Every type of driveway needs a form of drainage to carry rain or stormwater away from the driveway and direct it to the right place. The kind of drainage you use depends on the type of driveway, where you want to direct drainage and your budget. In this post, we discuss why driveways need drainage and some of the options you have when it comes driveway drainage.
What You'll Learn Today
- The Problems With Poor Driveway Drainage
- The Best Driveway Drainage Options
- Which Is The Best Driveway Drainage?
The Problems With Poor Driveway Drainage
A driveway with poor drainage is not just a problem for the driveway itself; it can also cause expensive problems in your home.
- If water pools on your driveway instead of draining away, it can damage the driveway by causing or expanding cracks. Standing water can also become a breeding site for mosquitoes and other harmful bugs.
- Poor drainage on a driveway can wash away soil and base material from under the driveway. This will weaken the driveway, usually leading to cracks, potholes and sinkage.
- On loose gravel driveways, poor drainage can actually wash away the driveway itself, leaving holes and bare patches.
- Your driveway could be draining water away, but in the wrong direction. If it directs stormwater towards your house, the excess moisture can comprise your home’s foundation. It can also increase dampness inside your home, which leads to mold.
- Poor drainage on your driveway can turn into a local problem. It adds to the amount of runoff that the city has to deal with. This increases the risk of flooding. It also introduces pollutants from your driveway like oils and chemicals into natural water sources. The problem is so serious that some countries and cities have laws regarding proper driveway drainage.
So, yes, driveways need drainage. And not just drainage, but well designed drainage.
The Best Driveway Drainage Options
Driveway drainage should not be an afterthought. It’s not something to build once you’ve already completed the driveway.
You should include drainage right from the beginning when you are planning and designing the driveway. That’s because drainage starts from the base of the driveway.
How you slope the driveway, the kind of materials you add to the base and the design of the driveway surface all determine how well the driveway will drain water.
Here are eight of the best driveway drainage options. In most cases, you’ll need to use at least two or three of these solutions together to properly control drainage and runoff on your driveway.
1. Driveway Placement
The first step in making sure your driveway has proper drainage is choosing the right location for the driveway.
Select the area of your home with the best drainage. Generally, avoid building a driveway on a low lying area where water from surrounding areas flows towards.
Water will accumulate on the driveway or under it, weakening it and reducing its lifespan.
If you cannot find an appropriate place for the driveway, consider doing some landscaping work first to create a suitable area for the driveway.
2. Driveway Gradient
After placement, the next major consideration is the slope or gradient of the driveway. A completely flat driveway is obviously bad. Water will pool on it instead of flowing away. A slight gradient helps direct the water away from the driveway.
If the area between your garage and the road is already sloped, that makes your work easier. You can design your driveway to have the same slope so water drains away.
But it’s not enough to add a gradient to your driveway; it also matters where that slope directs water towards.
Some cities have laws prohibiting directing rain water from pavements and driveways onto the street. You can also get into trouble with your neighbors if runoff from your driveway ends up in their yard.
As I also mentioned earlier, an improperly graded driveway can direct water towards your home, which is bad for the foundation and walls.
The best designed driveways direct stormwater towards a permeable area such as the yard or a swale.
3. Crowning The Driveway
You may have noticed that roads are not completely flat from one side to the other. There’s a high point in the middle of the road – called the crown – from which the road gently slopes to either side.
Driveways should have a similar surface profile that allows water to flow to either side of the driveway, instead of pooling on it.
Crowning a driveway is especially important if it is made from materials like concrete, asphalt or pavers that don’t quickly soak up rain water. If the driveway is completely flat, you’ll get pools of water standing on the driveway.
4. Permeable Base Materials
A well built driveway consists of a thick base (usually 4-6 inches thick) plus the driveway surface. The base is mostly there to support the top layer and prevent cracking, sinkage and potholes.
But it also plays a big role in drainage. It is one of the reasons why the base of most driveways is made with coarse aggregate such as gravel or limestone (5mm-20mm sizes).
The large pieces allow water to seep through the base and into the ground below. This prevents water from pooling up on the driveway or areas close to the driveway.
It also helps reduce runoff to the street, where it would add to the already stressed storm drains and sewers.
5. Use Permeable Surface Materials To Build The Driveway
One of the most effective ways of improving driveway drainage is making the driveway itself highly permeable.
And I don’t just mean the base materials, but the surface materials as well. This allows rain water to soak into the ground almost as soon as it falls, drastically reducing runoff.
One of the best materials for a permeable driveway is gravel. Because it’s not solid like concrete or asphalt, water passes through it easily. Another advantage is that a gravel driveway is one of the cheapest to build.
If you don’t like the feel or look of loose gravel, you can get grid/permeable pavers that you lay on top of the gravel. The pavers bind the gravel into a solid surface, but the driveway still allows water through.
You can also get regular solid pavers that are permeable. These are made with pervious concrete. And if you prefer the look of a blacktop driveway, you can get pervious or permeable asphalt that’s great for reducing runoff.
6. Channel Drain
In some cases, your driveway may not be permeable enough to soak up a lot of stormwater quickly, resulting in runoff and pooling.
Or you may not have a sufficiently large yard to direct rainwater to. In that case, channel drains are the best way to fix driveway drainage.
A channel drain, also called a trench rain, lets you collect a lot of runoff and direct it exactly where you want.
You can drain it somewhere that’s more appropriate or even harvest it in an underground tank.
Position the channel drain where runoff from the driveway tends to converge. This is usually the end of the driveway, but can also be somewhere in the middle.
Here’s a great video from This Old House on building a channel drain for a driveway.
7. Build A Swale
Another way to manage runoff from a driveway is to build a drainage swale. A swale is a valley or channel designed to catch or trap water and allow it to drain into the ground.
Often, a swale is built off a driveway to prevent runoff from going into the street or towards the house where it can damage the foundation.
Simple drainage swales consist of a wide but shallow channel dug into the ground where runoff flows off the driveway.
The channel is filled with grass, straw, gravel or rocks that slow down water flow, ensuring the water percolates into the ground rather than running off.
8. French Drain
A french drain combines a swale and a channel drain into one highly effective drainage solution.
A French drain consists of a ditch that’s covered by a permeable fabric on the inside and has a perforated pipe passing through it. It’s then covered with rocks, soil and grass.
The drain is located in the part of the yard where runoff from the driveway and other areas of the yard flows towards. Water from around the trench gets into the pipe, where it’s then redirected elsewhere.
A French drain can help with heavy runoff from a driveway. It can also prevent your yard from flooding or getting soggy.
Which Is The Best Driveway Drainage?
The best solution among all the ones we’ve discussed above depends on your particular situation. But I recommend picking at least 2-3. Having multiple drainage solutions ensures none of them gets overloaded or is unable to cope with particularly heavy rainfall.
Regardless of what type of driveway you have, make sure it’s graded properly and has a permeable base. From there, you can add a channel drain, a swale or use permeable pavers to further help with drainage.
On relatively flat driveways or driveways with a gentle gradient, a permeable material such as gravel or permeable pavers is usually enough to deal with drainage. You don’t need to dig trenches.
Driveways on steep slopes usually have heavy runoff. In such a case, even permeable pavers or asphalt may not be enough to absorb all that water.
That’s where channel drains, French drains and swales come in handy.
Whether you are building a driveway or looking to fix a driveway with poor drainage, I recommend talking to a professional about the best drainage options for your situation.