

tear it a new one

 

[BobbyLayne]

Rent a jackhammer and get a good workout in to be safe.

Hoolllllleeeee cooowwwww

 

[St. Louis Bob]

Totally in the complete replacement route, GB. $700 is more than worth years of worrying if it's going to crack or something.

 

[glvsav37]

Rent a jackhammer and get a good workout in to be safe.

Ripped up my garage floor a few years ago...felt F-in great. Jackhammers are a blast to operate. Takes out a lot of frustration.

I did hire a guy to move the broken up pieces...that part sucks.

 

[belljr]

Self leveler

 

[St. Louis Bob]

Rent a jackhammer and get a good workout in to be safe.

Ripped up my garage floor a few years ago...felt F-in great. Jackhammers are a blast to operate. Takes out a lot of frustration.

I did hire a guy to move the broken up pieces...that part sucks.

Got the new rider model?

 

[skycriesmary]

Totally in the complete replacement route, GB. $700 is more than worth years of worrying if it's going to crack or something.

Yeah, this is the route I've taken. Ugh...hoping this is the last unexpected expense. *right*

 

[Doctor Detroit]

If you're like me and have bodies under the old one, just pour over top and call it a day. Actually I do this every two years or so, I now have a second story slab.

 

[Kafka]

I'm a brick mason/concrete finisher; that works out to about 8$ a sq. ft. which is exactly what I charge for demo/pour...fair price. You definitely want to tear it out & pour new slab w/ fiber mesh/4000mix..otherwise the only guarantee you can get is that it will crack... just a damn dumb block layer's 2 cents...

 

[skycriesmary]

I'm a brick mason/concrete finisher; that works out to about 8$ a sq. ft. which is exactly what I charge for demo/pour...fair price. You definitely want to tear it out & pour new slab w/ fiber mesh/4000mix..otherwise the only guarantee you can get is that it will crack... just a damn dumb block layer's 2 cents...

Thanks for the feedback, he mentioned he was going to use 3500psi, and that was totally fine for indoor purposes. Maybe I should ask for the upgrade?

 

[daddo39]

I'm a brick mason/concrete finisher; that works out to about 8$ a sq. ft. which is exactly what I charge for demo/pour...fair price. You definitely want to tear it out & pour new slab w/ fiber mesh/4000mix..otherwise the only guarantee you can get is that it will crack... just a damn dumb block layer's 2 cents...

Thanks for the feedback, he mentioned he was going to use 3500psi, and that was totally fine for indoor purposes. Maybe I should ask for the upgrade?

There are other options, as someone else mentioned a leveling agent. The cost on this could be higher though. The 3500 psi is fine though

 

[Otis]

Do it right.

 

[Spike]

Couldn't you use old fencing instead of rebar to bind it?

 

[Da Guru]

I'm attempting to level out my concrete floor in garage, to renovate for new living space. There is about a 3" difference between high point and low point. I have the option of pouring over the old concrete and feathering out, and having the ceiling height be about 6' 9", or taking out the existing slab, and starting over, and building up to 7".

I've heard conflicting information whether or not old concrete and new concrete will bond, and if the concrete that feathered out less than 3" on top will crack.

The difference between pouring over or starting from scratch is about $700.

Anybody in the profession, or with experience care to lend an opinion?

Bust it all out and do it right. It you do it half assed in a year or two you will regret it.

 

[Tom Skerritt]

We floated our garage floor about 10 years ago. Concrete guys inserted rebar grid into existing sides and poured right on top. Results were beautiful. No issues since.

 

[Ditkaless Wonders]

I have heard of folks using garage space for more living space, and doing conversions in there, but given that there will have to be electrical, HVAC and other issues retrofitted (which means compromises), and given you are losing garage and storage space, doesn't it make better sense to do an addition or even to pop the top on the home elsewhere, maybe even over the garage?

 

[Tom Skerritt]

Considered building above the garage, but cost was enormous. We did a garage conversion. Only minimal plumbing retrofitting needed. Added a detached garage for $20K. Was the easiest and most cost effective thing for us to do. Was the best decision we could have made. Love it.

Added 500sqft living space and over $50K value to the house. And will only go up from there.

 

[skycriesmary]

I am doing a full ADU, using my attached garage (which is attached partially with a shared wall between the kitchen and second floor of garage). The garage had a room above it that I had previously rented out, but the tenant came in the main house to use the bathroom.

I took a full day class from a guy locally who has this blog, which is a great resource, if your thinking about doing something similar.

My total square feet will be about 600 square feet, and my goal is to keep it under 45k, which means it'll probably hit 55k.