Restoration of Parking Structures and Damage Prevention
Concrete Is Not Forever!
This article is intended to provide owners with some practical advice in maintaining and renovating concrete parking structures. Since its inception as a building material, great hope and confidence was placed in the durability of structural concrete. It can be said that many people believed "Concrete was Forever." Proof of this is found in ancient Rome, where "primitive concrete" structures still stand.
This belief most likely continued by observation of climate-controlled concrete buildings, which were protected from the harsh environments common to parking structures. This environment is characterized by temperature extremes, dynamic loads, moisture, freeze/thaw cycles and chemical attacks from chloride ions. Only with perpetual care, can concrete approach being "forever." The proper care and maintenance of structural concrete can make it an effective building material and substantially prolong the life of the forms we create.
In the best of all worlds, a parking structure is designed for durability. The concrete mix is appropriate for the environmental conditions. The mix is properly air entrained, has low water/concrete ratio, and is devoid of chloride ions.
A structure designed for durability promotes good drainage, has cover over reinforcing steel that meets or exceed current standards, is properly sealed, has sufficient expansion joints to accept movement caused by the forces which act upon the structure such as thermal, creep and shrinkage, freeze/thaw cycles, seismic and other dynamic stresses. Unfortunately, all parking structures do not possess these characteristics and therefore require more frequent and ongoing remedial action.
The goal is to commit to a program of maintenance and corrective action. Believing that concrete is truly not forever is the first reality associated with the understanding of concrete. This should lead to the logical conclusion that an ongoing commitment to care and maintenance is essential, and should translate into the performance of periodic and ongoing condition assessment. The second reality is that deferred concrete maintenance will result in much higher repair costs than ongoing and periodic repairs because of geometrical progression of deterioration. This translates into the need for adequate budgeting and setting aside funds for annual maintenance of parking structures. The third reality is the need to perform timely corrective and preventive action. This results in performing periodic repairs to maintain the integrity of the parking structure, which includes attention to the structural system, operational elements and aesthetic concerns.
Good concrete slab maintenance should include such items as repairs to expansion joints, routing and sealing of cracks and control joints to prevent water intrusion, periodic wash-downs to remove road salts, application of sealers or membranes to shed water and prevent chloride ion penetration, and other preventive maintenance practices. The frequency of these maintenance practices within parking structures varies by age and geographic location, the structural system, quality and type of design and construction materials, and other variables.
Goal of restoration
In spite of the best periodic maintenance efforts, parking structures deteriorate over time and require restoration to extend their useful life. Unlike enclosed climate controlled buildings, parking structures experience accelerated concrete deterioration due to their exposure to the harsh environmental conditions. It is not uncommon for some parking structures to require renovation with only 15 to 20 years of service, and experience repair costs that exceed $10 to $15 per square foot. This translates into capital expenditures, lost revenues, disruptions in the facility's operation and inconvenience to users.
The overall goal of the restoration process is to extend the life of the parking structure. The structural goal of the restoration effort should be to provide durable surfaces and waterproofing treatments to prevent further deterioration, reconstruct deteriorated floor slabs, and focus on repairs to the structural system of the parking structure to maintain safety. The aesthetic goal of the restoration effort should be to provide an eye-pleasing environment by painting and providing graphics and to promote a secure feeling with proper illumination. And, the restoration effort should be approached with the goal to help reduce future repair.
Approach to restoration
Since repairs can be targeted for the short- or long-term and have significantly different costs for each approach, an informed decision should be based on a cost/benefit analysis coupled with the future plans for the parking structure. The best approach to a thorough and cost-effective restoration effort should begin with a realistic and accurate evaluation of the parking structure's condition, and a clear vision of the term the repairs are intended to last. This is best accomplished through a combination of concrete testing and visual observations by an experienced structural engineer specializing in parking structures.
For those who envisioned that "Concrete is Forever," hundreds of examples of this flawed thinking exist. Realists understand that "Concrete is not Forever." It is simply another one of man's building materials. Not unlike other materials, it requires its own type of care and occasionally needs to be renewed. With proper care and maintenance, concrete will continue to serve as an economical construction medium to express our functional and creative desires.
James J. Kopencey is a senior parking consultant with DESMAN Associates who has over 24 years of experience in the parking industry. Robert D. Tober, P.E. is a Senior Associate and head of the Midwest Restoration Division for DESMAN Associates who has over 20 years of experience in the restoration of facilities. They can be reached at RestorationServices@desman.com