# How long before you can park on a new slab?



## tripower (Nov 16, 2006)

I'm having a garage build and the contractor is telling me that I should ait 4 to 6 weeks before parking a car on my new slab. Is he serious?

My buddy who built his garage (10 years or so ago) put his truck on his slab as soon as he saw the center of the slab finish drying and he hasn't had any issues with cracking. Your opinions?


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## cibula11 (Jan 6, 2007)

Better safe then sorry. I can't offer any info. that can help, but even if it was okay to park on, unless there is a hail storm coming and you HAD to park it inside. I would say just wait. It won't hurt. But I'm sure someone with some better suggestions will respond.


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## cibula11 (Jan 6, 2007)

I googled some info. and found this:

The 28-day strength of concrete is important because that is the basis of acceptance for most projects. For example, if a project specifies 4000 psi concrete, the concrete does not have to reach that level of strength for 28 days. Typically, it is expected that a concrete mix will reach 50% of its design strength in 3 days, 75% in 7days, and 100% at 28 days, as determined by breaking concrete test cylinders that are made on the day of placement.


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## tripower (Nov 16, 2006)

cibula11 said:


> I googled some info. and found this:
> 
> The 28-day strength of concrete is important because that is the basis of acceptance for most projects. For example, if a project specifies 4000 psi concrete, the concrete does not have to reach that level of strength for 28 days. Typically, it is expected that a concrete mix will reach 50% of its design strength in 3 days, 75% in 7days, and 100% at 28 days, as determined by breaking concrete test cylinders that are made on the day of placement.


Thanks, do you have a link?


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## Brik (Jan 16, 2007)

I read somewhere that the concrete in the Hoover dam is still curing to this day!

Yea, a month for full cure of a slab. You could likely park on in in 3 days (depending on temp, humidity, etc) w/o issues. The installer is just doing a CYA. 
Keep off it for as long as convenient and don't *************** to the installer when it cracks. All concrete cracks.


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## tripower (Nov 16, 2006)

Brik said:


> I read somewhere that the concrete in the Hoover dam is still curing to this day!
> 
> Yea, a month for full cure of a slab. You could likely park on in in 3 days (depending on temp, humidity, etc) w/o issues. The installer is just doing a CYA.
> Keep off it for as long as convenient and don't *************** to the installer when it cracks. All concrete cracks.


I know I won't sweat it too much. I will just seal the crack then paint the floor. I just didn't know if something catastrophic would happen, but like you said it is just a CYA. besides he will spend 2 to 3 weeks after the slab is poured framing and finishing so I don't anticipate waiting too long. But I do have a heavy toolbox I wonder if I can roll that out there?


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## Brik (Jan 16, 2007)

My house's foundation is poured. I believe the framers started in a day or two, forms off in one day. Not sure if an accelerative was used.


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## concretemasonry (Oct 10, 2006)

Three or four days should be OK in warm weather if you feel you really have to use it.

If it was me, I would push to get garage done in a couple of days and then park inside next week.


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## tripower (Nov 16, 2006)

Brik said:


> My house's foundation is poured. I believe the framers started in a day or two, forms off in one day. Not sure if an accelerative was used.


Well see that's what I was thinking. I mean, he wants me to stay off the slab for weeks but they start framing on the foundation with days of it's completion and this is what holds up the structure! Just doesn't make sense.


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## tripower (Nov 16, 2006)

A couple of related questions:

1. I would like to go ahead and use an epoxy sealant to paint the floor with before I move everything in? When can I do this (i.e. the amount of time I must wait after the slab is poured)? And what floor sealant do you recommend?

2. After a recent rain I noticed several low spots in th slab were the rain did not drain off. Is this normal? And I thought having the slab at an inch and a half grade should have taken care of any low spots and drained the water off the slab appropriately?


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## Brik (Jan 16, 2007)

I would follow floor coatings recommendations for wait time. Also, do it as soon as you can. The longer you wait the more junk, dust, dirt, stains and spills will need to be dealt with.

Low spots are not ideal. I would say, if they are not too pronounced and generally the garage floor pitches to the door then you are fine. There should also be a small curb where the door sits to prevent seepage under the door and the section where the wall sits should be level. Does that all make sense? I could post a picture if you want.


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## tripower (Nov 16, 2006)

Brik said:


> I would follow floor coatings recommendations for wait time. Also, do it as soon as you can. The longer you wait the more junk, dust, dirt, stains and spills will need to be dealt with.
> 
> Low spots are not ideal. I would say, if they are not too pronounced and generally the garage floor pitches to the door then you are fine. There should also be a small curb where the door sits to prevent seepage under the door and the section where the wall sits should be level. Does that all make sense? I could post a picture if you want.


Pictures would be great. So what to I do now about these low spots in my floor. They were quite obvious since I don't have the framing up and it rained so I was able to see exactly how the floor will drain. There were approximately three small depressions (approximately 1 foor by 6") in the slab that were obvious after the rest of the rainwater drained off. Obviously I cannot do anything with the concrete itself now. But can I do something with the epoxy coating such as layer it up in those areas to ensure that water from my car does not puddle up when sitting in my garage?


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## Brik (Jan 16, 2007)

Sorry for the crappy picture.


No thoughts on the dips other than to live with it. Anything else on top will just make a mess I think.










My picture shows how the floor should slope in relation to the foundation wall and the detail on the end of the apron, below the door. The driveway is just to the right, out of the picture. The slope rises to about 1" below the foundation wall toward the house.


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## Zero Punch (Nov 15, 2005)

"So what to I do now about these low spots in my floor. They were quite obvious since I don't have the framing up and it rained so I was able to see exactly how the floor will drain. There were approximately three small depressions (approximately 1 foor by 6") in the slab that were obvious after the rest of the rainwater drained off. Obviously I cannot do anything with the concrete itself now. But can I do something with the epoxy coating such as layer it up in those areas to ensure that water from my car does not puddle up when sitting in my garage?"

It sounds like you have a good pour. I install floor covering and all of the concrete floors we work on will have slight depressions whether machine or hand troweled. Many pours are finished so badly that we spend more time on prep than the install. 
If these three dips bother you that much I would use Ardex feather finish to fill them before applying your epoxy. It will dry a different color/shade of gray so if your using clear epoxy that may be an issue. If your using pigmented there should be no problem.


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## alelkes (Oct 30, 2008)

The Hoover dam that was built in 1933 - 35. The ingineers calculated if they won't disipate the heat what the curing concrete create, the curing time would have been 125 or so years. They circumvented this by using pipes through which the river water cooled it and didn't poured more than 6 to 10 inch thick sections. As of today the Hoover Dam still curing. Not much but still curing. The 28 days is an arbitrary arrangement after which most concrete construction is available to inspection, testing and use. Some major floor coating companies wait 45 days before they coat the surface. To cure the concrete, it needs WATER. Keep watering theat surface at least 1 to 2 weeks or more if you want have a good concrete on your hand. The concrete cures with WATER. 
As for coating the surface with epoxy it should be either shotblast or grind it with #16 or #30 diamonds. The surface must be rough to let the epoxy bond. Forget about anybodies suggestion washing it with pressure washer or any other way. 
Another alternative you have is polishing the surface. Exposing some or a lot of agragates. It could look stunning.
The difference between epoxy and polishing is the former may last 7 to 10 years. It could last only a year or two if you are unlucky and have water movement under the garage. In this case if the water evaporate it will lift anything off the floor including the epoxy.
The polished floor can breath because it has no topical coat on it. Hence, the evaporating water will simply go through it without damaging it. Antony


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