Following this process gives you control of cost and quality

Advocate Condell Medical Center in Libertyville, Ill., features architectural precast concrete.

Since it’s liquid before it’s cured, concrete can assume almost any shape defined by a form. In architectural precast construction, with myriad combinations of details, colors, textures, and finishes, the options are virtually limitless. But how can you extract the most value for the dollars and time you’re spending, while achieving your design objectives?

If a project you’re looking at might be a candidate for architectural precast, here are six steps to keep in mind. These steps act as a funnel, bringing you closer to your finished project as you move through them.

1. Specify PCI

PCI-member precasters undergo two rigorous, unannounced inspections annually. More than 120 areas are inspected by an independent auditing firm hired by PCI. PCI Certification meets IBC requirements, and eliminates need for special inspections.

A1 Certification ensures that bidders have an ongoing quality system (PCI MNL 117) and a history of quality assurance. To help assure high quality, specify PCI Plant Certification – Group CA – Commercial Products with an Architectural Finish. Most PCI precast producers offer guide specifications.

2. Select from samples

Samples are the first indicator of key architectural precast characteristics. Typically 12” x 12” x 1-1/2” in size, samples are a reference for all parties and are helpful in large projects with multiple approving entities with little precast concrete experience. Samples help identify potential issues prior to bid. Use them as an indication of color, recognizing that there may be variation in production. Samples are not for physical testing. You may request range samples to get an idea of color variation. Include your sample requirements in your specification.

3. Set a budget

Once you know what you can get for your money it’s relatively easy to set a budget. For example, if you need two colors in your architectural precast panels, you don’t necessarily need two separate concrete mixes. One mix design can be finished in different ways to create exciting contrasts and accents. Here are seven possible features of the precast concrete itself that you can work with your precast producer to adjust and achieve the expression you need and can afford:

4. Repetition is good

Good detailing is essential to an architectural precast producer’s ability to manufacture quality elements cost effectively. Repeating that good detailing from piece to piece is what makes even complex features affordable, by spreading out form-building costs. Another opportunity to control cost is to use the master mold concept, in which similar pieces are poured in the forms that accommodate a wide variety of piece sizes and shapes, and are adjusted for variations in size, window placement, and detailing form pour to pour.

Wood forms are frequently used because they are cost-effective and, properly maintained, can be used for up to 40 pours. Steel forms, while higher in initial cost, may be a more economical solution in projects with highly repetitive shapes, since the form surface is better able to retain its smoothness with minimal maintenance or repair. Steel forms can also be made adjustable to account for slight variations in shape. Other form materials may be recommended by the precast producer depending on the requirements of the job.

5. In panelizing, bigger is usually better

Your precast producer will often look for opportunities to increase panel size. This helps to economize shipping and erection, where up to 25 percent of architectural precast project costs are concentrated. Larger panels also mean less handling per square foot, which in turn reduces the opportunity for pieces to be damaged.

Here’s a sample chart that shows costs per square foot of architectural precast based on piece size and other factors:

Your precast producer will help you consider site constraints, including crane access, ensure that the proposed crane size will accommodate largest precast pieces where they are located on the building, and ensure that the elements can be delivered economically.

6. Compare mock-ups and production pieces

Precast concrete is made of stone and sand, natural materials with inherent variation that may vary from the sample. Concrete mass, differences in curing, and production practices also play a role.

Mock ups exhibit purposeful variation to target the degree of variation that you will accept, and allow you to review mixes, finishes, transitions, and architectural details. PCI’s standard viewing distance for mock ups is 20 feet, to obtain the most realistic impression of how most users will experience the building. Up to three mock ups may be required to determine an acceptable color range. Designers may also ask to damage a mock up and have it repaired, so they know what to expect if a repair is required on a production piece on the job site.

In the colder regions of the United States, the deteriorating effects of winter weather and maintenance can easily be seen in parking garages. Despite the inherent durability designed into these parking garage structures, deicing chemicals, plow activity, and freeze-thaw cycles all take their toll by corroding reinforcing steel and hardware, causing abrasion and impact damage to structural elements, and accelerating the deterioration of existing cracks and delaminations in the concrete. In addition, snow, ice, and rain residue carried by vehicle and pedestrian traffic hasten accumulation of dirt and debris.

Fortunately, these ill effects can be controlled with planned annual preventive maintenance. And springtime, which we hope is just around the corner, is the perfect time to initiate this type of program.

This spring, clean and inspect your parking garage.

As soon as temperatures are consistently above freezing, the exposed driving and walking surfaces should be power washed. Frequently, these surfaces have a textured, non-slip finish that can trap debris and deiciers. Over time, these harsh chemicals can penetrate deep into the concrete, where they can react with the reinforcing steel causing it to corrode. Power washing these surfaces will remove this harmful build-up before it has a chance to cause corrosion-related problems such as staining, cracking, spalling, and possibly eventual failure of the concrete.

Once the parking garage has been power washed, it is a good time to conduct an inspection of the waterproofing and structural elements. Inspections help identify damage caused by improper winter maintenance practices, wear and tear on critical parts of the structure, and any need for general or specific maintenance.

We typically recommend completing a formal assessment with formal reporting of findings, recommendations, and estimated costs about every five years, and informal inspections and review every year in between. This can vary based on the condition, age, and usage of the parking structure.

The annual inspection should include a leak survey, particularly below the roof level. Incidental damage caused by wear, ultraviolet light, and winter maintenance can manifest itself in localized leaking conditions. Leaking joints can cause damage to connections and surrounding concrete, and also create hazardous conditions. The best time for a leak survey is during or immediately after a rain event.

What if you find a problem?

All parking structures require some level of service life repairs and replacement maintenance. The good news is, you can plan for it.

Your formal inspection can be used to develop and/or validate a preventive maintenance and repair plan. A proactive maintenance program helps ensure that issues remain small, and that your parking garage stays open for business. Budget and schedule work to be performed on an annual basis to minimize disruptions.

With the exception of accidental damage, unexpected repairs and maintenance can and should be avoided.

If you would like more detailed information about any of these topics, or would like help developing or reviewing your maintenance program, give us a call anytime at
717-682-1414, or email fgenoese@high.net.

Franc Genoese is Senior Director of StructureCare, a service and consulting resource focused on developing and implementing preventive maintenance programs for garages of all construction types. StructureCare is an affiliate of High Concrete Group LLC.

Where do building models go when designers hand them off? In precast concrete projects, the basic information can be imported into new models that specialize in engineering functions. Tekla Structures is the leading software program for precast, melding engineering and drafting functions into one seamless process.

Tekla Structures, from Tekla of Finland, was initially developed in cooperation with a first-ever Precast Software Consortium whose aim was to find a software solution to take time and cost out of the process of developing drawings. Since the consortium effort, individual precast producers have further developed the software to further streamline and customize the software, with the ultimate aim of helping designers realize their visions.

The Millennium Science Complex, The Pennsylvania State University, State College, Pa. Designed by Rafael Vinoly, the architectural precast project was modeled in Tekla.

Design team benefits

Tekla Structures requires extensive prework by precast producers. The advance preparation yields important benefits for designers. First, the software provides a robust tool for better understanding of design options. Tekla 3D models can be used to conceptualize the project up front, helping owners and other project team members make design decisions faster. Models can be imported and exported, and provide a basis for design feedback that supports interdisciplinary coordination with better sharing of data among team members. As the project progresses, information becomes increasingly accurate so that the design and associated costs are more fully understood earlier in the process, and the risk of rework is dramatically reduced.

How it works

The key to successful precast design execution in Tekla is to impose a high level of discipline. Engineers and drafters follow a clearly defined set of rules that govern each piece, connection, and finish. Everything starts with a template model, powered by a huge visual basic data library that stores an extensive range of conditions, precast pieces and geometries, connections, and hardware – everything that goes into the building project. The program is set up so that, if an incorrect piece class or part is chosen, the final report will not produce the needed piece.

The stages to building a Tekla model reflect increasing discipline as work progresses.

Stage 1. Building/connecting—numbering the pieces. In this stage incorrect pieces can be deleted and others added.
Stage 2. Produce an erection drawing—piece numbers are locked in. Measurements are precise; deleting pieces is
more difficult.
Stage 3. Piece drawings—drawings are rendered. Changes are far more difficult; deleting links can make a model harder to work with.

Precast concrete offers design freedom through virtually limitless aesthetic options, from finishes through shapes and performance features, all of which are completely customizable. Tekla takes these advantages further, allowing designers and engineers to work together to fully interpret plans, foresee difficulties, and collaborate on ways to execute. A properly executed Tekla project overcomes the limitations of 2D software, speeding information flow, facilitating the checking process, smoothing previously contentious processes, and reducing the lead time for components.

Using Tekla, precast concrete producers can place the complex geometries of today’s leading designs within practical and economical reach. View more Tekla examples.

Tanya Kalaba is a design engineer with High Concrete Group LLC in Denver, Pa.  She holds a B.S. in Mechanical Engineering from the University of Sarajevo,  Sarajevo,  Bosnia. Kalaba is instrumental in advancing High Concrete Group’s building information modeling efforts.