It’s time to replace the old driveway and you want to make sure it lasts for the rest of your life. There are a few ways to make sure that happens. A lot of people get so concerned with finding the lowest price these days they don’t realize concrete longevity can vary dramatically. Concrete PSI, Proper jointing, Reinforcing, Depth and base requirements all make a big difference in how many years you will get out of your driveway.
The Ultimate Driveway is the one that holds up not only to the new Garbage truck driver’s bad choice but also the constant forces of nature that break it down day after day. A higher concrete PSI not only breaks under higher pressure, it also has a lower permeability. Ask your Contractor what they plan to use. Even though the IBC may only requires a 2500 psi concrete for your Tucson driveway doesn’t mean it’s going to be the right answer for you.
Concrete is brittle by nature and will crack. That is why it is so important to provide plenty control joints. This gives your concrete places to crack. The standard guideline for a 4” depth is joints at no more than 10’ intervals. In my opinion the number shouldn’t exceed 8’.
Because Concrete is so brittle on its own, the addition of a rebar grid is extremely important for a long life. Whether intentionally in the bottom of a control joint or through natural expansion and contraction your driveway cracks. The Cracks tend to walk apart with time. Rebar extends that time by decades.
It seems as though someone decided long ago that 4” of concrete was sufficient for driveways. This seems to be true for the most part. If the vehicles driven on it are light enough and there are adequate joints it cracks into smaller pieces in time but all in all holds up fairly well. It seems recently though more and more architects are increasing the depth of garage floors to 5”. That extra inch makes a huge difference in the load the driveway will take. If you have big commercial trucks driving on your driveway 6” is a minimum but for the largest of passenger vehicles 5” is going to be more than sufficient.
The other consideration that often gets overlooked in this part of the country is the base below the driveway. Most of Tucson has pretty good native soil below it. Certain parts of town have expansive soils however and many neighborhoods have fill hauled in from other areas. To assure a rock solid lifespan 3-4 inches of ABC (Aggregate base course) is a really good idea. Parts of Vail, Continental Ranch, Saguaro Bloom and Rita Ranch stand out as bad soil hotspots.
All of these considerations should be taken seriously when designing your driveway. A way to look at the price you will pay for a premium driveway is to divide the price by the 50+ years it will last you. More importantly though is to pick a Contractor with a sound track record of standing behind their warranties. Good luck with your new driveway.
Jon Molden
