preventing winter damage - hoffarch.comthe prime suspect in a case of ponding water is the drains....

6 PAPYRUS WINTER 2018–2019

Too often, building owners and facility managers findthemselves chasing after winter damage, rather thankeeping ahead of the storm. What if we could foresee

the toll snow and ice might take, so that something couldbe done to avert the damage? Although the specific ways inwhich winter may affect a building can be hard to predict, it’sworth examining cases of winter damage, while turning backthe clock to see what might have prevented the problem. For those concerned about how best to prepare for the

oncoming harsh weather, learning from others’ mistakes canhelp you avoid the same fate. Anticipating and managingthe potential impact of winter conditions can make all thedifference, come the spring thaw, between minor repairsand major rehabilitation. Moreover, failure to take properprecautions can create hazardous conditions, whether fromfalling snow and ice, slippery surfaces, or even dislodgedbuilding materials. Cold-weather building management shouldn’t begin and

end with the winter season. One of the most crucial compo -nents to preparing buildings for the onslaught of ice, freezingrain, and snow, is to conduct proactive building-enclosureassessments, and to perform the necessary maintenanceand repairs throughout the year. Warmer weather brings anopportunity to address conditions—from open joints andloose gaskets to insufficient drainage and poor ventilation—that can lead to bigger issues. Once icy moisture anddropping temperatures exploit deficiencies in the buildingenvelope, deterioration spreads quickly, with one damagedcomponent compromising the integrity of the next.By examining case studies of typical winter-related building-

enclosure failures, along with the suggestions of designprofessionals for preventing such problems, the prudent

facility manager or owner can determine what might bedone ahead of cold weather to fortify buildings againstsimilar distress.

Winter Problem #1: Ice DamsWhen asked for examples of winter-weather problems, thefirst thing many facility managers and design professionalswill bring up is ice damming: the frustrating—and potentiallydangerous—accumulation of ice and snow at roof eaves.As snow on the roof starts to melt, water flows down to theroof edge, where it collects and re-freezes. Over time, thisthawing and freezing creates a build-up of ice at the eave,and causes water to back up under the roofing material,eventually spilling over into the building interior. In addition, water that melts and re-freezes at the gutter

and drip edge begins to extend downward, forming icicles.With water continuing to flow down from the eaves, thesepointed shards of ice can grow to many feet in length, posinga tremendous risk to pedestrians and vehicular traffic below.

Prevention: Properly Insulate and Vent the AtticBuildings are often designed such that the thermalenvelope—the barrier that encloses the conditioned space ofthe interior from the unconditioned exterior—terminatesat the attic floor. However, in practice, air leakage into theattic from the building interior may be difficult to avoid.Recessed lights, HVAC registers, and other penetrationscreate sites of thermal transfer, and insufficiently insulatedmechanical equipment in the attic warms the surroundingarea. Unless the roof deck is kept cold in winter, snow that

BEST PRACTICES FEATURE ARTICLE

Preventing Winter DamageBy Steven J. Susca

Icicles might seem like charming seasonal decorations, but theymean trouble— both for the building, and for those below.

HOFFMANN ARCHITECTS, INC.

Snow and ice buildup at eaves.


collects on the roof will tend to melt, then re-freeze as itreaches the colder eaves. To maintain a cold roof temperature, soffit and ridge

attic ventilation should be balanced. A properly sizedventilation area creates a chimney effect, drawing warm,moist air up and out of the attic. An unbalanced systeminhibits the exhaust of warm air, which then collects atthe underside of the eaves, where it warms the roof justenough to melt the snow. So begins the cycle of meltingand re-freezing that leads to ice dams and icicles. Calculations may be done to determine the Net Free

Ventilation Area (NFVA) and the optimal size of soffit

and ridge vents; but for existing buildings, achieving theright balance can be challenging. For some complex roofconfigurations, adequate venting balance may not be possible. In those cases, the thermal envelope must be relocated

from the attic floor to the underside of the roof. Insulationinstalled in rafter bays and at eaves shields the roof from thewarmer air of the attic. For mechanical equipment, propertemperature and humidity-controlled intake and exhaustventilation is crucial not only to preventing ice dams inwinter, but to preventing mold growth in warmer months.

Prevention: Install Heat TracingIn some cases, building configuration makes preventingice dams difficult, as configurations of roof and exteriorwall interfaces may prove challenging to drain expedi -tiously. An electric ice-melt system using radiant heatingcable may be installed as part of a roof rehabilitation orreplacement project. Typically, heat tracing is installed at eaves, extending

down into gutters and, sometimes, down each leader toprevent ice from clogging drainage pathways. The ice-melting coils should be used in conjunction with ice andwater shield: a barrier sheet, typically composed of a rubberizedbitumen membrane. Installed under the roof covering, ice-and water-shield should extend from the edge of the roofto at least two feet (24 inches) inside the exterior wall line.Manufacturer requirements vary, but ice- and water-shieldis typically applied at eaves, valleys, ridges, hips, rake edges,transitions, chimneys, and penetrations.

Winter Problem #2: Falling Snow and IceSnow sliding from rooftops in a rural setting is unsettlingenough, but adjacent to a city street, it is downright terrifying.Unfortunately, this was exactly the scenario facing onegovernment agency charged with maintaining a historicalmilitary facility within a dense urban environment.

PAPYRUS WINTER 2018–2019 7

Prevention: Insulate and vent the attic.


Prevention: Install heat tracing.


Hazardous ice formations.



Although snow guards were in place along the steepbarrel-vaulted roof, many had bent under excess snowloads, and many of the fall-protection line brackets hadbeen ripped out of their anchorage points by the tuggingweight of accumulated snow. Dense traffic loomed below,immediately under the struggling snow-protection system,which, if compromised, would deliver a hefty payload ofsnow and ice to unwitting pedestrians and drivers below.

Prevention: Install Appropriately Sized and ConfiguredSnow GuardsEvaluating the slope, frictional coefficient, and anticipatedsnow load of a roof is key to providing sufficient snow guards.In the example of the barrel-vaulted roof above a busy street,installing additional snow guards at an intermediate heightbetween existing rows would reduce the amount of snow fall -ing onto lower roof areas, alleviating pressure on the system.More snow guards to share the load means less frequentreplacement of rails bent by excessive snow weight.

Accurately identifying the cause of loose snow guards isimportant to preventing recurrence. Adding fasteners canincrease strength, but if the anchorage was incorrectlydesigned, or fastened to an unstable substrate, redesigningthe system might be necessary. Routine inspection of snowguards after each winter season—and replacement of com -promised pipe rails or guards—provides reassurance that,come cold weather, the system is ready to weather the storm.

Prevention: Correctly Size Replacement DrainageElements Promptly replacing gutters and leaders as they reach theend of their lifespan is important to a well-maintainedroof. However, swapping those drainage elements forundersized replacements can do more harm than good.Case in point: one well-meaning facility retained a

contractor to replace aging gutters. When the façadesbegan accumulating a great deal of ice in the winter, thecontractor installed heat tracing and added screens overthe gutters to collect debris. This only made matters worse.One action might have prevented the years-long effort tostem the overflowing drainage system and ice-coveredfaçades: correctly sizing gutters.Unfortunately, the replacement gutters were too small

for the roof area, so they were overwhelmed with water andsnow during storms. Keeping gutters free of debris isimportant, but the screens and heat-tracing only served toencourage ice-dam formation in the saturated gutters.Replacing the drainage system with an appropriatelydimensioned one solved the problem.

Winter Problem #3: Snow Loads on Flat Roofs News stories about roofs collapsing after a blizzard havejustifiably made facility managers jittery when winterweather deposits multiple feet of snow—and sometimesmassive snowdrifts—on a flat roof. That said, the answeris not to do what one corporate headquarters did on


Prevention: Sufficient snow guards.


Prevention: Appropriate drainage.


Snowdrifts and leaks.


its sprawling campus of low-slung buildings: bring inthe snowblowers. Aiming to protect newly installed roofs from snow damage,

the well-intentioned facilities team quickly responded byblowing snow off the roof and, unfortunately, cutting up thenew roof assembly in the process. Furthermore, removal ofsnow in this manner can result in an unbalanced load onthe already overloaded structural roof supports, creatinghazardous conditions.

Prevention: Remove Snow According to ManufacturerStipulationsRather than react to a snow event, which can lead to impul -sive and possibly detrimental actions, the better approachis to plan for winter weather before the season getsunderway. Check with roofing manufacturers to identifysnow-removal methods that will not void the warranty orrisk damaging the roof assembly in the process. A designprofessional can assist in determining how much snow istoo much, making it easier to determine when removingsnow from a roof area is necessary.

Prevention: Address Ponding WaterBlockages in roof drains can lead to standing water, theweight of which can cause deflection in the structuralsystem. This low point on the roof then collects morestanding water, causing more deflection, and so on. In thewinter, ponded water turns to ice, which, combined with

snow loads, may pose a structural concern. Clearing blockeddrains ahead of the winter season, as well as periodicallyduring the cold weather months, can break the cycle ofponding and deflection. In some cases, inadequate slopeto drains may be the issue, which is best addressed wellahead of winter weather.

Winter Problem #4: Flooding and Heaving at Entrywaysand PlazasWith freezing water leading to displaced pavers and sheetsof ice, it’s no wonder many plaza owners give up and cordonoff outdoor areas for the winter season. At some point,though, people must traverse at least some outdoor pathor entrance area to reach the building, and the risk offalls and injury due to slippery and uneven surfaces mustbe addressed.

Prevention: Install and Maintain Appropriate DrainsThe prime suspect in a case of ponding water is the drains.When constructing a plaza, it’s crucial to design robustdrainage to clear water not only at the paving surface, butat the membrane level below. Water that becomes trappedbetween the waterproofing layer and the pavers can freezeand expand, pushing pavers out of alignment, which leads


Prevention: Address ponding water. Prevention: Maintain drains.

Prevention: Remove snow correctly.

Slippery, uneven surfaces.






to broken pavers and an irregular walking surface.

Even if drains are designed and installed correctly,they cannot function if they are clogged with debris.Regularly clearing out of drains is essential to keepingwater from ponding.

Prevention: Create Adequate Slope to DrainsWater runs downhill, which means that the lowest points ofa plaza should be at drains. If water is collecting elsewhere,it may mean that the plaza does not have the correct slope.Sometimes, poor drainage can lead to heaving of plazapavers, which in turn creates a low point on the walkingsurface that collects water and ice.

In that case, rehabilitation of the drainage system andre-setting or replacement of pavers may solve the problem.However, it may be that the plaza does not provide adequateslope to drains even with pavers set correctly, in which caserehabilitation and re-grading of the plaza may be the onlylong-term solution.

Winter Problem #5: Concrete Damage at Balcony RailingsIn many instances, lightweight aluminum railing posts atconcrete balconies are directly embedded into the concreteat the edge of the slab. If not properly finished and sealed,gaps between railing members will allow the railing stan -chions to fill up with water. As the water freezes, it expands,which can cause expansion of the aluminum post where itenters the concrete. This, in turn, results in cracks at theedges of the slab.

Eventually, pieces of concrete may break away, posing ahazard to people below, and compromising the structuralintegrity of the railing. Deicing salts used on the balcony

can accelerate the damage by helping to initiate corrosionof embedded reinforcing steel.

Prevention: Evaluate and Repair Post-Slab InterfacesWhere railing posts are embedded in concrete, cracks andspalls should be repaired promptly to avoid hazardousconditions. Evaluate guardrail components for potentialpoints of water entry into the railing system. At the edgesof balcony slabs, applying a waterproofing coating may beconsidered to ensure further protection against water


Prevention: Establish adequate slope.

Cracks at slab edge.

Prevention: Repair post-slab interfaces.

Prevention: Install weeps at rail posts.






Freeze-thaw and salt damage.

Prevention: Maintain coatings and seals.

Prevention: Consider adjacent elements.

infiltration, although some substrates and situations maycontraindicate application of a coating.

Prevention: Install Weeps at the Bottom of RailingStanchionsEven if all these recommendations are implemented,water will usually find its way in. For this reason, it must beprovided with an escape path from the railing stanchion toprevent it from causing damage. Installation of small weepholes at the bottom of the railing stanchion to allow waterto drain will help to ensure the integrity of the balconyrailing system.

Prevention: Install New Post AnchorageIf railing-post sleeves are deteriorated, poorly installed, orimproperly specified, it may be necessary to either replacethe railing system entirely or, if the railing is intact, replacejust the post anchors. After the concrete has been repaired,a bracket may be fastened to the top of the slab. Not onlydoes this rehabilitation measure spare the expense ofreplacing the entire assembly, but the surface mount alsoreduces the potential for water infiltration.

Winter Problem #6: Façade Deterioration from ExposureWinter weather is hard on vertical building elements, aswell as horizontal ones. As wind, rain, and snow batter thebuilding exterior, façade elements eventually succumb tothe ravages of winter. Failed coatings and glazing compound can leave

windows and doors exposed to deeper damage from theconstant presence of moisture. Curtain-wall mullions maybecome displaced when subjected to freeze-thaw cycles,and masonry structures may show signs of efflorescence, ormigration of salts to the surface. Where the façade meetsplazas, sidewalks, or roads, deicing chemicals may acceleratedamage from exposure and freeze-thaw cycling.

Prevention: Maintain Coatings and SealsWhen water can find a way into the façade, it can causesignificant damage, especially as it expands when freezing,and contracts as it thaws. To protect sensitive façade elements,it’s important to prepare well ahead of cold weather byreplacing worn coatings, repointing open mortar joints,replacing failed sealant and gaskets, and replacingdamaged materials.

Prevention: Pay Attention to Adjacent BuildingElementsWhere different materials intersect, there is potential fordamage from differential movement. As each materialresponds to fluctuating temperatures, one is likely toexpand or contract differently from another, which placesstrain along the plane where they meet. Even one long span of a single material can undergo

movement stress, if that building element is restrained





from moving according to its natural tendency. Providingadequate expansion joints to allow for fluctuating materialvolume as the seasons change is essential, and othermeasures may be necessary, depending on the materialsand configuration.

Winter Problem #7: Damage to Building Elements fromDeicing ChemicalsFaçade elements adjacent to walking and driving surfacesneed to be protected from caustic deicing chemicals, whichcan lead to corrosion, scaling, and disintegration. Optingfor less damaging ice-management compounds not onlyprotects vulnerable façade materials, it spares exteriorstairs, plazas, and garages, too.

Prevention: Choose the Right Deicing StrategyRock salt (sodium chloride) may be the most common andleast expensive deicing chemical, but that does not mean itis the best choice. When its corrosive and destructive proper -ties are considered, it may prove the more expensive option,given the costs of rehabilitating the damage it does.

Calcium chloride is a better option, although it is still acorrosive compound. Better still is calcium magnesiumacetate (CMA), an ice-loosening chemical that does notmelt snow, but instead creates a slurry that prevents icefrom bonding to the surface. Caveats are that CMA mustbe applied before snowfall, and that mechanical removal ofthe loosened ice and snow is required. Addition of grit orsand can improve traction, and reduces the amount ofdeicing chemical needed.Proprietary products are also available, combining deicing

chemicals like potassium chloride with performance-enhancing additives, such as corrosion inhibitors. Proprietaryorganic ice-melting chemicals are another option. For anydeicing product, it is important to check the operating

temperature range, as lowest effective temperatures can rangewidely, from –20°F for calcium chloride to +20°F for CMA.

Winter Problem #8: Parking Garage Snow RemovalNot only are parking garages subjected to the weatherinside and out, but they also must endure caustic deicingchemicals, sharp snowplow blades, and snowdrifts that cantake an entire season to clear. Even if the facility is thoughtfulabout which deicing chemicals are used, “fenderbergs”—mountains of deicing chemical-laden snow barnacled tocar fenders—carry in a mix of harsh compounds.

Prevention: Protect Vulnerable SurfacesWithout benefit of precipitation to clear away accumulateddeicing salts, garages are subjected to high concentrationsof damaging chemicals. Periodically washing parking decksand clearing drains to remove accumulated salts preventschemical-laden standing water from causing deterioration.


Corrosion and deterioration.

Prevention: Choose the right chemicals.

Prevention: Apply deicers judiciously.




Surface treatments, including traffic-bearing membranes,penetrating sealers, and migrating corrosion inhibitors,require periodic reapplication to remain effective. Areas ofwear can open up the concrete to damage from chloride-containing water. Repair of cracks and spalls and replacementof joint sealant are important maintenance efforts that helpprotect the garage from water and deicing chemicals.

Prevention: Use Rubber Plow BladesExpansion joints, drains, and other uneven surfaces can takea beating from standard steel snowplow blades. Outfittingthe plow with rubber-tipped blades can prevent damage tosoft joint materials, edges, transitions, and coatings that areoften sites of premature deterioration. Sometimes, plow operators may avow that they are using

rubber blades, but rust streaks on the surface of the concretetell a different story. If the rubber has worn away in placesto bare metal, or if metal blades are used on occasion,damage can still occur.

Winter SolutionsWhile these simplified tips may help in developing a generalapproach to winter weather management, they are no sub -stitute for a comprehensive building envelope evaluationand customized snow and ice removal program. For a given


Damage to expansion joints and parking decks.

Prevention: Protect surfaces.

Prevention: Use rubber-tipped blades.

Exterior envelope assessment of the 20 buildings at this facilityhelped the institution prevent and treat the effects of harshwinter weather.

At this parking garage, investigation revealed winter weatherdamage. To repair defects, the facility is undergoing a comprehensiverehabilitation, after which a diligent maintenance program willhelp prevent further deterioration.







problem, there may be many possible causes, and correctlydiagnosing the issue is the key to resolving it. Preventingwinter damage does demand some degree of imagination,along with the experience to anticipate likely issues.

Repairs and protective measures must be appropriatelydesigned and correctly implemented, or they can do moreharm than good. Knowing the composition, construction,exposure, and usage of a building allows for winter repairand maintenance programs that are cost-conscious andeffective. With the right program, recovery from badweather can proceed in a pre-determined, systematicfashion, minimizing disruption to operations.Protection from winter weather doesn’t begin with the

season; keeping building elements in good repair all yearlong is the real solution to the annual onslaught of ice andsnow. A building that is well-maintained and watertight willfare much better through winter storms than will one thathas been compromised by cracks and deterioration. AsBen Franklin’s adage counsels, “An ounce of preventionis worth a pound of cure.”

Steven J. Susca, PE is Senior Engineer with Hoffmann Architects,Inc., an architecture and engineering firm specializing in therehabilitation of building exteriors. As one of the firm’s mostexperienced engineers, he provides building-system analysisand structural evaluation for roofs, façades, plazas, and parkinggarages, including remediation and prevention of damage to thebuilding envelope from winter weather. He may be reached [email protected].

Winter weather and indiscriminate use of deicing chemicals ledto widespread damage at this plaza, which was reconstructedto incorporate preventive measures, including heat tracing.

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preventing winter damage - hoffarch.comthe prime suspect in a case of ponding water is the drains....

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