Crack in Brand New Basement Floor????
We hired a reputable contractor in our area and they poured the new floor in one day. They told us it would take a week to cure and then we could put our things down there (just storage boxes, etc).
This past week I noticed a 10ft long crack in the BRAND NEW floor! The width could fit a dime in it. I am FURIOUS because we paid big bucks for a new floor and now it's cracked up!
What went wrong here?? Is it the contractor's fault? I called them and they said it's a "curing crack" and there's nothing they can do about it.
I would appreciate any insight anyone could give me on this.
Thanks much!
Answers:
When installed properly, concrete is one of the most durable and long lasting products you can use around your home. But it is important that concrete contractors follow well-established guidelines with respect to concrete placement. Durable, high strength, and crack resistant concrete does not happen by accident.
Why Concrete Cracks
Reason #1 - Excess water in the mix
Concrete does not require much water to achieve maximum strength. But a wide majority of concrete used in residential work has too much water added to the concrete on the job site. This water is added to make the concrete easier to install. This excess water also greatly reduces the strength of the concrete.
Shrinkage is a main cause of cracking. As concrete hardens and dries it shrinks. This is due to the evaporation of excess mixing water. The wetter or soupier the concrete mix, the greater the shrinkage will be. Concrete slabs can shrink as much as 1/2 inch per 100 feet. This shrinkage causes forces in the concrete which literally pull the slab apart. Cracks are the end result of these forces.
The bottom line is a low water to cement ratio is the number one issue effecting concrete quality- and excess water reduces this ratio.
What you can do about it:
Know the allowable water for the mix the contractor is pouring- or be very sure you have chosen a reputable contractor who will make sure the proper mix is poured. It is more expensive to do it right- it simply takes more manpower to pour stiffer mixes.
Reason #2 - Rapid Drying of the concrete
Also, rapid drying of the slab will significantly increase the possibility of cracking. The chemical reaction, which causes concrete to go from the liquid or plastic state to a solid state, requires water. This chemical reaction, or hydration, continues to occur for days and weeks after you pour the concrete.
You can make sure that the necessary water is available for this reaction by adequately curing the slab.
Reason #3 - Improper strength concrete poured on the job
Concrete is available in many different strengths. Verify what strength the concrete you are pouring should be poured at.
Talk to the ready mix supplier
Consult with the Ready Mix Concrete Association in your area.
Reason #4 - Lack of control joints.
Control joints help concrete crack where you want it to. The joints should be ΒΌ of the depth of the slab and no more than 2-3 times (in feet) of the thickness of the concrete (in inches). So 4"concrete should have joints 8-12' apart.
Read more about control joints here.
Other reasons:
Never pour concrete on frozen ground.
The ground upon which the concrete will be placed must be compacted.
The sub grade must be prepared according to your soil conditions. Some flatwork can be poured right on native grade. In other areas 6"of base fill is required along with steel rebar installed in the slab.
Understand what you contractor is doing about each of the above listed items and you will get a good concrete job.
Other answers:
No expansion joint?!
No expansion joint?!
It is not uncommon for concrete to crack
when curing. Sometimes it simply can not be helped.
Sometimes it can be caused by the dirt underneath
not being compacted properly.
Although it's probably too late now. you can get
special mixes of concrete that are lower risks
of cracking but they cost more...
did they cut "stress relief" joints in concrete or expansion joints?
like you see in sidewalks every 4 foot ot the 8 by 8 pattern you see in drivways and xways.
ALL concrete cracks - part of shrinkage process - but the cuts or joints usually lets it run along them so it is not visable.
you can fix the crack - by routing and etching and refilling but you will have a crack someplace else - basement curing can take months to finish, depending on the mosture level. also with a (90+ year old house - you always are going to have "stuff" going on.
Jewells
29 months and still here
Hi,
I am no expert on this but I have been in many new homes where the floor is cracked. Seems that it should be avoidable.
There is a additive that could be put in the concrete but they don't use it because of the expense.
One other thought. After the floor is poured there is a period of curing time were the floor should be kept moist by lightly spraying with water.. Was that done?
When the concret dries out it shrinks causing the cracks. If it does not dry out too fast then the cracks will not be as big.
There are some concret coverings that are like a plastic covering that will cover the cracks. You put the covering over you whole floor and it can have designs in it and have different colors.
I see this a lot in Florida on the driveways. Looks real pretty.
Check yellow pages to find contractor.
Just some thoughts.
Bob
Nothing you can do. Every basement floor has them. I f you finish you basement, the carpet or tile will cover them.