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We're interviewing general contractors for a project to replace siding & windows on our house, and build a detached garage & driveway.

The main issue of concern at the moment is the concrete driveway. Since we have a small lot (5000 ft2)and will be paving over most of it, I'm worried about drainage. Where will all that water go?? We don't want to end up with a swamp in our backyard, or under our house.

What questions should we be asking our general contractor to determine if he is competent to build the concrete driveway?

Is it best to put in some sort of french drain underneath or alongside the driveway? Or can we rely on grading the surface dirt so that we redirect water towards the street?

So far the GCs I've interviewed have not said much about drainage until I pressed. One guy said we should grade the area under the house by adding dirt.

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We're interviewing general contractors for a project to replace siding & windows on our house, and build a detached garage & driveway.

The main issue of concern at the moment is the concrete driveway. Since we have a small lot (5000 ft2)and will be paving over most of it, I'm worried about drainage. Where will all that water go?? We don't want to end up with a swamp in our backyard, or under our house.

What questions should we be asking our general contractor to determine if he is competent to build the concrete driveway?

Is it best to put in some sort of french drain underneath or alongside the driveway? Or can we rely on grading the surface dirt so that we redirect water towards the street?

So far the GCs I've interviewed have not said much about drainage until I pressed. One guy said we should grade the area under the house by adding dirt.

As for concrete driveways, we've discussed this one plenty of times. Just search through the Home Improvement & Repair section and you'll find threads about them. As for drainage, there are two cardinal rules: 1) keep water out from under your house, and 2) keep your water from draining onto your neighbor's property.

I would not recommend putting fill below the house, as that can make it difficult to make repairs later on--just make sure that the land that approaches your house is sloped away from it. If the driveway comes right up next to your house, it needs to be sloped away from your house, too. If the driveway comes right up next to your house, it needs to be sloped away from your house, too. If you have a properly-built fence, you can use the fenceline as a good place for a shallow trench to collect and direct water that's coming away from your house or back yard towards the street. And otherwise, just make sure that dirt is nearly as high as your concrete driveway and that the concrete driveway is sloped towards the street; both of these measures prevent ponding.

No matter who you use, stay on top of them when it comes to grading. Check sight lines to make sure that water is going where it should and that there are no high spots. I've had them use a transom and then lie to my face that the site was adequately graded, just to avoid doing more work. Maybe turn on your garden hose when they tell you it's done, and check to see where it goes.

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If there is a sufficient slope from the back yard to the street or ditch in front, you can use the driveway for drainage. I have a very slight slope, something like 1/4 inch per 10 feet, and that is still enough to drain water. Ask the contractor about putting a slope in the driveway, as well as a swale down the middle to channel the water. If you cannot get even a slight slope, or if water ponds in your backyard and cannot get to the driveway for drainage, you may need to look into installing a drainpipe underneath or alongside the drive.

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I had a driveway and garage done a little less than a year ago. Some of the things you are uncertain about may be dictated by the city. In order to get my garage slab permitted, the city required it to be a certain elevation above the street grade. They inspected it for compliance and even required an alteration to the forms before the pour was done. That, of course, dictated the driveway grade.

I still haven't addressed the landscaping that needs to be done so that my driveway doesn't look out of place because I've been fretting over the drainage issue. The run-off from a heavy rain still takes the same routes to the street (I have a ditch in front rather than curbside gutters) as it always did, but I was afraid of what would happen if I leveled the rest of the yard to the driveway. Fortunately, the landscaping guy that I talked to a few days ago seems to think an inexpensive drainage system will do the trick. I'm still not completely comfortable with how it will all work out, and I wish I could have budgeted some money for landscaping at the time, but I was just too flat broke.

By the way: the flatwork was expensive--over half the total project, but in comparison to the old, broken-down asphalt, the change is remarkable. I'm glad I did it even though I still mourn over all the money it ate.

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The best drainage is always accomplished with a drainage swale. The swale should sit on the property line between your home and your neighbors home. Swales should be about 3' wide and about 6" deep and should have a very slight slope towards the street. If you are worried that the new driveway will damn up water around the property, you should consider french drains made of 4" slotted PVC and wrapped in a vegetive barrier that will prevent root growth. Drainage grates should be placed about every 20' in low areas. A french drain is very effective, but more expensive. So a drainage swale system is always more desirable, and in most cases can be acomplished with a little forethought.

The concrete driveway should be made up of 4" concrete with #3 rebars in a grid at 16". Concrete needs to be 2500 or greater PSI w/ 1" rock. Wood expansion joints need to be about 15' apart, and the driveway should be 10' wide. This is a very ridgid design, but if you plan on parking large trucks on it, you need to go to a 6" slab with #5 rebars.

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