Snow damage to fences, walls and patios

This guide is part of our Montana Winter Property Guide. It is about diagnosis rather than construction. Good building details are in our landscaping guides, linked below, and our page on freeze-thaw cycles and what they do to a property covers the underlying process. Note that some sources here are trade or contractor material rather than public agencies, and we say which.

How much does snow actually weigh?

More than people expect, and the range is huge. FEMA's Snow Load Safety Guide says one foot of fresh snow ranges from 3 pounds per square foot for light, dry snow to 21 pounds per square foot for wet, heavy snow. One inch of ice weighs a little less than 5 pounds per square foot, and a foot of ice about 57.

That guide was written for roofs, but the numbers explain what happens lower down. A wet drift leaning on a fence or a plow pile shoved against one is a side load on posts that were designed to stand up and resist wind, not to hold back snow. Pile snow away from anything you care about: see where to pile snow.

Why do fence posts lean after winter?

Frost heave is the usual suspect. ProFence, a fence contractor in Pennsylvania and Virginia, explains the mechanism: as water in soil freezes, it forms thin layers called ice lenses that grow and push the soil upward, and anything embedded in the ground moves with it. When the ice melts, the soil settles unevenly, leaving posts loose or misaligned. It says the problem is worse in moisture-holding soils such as clay and silt.

Our fence repair page describes what we see in this area in the same terms. Frost heave lifts shallow-set posts a little more each winter until the line goes wavy. Posts rot at ground level where wet soil meets air. Wind takes out panels, usually the same exposed run every time, and gates sag because a gate is a lever and its hinge post carries a load the line posts never do. A winter usually makes one of those visible rather than causing it from nothing.

Does snow damage some fence materials more than others?

Each material fails in its own way. Western Fence & Landscape Supply, a fence supplier in Boise, Idaho, says vinyl does not absorb water or corrode but becomes less flexible in the cold, so it is more likely to crack if hit by a shovel, a chunk of ice or a heavy drift. It calls wood the most vulnerable to winter weather, because moisture can make it swell, crack or rot, and snow piled against it can trap moisture near the base and weaken the posts.

The same supplier says chain link is the most winter-tolerant of those three, since its galvanized coating resists rust and wind can pass through the mesh, with shifting posts as its main weakness. Those are a supplier's general observations rather than test results. Our guide to choosing the right fence for Montana compares them for a new build, and custom fencing is what we build.

What should you check on a fence when the snow goes?

Walk the whole line on a dry day. Sight down it for waves, then push on each post at chest height. A post that moves at the base has lost its grip. Look for soft wood at ground level, cracked vinyl rails, split brackets, broken panels from plow contact and snow-bent wire or rails. Check that gates still latch, and watch the gap at the latch side, which often shows hinge post movement before the post looks crooked.

Do not rush to fix movement while the ground is thawing. It is hard to set anything solidly in saturated ground. Bracing a failed section temporarily and waiting for firmer ground is usually fine. If a section is down, send us a photo: our fence repair team can tell you whether the failure is isolated or whether the whole line was set too shallow.

How deep should a fence post be to avoid frost heave?

Below the frost line is the standard answer. ProFence says posts should be set below the maximum depth the ground freezes, which it says is typically 3 to 4 feet depending on region. That is a Pennsylvania and Virginia contractor's general figure, not a Montana rule, and we did not verify a single frost depth for Missoula or Ravalli counties. Your local building department can tell you what applies to your site and structure.

Drainage does much of the work. ProFence recommends gravel at the bottom of the hole to promote drainage, and backfill that lets water drain away from the post. It also describes frost sleeves, which create a buffer between post and soil to reduce the frozen soil's grip. Our fence installation cost factors explains why post setting drives a good part of a quote, and what to expect on fence installation day shows how it happens.

Can snow damage a retaining wall?

Yes, mostly through water. Our retaining wall page describes why: saturated backfill is heavy, and in western Montana it also freezes and expands. That is the load most failed walls were never built to carry. Meltwater from a snow pile on the high side of a wall adds to it, so do not stack plowed snow behind one.

Indiana Department of Transportation's retaining wall inspection manual lists what inspectors look for, including bulging, vertical and horizontal rotation, separation, cracking, settlement, freeze-thaw damage, leakage and erosion. On a home wall, that translates to a belly in the face, a top that has tipped forward, or joints opening up. Our guide to signs a retaining wall is failing goes further, and when a retaining wall needs a permit or engineer matters if it needs rebuilding. If a wall holds up a driveway or sits near a building and has moved, get a professional to look before loading it again.

Why do patios and pavers heave in winter?

The base is usually the reason. On our hardscaping page, we describe the enemy as freeze-thaw: water gets into a poorly built base, freezes, lifts the surface and thaws again. After enough cycles, a patio that was flat in September is heaved and uneven by spring. Preventing it is about the depth and compaction of the base and whether the finished surface sheds water away from the house.

Some movement settles back as the ground thaws, so wait before judging it. Look at the patio once the ground has fully drained. If pavers have stayed lifted, or a low spot now holds water, that section probably needs to be lifted and rebuilt rather than topped up. Our guides to why patio base preparation matters, flagstone patios and freeze-thaw and pavers or poured concrete go through the options.

What causes concrete to flake after winter?

That flaking is called scaling. A Concrete in Practice technical sheet says scaling is local flaking or peeling of a finished surface as a result of exposure to freezing and thawing, usually starting as small patches that may merge. Light scaling does not expose the coarse aggregate. Moderate scaling exposes it and may involve the loss of 1/8 to 3/8 inch of surface mortar.

The sheet says most scaling comes from concrete with too little entrained air, excessive calcium or sodium chloride on concrete with inadequate strength, air entrainment or curing, finishing while bleed water is on the surface, and insufficient curing. It also warns that poor drainage, including plowed snow that keeps a surface wet for long periods, greatly increases the severity. It advises against deicing salts in the first year after placing concrete, and using clean sand for traction instead. Our guides to new concrete and de-icers and how de-icing salt damages plants and concrete have more on that.

Are cracks in a patio or walkway serious?

Not always. A companion technical sheet says concrete expands and shrinks with moisture and temperature, and irregular cracks are unsightly and difficult to maintain but generally do not affect the integrity of the concrete. Contraction joints are pre-planned cracks, and isolation joints let a driveway or patio move separately from walls, stairs and garage slabs.

What matters is whether a crack changes anything. A crack that stays closed and level is mostly cosmetic. One that opens up, steps so that one side sits higher, or tips a slab toward the house needs attention, since it may be a trip hazard or send water where it should not go. Our guide to grading a yard away from the foundation covers that last point, and yard cleanup after the snow melts puts it on the spring list.

Can plows and shovels cause this damage?

They can, and it is usually visible as gouges, chipped edges and scraped caps rather than slow movement. Our guide to snow plow damage prevention covers who is responsible and how to reduce it. Mark fence corners, low walls, patio edges and steps before the first storm, using snow stakes and markers, and talk through edges with whoever clears your property.

For wood or composite surfaces above ground, see clearing snow off decks safely. And when you are clearing by hand next to vinyl in very cold weather, follow the supplier's advice to avoid metal shovels or plows that can crack panels.

Who can repair winter damage to fences and hardscape?

We do both: fence repair, custom fencing, hardscaping and retaining walls across Missoula and the Bitterroot Valley. We will tell you whether something needs repair or replacing, and when a project needs an engineer. To avoid new damage next winter, talk to us about snow and 24-hour storm services and agree where the snow goes before it falls. Call (406) 215-7319 or send us the details for a free estimate.

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