Ask The Expert
I’ve got an asphalt driveway that is in poor shape and I don’t want to go through another winter with it being in this condition. The reason I went with asphalt was because it was more economical but I have to keep fixing potholes. If I change to a concrete driveway, would I need to use rebar?
You don’t need to use rebar but I would recommend concrete mesh. The mesh binds and holds the concrete together. You only need rebar if you are bringing in heavy loads or were having over-standard trucks parked on the driveway. Under everyday residential conditions, you don’t need rebar. Go with a 3000 psi concrete, four inches deep with the mesh and you’ll be fine. Include plenty of expansion joints and V grooves.
First you’ll want to break out all of the old asphalt. If you see any low spots, bring in dirt and compact. Then lay your mesh. You can work the mesh one of two ways. You can lay it directly onto the ground, but then you need a hook to pull it up into the middle of the concrete; or, you can tie the mesh onto dobies, which are small concrete blocks that you wire tie the mesh on to keep it suspended. Either way, the mesh needs to be in the middle of the concrete when it dries. This gives it additional strength and holds it together. If you decide to go with professional finishers to float and pour, they’ll pull it up with hooks. Pros typically don’t use the dobies because they’re easy to trip on and it slows the process down. Next you would form and pour your concrete. Add a salt or broom finish, whatever you like. If you want you can add a concrete sealer when finished to help prevent against oil saturation.
It’s the nature of concrete to crack and it cracks in areas of least resistance. The thicker it is, the harder it is to crack. If you put V grooves in, it will crack in that groove as opposed to the middle of the slab. For example, you’d put one expansion joint at the garage and at the stoop, then about every 10 feet for the length of your driveway. Use a piece of concrete felt or PVC strip for the expansion joints. The felt is about ¾” wide by 4” depending on your slab. You want that concrete to be able to move and slip and slide. If there’s not enough movement, it will start to crack.
If you picture your expansion joints running horizontally, then your V grooves would run vertically, up the middle. Once these are in place, if it wants to crack, it’s either going to move at the expansion joint or, in theory, crack inside the V groove.
If you do intend to park heavy trucks on the driveway, then you’ll want to go to a six inch slab with rebar.
That’s why a lot of delivery trucks don’t park in your driveway. You’ll always see them parked out on the street because they don’t want to be responsible for any damages.
After it’s finished, block off the driveway and don’t drive on it for seven days.
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Robert Lamoureux of IMS Construction, Valencia, CA, has 30 years experience as commercial general, electrical and plumbing contractor. The opinions expressed in “Your Home Improvements” are not to replace the recommendations of a qualified contractor after a thorough visual inspection has been made.