The Definitive Guide to Fixing a Sinking Driveway
Are you feeling a little down at the moment? Jokes aside, a common problem for asphalt driveways is sinking spots or potholes. Properly maintained, an asphalt driveway has a lifespan of 25 to 30 years.
There’s simple annual maintenance you can do to keep your driveway in tiptop condition. A sinking driveway can indicate real trouble or may just need a simple fix. As long as your asphalt is fairly new and in decent condition, you can often DIY a patch and seal (although you may not want to), but if your asphalt is old, you want a professional opinion.
Read on to learn more.
Simple Fix or Sinking Driveway?
Asphalt driveways most commonly sink because the underlying soil is compromised. From top to bottom:
- Seal Coat (if your driveway is over a year old)
- Asphalt and aggregate
- Compacted soil
Before repairing your sinking driveway, check the condition of the asphalt. Tire prints in the asphalt indicate poor construction – an incorrect mix of asphalt and aggregate.
Sinkholes indicate a problem with the foundation. Usually, there are several inches of crushed rock beneath two to four inches of asphalt. Too little gravel or incorrectly compacted soil could be the culprit.
If there’s tilting or heaving in freezing weather, followed by buckling during the thaw, there’s a problem with drainage. Drainage must be corrected before repair or you’ll end up repeating the process over and over.
Sinkholes, Potholes, or Alligator Cracks?
Sinkholes are when the foundation beneath the asphalt has somehow settled or washed away and the asphalt bends into the hole. Over time and use, the asphalt will crack and become a pothole.
Minor sinkholes can get repaired with a simple patch, but getting the underlying problem may be a challenge. Large patches of sinking driveway indicate foundation trouble that must be professionally addressed.
Potholes are when the asphalt is broken or carried away. Small potholes a few inches in diameter are easy DIY fixes. Larger, deeper holes or extensive cracking indicate a problem that should be dealt with using professional equipment.
Alligator cracks look like the scales of an alligator or a spider web. These small cracks happen with time and should be maintained annually to prevent additional damage. Skipping maintenance means moisture can collect and become a pothole over time.
Some problems left alone could leave you with an entire sinking driveway! Potholes only grow larger over time. The more asphalt that washes away, the more damage to the remaining surface and foundation.
DIY or Call a Professional?
As mentioned before, there should be a crushed stone (gravel bed) several inches thick. This bed of gravel should be placed either on undisturbed grade or on mechanically compacted fill soil. A sinking driveway is commonly caused by the underlying fill soil collapsing because of organic material (like stumps and roots) decomposing and collapsing, or fill dirt that was not properly compacted.
More worrisome, your sinking could be caused by erosion due to improper drainage, a broken irrigation line or other plumbing issues, or environmental factors like unstable marshland or an underground spring.
If your spots of sinking driveway are extensive, you will need to get a professional opinion and possibly a soil engineer to diagnose the underlying problem. In the meantime you can take these steps:
- Contact your builder if your home is new
- Check your downspouts and rainwater drainage
- Check your irrigation system
If your repairs are small and you plan to proceed with DIY, follow the lead of the professionals. Repair isn’t surgery, but you can attack the problem with surgical precision.
Prep the Patient
First, address the driveway. Thoroughly clean the area that needs to get repaired. Completely remove dust, debris, moisture, weeds or anything that will keep the patch from sticking.
If you decide to use a pressure washer to do this, you must wait until the area is completely dry. In hot summer months, this may take 48 hours. A better choice is a stiff bristled brush and a blower or vacuum.
For weed removal, use a torch to burn weeds or a garden weed puller to get to the roots. Roots left behind will eventually break your patch again. If your cracking is wide enough that you have small saplings, you must remove the affected area and all vegetation to prevent grow back.
DIY Asphalt Pothole Repair
You need to be sure you want to purchase some new tools. If you didn’t rent or purchase a torch before, you will need it now.
You also need a bag of cold patch compound and an asphalt tamper. A tamper has a large, flat, square head and weighs about 10 pounds.
Ten pounds of cold patch asphalt repair aggregate will cover a one-foot square to a depth of one inch. Calculate how much you will need and allow for some overfill to tamp down. Your asphalt layer isn’t much deeper than three inches or so, sometimes much less.
After you’ve removed surface debris, check if your pothole extends below the asphalt layer. If it does, you will need to fill the hole in with sand or gravel to the asphalt level. Cut the edge of the hole to the “good” asphalt.
Use the torch and heat up the asphalt surrounding the hole to help it bond to the patch. Now fill the hole with cold patch – overfill by about 2 inches. Spread the material evenly with a rake or the side of your foot.
Now use the tamper to pound the material into the hole. Add more patch compound if necessary for an even finish. Repeat as necessary throughout your sinking driveway.
DIY Alligator Crack Repair
Alligator patches are easier. Although, if your driveway is old or the patch is large, call a professional. You’ll need alligator crack compound and an asphalt squeegee. You will follow up with sealing.
Alligator crack compound is liquid. It self-levels to some extent and dries to a harder surface than cold patch compound. You average about 20 square feet to the gallon if the cracking is not too deep or extensive.
After prepping the driveway, pour a generous amount of compound over the cracked area. Using the squeegee, smooth the material over the cracks to a depth of about 1/4 inch. Add additional compound and smooth as needed.
Several thin coats last longer than one thick coat. Allow the compound to dry several hours or a day before sealing. Seal coat the entire driveway to maintain your work.
DIY Sinkhole Repair
If your sinkhole is just a shallow depression, you may treat it like an alligator crack. Pour compound into the depression about 1/4 inch deep. Allow this area to dry several hours or overnight. Pour another 1/4 inch and repeat this process until the hole is filled. Seal several days later.
Larger sinkholes that crack the asphalt require more effort. The way to repair a large sinkhole is to cut the spot out and treat it like a pothole.
You must correct the underlying condition (usually drainage) before beginning repairs. Ignoring this step can mean the next repair is an entire sinking driveway.
Dig out and replace the gravel bed. Use a vibratory compactor on the earth and the gravel every two inches before filling the hole with a cold patch.
Sealing Your Asphalt
Asphalt sealer is liquid and contains sand or clay to help it stick to your asphalt. If your asphalt is new, allow it to cure for several months before sealing. This will help prevent moisture from cracking the surface during the first freeze.
Apply sealer to a clean surface in a thin, even coat. Use a wide two to three-foot straight blade squeegee to spread the sealer to the manufacturer’s recommended depth. Thicker coats do not offer more protection. Allow the sealer to dry several hours before walking on the surface, a day before driving over it.
If you have just minor cracking or sinking, DIY driveway repair is possible. The right tools, materials and time will make for a good-looking result. Repair the underlying issues to avoid making the same corrections over and over.
Larger problems or a widespread sinking driveway require professional advice and correction. Some serious problems have to do with incorrect asphalt to aggregate ratios, but most common problems are caused by poor compaction of the soil or water washing away the foundation.
Deep or large potholes require replacement of the gravel layer as well as the asphalt and may require several layers of material. Don’t wait to repair potholes. Potholes will only grow larger, more costly, and more dangerous.
Of course, if all of this sounds overwhelming or confusing, give us a call. Our highly qualified technicians are always ready to give you a free estimate for repairs.
We provide services for both commercial and residential customers. We’ve been western New York’s main source for asphalt repair for over 30 years. For six years straight we’ve received Angie’s List Super Service award for being number one for service in our area.