The driveway is the most important area of concrete flatwork. It carries the most load, is the most costly to install and repair, AND has the most potential to fail. I mentioned previously that small cracks in your concrete slab foundation are to be expected and will have no impact on the performance of your foundation. The driveway is a different story. Where the slab portion of your house foundation is rarely supporting anything, the driveway IS the foundation; supporting cars, trucks, boats or whatever. Cracking in your driveway should be watched very carefully. It could be an indication that something underneath isn’t right.
Concrete has a very great compression strength. That is, a block of concrete can hold a great deal of weight directly. However, concrete does not have a tremendous amount of tensile strength. Spans of concrete usually require loads of steel reinforcement and special compounds and mixing or they will not support any substantial weight. A slab differs from that because it is set on compacted earth with a gravel base and is basically supported by the ground. That is why soils testing is so important. If the soil expands a great deal there is the potential that when expansive soil loses moisture, it will shrink and leave voids underneath. This is especially common under driveways.
Be sure to discuss the placement of your driveway with the concrete contractor and the landscaper. There may be a need to install conduit or some pipe underneath the flatwork during prep. This allows for wiring and drip systems to be run from one side to the other. It may also be needed to provide a clear drainage path. If there is ANY potential for water to run under a driveway, it is critical that there be drainage pipe. Water will erode the material under the driveway and it may cave in.
Patios and sidewalks are typically poured at the same time as the driveway. When prepping, the owner builder should make sure that all concrete flatwork has expansion joint and is designed to flow away from the house. Most municipalities also have a 2” clearance required between concrete and the stucco weep screed.
Sidewalks and patios are traditionally are given a brush finish. With the advent of custom concrete design, colored concrete and stamped concrete, that is changing. Many builders and owner builders are customizing their concrete flatwork with colored, stamped concrete and even have designs etched into their flatwork. It is amazing what is possible. More and more concrete contractors are offering custom options to their clients. Discuss what is available and view their portfolio. Figure out early on what the costs would be if you decided to go in that direction.
Be aware that most colored or stained concrete flatwork requires additional maintenance each year. This may include sealing or even color refresh.
When Should I do Flatwork?
The owner builder will schedule driveways and patios towards the end of construction, just prior to landscaping. The later in the process, the better it is. This will reduce the chance that someone will drive up onto the driveway and mark up your flatwork. Be sure to put up yellow tape or a barricade in front of fresh concrete. You should not walk on fresh concrete flatwork for 24 hours after the pour.
Pavers are a popular alternative to concrete flatwork. There are a variety of textures, shapes, sizes and colors. Pavers can add character to your homes exterior. The underlayment preparation is important because there is no reinforcement for pavers and they are not bonded together with mortar. Underlayment should be compacted because it will be carrying the weight of any vehicles.
Stamped and Colored Concrete
Rather than a standard brushed finish, the owner builder may choose to finish either by coloring, staining and /or stamping their concrete. The concrete contractor can use a variety of methods to color the concrete and stamping is easily done with plastic molds. While concrete is semi-set, a mold will be used to establish patterns on the surface of the concrete.
Once finished, stamped and colored concrete must be sealed. Sealing needs to be done on a yearly basis to protect the color and finish of the flatwork. Consider the maintenance costs and the additional hassle of colored and stamped concrete before choosing.
Colored, stamped patios, driveways and sidewalks will add character and value to your project. Always be sure to use a licensed and bonded subcontractor with good references. Get at lease three bids for every area of construction.