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How To Pour a Concrete Driveway (And Tie-in to an Existing One)

February 26, 2018

Tying into an existing concrete driveway involves digging, spec-ing, sloping, pouring, and brooming.

Video Transcript:

Hi. This is David Odell with Odell Complete Concrete. What we're gonna do here today is add on to this driveway. The existing driveway is pretty standard. It's about 8 feet wide. In other words, you can't exit the vehicle on either side and then get out on the concrete. Adding concrete to something like this is really popular, so you can get out of the vehicle on concrete and walk into the front door.

We're gonna add an additional 8 feet here, so our total now is gonna be 16 feet. Not quite big enough for two cars to exit on both sides on the concrete, but you can definitely get out on one side or the other, depending on how you park it.

Specify the steel and concrete mix for the driveway

In this particular add-on, the person I'm working for here is a retired inspector for the City of LA, I believe it was. And he designed his own specs on this one. He's calling out for a 6-inch deep concrete, with a 3250-PSI straight cement, and also he's gonna go with wire mesh.

Typically, I don't really put wire mesh in stuff, I go with rebar, but he likes the wire mesh.

And then also we're not gonna dowel into the existing driveway, we're just gonna go 6 inches deep. This is a little different design than what I usually do, but I have done these. And normally where you do this particular scenario, but without the wire, would be probably an apron approach, which is a public works area.

You go 6 inches, then you go the big rock, and you'd go the 2500 or you'd go 3250, one or the other.

We had this all dug out and formed. We had it all set up and ready to pour in about four hours. Just the three of us.

Slope the driveway to the right drainage path

The existing driveway was sloping to the street pretty good, so we're gonna slightly slope this addition towards the existing driveway, then the water should run out the approach. The reason we're stopping the concrete at this point is that beyond this point is public works. In other words, if we go pour out there, we probably have to get a permit. And then it may or may not be... They may not let us do it. So, we're gonna stop the concrete there. And then in the future, if they're gonna do some work over there, they can without it disrupting the concrete.

This particular dirt was pretty hard. You can see we're using the electric jackhammer in here, with a clay spade on it, and that breaks it up pretty nicely. We are taking this dirt out in chunks like concrete would break, nice pieces you can actually pick up by hand and throw them in the wheelbarrow.

Though we have our line stakes out and they're 8 feet off of the concrete on either end, and they're set to the inside of the form. That way, when my line is pulled, it doesn't interfere with the stakes and also my 2x4 can run past the line stakes without interrupting those as well.

Prep the hole for concrete

You can see some pretty good size dirt clods in there that didn't quite break up during the removal, so what we'll do is we'll run a plate compactor over everything. It'll smash all those dirt clods into the ground, and be a nice flat surface.

There is the plate compactor there in the background. Here's the wire mesh we're gonna be using. They're 6-inch squares and they're 10-gauge wire. When you roll these wire mesh rolls out, it's crucial that you do it with two people because if you don't have someone holding the other end down it could spring up and roll up on you and prong you. The prongs could jab you 'cause they'll roll up pretty quickly.

Though we got a good 6 inches, 6-1/2 inches right around that neighborhood of depth, the compact was dropping it probably another 1/2 inch with that. So, we got 8 feet wide and this wire mesh is 5 feet, so we're gonna have a nice overlap in the middle with this wire. Also, this retired inspector wanted dobies, so we put some dobies in there. We got the big dobies because it didn't matter in this case, because we're 6 inches deep, so I knew we had space.

And the first thing I noticed the retired inspector did, was check the ticket on the concrete truck, which is a good sign that he's done that before a few times. He wanted to make sure that the mix design was right, the batch time was right, the different batch plan, how long it was loaded, things of that nature, make sure he had the right PSI.

He was shocked when he did look at the ticket though, 'cause I beefed it up to 45, so he went, "Wow. This is unusual." So, I had no more complaints, no more worries and no more inspections at that point, once I beefed it to 45 from the 3250 it requested.

Expansion joints in a concrete driveway

Well, here's your joint. I already went through that with my cutter tool and that goes down about 2-1/2 inches, so it's definitely deep enough for a 6-inch slab, of course, 'cause you really only need to go 25% depth.

The cutter breaks the aggregate, it separates the aggregate from one another so they're not overlapping anymore. Then we follow it up with just a three-quarter deep 1/2-inch radius. You could potentially just trowel over these joints after you run that two and a half-er.

And it will still crack on that straight line because the aggregate is separated at that point. That's what you call a weakened plane joint.

You can do those inverted as well, in other words, from the underneath, but that's a whole different story. A lot of people do those inverted weakened plane joints underneath by accident, and that could be dependent upon the grade or other obstructions underneath.

Finishing the concrete slab

So, what we've done is we've both flooded with the magnesium 3-1/2 footer. We hit it with big blue. We hit it with the funny trowel, walking edged it, maybe a little hand touch-up here and there, and then we broomed it with a 50% horse hair, 50% nylon broom.

That's what it looks like when you're done, magnificent. Now, we're cleaning up the excess dirt on the driveway, put a 1994 Caddy, I believe that was. It's a convertible. Here is the nice-looking joints. Broke it up real nice and evenly. We're on a cold joint, and we're not doweled into the other driveway, so it didn't really have to match up.

—David Odell owns Odell Complete Concrete in southern California. His YouTube channel is updated regularly. sometimes you can see him in Professional Remodeler magazine, too.

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