PAVEMENT PROBLEMS
Edge Crumbling: Why Your Pavement Is Breaking Apart at the Sides
The outer edges of the driveway or road are cracking, breaking off in chunks, and getting narrower each year.
Edges fail first, and here is why
The middle of a pavement is confined on all sides. The edge is not. It has pavement on one side and air on the other. Any load applied near that edge tries to push it sideways and down, and there is nothing holding it back except whatever shoulder material is there.
On most driveways and private roads the shoulder is dirt, decomposed granite, or nothing. Over time that material erodes away from spring runoff and plow throw. Once there is a drop-off at the edge, every tire that rides the edge is loading unsupported pavement.
Thickness plays a role as well. Pavement is often thinner at the edge than in the middle, because that is where the paver ran out and where compaction is hardest to get. Thin, unconfined, and unsupported is a bad combination.
Local causes
Plows do a lot of this. The blade rides off the pavement edge, catches, and pulls material away. Repeat that a few dozen times a winter and the edge is chewed back several inches.
Water finishes the work. Snowmelt concentrates at the edge because that is the low side. It saturates the shoulder, undermines the pavement from beneath, and then freezes and breaks the unsupported lip off. Tree roots and vehicles parking half on the pavement are the other two common contributors.
Delivery and garbage trucks do a great deal of edge damage on narrow private roads. They have to drop a wheel off the pavement to pass or to turn, and each time they do the edge takes a full axle load with nothing under it.
What can be maintained and what cannot
A tight edge crack, meaning the pavement is intact but a separation is opening parallel to the edge, is good crack sealing work. Hot rubberized sealant keeps water out of that joint and buys real time. Sealcoating the surface near the edge helps too.
Once the edge is broken into pieces and the material is actually gone, sealing accomplishes nothing. There has to be something to seal. Rebuilding a lost edge means new asphalt and shoulder work. That is a paving contractor. We do not pave, patch, or overlay, and we will say so rather than take the job.
Look at where the crack sits before deciding. A separation six inches in from the edge usually means the edge is already unsupported and moving. That one is a warning, not a routine crack.
Protecting the edge you still have
Backfill the shoulder. Bringing gravel or decomposed granite up flush with the pavement edge removes the drop-off, supports the asphalt laterally, and stops the blade from catching. It is inexpensive and it is the single most effective thing most owners can do.
Keep vehicles off the last foot of pavement where you can, keep runoff from concentrating along one edge, and stake the edges before snow season so operators know where the pavement ends. Call (530) 587-4161 and we will look at it and tell you whether the edge is still sealable.
Do shoulder work in summer when material can be compacted, and check it again every spring after runoff. Shoulders erode quietly, and nobody notices until the drop-off is two inches deep.
Quick answers
Should I install a concrete curb to protect the edge?
Curb does confine the pavement and it works. It also creates a new joint that needs sealing and a hard object for the plow to find. On a private road up here, a well-maintained gravel shoulder is often the more practical choice.
My edge is crumbling in only one spot. Is that different?
Usually it means water is concentrating there. Look uphill for a downspout, a swale, a culvert outfall, or a snow stacking pile. Fix the water source or the same spot will fail again after repair.
Can I fill the broken edge with gravel and call it done?
As a stopgap to stop the drop-off from getting worse, gravel against the edge is reasonable. It is not a repair of the pavement itself. The broken material still needs to be cut out and replaced eventually.
More in the pavement guides and the FAQ, or see every pavement problem we get asked about.
Not sure what you are looking at?
Send a photo or call (530) 587-4161. We reply within one business day and we will tell you straight whether it is something we can maintain or something that needs a paving contractor.