Thread: Driveway

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Absolutely. Deteriorated/missing wood strips is concrete driveways, walks and patios present a hazard to foot traffic. Ask any gal who has snapped off a high-heel in such.

Dan, I post this every once in a while. I think it is good info for anyone that is not familiar with concrete flat work terms. Yours is a construction joint. They placed the garage and then driveway separately.

This from the (ACI) American Concrete Institute.
There are three broad types of joints: isolation joints, contraction joints, and construction joints.
Isolation joints: permit slabs to move (very slightly) vertically and horizontally.
Contraction joints: prevent vertical movement but permit slight horizontal movement.
Construction joints: Are stopping places for a days work.

Isolation joints are are often called expansion joints. These joints permit horizontal and vertical movement between the slab and any walls, columns, or footings that the slab abuts. These are used because the movement of the slab is likely to be different from the walls, columns or footings. (Note isolation joints should be full thickness of the slab)

Contraction joints are either sawed or hand tooled joints. (Not done with trowel) These joints are to keep the slab from curling to much and to avoid random cracks. (Hence the term control joint) These joints should be placed no more than 15-20 feet apart. In driveways and sidewalks, joints should be spaced at intervals equal to the slab width, but if the width is more than 10-12 feet, the slab should have a longitudinal joint down the center.

Construction joints. In concrete slab on grade, construction joints should be made to function either as contraction joints by using keyed bulkheads (side forms) or as isolation joints by lining the bulkhead with a perforated sheet material.
If construction joints are located where neither a contraction joint nor an isolation joint is wanted, rebar or wire mesh should be used.

Construction joint is what you have. Therefor it is not required that you have isolation joints where one slab meets the next. They may not have wanted them for a number of reasons including looks, attracting termites, allowing water between slabs etc. Isolation joints more important at foundations, footings, and columns. Since they did not use isolation joints they should have used rebar so driveway did not settle. Of course it probably would not have settled if sub grade was compacted properly or maybe water is getting between slabs and undermine driveway.

David Banks
Contraction joints are either sawed or hand tooled joints. (Not done with trowel) These joints are to keep the slab from curling to much and to avoid random cracks. (Hence the term control joint) These joints should be placed no more than 15-20 feet apart. In driveways and sidewalks, joints should be spaced at intervals equal to the slab width, but if the width is more than 10-12 feet, the slab should have a longitudinal joint down the center.
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And in really hot climates, even closer. If they're not placed every 8 feet here, and they almost never are, you can bet on cracks in a very short time period. Builders don't like it because they think too many make for an ugly drive. Go figure. A crack is prettier?

The more the merrier!

"Isolation joint" is not a construction term that I used, but, when defined, there is nothing wrong with it. For the past 45 years, I have used "expansion joint," "construction Joint," and "control" or "contraction joint."
The purpose of an expansion joint is to allow concrete to expand or contract at intervals determined by the conditions of the locale and construction. Thom is correct that in certain areas, hot with expansive soils, the closer, the better for preventing random cracking. However,
soil conditions, quality of the concrete, and the degree of curing can
have a large influence on the performance of the concrete. Placed on
a sandy soil with a low plasticity index (not very expansive) using a low
slump concrete (no excessive water), and wet cured well for at least
seven days can produce slabs that perform well with expansion joints
spaced at 15 to 30 feet apart. As for veritical movement, if one does
not want it, slip dowels should be used to maintain a flushly aligned surface. Control joints are usually used between expansion joint spacings to force contraction cracks at those location when they occur. To be
effective, the kerf in the slab should be about 1/3 of the depth of the slab, but not less than 1-1/2 inches. Those little scored marked will not suffice. On large projects, control joint are often provided by saw kerfing
the concrete while it is still green using a special rolling concrete sawing
behind which the operator walks. Of course, with enough expansion joint, control joint may not be needed. Construction joint can serve as either expansion or control joint when they are installed as such, but their main purpose is to provide a means of stopping a large placement of concrete
or to allow for concrete placement to continue at a later time. When continuity of the structure is required, load transfer devices must be used
so that reinforcing continues on as though it were not interrupted. As for filling and sealing joints, there are several means available. The wood filler is the poor man's way, usually seen in residential construction (even supposedly expensive homes). Asphalt-impregnated fiberboard is often used in commercial construction as the joint filler. Greenstreak manufactures a plastic cap that slips over the top of the filler material and has embeddment strips for locking the cap into the concrete on each side of the joint. This produces a less expensive joint cover than using self-leveling sealant which is another method of sealing the joint. When using sealant, a backer rod should be used to improve the performance and longevity of the sealing material. Greenstreak also makes pre-formed control joints which eliminates the need to sawcut or otherwise cut in those joints. Most home-building concrete contractors seem totally unfamiliar with these latter methods. There are also much fancier ways of treating joints in concrete that might be used in high-end projects. In a large nutshell, that's the essence of my knowledge on concrete joints.

George E. Clower, AIA

George,

Welcome to THE inspection board and thanks for the information.