ISSUE 2/2008  V O L U M E 2 5  N U M B E R 2

Journal of architectural technology published by Hoffmann Architects, Inc., specialists in the rehabilitation of building exteriors. Is That Traffic Coating Necessary? Surface Treatments and Parking Structure Protection

Lawrence E. Keenan, PE, AIA and Robert A. Marsoli, Jr., EIT

Elastomeric traffic-bearing mem- there are locations where no mem- branes are showing up on garages brane performs well, such as those old and new, and their popularity has areas requiring a flexible membrane soared in the past decade. A beautiful that are subject to snow plows. coating that locks out harmful moisture So…what is the best solution? It’s and chlorides must be a reasonable helpful to begin by looking at the rea- long-term investment, right? Not only sons why deck protection is necessary. is this not necessarily true, in some cases, applying such coatings can be a The Problem costly mistake. It is true that parking decks must be cared for to ensure that In northern climates, parking decks are they will be here after we are not, but subjected to extreme corrosive and there is a growing preconception that deteriorating environments. Moisture, installing a traffic-bearing membrane is laden with chlorides from deicing a one-way ticket to the garage equiva- chemicals, tracks into garages or hitch- lent of immortality. While a traffic- es a ride as ice formations behind the bearing membrane may, in fact, be the wheels of vehicles (tenderly referred best solution for many situations, this to as “fenderbergs” by those in the re- is a big-ticket item, and thorough con- pair industry) and ultimately soaks into sideration is necessary to determine the concrete surface. The dissolved if this costly investment is the correct chlorides then migrate to embedded solution for your garage’s needs. steel reinforcement through the pores in the concrete or take the highway Traffic-bearing membranes are not and penetrate through cracks. Once perfect. In order to withstand the they reach the steel, the salts cause punishing abrasion which a parking expansive corrosion, ultimately result- deck must endure, the membrane Traffic-bearing membranes look appealing. ing in unsightly, destructive, and costly must be hard and durable; however, But are they worth the price? deterioration of the structure. the membrane must, at the same time, be soft and flexible to bridge Moisture’s ability to transport corro- over moving cracks and joints without sive chlorides is not its only damaging failure. Since very hard membranes property. Coupled with cold weather, are generally inflexible, and more pli- water can damage concrete decks as it able membranes don’t hold up well to expands and contracts during freeze/ abrasion, choosing the right mem- thaw cycles. Air entrainment, the de- brane is a balancing act. In addition, liberate incorporation of microscopic

As Director, Engineering with Hoffmann Architects, Inc., Lawrence E. Keenan, PE, AIA has extensive experience in parking structure rehabilitation, including investigation, repair, and surface treatment consultation. Project Coordinator Robert A. Marsoli, Jr., EIT is involved in a number of garage remediation projects, from design through administration. JOURNAL

The Objective from the boiled linseed oil that was Ultimately, the goal previously used. Today, an industry of all deck protec- dedicated solely to concrete protec- tion is to stop water tion offers a dizzying array of products from getting into to treat concrete before, during, and the deck. Perhaps after production, both inside and this is an over-sim- out. For existing parking structures, a plification, but not number of waterproofing agents are by much. No water, available that can be applied to the no deterioration. surface of the deck; the following is a The tricky part is look at some of these product types that water comes in and their properties. more than one form. Penetrating Sealers Liquid water is an These liquid-applied treatments, which Cracks are routed and sealed before application of a penetrating obvious villain, as is include silane, siloxane, and silicates, sealer. the expansive force stop water entry by penetrating deep of ice and snow, but into concrete and forming a bar- air bubbles in concrete, releases the water vapor can be just as damaging. rier that prevents liquid water from internal pressure created by freezing For example, a chloride-laden deck entering, limiting chloride ion migra- water by permitting moisture to flow can actually draw moisture from the tion and freeze-thaw damage. These from bubble to bubble. Still, although air and continue to deteriorate even treatments are also vapor permeable, this solution to freeze/thaw degrada- after your best efforts to keep it dry. allowing them to be used at locations tion has been known for years, garages In fact, calcium chloride, the most where other coatings may not be ap- continue to be constructed with popular and effective of all deicing propriate, such as slabs on grade. Be- insufficient air entrainment, leading to chemicals, is commonly used on con- cause they are inexpensive and quickly premature breakdown of the concrete struction sites for dust control. It is applied, with little or no down-time, as freezing water destroys it from the sprinkled onto the dry earth and wets penetrating sealers offer a good first inside out. the surface by pulling moisture from line of defense for a parking structure Water is at the heart of most parking the air. Unfortunately, it works equally that is in good overall repair. As invis- deck deterioration. Moisture can well at saturating your parking deck. ible penetrants working below the surface of the concrete, these sealers facilitate reactions between certain Remediating the effects of chloride ion do not affect deck line striping, saving aggregates and alkali hydroxides in the attack, freeze/thaw damage, or mois- on project duration and cost. concrete, creating a cycle of expansion, ture-driven chemical reactions is both cracking, and further moisture intru- difficult and costly, so preventing water However, these coatings can be short- sion. This alkali-silica reaction, or ASR, infiltration—whether liquid, solid, or lived solutions, requiring reapplication is very difficult to stop once it has be- vapor—is top priority. While keeping every five years or less. They also do gun. Other minerals, notably sulfates your garage perfectly dry is an impos- not bridge cracks, so they only limit and ettringite, migrate via penetrating sible task, through thoughtful product moisture and chloride penetration in moisture and can crystallize and lead selection, you can limit the degree intact concrete. Because cracking can to spalling, cracking, delamination, and to which moisture can penetrate the be an ongoing process, the ability to even loss of integrity of the concrete. parking deck. As such, there are a bridge new cracks as they form may Because parking structures are ex- variety of products on the market that be important in parking decks that posed to the elements inside and out, showcase the best protection chemis- already have evidence of concrete they are more susceptible than other try can currently achieve. distress. building types to deterioration due to moisture, temperature cycles, and Methacrylate and Epoxy Healer/Sealers The Options contaminants. Even the best designed As the name implies, these coatings and constructed garages need some Technological advances in the chemi- both repair cracks and seal pores, so help to survive this onslaught of cor- cal industry in the past 30 years have they can be used to restore a deck rosive forces. brought concrete sealers a long way that has already undergone some de-

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terioration. Like the penetrating seal- ers, low-viscosity methacrylates and epoxies fill the pores in concrete to create a barrier to liquid-water-driven chloride intrusion. They can also be injected or gravity-fed into cracks to structurally heal them. Where desir- able, the healer/sealers can also limit vapor transmission, although care must be taken not to lock moisture within the deck. With a moderate price tag, this class of surface treatments offers a good solution for parking structures that are starting to show some signs of distress, both to treat deterioration At right: Gravity-feeding an that has already occurred and to pre- epoxy healer/sealer into cracks vent continued water-related damage. on a concrete deck. Above: Test core showing ep- Where methacrylate and epoxy heal- oxy penetration to the bottom er/sealers fall short is in wet or soiled of a crack. fractures, to which the materials won’t adhere, and in moving cracks, which and provides skid resistance. Together, Super-Rigid Elasto-Epoxythane Traffic- are likely to re-fracture. On parking these yield an attractive, easy-to-clean Resisting Armor decks exposed to continuous sunlight, surface that can give a “face lift” to This surface treatment combines the epoxies can degrade quickly under UV older, crack-riddled parking decks. best of all of the above. Although radiation, so consider methacrylates abrasion defiant, it is flexible enough for these areas. For enclosed parking However, a traffic-bearing membrane’s to bridge moving cracks, locking structures or other areas where fumes assets are also its downsides. Flexible out all moisture and chlorides. It is might be a problem, offensive odors varieties offer superior crack-bridging, environmentally friendly, low odor, and from methacrylates might prove pro- even for moving cracks, but they don’t available in a wide variety of colors hibitive. Unlike the penetrating sealers, hold up well to abrasion because to match any decor. Unfortunately, it healer/sealers aren’t just coat-and-go; they are soft and yielding. More rigid also, as yet, does not exist. surface preparation necessitates shot varieties, designed to better withstand blasting, which means increased down abrasive forces of heavy traffic, are The Criteria time and cost. Also, pavement mark- too stiff to bridge these moving cracks. Until such time as the super-rigid ings must be reapplied. So while traffic-bearing membranes, elasto-epoxythane traffic-resisting ar- as a class of surface treatments, may Traffic-Bearing Membranes (Elastomeric) mor is developed, we will have to settle seem to have all the right stuff, no In parking structures with dynamic for the solution of selecting the best of one membrane, in practice, actually cracking, shrinkage, or more advanced the available surface treatments for the does. Before opting for one of these damage, a traffic-bearing membrane parking structure’s characteristics, con- very expensive coatings, consider, too, may be the only option to address dition, and situation. To that end, there that they require lengthy down-time the ongoing deterioration. Unlike the are a number of criteria we can use to (preparation and application takes sealers, these do not penetrate the determine which products would offer several days) and considerable ongo- concrete, but remain on the surface the best-performing option for the to create a barrier that locks out ing maintenance (re-coating, or at least cost, in terms of both initial investment moisture and chlorides. Most elasto- top-coating, every five to ten years) and long-term maintenance expense. meric membranes have two layers: a for the life of the garage. Once a base coat that provides the water- traffic-bearing membrane has been in- Deck Type. Over the years, many dif- proofing protection, and a top coat, stalled, it’s nearly impossible to return ferent types of parking decks have which protects the base membrane to an uncoated surface in the future. been developed. For the purpose of

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investigating surface treatment options, do not create a single, contiguous, concrete as the wearing surface are however, deck types can be simplified monolithic structure. Instead, the indi- preferred. into two basic categories: cast-in- vidual members meet at sealant joints. Concrete Quality. Knowing the qual- place and pre-cast concrete. Extending around each pre-cast unit, ity of the concrete offers insight into Cast-in-place decks. Usually composed these joints add up to miles of sealant the type of deterioration to which of a single, contiguous, reinforced slab that must be maintained and periodi- it would be most susceptible. This of concrete spanning a concrete or cally replaced. Even if cracking isn’t an is most often achieved by order- steel frame, cast-in-place decks are issue, water migration through failed ing a petrographic analysis of a test constructed onsite. Due to its nature, joints can be just as damaging. sample. A petrographic analysis is an concrete shrinks as it cures, which, Aside from routine sealant mainte- extraordinarily useful tool in determin- coupled with the external restraint nance, surface protection require- ing what is wrong with concrete or stress from the structure to predicting what will be wrong which it’s attached, can lead with concrete in the future. to crack formation. Cracks, This analysis can detect most as we’ve seen, are water- durability issues, such that borne chlorides’ direct route the most appropriate level of to reinforcing steel. Once protection can be selected. established, these cracks Chloride Content. Chlorides form natural expansion are detected by removing joints that open and close concrete samples from varying with changing temperature depths and analyzing them in and humidity. a laboratory. If chlorides are Consequently, protective moving through the concrete techniques tend to focus quickly, the deck protection on these moving cracks. If system must be aggressively cracks are few and the deck enhanced to stop further is chloride-free, then routing migration. If the chlorides and sealing cracks and apply- have reached the level of the ing a low-cost sealer may be reinforcement, chances are de- appropriate. If the deck is terioration has already begun. riddled with cracks that can’t Low-cost sealers are no lon- be adequately sealed, then Applying a low-cost sealer to a concrete deck can be a quick, effec- ger an option. Deck protec- elastomeric membranes begin tive, low-maintenance option. tion that retards water vapor to look like a good option. intrusion or effectively inhibits corrosion is now necessary. Pre-cast decks. Cast off-site under ments are typically minimal and controlled conditions, pre-cast decks Age and Deterioration. While there is usually can be addressed with simple are lifted and welded into place after nothing inherently wrong with old low-cost penetrating sealers. Heav- they have cured and, to some extent, concrete, the life of a deck does tend ily cracked decks may be routed and dried out. Because the concrete used to follow a natural progression. Un- sealed or treated with rigid epoxies or for this type of construction is typically less design or installation defects are healer/sealers, since these cracks are high-strength and more dense than at issue, a new deck can be effectively typically non-moving. However, the its cast-in-place counterpart, pre- treated with low-cost sealers that limit irregular surface of the pre-cast deck cast decks should rarely experience the intrusion of chlorides through the does not readily lend itself to flexible cracking. However, this manner of concrete. membrane-type coatings. The leading construction is favored for fast-track edge of each panel quickly becomes a Further in the life of the deck, a more projects, and the end result is rarely wear point, bumping against automo- positive barrier, such as a moder- defect-free. bile tires or catching the tip of a snow ately-priced epoxy sealer, may be Because they are factory-made and plow. Protection techniques that necessary to retard moisture entry. must be lifted into place, pre-cast units that soak into the deck and keep the (continued on page 6)

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When Coatings Go Bad

A coating applied successfully to an elevated deck may have disastrous effects in the same garage when applied to a slab-on-grade. Why? As water levels and humidity change, ground moisture seeps up into the concrete slab. Vapor barriers, often installed under slabs-on-grade, are designed to block this moisture from entering the slab, but, in reality, breaches in that barrier or cracks in the slab can still permit water en- try. If an impermeable coating is applied to the top surface of the deck, that moisture becomes trapped between two impenetrable surfaces. Unable to escape, the water sits in the slab, leading to chloride and freeze-thaw degradation. Even with no vapor barrier present, moisture in the ground rises within the slab and becomes trapped within the deck. Therefore, leaving the slab-on-grade uncoated is the best course of action. On an elevated deck, that permeability gradient is reversed. Moisture enters the deck from above and migrates through the slab to the underside, where it evaporates. Even with a waterproofing membrane protecting the top surface, the deck is still susceptible to water entering at cracks, joints, and failed coating sections. Coating the bottom of the deck with an impermeable coating invariably leads to trapped moisture and accelerated deterioration. For this reason, the underside of an elevated deck should be treated similarly to a slab-on-grade: leave it uncoated. One often-overlooked fact is that paint is also a coating. Many of the concrete paints on the market are epoxy-based and relatively impervi- ous to moisture. Even if a vapor-permeable paint is used, successive reapplications increase the coating thickness and so decrease its permeability. Over time, what was once a high-permeability surface can become surprisingly resistant to moisture migration. With the eventuality of peeling paint, spalls, rust, and cracks taken into account, a deck underside that’s been painted for appearances’ sake begins to lose its appeal, as compared with a simple, uncoated one that’s still intact. As the adage goes, location is everything. Knowing which surfaces in a parking structure can accept an impermeable coating and which are best left bare is critical to prolonging the life of your garage.

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(continued from page 4) warranties require that Aesthetics. While a simple sealer can snow removal equip- help prevent water infiltration, it won’t ment have rubber tips; change the parking deck’s appearance. others do not cover An elastomeric membrane, on the snow plow damage other hand, will change the look of the outright. The truth garage and provide a uniform, fresh- is, most snow plow looking surface that’s easily cleaned companies have never of dirt and stains. For a crack-riddled heard of rubber snow older garage, this can be a welcome plow tips, let alone change. In a newer garage, however, know where to buy the existing concrete surface probably one. Unless the garage looks fine as is. Using paint on a deck management oper- to improve its appearance can have ates their own snow problematic effects, as paint, too, is a removal equipment, type of coating. (See sidebar, “When Edges of pre-cast concrete units at sealant joints catch snowplow it’s a given that steel Coatings Go Bad,” page 5.) tips, quickly wearing away surface treatments. Here, coating patches were used as a temporary fix. will touch pavement at some point in the The Solution Unfortunately, this option is often life of the garage. The preferred protection techniques overlooked or skipped. Therefore, coatings at exposed decks stop deterioration before it begins. must be armored against such an Ultimately, if not properly protected, If a parking deck is well maintained onslaught. There are coating systems a deck may require a traffic-bearing from the start, with sealers applied tough enough to repel the steel tips membrane to provide the best de- early and cracks promptly addressed, and let sparks fly, but these super- fense. However, as these membranes then surface treatment choices can rigid coatings do not bridge cracks. are costly and require maintenance evolve over time as the garage ages The best solution, therefore, depends and periodic reapplication, waiting to and its needs change. If, on the other on finding the right compromise address signs of trouble until there hand, conditions are such that distress between rigidity and flexibility for a are no other options is not the best is advanced and progressing rapidly, specific situation. course of action. Remember, once more immediate and aggressive action a deck has begun to deteriorate, the Cost. While the saying, “you get what must be taken to slow deterioration coating can only retard further dete- you pay for,” can be applied just as and minimize its impact. rioration, not stop it. well to surface protection as it can Should you follow the trend and Exposure. Whatever the protection to anything else, in terms of quality apply that traffic-bearing membrane? system that is employed, it must with- materials selection and skilled ap- Look first at your parking deck type, stand the rigors of its environment. plication, it’s also true that lower-cost concrete age and quality, and level UV degradation may be a problem for systems are usually lower-mainte- of exposure to traffic and weather. some coatings on a top deck. Epoxies, nance alternatives. Don’t overspend. Don’t invest in a surface treatment in particular, have difficulties when ex- If an inexpensive sealer would suffice, until you’ve assessed your garage’s posed to direct sunlight. Soft, flexible installing a traffic-bearing membrane condition; through investigation, test- membranes may not withstand abra- because it’s the high-end option may ing, and evaluation, a qualified architect sion in high-traffic garages or on a typi- mean investing in a costly system that or engineer can help you navigate the cal turning radius and will fare poorly doesn’t perform any better in that array of available coating options. If against snow plows. A coating that situation—and may even perform that means shunning the coating-of- looks like new after many years in an worse. Plus, once the membrane is the-moment in favor of a low-cost, apartment garage may not withstand a in place, it must be maintained and, low-upkeep alternative, so be it. The year at an airport or shopping mall. eventually, replaced. More moderate- right parking structure protection ly priced treatments, such as pene- program should not only protect the Snow Removal. Do not underestimate trating sealers and epoxy healer/seal- deck today, but anticipate the main- the damage that can be inflicted by ers, will no longer be options. (See tenance needs of tomorrow. Now the average snow plow. Most coating sidebar, “Don’t Seal Your Fate,” page 8.) that’s a bandwagon to jump on.

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Parking Structure Rehabilitation Hoffmann Architects’ exclusive focus on the building exterior makes the firm uniquely suited to resolving distress, failure, and wear in parking structures. Beginning with a review of existing conditions, Hoffmann Architects’ design West*Park Garages in McLean, VA. University of Health Center team assesses the type and extent of Investigation of Four Garages. in Farmington, CT. Garage Assessment. deterioration. Based on the parking structure’s individual characteristics, Pfizer, Inc. Embassy Suites Hotel Nashville at the project architects and engineers New London, Connecticut Vanderbilt develop a plan to resolve water infiltra- Peapack, New Jersey Nashville, Tennessee tion and distress before more serious, Basking Ridge, New Jersey Garage Assessment and Repairs lasting damage can occur. The firm Garage Repairs then prepares detailed documents for Quinnipiac University competitive bidding. Contract admin- One Beacon Street Anthem Campus istration services see that the project Boston, Massachusetts North Haven, Connecticut reaches successful completion. Garage Survey and Slab Repairs Garage Evaluation Hoffmann Architects has developed Conversion of a Subgrade Movie Theatre into a Garage Legg-Mason Building parking garage rehabilitation and wa- Baltimore, Maryland terproofing solutions for a number of The George Washington University Building Envelope Survey, including Garage facilities, including: Ross Hall Washington, District of Columbia One Financial Plaza Foxwoods Resort Casino Garage Investigation and Repairs Hartford, Connecticut Great Cedar Garage and Garage Rehabilitation Grand Pequot Garage Seneca Niagara Hotel and Casino Mashantucket, Connecticut Niagara Falls, Elizabethtown Gas Condition Investigation and Repairs Garage Evaluation Union, New Jersey Garage Survey Chase Manhattan Centre Phoenix Life Insurance Company Wilmington, Delaware Hartford, Connecticut Town Center Garage Survey Garage and Plaza Investigation and West Hartford, Connecticut Repairs Garage Investigation and Repairs M & T Bank Headquarters Buffalo, New York American Center Cold Spring Harbor Laboratory Garage and Plaza Investigation and Vienna, Virginia Cold Spring Harbor, New York Repairs Garage Survey Garage Rehabilitation Hartford Square North The Crowne Plaza Times Square Archstone Murray Hill Hartford, Connecticut New York, New York New York, New York Garage Repairs Garage Investigation and Repairs Garage Investigation

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JOURNAL is a publication of Don’t Seal Your Fate Hoffmann Architects, Inc., specialists in Not all surface treatments are compatible. The parking deck protection you the rehabilitation of building exteriors. choose now may limit your options in the future, so consider both immedi- The firm’s work includes investigative and rehabilitative architecture and ate performance goals as well as long-range planning before committing to a engineering services for the analysis coating. Investigate, too, any applications that may already be in place. and resolution of problems within For example, if you are looking for a “quick fix” to get you through the winter, roofs, facades, glazing, and structural systems of existing buildings, plazas, a less-restrictive sealer that penetrates the slab—rather than one that coats terraces and parking garages. the surface—might be a good option, because a wide variety of surface treat- ments can be applied over it in the future. Epoxy healer/sealers can cover Please send news, technical information, such penetrants, and they provide a good base for membrane systems, should address changes or requests for free you choose to install one down the road. However, once you opt for a traf- subscriptions to Editor, Hoffmann Architects JOURNAL, 2321 Whitney fic-bearing membrane, you must stick with a traffic-bearing membrane, as Avenue, Hamden, CT 06518. there is no way to effectively remove it without severely damaging the slab. For information on the services To determine which coating types can generally cover an existing application, offered by Hoffmann Architects, Inc., as well as which options remain following a proposed treatment, check the contact our Marketing Coordinator at accompanying table. 800-239-6665 or:

2321 Whitney Avenue Hamden, CT 06518 Compatibility of Existing and Overlaid Garage Surface Treatments 203-239-6660

500 Fifth Avenue, Suite 830 Future Sealer New York, NY 10110

Migrating 212-789-9915

Corrosion Penetrating Epoxy Traffic-Bearing

• • Current Sealer Inhibitor Sealer Healer/Sealer Membrane• 1001 Connecticut Avenue NW, Suite 825 Migrating Corrosion Inhibitor Washington, DC 20036 • 202-530-1100 Penetrating Sealer •* • • Epoxy Healer Sealer • • For more information on the topics Traffic Bearing Membrane discussed in this article, visit us on the • web at www.hoffarch.com or contact * Compatibility of penetrating sealers should be taken into consideration us at [email protected].

Editor: Alison Hoffmann Production: Margaret Bailey

Hoffmann Architects, Inc. 2321 Whitney Avenue Hamden, CT 06518

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