What this comes down to
- A deck pier set to code can still heave, because frozen soil grips its sides and lifts it.
- Water expands about 9 percent as it freezes, and concrete cracks when that pressure beats its tensile strength.
- Concrete exposed to deicing salts should reach 4,000 psi and be air-entrained, says the Portland Cement Association.
- Soil that stays saturated into late fall is the main driver of heave, and downspouts and sump hoses feed it.
- Frost ran about 10 to 20 inches deep across Illinois in the winter of 2013 to 2014, the State Water Survey reports.
- Perfect Work lists ledger board repair from $495 and deck stair repair from $225 when frost has moved a connection.
Frost damages concrete by turning the water already inside it into ice. The ice pushes outward, and every freeze repeats the push. Over a few winters a solid stoop can scale, crack and sometimes shift.
This guide explains how freeze-thaw acts on concrete and on the footings under decks and porches. Four sources back it: a cement trade body, the state water survey, a city and a national lab.
What does freeze-thaw actually do to concrete?
It turns pore water into ice, and ice takes up more room than water. The Portland Cement Association says water expands about 9 percent as it freezes. That pressure builds inside the pores of the concrete.
When the pressure exceeds the concrete's tensile strength, the pores rupture. The association says repeated cycles cause expansion, cracking, scaling and crumbling. A single freeze does little, and the damage adds up with every cycle.
Small, evenly spread air bubbles help by giving the ice room to expand. The association's concrete freeze-thaw guidance also names good curing. Low permeability protects too.
Why do deicing salts make concrete flake?
Salt speeds up scaling, the flaking of the top layer of a slab. The Portland Cement Association lists sodium, calcium, magnesium and potassium chloride as deicers. Scaling resistance depends on strength, low permeability and air entrainment.
The association says concrete exposed to deicers should reach 4,000 psi first. That is before repeated freeze-thaw cycles, so it is a target for new pours. A finished stoop cannot be strengthened, so a weak one keeps flaking.
Scaling looks like a rough, pitted, peeling top layer. It is a surface problem until it exposes the stone underneath. A crack that runs through a step is a different problem, and it needs a closer look.
How deep does frost go in Illinois?
Less deep than most people assume, though it varies by winter and by site. The Illinois State Water Survey reports 10 to 20 inches statewide in the winter of 2013 to 2014.
A 1980 to 1996 study found deepest frost of 5 inches in the far south and 30 in the far north. The same state frost depth in Illinois report lists the causes of that variation.
Soil type, soil moisture, vegetation, snow cover and exposure all change the depth. Snow and plants insulate the ground, and drier soil warms and cools faster than wet soil.
Footing rules add a margin to these numbers. The guide to deck footing depth explains why DuPage villages inspect at 42 inches. The base of a footing below the frost line has soil above it to freeze, not soil beneath it.
How does frost lift a deck footing or porch pier?
By gripping the sides of it. A Grand Rapids, Minnesota, handout describes frozen ground gripping the upper pier and lifting it. It calls that likelier than frost below the footing.
The frost heave footing handout says piers can move even when built to code. They carry loads near their design limit and have no structural link to each other. Frost can surround them.
Water is what makes it happen. The handout names soil that stays saturated into late fall as the main concern. Its sources are downspouts, sump pump hoses, poor drainage and heavy late-fall watering.
What does frost damage look like around a house?
| Where you see it | What it looks like | What it points to |
|---|---|---|
| Stoop or step surface | Rough, pitted, peeling top layer | Scaling from freeze-thaw, often worse with salt |
| Cracks through a step | Cracks that widen each winter | Water freezing in the crack or a base that moved |
| Step or stair at the wall | A gap that opens in cold weather | Movement of the step or the soil under it |
| Deck at the ledger | A gap that grows in winter | Footings heaving under the deck |
| Post base | Soft wood where post meets concrete | Water held at the connection |
A gap at the ledger is the one worth acting on. The guide to a deck pulling away from the house shows how to tell which end moved. A soft post base points to the posts that rot guide.
How can I keep water away from concrete and footings?
Send roof water well away and slope the ground away from the house. The Building America Solution Center says to slope soil 0.5 inch per foot for 10 feet. The Pacific Northwest National Laboratory runs it.
Its grading away from foundations guide says no waterproofing is completely reliable. The defense is soil that never becomes saturated. Snowmelt can refreeze into an ice ridge that pushes water back toward the house.
The Grand Rapids handout names downspouts, sump pump hoses and late-fall watering as sources. Pointing each one away from piers and steps is the cheapest job on this page. The fall maintenance checklist puts the jobs in order.
What does frost damage cost to repair?
Perfect Work Remodeling & Repairs lists ledger board repair from $495 and stair repair from $225. Joist repair starts at $125 each. These are starting prices, not quotes. A heaved footing adds to them.
| The work | Starting price | What moves it |
|---|---|---|
| Deck stair repair | From $225 | Whether the stringers rotted or the pier moved |
| Full stair rebuild | From $795 | Rise, run and footing condition |
| Ledger board repair | From $495 | How far the ledger pulled and the band joist behind it |
| Joist repair or sistering | From $125 per joist | Number of joists and access |
| Handyman hourly rate | $65 per hour | Hours on site and materials |
| Minimum service call | $99 minimum | One visit and travel |
These prices cover the wood and the connections above the concrete. A scaled step or a cracked slab is a concrete repair and is priced separately, as its own job.
What cannot be determined from the surface?
How deep a footing goes. Poured concrete hides its depth. A heaving pier may be shallow, or it may simply be gripped from above. Only a measurement at an open hole tells which.
The strength of old concrete is the other unknown. Its air content and mix are not visible, so a stoop that scales cannot be graded by eye. A core test would settle it, though few homeowners need one.
Freeze-thaw questions
Does freeze-thaw crack concrete?
Yes. Water in the pores expands about 9 percent as it freezes. If the pressure beats the concrete's tensile strength, the pores rupture. The Portland Cement Association says repeated cycles cause cracking, scaling and crumbling. Air-entrained, well-cured concrete resists it far better.
How does Perfect Work check for frost damage at a deck?
Perfect Work Remodeling & Repairs checks where the wood meets the concrete. It looks for movement at the ledger, the post bases, the stair stringers and the piers. It also looks at drainage, because wet soil drives heave. Findings come before any price.
Can a footing below the frost line still heave?
Yes. A city handout from Grand Rapids, Minnesota, says piers can move even when built to code. Freezing ground that grips the upper part of a pier can lift it. The handout names soil saturated into late fall as the main concern.
What does a frost repair from Perfect Work include?
Perfect Work Remodeling & Repairs repairs the wood and connections that frost has moved. That covers the ledger, stairs, joists and post bases. Ledger board repair starts at $495 and stair repair at $225. A heaved footing is added once it is seen.
Should I use salt on concrete steps?
Go lightly, especially on a new step. The Portland Cement Association wants deicer-exposed concrete at 4,000 psi and air-entrained. Salt speeds up scaling on weak or poorly cured concrete. Clearing snow early keeps the need for salt low, and a broom does the job.
When is frost most likely to move a deck?
After a wet fall. Soil that stays saturated into late fall freezes with the most water in it. Check the ledger gap, the stairs and the post bases after the first hard freeze. Check them again when the ground thaws.
Keep the water out, then watch the connections
Frost damage starts with water that was allowed to sit. Moving downspouts and fixing the grade costs far less than a rebuilt stair or ledger. The best time to check is after the first hard freeze.
A visit from Perfect Work Remodeling & Repairs starts where the wood meets the ground and the house. The structural wood repair page lists the work that can follow once the cause is clear.
Call Perfect Work at 630-297-7888 · Book a deck check