The Saint Paul Alley Pad: Garage Aprons, Parking Pads and Their Upkeep

Saint Paul builds much of its parking around alleys. The zoning code sends access to off-street parking through an improved alley wherever one is available, Public Works counts about 2,225 alleys running roughly 330 miles, and when the city had households surveyed about alley plowing in 2019, 91 percent of respondents said they used the alley to reach a garage, parking spot or driveway. The pavement involved is often a short pad between a detached garage and the alley, and it has problems a front driveway does not.

This guide covers that pad: who owns which strip of pavement, what the city does and does not do in the alley, how winter plowing works when the city has never plowed alleys, why water collects at the garage slab, and how to choose between sealing, patching and rebuilding. It relies on the city's own rules and figures, the USDA's soil descriptions and NOAA's climate normals for the airport station, and it leaves out anything those sources do not support.

Why so much parking comes off the alley

The rule is written into zoning. The Department of Safety and Inspections' residential parking handout says access to off-street parking must be from an improved alley when one is available, with an exception for corner lots, which may take access from the side street. Parking cannot sit in a front yard or a required side yard, and a front-yard driveway, where one exists, can be no wider than 12 feet except near the garage door. On a typical interior lot with an alley, new parking goes in back.

The housing stock explains the rest. The city's 2018 housing inventory, using 2012-2016 census estimates, counted 52,147 housing units built in 1939 or earlier out of about 119,625, and found that 57 percent of single-family, duplex and triplex buildings dated from before 1930. No asphalt surface has lasted as long as those houses, so the pad behind a 1920s house is a later addition or a later replacement, and on many lots the pavement shows more than one generation of work, each with its own base, thickness and edge.

Who owns what: the alley, the apron and the pad

Three pieces of pavement meet behind a typical garage, and they have different owners. The alley is public: state law and city ordinance define an alley as a public way no wider than 30 feet. The city's upkeep there is minimal, limited to pothole patching and an annual spring sweep, and alleys come in four kinds: paved, oiled, gravel that Public Works maintains, and unimproved gravel, dirt or ungraded strips the city does not maintain at all. The apron and the connection between a private pad and the alley are the owner's to maintain, and so is the pad itself.

That split decides who pays for what. A pothole in the alley surface is a call to the city, whose pothole crews work arterials first, residential streets second and alleys third, and larger holes before smaller ones. A broken apron where the pad meets the alley is the owner's job. Rebuilding a whole alley is a city project: Public Works picks alley reconstructions each year based on funding and condition, and assessable costs to the abutting owners typically do not exceed 25 percent of the project cost.

A practical consequence: where a smooth asphalt pad meets an oiled or gravel alley there is a step, and it breaks down from both sides. Tires drop off it, loose stone grinds against it and a plow blade catches its lip. Keeping that transition supported and sealed is one of the more useful things an owner can do for an alley pad, and once it has crumbled it becomes a job for asphalt patching.

Winter behind the garage: private plows and nowhere to put the snow

The city has never plowed, salted or sanded alleys. Keeping them open is the abutting owners' responsibility, and many blocks handle it through an alley captain, a volunteer who collects money from the neighbors and hires a private plow. In the 2019 University of Minnesota study for the city, 66 percent of respondents with an alley had an alley captain, 12 percent said their alley was not plowed at all, and 36 percent said it was plowed after a 2-inch snowfall. The city keeps no official list of alley plow contractors.

Two rules shape where the snow goes. Snow from alleys, driveways, parking lots and sidewalks cannot be pushed into the streets, and the city's snow guidance says snow should be stored on the property or hauled away by a contractor. A private alley plow therefore pushes snow to the sides, and the sides are the aprons and pad edges. That puts a steel blade and a heavy bank against exactly the pavement the owner maintains, storm after storm.

Some habits reduce the damage. Marking the pad edges with stakes before the first snow gives the plow operator a line to aim at. Asking the alley captain whether the contractor runs a rubber or polyurethane cutting edge costs nothing. Keeping the bank on the pad's low side lets meltwater run away rather than across. The snow emergency post covers the street side of the same problem.

Water at the garage slab

The most common trouble spot on an alley pad is the seam with the garage. The garage floor is a concrete slab and the pad is asphalt, and the two move differently through the roughly 78 days a year when pavement at MSP crosses 32 degrees. The seam opens, water from the roof and the melting bank runs into it, and in March, the worst month for freeze-thaw with nearly 18 crossings on average, it freezes and pries. The asphalt beside the slab settles or lifts, and water starts running toward the garage door instead of away from it.

The ground under the pad sets how bad it gets. The city's surface water plan maps much of the upland as Chetek and Mahtomedi soils, sandy outwash the USDA rates somewhat excessively to excessively drained, where water passes through quickly. Where the Waukegan series puts 20 to 39 inches of silt over the sand, or where a lot carries old fill, water lingers and frost heave has the fine soil it needs. Two pads on the same alley can behave very differently for that reason alone.

The fix is mostly slope and a sealed seam. The Minnesota Asphalt Pavement Association's design guide calls for at least a 2 percent slope on paved parking, which on a 20-foot pad works out to about 5 inches of fall. Hot-pour filler in the slab seam each spring, and a pad graded to shed water toward the alley rather than the garage, prevent most of the damage. Crack filling describes the seam work in detail.

Seal, patch or rebuild an alley pad

Sealing suits a pad that is intact but gray and porous. The coating protects the surface from water and sunlight, and on a short pad it goes quickly, though a crew's minimum charge makes the per-foot price higher than on a long drive. The coat should stop at the garage slab and at the alley edge rather than run onto the public alley surface. The driveway sealcoating page covers products and timing.

Patching fits a pad with one bad area: a sunken corner by the garage, a broken apron, a pothole where a delivery truck turned. The failed section is cut out square, the base rebuilt and the hole filled with hot mix, and the pad is sealed once the patch has cured, usually in the same season.

Rebuilding is the answer when the pad has failed across its surface, drains toward the garage or is still gravel. The city requires parking spaces to be paved with asphalt, standard or pervious concrete, or pavers, and rules out gravel and crushed rock. A parking area of three or fewer spaces needs no permit and carries no application fee under the city's handout, but it must meet the setbacks: 1 foot from a property line along the alley and 4 feet from side and rear lines. A new curb cut to the street is a separate permit from Public Works.

• Intact, gray, porous surface: clean, fill cracks and seal
• One failed area or a broken apron: cut out, rebuild the base, patch with hot mix, then seal
• Widespread failure, water running toward the garage, or a gravel pad: rebuild to code