It's normal for asphalt driveways to sink a bit over time. But when your driveway has sunk to the point where it's 4 or 5 in. lower than your garage floor, it's time to fix it. If you don't, water will pool in the depression, seep into the soil below, and eventually destroy the driveway.
Asphalt companies charge about $1,000 to dig out the old portion and install a new apron. Concrete contractors charge even more. But you can rebuild your asphalt driveway apron yourself. The entire job takes a full day and it's not much fun. But the materials and tools only cost about $250, so the savings is worth it.
You'll need a diamond blade for your circular saw, a tamper, a pry bar and a short square-blade shovel. Plus, you'll need enough cold patch material to fill in the trench you make (sold at home centers). To figure out how many bags you'll need, refer to the depth and width tables on the bag. Finally, you'll need mineral spirits and rags for cleanup.
Cold patch cures by solvent evaporation, and it takes about 30 days to reach a full cure. So the best time to do the project is during an extended warm, dry spell. You can do it in spring or fall, but cold weather and rain will greatly extend the cure time.
This is a messy job, and no matter how careful you are, you're going to get tar on your clothes and shoes. You can't wash off the tar with soap and water. So wear old clothes and shoes that you can toss into the trash when you're done. If you have to go into the house during the project, leave your shoes outside so you don't track tar into the house.
Here's how to make the repair.
Cold patch works only when it's compacted and “keyed” into at least two vertical surfaces. So don't think you can build up the driveway height by pouring cold patch on top of the old sunken asphalt—the patching material will just break off in chunks. Instead, you'll have to cut out the sunken asphalt (Photo 1). After it's cut, lay a block of wood on the soil at the edge of the driveway, shove a pry bar under the old asphalt, and pry against the wood block. The old asphalt will lift up and break off in sections. Remove all the cut asphalt and scrape off any caulking material sticking to the edge of the garage floor.
Next, build a starter row of patch material (Photo 2). Once the starter row is in place and tamped, apply additional patch material in 1-in. layers (Photo 3). Resist the temptation to completely fill the area and compact it in one fell swoop. You simply can't exert enough compaction force with a tamper to properly key it into the vertical surfaces—the patch material will just creep out the sides when you drive on it. Once your tamped layers are level with the garage floor, add a final topping layer. Then lay down wood scraps and use your vehicle to do a final compaction (Photo 4). Clean all your tools with mineral spirits and dispose of the rags properly to prevent spontaneous combustion. The instructions say you can drive over the patch immediately. But tires may still make slight depressions in the asphalt until it's fully cured, which takes 30 days. So leave the plywood in place for a few weeks at least.
Pavers Are Another Option
Another approach to fixing a sunken driveway is to make an apron from paving brick. It's attractive, you can do it yourself, and you can easily reset the pavers if the soil settles again. Follow these steps:
- Snap a chalk line parallel to the garage door. Make sure it's out far enough to include all the settled asphalt. Lay out a row of your paving bricks, starting against the garage floor slab to position the chalk line at a full brick.
- Cut through the asphalt (it's usually 2 to 3 in. thick) along the chalk line. Be sure to wear hearing and eye protection.
- Remove the asphalt and dig a 12-in.-deep trench. Angle the wall of the trench slightly under the remaining asphalt. Rent a plate compactor and run it along the trench at least four times to compact the soil. Line the sides and bottom of the trench with landscape fabric. It's available from landscape suppliers.
- Spread a 2-in. layer of Class V or other compactable gravel, dampen it and run the compactor over it four times. Continue to spread and compact the gravel in 2-in. layers until it's 3 in. below the existing driveway.
- Install paver edging along grass edges and spread a 1-in. layer of coarse sand. Don't compact it.
- Set your pavers, compact them with the plate compactor and fill the joints with sand. Be sure to use joint stabilizing sealer to keep the sand from washing out.