TL;DR
The best time of year for retaining wall and drainage work is fall, before frost arrives. At this time of year, the soil is drier and easier to excavate, so structures installed now are ready when the spring thaw sends meltwater down the slope. By contrast, doing the work toward the end of November, when the ground has begun to freeze, is much more challenging.
When Water and Slopes Are Winning, Structure Is the Answer
Slopes in communities like Eden Prairie, Minnetonka, Chanhassen, and Chaska share a common problem: the glacial till and heavy clay that dominate the area cause water to run across the surface instead of soaking in. Because of this, soil tends to push downhill with each new storm.
Fortunately, retaining walls, proper drainage, and erosion control can solve this problem. And the time to do this type of landscape work is now, before winter arrives.
Retaining Walls: Function First, Beauty Second
Retaining walls should be structural first and decorative second. Their job is to hold back soil and prevent erosion after Twin Cities storms.
Retaining walls can also turn unusable slopes into usable ground, perhaps for a patio or a level lawn. But they can be prone to bulging.
The best way to prevent this is to use a compacted aggregate base and free-draining backfill. Drain tile behind the wall and geogrid reinforcement can also help where wall height or surcharge load makes it necessary.
Most wall failures come down to trapped water freezing and expanding behind the wall. Avoiding this is relatively straightforward with the right components and approach.
Drainage and Drain Tile: Move Water Before It Freezes
Standing water is the main issue for many retaining walls. It becomes a problem when it saturates the soil next to the foundation, kills the surrounding turf, and then freezes and thaws repeatedly through the winter. This continuous expansion and contraction can cause significant damage over time.
The best solution is perforated drain tile wrapped in filter fabric and bedded in washed rock. This setup lets water exit quickly before it has a chance to freeze. It can be combined with catch basins, downspout extensions, and even a routed sump discharge if necessary.
Grading and Erosion Control That Holds
One of the best ways to deal with drainage issues is professional grading, so the soil slopes away from the house. Creating a 6-inch drop over the first 10 ft can eliminate many wet basement issues.
If regrading a slope isn’t practical, you can use other options like deep-rooted native plants, erosion blankets, and terracing. These options tend to be low maintenance and are something many Minnesota homeowners want in place before the cold arrives. Just be aware that deep-rooted plants can take a few seasons to become fully effective.
Why a Design-Build Team Gets a Better Result
The strategies in this guide work best as a package. Walls, for example, perform best when combined with planting, grading, and drainage.
That’s why it pays to work with a team that can handle all of these tasks together. Our design-build team can assess your site and install these systems as one project, so you’re not juggling separate vendors.
FAQs
Can retaining walls and drainage work be done in the fall?
Yes. Fall is usually the best time for retaining wall and drainage work, because the work becomes much harder in November and December once the ground starts freezing.
How long does a typical drain tile installation take?
Typical drain tile installations take 1 to 3 days, but a larger property that needs multiple drain lines may take up to a week and a half.
What causes erosion on a sloped Minnesota yard?
The main cause of erosion on a sloped Minnesota yard is water moving over the surface before the soil can absorb it. Clay soils are particularly prone to this, which strips away the topsoil.
How much does a retaining wall cost?
Retaining walls are typically priced per square foot of exposed wall face. You’ll usually pay between $40 and $85 per square foot, although premium options are available depending on the materials you choose.
Do I need a permit for a retaining wall in the Twin Cities?
Under the Minnesota State Building Code, retaining walls over 4 ft tall generally need a permit, and shorter walls that support extra load may need one too. Requirements vary by city, so check with your local building department before you start.
Solve Retaining Wall Issues Before Winter
Tackle your slope, drainage, and retaining wall issues before freeze-thaw cycles set in. Contact Pierson Garden & Landscape or call (612) 251-9910 to start your project.