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Driveway slant in toward hsg/garage

Hi! I have a nightmare of a driveway. My Garage is attached to the house & the driveway slants in. When it rains, it floods into the garage & house. The Driveway is Asphalt.

To complicate the matters more, on each side of the driveway, the ground (grass ) is about a good foot & an half higher.

I was thinking of some sort of trench or something with a grate, to catch the water, but not sure if that would solve anything.

I would greatly appreciate any advice on this problem.


A. Spruce
Re: Driveway slant in toward hsg/garage

Installing a catch basin won't get you very far if you can't drain/divert the water to somewhere else. If you've got the ability to regrade or install a drain that will carry the water around the house/garage, that will be the easiest and least expensive. If you do not have the means to divert the water, then installing a catch basin with a sump pump would be needed so that the water could be pumped to where it can be gotten rid of.

Re: Driveway slant in toward hsg/garage

A trench drain (also called strip drain or channel drain) is often used in these situations.

As the photos in the sites below indicate, a portion of the asphalt has to be removed with a diamond saw blade or jackhammer (rented tools) and a trench drain installed along at least 80% of the driveway width.

The big box stores sell 4" plastic Fernco strip drain sections that are connected together, but any vehicular traffic would require stainless steel top grating instead of plastic (the bottom portion of the drain can be plastic).

Use 4" plastic drain pipe coming out of the trench drain to get to the side of the garage & install a 3 or 4 gallon catch basin to catch the inevitable sand that accumulates from such a drain, then continue the 4" drain pipe to either an outfall in the yard, or dig down & install a drywell to catch the runoff from the driveway drain.

Use a 3' torpedo level to make sure you have 1/8" pitch away from the front of the garage---the drain itself also must pitch toward the side of the garage where you will arrange for runoff or a drywell.

Those red 5 gallon plastic gasoline containers they sell at the automotive stores are an excellent & low cost way of making a catch basin---simply cut the two 4" holes and one 6" hole you will need & you have your catch basin.

A 6" X 30" plastic access pipe would be connected to the top of the catch basin with a pipe cover so that you can reach down & periodically scoop out the sand from the catch basin---this will keep everything working for years---keep any dead leaves off the drain & periodically remove the grates to clean the strip.

Most of these items have to be bought at a pipe supply house that carries drain items & caters to landscape & plumbing contractors---most will sell to a homeowner.

There are sizing calculations to determine how much water comes down your driveway during a heavy rain, but for residential applications 4" diameter drains & piping is usually adequate; however 6" grating is often used to prevent the storm water surge from overwhelming the grating & going into the garage or house.

You will need to call your local town building inspector to determine if you need a permit for this work---they may use their own calclation of trench drain sizing to insist that you use a 6" trench drain based on the gallons of runoff times the size of your driveway.

Typically, on a 20' X 20' driveway = 400 sq.ft. X .023 (gpm of runoff per sq.ft.)= 9.2 gpm X 60 = 552 gph runoff---4" diameter stock can handle up to 2000 gph runoff.

Google "sizing a driveway trench drain" if you want to further determine how many gallons of water to expect in a rainstorm.


Re: Driveway slant in toward hsg/garage

Thanks very much for your reply on my desperate situation. This will be the ticket!


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