Built Below 42 Inches for Michigan Winters

Eight things we build

Most Michigan jobs start with a place to stand or park. We build paver patios for walkout basements and three-season rooms, and paver driveways that hold up to road salt and plow edges. Beyond those, the work splits into six more categories.

• Retaining walls for grade changes around pole barns and up north cabins.
• Walkways and steps that connect a driveway to a front door without a frost heave.
• Grading and drainage to move water away from a foundation before it freezes.
• Outdoor kitchens and fire pits built on a base that will not shift.
• Gravel driveways with a 21AA base and a surface layer that stays put.
• Pool decks and coping around an inground pool, set below the frost line at the edge.

What you sign, and when

You are present at two moments on the job. The first is the walkthrough, where we agree on the layout and the written price. The second is the sign-off, when you walk the finished work and check the lines. Everything between runs on a schedule you approve in writing.

The written price covers the dig, the 21AA base, the drainage, and the surface. Work proceeds in that order, and you see each step before the next one starts. The process page lays out the sequence. The cost guide explains what drives the number.

Frost runs 42 inches. The base runs deeper.

Frost depth in Michigan is about 42 inches across the Lower Peninsula and 60 inches in the Upper Peninsula. That is the line where the ground freezes solid in winter. Anything built above it sits on soil that moves up and down as the temperature swings.

Freeze-thaw does the damage. Water in the soil freezes, expands, and lifts whatever is on top. A patio slab heaves at one corner. A driveway cracks along a joint. A retaining wall goes out of plumb as the soil behind it freezes and pushes outward. The fix is not a thicker surface. It is a base that sits below the frost line so the ground underneath never moves.

This matters in the Detroit metro area, where clay holds water and heaves hard. It matters in Northern Michigan and the Upper Peninsula, where the frost goes deeper and the season is shorter. It matters in Grand Rapids and West Michigan, where sand drains fast but still needs a base deep enough to stay put.

Digging for Michigan conditions

The dig sets the depth. In Michigan, that means excavation below the frost line, about 42 inches in most of the Lower Peninsula. The 21AA base is placed in lifts and compacted so it locks together. Sand across much of the state means the base has to be thick enough to spread the load, and the edge restraint has to hold the pavers in place.

Drainage is the second half of the job. Water has to leave before it freezes. Behind a retaining wall, that means free-draining backfill and a drain pipe at the base. Below a patio, it means a slope away from the house and a way for water to escape at the edge. Taller walls get geogrid, a reinforcing layer that ties the wall back into the slope.

Material is specified by MDOT gradation, and 21AA is the common driveway and patio base. The season window runs from roughly April to November. Frozen ground stops compaction in the winter, so the dig and the base work happen in that window. Glacial clay in the Thumb and the southeast needs different handling than the sand elsewhere, and till and rock in the north slow the dig.

Where the price comes from

Two things set the price on a job here. The first is depth. Digging below 42 inches of frost moves more soil, and that soil has to go somewhere. The second is the joint detail. Road salt attacks the sand in the joints, so the edge restraint and the joint sand have to be specified for the load.

Sand subgrade over much of the state makes compaction and edge restraint the other cost line. Sand does not hold an edge, so the base has to be contained. The price reflects the depth of the dig and the quality of the drainage, not the surface material.