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Details of a frost lens proof structural pier (C) Daniel FriedmanBuckled Foundation Damage
Frost Heaves vs. Frozen Soil Pressures

  • FOUNDATION DAMAGE by ICE LENSING - CONTENTS: definition of ice lensing; how ice lensing can lift a post, pier or foundation wall. Distinguish between ice lensing damage to foundations and frost push or frozen soil horizontal pressure on a foundation wall.
  • POST a QUESTION or READ FAQs about frost heave vs. frozen soil lensing damage and pressures and their effects on footings, foundations & posts or piers
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Foundation damage due to frost heaves or ice lensing:

Here we explain the difference between the vertical lift of frost heaves and ice lensing (or frost lenses) and we include details of the construction of a frost-lens-proof structural pier, and we provide data on the amount of soil pressure and expansion exerted by water and freezing.

This article series explains of the the causes of foundation cracks, buckling, or collapse in areas of freezing weather, clay soils, or wet soils.

Photo (above) shows a crew constructing a structural pier (in clay soils) that successfully resists ice lens lifting in Two Harbors, Minnesota.



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Frost Heaves Compared with Frozen Soil Impacts on Foundations

Stage construction, Lon Church, Summerblue (C) Daniel FriedmanFound here: Details of an ice-lens-proof structural pier construction in Minnesota. Can foundation insulation cause cracked, bulged, or buckled foundation walls?

What is the difference between ice lensing and freezing earth pressure? How much pressure is exerted by wet, freezing soil? How do we prevent foundation damage - key steps.

Article Contents

There are two distinct problems associated with frozen ground and its effects on building foundations: frost heaving and pressures from frozen soils.

Details About Ice Lenses in Soils

Frost heaving is what makes roads buckle during the winter in many northern states and provinces.

It is caused by small plates of ice called ice lenses that form a foot or more below the surface. Ice lenses draw water from surrounding soil by capillary action, typically growing up to 1/4 inch to 2 inches in thickness and up to several feet across.

Often frost lenses form in multiple layers, adding to the total soil movement in an upwards direction. Ice lenses form in porous silts and also in clays that can support capillary action.

They need extreme cold, combined with a subsurface water source - that water might come from ground water, surface runoff, or even roof runoff around a building. Roads and sidewalks are good candidates for frost heaves because melted snow provides a good water source as well, and frost can penetrate deeply into the soil because roads and sidewalks are cleared of their insulating snow cover.

Where the direction of heat loss is upwards to grade, ice lenses form horizontally. In these cases, ice lenses push mostly upward, not laterally. Theoretically, a frost heave could lift a building foundation wall or a pier if the soil above the ice lens were frozen to and adhered to the foundation wall or pier surface.

Healy has seen concrete piers for highway sign posts lifted as much as an inch per year by frost heaving, but he has never seen frost do structural damage to foundations.

Where the direction of heat loss is horizontal, as through a retaining wall or the wall of a frozen basement, ice lenses could form in the vertical plane and push laterally.

Constructing a Frost-Lens-Push-Proof Stage for Summerblue Arts Camp in Two Harbors, Minnesota

Stage construction, Lon Church, Summerblue Summer Blue Arts Camp Two Harbors Minnesota (C) Daniel FriedmanIndeed frost lenses or ice lenses can lift a building foundation by adhesion to the foundation sides, especially at a a building corner.

We (DJF) observed this condition at a 1960's home in Poughkeepsie, NY, where a building corner was lifted each winter by freezing wet ground.

Even though the wall's footings were below the frost level, ice lensing against the top few feet of the buried portion of the foundation wall was causing an annual movement problem that cracked the masonry blocks in a stair-step pattern at the building corner, and cracked the drywall in the bedroom above.

The owner dug at the problem corner, found a ground water source, a spring, and cured by installing drainage to remove the water problem.

Soil frozen against a foundation wall or a pier, or ice lenses where there is a lot of ground water, can also pinch and lift piers and posts.

When Lon Church, director of Summer Blue Arts Camp - [link at article references] in Two Harbors, Minnesota, decided in 2001 to construct an outdoor stage platform that would be exposed to both clay soils and very cold weather, we wrapped the platform's piers in several layers of 6-mil polyethylene plastic to reduce the ice grip around each pier, thereby reducing the ability of ice lenses in the freezing soil to lift the piers supporting the stage.

In our deck construction photos (see the center post in both photos above) you can see that we brought the poly well above ground level during construction.

Frost heave protection for post buried in clay soil in a northern climate - Summerblue Arts Camp, Two Harbors MN (C) Daniel Friedman Lon Church 2001

Above you can see the plastic wrap being installed around posts during pier installation in 2001. (The "© 2009" on this photo is from when it was published online. The picture was taken and first © in 2001.)

We discuss this deck post installation job at DECK POST CONSTRUCTION.

In our "Summerblue Arts Camp" winter 2009 photo below you can see the same piers, still protected by plastic though the plastic isn't quite visible.

Stage construction, Lon Church, Summerblue Summer Blue Arts Camp Two Harbors Minnesota (C) Daniel Friedman

Eight years after construction (in 2009), and after a number of very cold Minnesota winters, we had seen no frost movement in the piers for this outdoor stage. -- DJF.

In the 2009 photo above the front or audience side of the stage is to the left.

We describe the deck board installation for this stage at DECK FLOOR INSTALLATION TIPS where we show the jig used to force deck boards into position.

More than sixteen years after the original construction, Inspecting this Two Harbors MN Summerblue arts camp stage in October 2017, we found that the posts as originally constructed by Lon Church and his crew, had remained in place and the deck surface had remained almost perfectly flat.

Summerblue Arts Camp Two Harbors MN Stage on 11 October 2017 (C) Daniel Friedman Lon Church

In the photo above (October 2017) you'll note that the stage was constructed with a deliberate but slight slope from back to front, placing the lower edge of the stage closest to the audience - at the right side of the image.

Corner post at outdoor deck / stage, Summerblue Arts Camp 2017 (C) Daniel Friedman Lon Church

Above: one of the corner posts of the Summerblue stage. You cannot see the plastic with which we wrapped these posts in 2001, as it remains buried in the clay soil. But the absence of frost heaving at the stage suggests that these posts have performed well.

Chloe Church at Summerblue Arts Camp (C) Lon Church InspectApedia.comThe installation and long term performance of this outdoor performing arts stage floor are described in

How Much Does Wet, Frozen Soil Expand to Cause Pressure & Damage to Foundations?

Foundation collapse, repair (C) Daniel FriedmanOur photo shows excavation and a new foundation under a home that suffered a catastrophic foundation collapse.

The foundation wall in the right of this photo collapsed inwards into the garage, due to pressure from water-soaked earth that was caused, in turn, by surface runoff from a hill that sloped directly towards the home's rear wall. -- DJF

Soil that expands due to freezing is a separate problem from frost heaves or frost lensing.

The necessary ingredients are water-saturated (often clay-containing) soil and continuous freezing temperatures. Water-saturated soils, where clay is involved, can hold up to two-thirds water by volume, and water expands by 8 percent when it freezes.

So the total volume of soil can expand by as much as 5 percent during freezing conditions.

Unlike ice lenses, this freezing soil expansion exerts force in all directions.

The force exerted by freezing soil against a foundation wall, according to Heley, could be enough to crack the un reinforced walls in Duluth, and we confirm that this phenomenon can occur even further south, to the limits of areas of freezing soils.

Even if the foundation wall does not cave in, the expanding mass of freezing soil may make a mess of exterior insulation or waterproofing coatings, as was reported in Fargo ND.

As the soil expands, it may drag the exterior insulation or waterproofing foundation membrane with it. For this reason, some builders drape a loose layer of polyethylene plastic over their waterproofing or exterior insulation to act as a slip joint, such as we described for the outdoor stage piers.

Others, like Heley, put foundation insulation on the interior.

Some of the information in this article is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

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Continue reading at FOUNDATION FAILURES in CLAY SOIL or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see BULGED vs. LEANING FOUNDATIONS

Or see DECK BOARD GAPS, SPACING GUIDE

Or see FOUNDATION FAILURES in CLAY SOIL

Or see FOUNDATION FAILIURE by INSULATION - insulation causing foundation buckling or damage

Also see FROST HEAVES, FOUNDATION, SLAB.

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FOUNDATION DAMAGE by ICE LENSING at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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