Notice that the cracks on each side started at the edges of the cmu walls. The driveway slab had nowhere to move so when it expanded in the transverse direction it cracked.
You cannot confine concrete to a rigid fixed space and not expect it to move. There should have been expansion joint materials installed.
Also, lack of use of reinforcing steel in Florida driveways does not help keep it together when push comes to shove.:twisted:
I think we’re all in agreement of lack of the expansion joint but not as in the reference in the link you provided. We are talking for independent movement, floating, not actual expansion of the slab itself. And your link would only be appropriate in warm climate as you better have joints every 100-200 sq. ft. for freezing soils.
I agree with the expansion joint theory but here is another angle, admittingly far out but I have seen what I am about to describe. With the garage floor being concrete continuous thru the driveway and down to the concrete street you have the possibility of “street creep”. This is expansion of the concrete mass from the street all the way into to the back side of the garage. It can be compounded by heavy trucks swingging hard into a cul-de-sac and the harmonic energy goes through the street slab all the way through the home. I saw a wood frame home actually having drywall cracking from this very condition.
You need to look at the pictures again.
Take a look at the crack. it is in line with the exterior of the garage indicating that the slab was poured on top of the footing foundation with rebar in the driveway slab. It cracked from shrinkage and shows some displacement. I guess the sawed control joints was not enough to contol the shrinkage.
Since I don’t think the foundation went down, there must have been some grounde expansion or it is just slab curl due to the top surface drying quicker than the bottom.
The article I posted is to show that not all Engineers believe in slab expansion and the reason why.
Similar detail I remember from building in Florida in 1970.
I cannot buy into your theory, shrinkage had nothing to do with this. I have never heard of rebar into a floating slab from a foundation, if that’s what you are saying.
I will be onsite when they saw it open for my own info, stay tuned…
I am interested to know in what they find also. Keep me posted. When they are done digging up that slab maybe they can go dig up my pipe and see what’s up with that.:mrgreen:
We are talking about a concrete driveway, not the house slab.
Your image is accurate in relation to the slab and foundation of the home. But does not apply to the driveway.
The driveway is just 4-6 inches of concrete…Most don’t even have footers or steel reinforcement.
The use of an expansion joint is not to allow for expansion, as much as for movement. The driveway and house will settle differently over time. The two should be independent of each other.
At no point can I recall building code in Florida, (which was not uniform until 2001 FBC) requiring driveways to be attached to the foundation of the home.
The slab of the driveway got poured on top of the 2 block high foundation and that is why it stayed where it is.
Look at the picture and the line of the foundation below that we do not see.
The only control line is the one going across the slab. The rest is just decorative stamping. It looks to me like a decorative layer has been added over the top of the original driveway. My guess is that there is a control joint, underneath the decorative layer. Also most houses in South Florida are built on a monolithic slab not a stem wall. The driveway is usually poured way after the house is built, and the fact that the finish runs over the slab for the house would indicate that it is just a thin layer. also far more likely for the house to have settled than for the driveway to have risen. The weight of a two story house imposes a far greater load than that of the 4-6" of concrete in the driveway.
