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Robert Lamoureux: Switching from asphalt to concrete

Your Home Improvements

Posted: November 5, 2010 11:13 p.m.
Updated: November 6, 2010 4:55 a.m.
 

Hi Robert,
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 in the first place was because it was more economical and I preferred a black surface as opposed to concrete gray. There a couple of pot holes that I have repaired in the past but they are a recurring problem. If I were to change it to a concrete driveway, would I need to use rebar? Thank you,
Dale H.     

Hi Dale,

You would not need to use rebar, but I would recommend concrete mesh. The mesh binds and holds the concrete together. I would only put in rebar if I were bringing in heavy loads or were having over-standard trucks parked on my driveway.

Under everyday residential conditions, you don’t need rebar. Go with a 3,000-psi concrete at 4 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 3/4” wide by 4” depending on your slab. You want 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 6-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 damage. 

After it’s finished, block off the driveway and don’t drive on it for seven days. 

Hi Robert,
Your column is the first thing I read in the paper every week. I have a question about my home. We poured a front porch in 2007. Recently, I’ve noticed that the whole porch is pulling away from the house. Why? Thank you,
Gaye B.

Hi Gaye,
This can be caused by a couple of different things. If it wasn’t pinned to the foundation, the entire porch can move.
Pinning is when we come in and drill and install rebar. When the new concrete dries around the rebar, it becomes permanently attached and will not move.

Another reason the porch is moving is because of improper compaction. The ground under the new pour was never compacted, so the weight of the concrete is sinking and separating from your home.

For the repair, you need to demo it out completely and add your pins. Take two or three pieces of rebar and put a 90-degree bend in them. Now you will have steel inside the new concrete that is both vertical and horizontal, so when it bangs it will be held strongly in place. 

Once you have the pins installed, reform and repour. Unfortunately, this happens a lot. People don’t pin new concrete to the foundation. Pinning works so well that even if you do get a little ground settling, the new pour will hold up against the foundation.

Hello Robert,
I had leak inside the wall between my garage and house. The drywall along the floor was wet so I cut out an area about 10 feet long and 1 foot high, but there was plywood behind the drywall. We fixed the leak and repaired the drywall but did not replace the plywood. Now I’m thinking it was only 10 square feet but the plywood was there for a reason and we should have replaced it. Should I just nail that piece back in there? Thank you,
Mark W.

Hi Mark,
You’re talking about the sheerwall. This is a structural element of your home and it does have to be replaced, but not with the same piece you removed. Even though you removed 1’ x 10’, you have to go up a minimum of 2 feet and tie in new sheerwall to keep the structural integrity. You may want to snap a chalk line at the 2-foot mark and make a clean cut all the way across. 

Keep in mind that when you add the new plywood, don’t match up on any existing edges. Make sure to stagger the new piece as needed so you don’t line up any seams. 

We have designed a custom, full-color The Signal/Your Home Improvements T-shirt we will give you if we answer your question. The T-shirt is available to be picked up at our office.

Robert Lamoureux has 25 years experience as a general contractor, with separate licenses in electrical and plumbing contacting. He owns IMS Construction Inc. in Valencia. His opinions are his own, and not necessarily those of The Signal. Opinions expressed in this column are not meant to replace the recommendations of a qualified contractor, after that contractor has made a thorough visual inspection. Send your questions to Robert@IMSConstruction.com.

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