Precast Housing Structures

Precast Housing Structures
Hi, my name is ____________. Welcome to PCI’s Precast Housing Structures Box Lunch!

This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation. “Precast/Prestressed Concrete Institute” (PCI) is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members are available on request.

Learning Objectives After viewing this program, you will be able to:
Identify the different precast/prestressed concrete systems used in housing Explain the benefits of using precast/prestressed concrete in housing structures Discuss the design considerations for precast/prestressed concrete housing structures

Agenda Housing Design Challenges
Benefits of Precast/Prestressed Concrete Precast Housing Applications Early Precaster Involvement Precast Housing Design Considerations Precast Housing “Design Project” PCI Resources Questions/Discussion We’ll discuss the benefits of precast and prestressed concrete for housing projects and take a look at several example applications. Then together we’ll undertake the Precast “Design Challenge” to apply what we’ve learned to a real-life housing project. You’ll have an opportunity for questions at the end.

Housing Design Challenges
General challenges for all housing? Specific challenges? Single-Family Multi-Family Student Housing Condominiums Hotels/Motels Retirement Housing Assisted Living Before we talk about precast or prestressed concrete, let’s review the design challenges of housing and residential buildings. What are some general design challenges for all housing? What are some specific design challenges for the each type of housing? [The presenter should ask class participants to help identify housing design challenges. Most common challenges will be provided on next slide.]

Housing Design Challenges
Create attractive appearance for both tenants and neighborhood Eliminate noise or vibration between floors or rooms Minimize floor-to-floor heights to meet zoning codes and maximize the number of levels Withstand damage from fire, users, moisture, severe weather, vermin, earthquakes Minimize energy use Fit in with campus architectural style (student dorms) Create open spaces on lower floors for gathering areas, dining room, etc. Create secure balconies Construct the building quickly to speed occupancy or shorten loan periods Provide high quality, low-maintenance facade Housing structures present a variety of design challenges: Create attractive appearance for both tenants and neighborhood Eliminate noise or vibration between floors or adjacent rooms Minimize floor-to-floor heights to meet zoning codes and maximize the number of levels Provide durability to withstand damage from fire, users, moisture, severe weather, vermin, earthquakes, etc. Minimize energy use Fit in with campus architectural style (student dorms) Create open spaces on lower floors for gathering areas, dining room, etc. Create secure balconies Construct the building quickly to speed occupancy or shorten loan periods Provide a high-quality, low-maintenance façade Let’s see how precast or prestressed concrete can meet these challenges…

Benefits of Precast Design Flexibility Controlled Production
PCI-Certified Quality Safety & Security Sustainability Layout Flexibility Low Maintenance Acoustical Control Mold Resistance Controlled Environments Expansion Capabilities Economy

Design Flexibility Your choice of color Simulated textures
MNL-116 tolerances [Image information: Precast single family home, Chicago, IL] Architectural precast panels offer tremendous flexibility for housing design. Form liners, molds, and other treatments can be used to create aesthetically pleasing exterior surfaces without additional finishing materials. The designer can add pigment to the concrete and provide several tones within one panel by using various surface finishes. These capabilities give designers more versatility in designing panels while minimizing the number of components. No other exterior cladding material offers these customization properties. For manufacturing procedures and testing requirements, quality-control recommendations, and dimensional tolerances for types of units required, comply with PCI MNL 117, ‘Manual for Quality Control for Plants and Production of Architectural Precast Concrete Products.”

Design Flexibility Exterior finish materials Stucco Paint
Ceramic tiles Brick veneer Stone veneer Terra cotta Precast also takes all common exterior finish products: stucco, paint, ceramic tiles, brick veneer, stone veneer, and terra cotta. The clay products are thinner than their standard counterparts so that they may be embedded directly into the panel at the precast plant. The brick-faced precast units shown here can be erected quickly as one large panel, at any time of the year. This application has become more popular across the country due to escalating costs for field labor and the scarcity of skilled craftsmen. Also, not having to store brick or other materials on site reduces the risk of vandalism and theft.

Controlled Production
Casting components under factory-controlled conditions benefits a project in many ways: More control over final appearance Tighter tolerances Precaster as team member Elimination of several trades and materials Production regardless of weather conditions The designer can exert more control over the final appearance of the structures using precast because they can view finish and range samples as well as mockup panels prior to full scale production Plant production’s high standards of quality control result in tighter tolerances that ensure a smoother, faster fit during erection. The PCI certification process, which we’ll discuss next, further ensures consistently high quality and true compliance with the design integrity established by the professionals. As the single source for so many architectural and structural components, and the source for brickwork, natural stone, or other finishes, the precaster works closely with the construction team to ensure satisfaction with the design and alleviates any on-site challenges that might arise. When using precast panels, several trades and materials are eliminated from the construction process, resulting in savings. And finally, precast can be produced indoors regardless of weather conditions.

PCI-Certified Quality
Independent auditors… test raw materials inspect finished products inspect internal QA/QC reports Raw materials testing Since 1967, PCI’s Plant Certification program has ensured that each plant has developed and documented an in-depth, in-house quality system based on time-tested national industry standards. Every member of the Precast/Prestressed Concrete Institute who produces these products must undergo two unannounced, two-day inspections each year by outside quality-control auditors. The certification process is very specific to the products being produced at each individual plant. Each type of product a PCI-certified plant creates must undergo its own inspection, since each requires different methods for casting. Also, required inspections of the plant’s internal QA/QC reports provide a documented history of each project piece. Product inspection

The advantages of PCI certification include: Prequalified bidders Expanded design options Lower costs Faster erection Reliability No added cost Owners, architects, engineers and contractors all benefit from precast concrete plants that have been certified by PCI. Prequalified bidders: There are no surprises during the construction process when quality has been included in the specification process. Expanded design options: Certified plants can quickly be identified that can produce any special needs or unusual designs. Lower costs: Doing the job right the first time reduces material and labor costs. Certification also helps produce uniform, consistent products that eliminate waste due to differences in colors or texture and minimizes the approval process for mockups. Faster erection: Quality products mean more efficient production, a systematic staging schedule and tighter tolerances. Reliability: Established producers, many of which have been in business more than 25 years, can be counted on to produce a product consistent with the design specifications. No added cost: There is no cost to the owner or specifier for using a certified plant. The auditing fees are paid by the producer as a cost of doing business.

Many organizations and government agencies either mandate or recommend PCI plant certification: AIA Masterspec Federal Aviation Administration Bureau of Reclamation, U.S. Dept. of the Interior Federal Bureau of Prisons Federal Highway Administration U.S. Army Corps of Engineers U.S. Veteran Affairs U.S. Department of the Navy General Services Administration 30+ State Departments of Transportation The American Institute of Architect’s Masterspec Program also requires PCI plant certification. Your AIA Masterspec can assist you further with specifications for both architectural and structural precast.

Safety and Security A precast structure can increase the safety and security of its occupants: Fire Resistance Earthquake Resistance Vermin Resistance Blast/Wind Resistance Precast’s durability and strength provide a number of safety and security benefits for housing structures.

Safety & Security: Fire Resistance
Precast concrete offers superior fire resistance Fire resistance is important in all housing, but especially in retirement and assisted-living centers, where ambulatory concerns make fire resistance a top priority. As the population ages, these two types of housing are experiencing significant growth. Precast concrete’s inherently noncombustible composition gives it fire-resistant qualities that no other building material can match. Senior housing and assisted living

Fire Safety: A Balanced Design Containment Detection Suppression Education Good fire safety in a housing structure requires a balanced design: Containment, Detection, Suppression and Education. All four components are critical to ensuring the best protection possible, and no one element makes another redundant. Precast concrete’s superior fire-resistance makes it especially useful for satisfying the containment portion of this balanced design. [optional notes for the other parts if time allows] Detection involves placing sensors and monitors, especially smoke detectors or built-in warning systems, where appropriate during the design stage. These devices ensure the danger is recognized as soon as possible. They work with the compartmentalized design to alert residents and fire fighters to the danger and contain the fire and smoke so residents can vacate the premises and fire fighters can put out the contained blaze efficiently. Suppression includes the use of sprinkler systems, fire extinguishers, fire hoses and other properly located equipment designed to actively fight the blaze. These must work in conjunction with the other three elements of the balanced design, as any one element could be incapacitated by the fire. Education also is a vital tool that many overlook, and it is one that designers can help reinforce. Residents and visitors both need reminders and maps to ensure they know what to do in an emergency and can locate the exits quickly.

Precast structures can… provide up to a 4-hour fire rating reduce costs of meeting fire-rating requirements reduce extent of fire damage and cost of repair Containment focuses on isolating the fire inside a contained compartment. The ideal approach is to use prestressed concrete hollowcore slabs and precast beams, columns and walls. If a fire breaks out, precast’s inherent non-combustible composition ensures the flames are contained. It also provides significant durability to withstand degradation from heat that can weaken structural supports and cause upper levels to collapse. Precast’s natural ability to resist fire reduces costs in meeting fire-rating requirements. For instance, 8-inch hollowcore plank provides a 2-hour rating. A 4-hour rating can be achieved by adding a cast-in-place topping. Similar ratings also can be achieved for wall panels. Combining hollowcore and precast panels creates a durable, fire-resistant structure that is unbeatable in design and saves money long-term.

Insurance Cost Comparison* Insurers have noticed the fire-resisting advantages precast concrete offers these structures. A recent study at the University of Michigan found that the added cost of building with concrete and masonry was offset quickly by significantly reduced insurance costs. These expenses grow over time as annual premiums mount. Wood Frame Concrete & Masonry Construction Cost Annual Insurance Cost Insurance Cost Per Unit $960,000 13,210 550 $1,033,000 1,429 59 Building cost difference: $43,000 Annual insurance cost difference: $11,781 The table shows typical ISO simplified fire class rates effective These rates are 80% coinsurance and are per $100 of insurance per year. The rates assume concrete block bearing walls, hollowcore plank floors and roof with a fire resistive rating of not less than one hour. *University of Michigan study

Safety & Security: Earthquake Resistance
When building in a seismic zone you can take advantage of precast’s… panelized systems new connection techniques Precast concrete panelized systems can meet the requirements for any seismic zone. Also, new connection techniques that help re-right buildings after a seismic event can ensure that buildings aren’t permanently or structurally damaged by an earthquake, allowing them to reopen quickly.

Safety & Security: Earthquake Resistance
PRESSS Research Project At 420 feet tall, the Paramount in San Francisco holds the title as the tallest precast concrete building in a high-seismic zone. The 39-story mixed-use project offers 486 apartments in 547,000 square feet plus an 8-story, 113,000-square-foot, 350-car parking structure. The Paramount, San Francisco, CA

Safety & Security: Vermin Resistance
Precast is resistant to vermin such as: Termites, carpenter ants and similar insects Rodents Because it is a dense, inorganic and inedible material, precast is resistant to termites, carpenter ants, rodents, and other nuisance animals that frequently damage or infiltrate wood-frame structures.

Safety & Security: Blast/Wind Resistance
Precast is resistant to: Blasts/explosions Wind and wind projectiles The dense mass of precast concrete components and its panelized design helps meet federal requirements for blast-resistant structures. Precast concrete also can be used to create planters and other street level barricades prescribed by government regulations. This density also makes precast concrete extremely resistant to strong winds and wind projectiles as we’ll see in the following series of slides.

Sustainability Precast concrete is a sustainable material:
Minimizes energy use Decreases site disturbance Uses local, recycled materials Can be recycled Requires low maintenance, fewer chemicals Improves indoor air quality Helps meet LEEDTM certification (up to 27 pts.) Precast concrete is an ideal material for sustainable building practices. For example, an integrally insulated panel provides high energy efficiency. Also, precast’s high thermal mass inherently minimizes energy consumption naturally. Precast construction methods allow for decreased site disturbance. Concrete typically is produced locally, generates no job waste, and uses recycled materials such as aggregate and fly ash to reduce the amount of cement used. It also can be recycled later (for example, as aggregate for road base). Precast concrete components offer high durability, which means fewer chemicals are needed to keep it clean and maintained. Precast concrete can also increase indoor air quality: it doesn’t outgas toxic chemicals and, when designed with unfinished surfaces, can reduce need for paint or other surface applications that do outgas; it reduces airborne contaminants because it is not fabricated or cut on site; and it is not susceptible to mold growth because it is not damaged by moisture. Finally, precast’s “green building” properties can help achieve LEED certification.

Sustainability Creating insulated wall panels
Here you can see precasters creating insulated wall panels. The panels consist of a layer of precast that is poured into the form, after which the insulation is placed and another layer of concrete is added. Creating insulated wall panels

Layout Flexibility Precast concrete components provide layout and structural flexibility: Long spans permitted by hollowcore and hybrid precast flooring systems Load-bearing capacities of wall panel systems Space-saving thin cross-sections Precast hollow-core slabs and double tees provide long, clear spans, opening interior spaces in projects from office buildings to parking structures to designers to maximize functional layouts. Also, hybrid precast flooring systems such as double wall or carbon cast flooring can be used. Load-bearing precast wall panels can reach heights of 55 feet, while double tees can span 80 feet or more. Precast concrete insulated sandwich wall panels provide a thin cross-section that maximizes interior floor space while minimizing the footprint. A typical precast panel can be 8 inches thick (3-inch exterior wythe, 2-inch insulation layer, 3-inch interior wythe). Saving space over other construction materials throughout the building cuts material cost, speeds construction and produces a more energy-efficient building.

Low Maintenance Precast concrete requires very little maintenance:
Caulking every 15 to 20 years Fewer joints — less moisture penetration Precast concrete panels require caulking only every 15 to 20 years to maintain their reliability. This makes precast easier to maintain than other façade materials. The panels’ fewer locations for moisture penetration prevents unsightly stains or damage to interiors. Joints can be inspected quickly to find any locations that need attention. Precasters work with designers and owners to ensure building management understands the new maintenance needs required to keep the building looking new for decades.

Acoustical Control Precast concrete offers:
Acoustical control (STC ratings of up to 50) “Solid feel” with less vibration Precast concrete’s mass and insulation create strong acoustical performance, producing a quieter, less disruptive environment, particularly in taller structures that use hollowcore slabs for flooring. Its mass and damping properties also reduce vibrations for buildings where that is desirable, including housing, schools and hospitals.

Mold Resistance Precast resists mold growth Inorganic material
Fewer joints — less moisture penetration Because concrete is an inorganic material, it will not aid the growth of mold spores. Typical panel layouts provide fewer locations where moisture can penetrate, and these joints can be inspected and repaired quickly and easily if necessary. In addition, precasters work with designers to create a system of water control to ensure rainwater is directed away from the building in an efficient manner to alleviate any residual moisture that could penetrate the building or allow mold to gain a foothold. Also, precast can be erected more quickly than other construction methods, allowing for faster enclosure of the structure itself and minimizing exposure to wet weather.

Controlled Environments
Precast is especially suited for structures that require extreme cleanliness because it: Resists mildew and bacteria Withstands harsh chemicals Provides air tightness Precast concrete designs can be provided for buildings with functions that require extreme cleanliness, particularly food-preparation, processing and delivery areas or laboratory research areas. The durability of precast panels ensures they can resist mildew and bacteria while withstanding regular cleaning by harsh chemicals. Freezer compartments that often are required in food-processing plants can be created with precast panels, providing the tight insulation required while also supplying the separation from surrounding surfaces that can induce humidity or ground water to freeze and disrupt the structure.

Expansion Capabilities
Precast allows for expansion: Adding new adjoining space Merging a new space with existing structure Adding second levels onto existing roof Precast systems can provide the option for expanding a building in the future when needs grow or change. This can be accomplished by either adding new adjoining space or merging the new space with the existing structure. In some cases, an existing facility clad with precast panels can be expanding by disconnecting the nonload-bearing panels on the end wall from the framing and adding panels and framing on each side. With the new structure in place, the end panels, in many cases can be replaced. Precast designs also can provide the structural support so a second level can be added onto the existing roof if later desired, expanding the structure without eliminating any green space. These design considerations should be accounted for in the original design of the facility. Because the panels are produced under factory-contolled conditions, the textures and designs of the new addition can reflect the original aesthetic look created for the existing structure. The result is an addition that offers a similar look to the original precast design.

Economy Precast concrete is economical: Initial costs Life-cycle costs
Lower contractor costs Shorter financing periods Lower material costs Life-cycle costs Lower energy use Smaller HVAC equipment Lower insurance costs Precast’s speed of construction can eliminate months from a construction schedule, resulting in less time to carry financial bonds, lower contractor costs and risk, elimination of expenses for other trades and reduced subcontractor costs by giving more responsibility to a single-source supplier. Total precast concrete systems save money combining both architectural and structural components into one piece. A smaller amount of footing is required due to the thin cross-section of a precast wall compared to a masonry design (8 inches versus 16 inches). This also reduces the overall weight of the structure cutting the size of flooring packages by as much as 25 percent over the cost of a brick/block/steel construction. The actual savings will vary with project based on its specific needs, logistics, location and budget. By working with the precaster early in the design phase, the full benefits that can be achieved with precast concrete can be included in the design. Efficiencies in component size, connections, delivery and erection can be factored into the design, maximizing the benefits offered by precast concrete. Compared to other materials, precast provides superior life-cycle costs because of its durability and energy efficiency. Studies have shown that most of the additional costs can be directly offset by reducing the monthly payments for insurance, power, and smaller HVAC equipment.

Economy Keys to economical use of precast: Repetition in fabrication
Efficient delivery Efficient installation The more repetition you can achieve, the more you can save. Forms typically are made of wood and are expensive. Minimize the number of molds and maximize the number of castings from each mold. Precast components can be very large, so it’s important to make sure they are efficiently delivered and staged on site. Finally, you must have close access for ease of erection. Avoid circumstances that require double handling in and under installation.

Precast Housing Applications
Hotels/Motels Single-Family Multi-Family Retirement Housing Assisted Living Student Housing [Image Locations: The single family home is from Atlanta, GA. The Hampton Inn is from Columbia, SC] Next we’ll discuss the different housing applications for precast or prestressed concrete. But first… What are some common design challenges for all housing? What are some specific design challenges for the each type of housing? [The presenter should ask class participants to help identify the special design challenges of housing and residential buildings. See below for model answers.] Model answers: Common design challenges for all housing: attractive appearance low maintenance fire resistance low energy use acoustic control moisture resistance quick occupancy. Multi-family buildings, condos, and hotel buildings present additional challenges: eliminating noise between floors or adjacent rooms creating secure balconies minimizing floor-to-floor heights to meet zoning codes and maximize the number of levels withstand damage from users fit in with campus architectural style (Student dorms) open spaces on lower floors for gathering areas, dining room, etc. (dorms or assisted living)

Precast Housing Applications: Hotels
Hotels and motels made of precast or prestressed concrete can meet the needs of both the owners and customers. Attractive appearance Fire resistance Moisture resistance Acoustic control Durability Long clear spans Structural support Quick construction Image location: Wind Watch Marriott Hotel, Long Island, NY Recap of specific design challenges for hotels and motels… Minimize floor-to-floor heights to increase the number of levels, even under strict zoning requirements. Reduce noise between rooms Minimize impact noise and vibration between floors Provide structural support for many small rooms above open, column-free ballrooms and conference areas Create high fire resistance Use durable materials that won’t show dents and other misuse Offer low moisture penetration around facilities such as pools Speed construction to provide faster return on investment and meet reservation commitments

Precast Housing Applications: Hotels
Hilton Garden Inn Precast or prestressed concrete offers many different design options for hotels, and precasters are both willing and able to work with the specific branding of each hotel company. Comfort Suites

Precast Housing Applications: Single Family
For single-family homes, precast/prestressed concrete benefits designers, builders and owners: Design flexibility allows the home to match the flavor of an existing neighborhood Fire resistance Long spans eliminate supporting beams and open up spaces All-weather installation ensures schedules can be met Monolithic production that eliminates entry points for moisture in foundations and facades [Image location: Precast single family home, Chicago] Chicago developer Affordable Concepts has been extremely successful with this design for an all-precast concrete home. Created by Piekarz & Associates, it uses vertically-oriented soundwall panels in a horizontal format to create a brick-like single-family design. The structure can be enclosed in less than a day. The homes are created with 18 precast concrete panels measuring 20 feet wide and 10 feet tall. Although not as large as typical architectural precast panels, they are secured by the same bolted connections. The resulting precast concrete façade requires little maintenance, while providing a weather-tight envelope that resists moisture penetration better than real brick. The homes are more resistant to wind and insect damage and the exterior is more durable than vinyl siding, adding structural stability, acoustic control and protection from damage and abuse.

Hollowcore plank offers a strong option as a single-family floor, especially on the first floor, where it can eliminate basement columns and free up the space for more flexible living options. Precast hollowcore plank at first floor

This design works especially well with homes on a sloping grade, where precast plank can open up the lower floor into a more spacious and accommodating floor plan. Finished residence with precast plank at first floor

Precast Housing Applications: Multi-family
Precast or prestressed concrete multi-family housing structures can satisfy needs of both designers and tenants. Attractive exteriors that fit into surrounding neighborhood Durability Easy maintenance Acoustic control Minimize floor-to-floor heights and maximize number of levels Fire resistance Secure balconies Quick construction Precast or prestressed concrete can meet the specific design challenges of multi-family buildings: Attractive appearance that appeals to tenants and fits into surrounding neighbor hood eliminating noise between floors or adjacent rooms creating secure balconies Shallow cross-section, which reduces material costs and helps meet building height requirements in some zoning areas. withstand damage from users As you can see in this example, it’s easy to use hollowcore plank to create balconies that add living space and outside views. Breakers Condos

3-Family Partnership Homes

The Chicago single-family concept we saw earlier now has been expanded beyond detached homes to include a series of two-family townhomes with 32 living units. The homes replicate the original design except they share a common demising wall that offers a four-hour fire rating. Note that every other home features a set-back as well as a flat or gabled roof, adding distinction and setting each apart from its neighbor. Precast concrete two-family housing

Precast Housing Applications: Retirement
Retirement facilities present many of the same design challenges as multi-family housing—challenges that are easily met by precast or prestressed concrete. Attractive exteriors that fit into surrounding neighborhood Fire resistance Low maintenance Acoustic control, and Quick construction to provide faster occupancy Orchard Park Senior Housing

Precast Housing Applications: Assisted Living
As our population ages, more retirees are looking for a comfortable housing situation that meets all their needs. In some cases, these options allow additional medical services to be provided in another portion of the building within the same facility. Precast/prestressed concrete offers key advantages in these facilities, including: Fire resistance Acoustic control, and Economic construction that helps contain long-term financial costs for residents Prospect Heights

Precast Housing Applications: Student Housing
Transitory students can be rambunctious, but they also require privacy for studying. Precast/prestressed concrete structures offer key benefits: Durability Acoustic control Fast erection, which can ensure facilities are ready when students arrive Design flexibility, allowing the residence to blend with existing campus structures of any type The new 148-student residence hall at Curry College in Milton, Mass., shows how precast or prestressed concrete components not only can meet the functional needs of a school’s building program but its aesthetic needs as well. Architects at Whitney Atwood Norcross Inc. in Boston, specified hollowcore plank due to its durability, speed of construction and economics. The project was a fast-track job that needed to fit into the existing campus. Using masonry walls and load-bearing plank cut construction time by about two months, reducing it to seven months. Curry College

A new residence hall built at Renssalear Polytechnic Institute in Troy, N.Y., depends strongly on its hollowcore floor and roof slabs and its masonry exterior. The use of these materials in the Gregory J. Seleman-designed building provides fire safety and durability, two of the most important factors in such construction. Renssalear Polytechnic Hall

This new residence hall at Cornell University in Ithaca, N.Y., was designed by The Hillier Group of Princeton, N.J., and uses concrete plank and masonry bearing walls for several reasons, including cost-efficiency and a more rapid speed of construction over steel framing. The innovative design approach to this structure, with its articulated entrances and balconies, more closely resembles an upscale residential complex than the generally-accepted notion of a college dorm. Residence Hall: Ithica College

Precast Housing Applications: Modular Housing
Precast modules offer great opportunities for adding onto existing buildings or for creating projects with fast-track solutions in college dormitories, hotels and other housing structures. Precast concrete modular hotel room

Precast Housing Applications: Modular Housing
The modules can be delivered with some attached furnishings, such as bathroom fixtures, already in place. Furnishings can be added quickly to create a durable, fire-resistant, acoustically controlled room. By installing fixtures and other accessories prior to delivery, job-site time is minimized, bringing the project on-line more quickly and generating revenues faster. Module interior

Early Precaster Involvement
The precaster can provide: Technical advice Engineering support Aesthetic guidance Economical solutions and product suggestions Your precaster should be part of your team from the design stage. The precaster can help devise precast solutions for structural challenges specific to your project. For architectural precast solutions, you can take advantage of the precaster’s expertise to ensure the desired combinations of mixes, finishes, shape and detailing can be achieved technically and economically. By including the precaster as part of the team from the start, you'll get the valuable design and engineering help necessary to bring your project in on schedule and within budget.

Precast Housing Design Considerations
Exterior Finish Interior Finish Wall Panels Floor/Roof Systems Home Utility Systems These are some of the main items you’ll have to consider when designing housing for precast.

Exterior Finish Options for exterior finish: Create/simulate texture with form liner (without additional materials) Create/simulate texture with sand-blasting and acid etching Embed materials during panel manufacture A wide range of textures and colors can be achieved simply with the use of pigments and form liners, or post-casting processes such as sand-blasting or acid etching. Precast can take all common exterior finish products for commercial construction: stucco, paint, ceramic tiles, brick veneer and stone veneer. Using embedded materials can be more economical for at least four reasons: 1) less material is used; 2) erection is much quicker than conventional masonry work; 3) not having to store brick or other materials on site reduces the risk vandalism or theft; and 4) having a solid concrete surface eliminates the need to install additional vapor barriers or base coats.

When using embedded materials… Plan ahead in case special molds are required Consider a modular design to reduce number of cuts and adjustments Different manufacturers have different capabilities for the finishes but for large enough projects they could easily adopt other techniques. For some finishes, the decision has to be made early because it might require special molds to be made. For example, if thin brick is to be embedded into the panels, the designer could take it into consideration and design the building on a modular scale so that fewer odd cuts and adjustments have to be made on the plant when casting the panels. This photo shows a form liners with special gaskets that allow clay products to be placed accurately within the precast form in almost any pattern desired. As shown here, thin bricks are placed face down in the gasketed liner. Concrete, placed over the thin bricks, bonds with the bricks. At the same time, the concrete becomes the exposed-joint material between the brick units, as seen in the inset photo.

Interior Finish A designer can use many interior finishes. . . Plaster Paint Wallboard Furring strips + wallboard Panels may be plastered directly for a smooth finish or be painted where uncovered concrete is an acceptable indoor finish. Both processes could be done with conventional tools and do not require any special considerations when applied to precast walls. Often the interior of the precast walls is furred with 2x lumber to allow space for utility lines and traditional interior finishes such as drywall. The furring strips could be attached to the precast walls with conventional concrete screws.

Wall Panels Options for precast wall panels/insulation: Solid panels Integrally-insulated panels The two most common precast wall panels options for housing are solid and integrally-insulated panels. The solid panels do not have embedded insulation and are easily manufactured at any precast plant. They can be insulated on the inside or outside with the use of furring strips as described earlier. An integrally-insulated panel is manufactured with the insulation sandwiched between two concrete surfaces, or wythes. The advantages of the solid panel include: 4 hr. U.L fire rating Greater load bearing the end user is used to "finished" drywall applications for hanging items When furring and drywall is used, there is the added flexibility of electrical location and ability to change outlet location greater thermal dynamics of a solid panel means less chance of bowing choice and thickness of insulation is open to design criteria The advantages of an integrally-insulated panel include: Insulation is pre-installed, reducing labor costs during construction Ability to pre-install electrical conduit and other utility systems in the factory

Floor/Roof Systems Options for precast/prestressed flooring: Hollowcore plank Hybrid precast flooring systems The main options for housing are hollowcore and hybrid precast flooring systems. Hollowcore offers several benefits, including design flexibility for floor penetrations, cost effectiveness, sound attenuation, and fire resistance. Some precast producers have developed hybrid systems such as double wall or carbon cast flooring to meet specific design requirements. For example, double wall flooring panels are finished on the underside. The processes for creating hollowcore and flat panels are quite different. Hollowcore slabs are continuously extruded on a special machine, and their thickness can be varied on the machine. Thicknesses up to 15 inches are possible. The thickest slabs have widths of up to 96 inches (typically 48 and 96). The length of the panels depends on the desired span, but it can go up to feet for the 15-inch thick panels. Reinforcement in the panels is governed by local design requirements. Slabs and roofs are designed by a licensed engineer for each project according to spans, loading, deflection, shear and fire resistance.

Home Utility Systems Options for installing home utility systems (electrical, plumbing and HVAC): In the precast plant On site Many people not familiar with precast concrete wonder how the electrical, plumbing and HVAC are put into the precast components. Generally speaking, there are two common ways for running utility lines through the panels. The most common and efficient method is to install the systems at the plant where opening locations have to be planned carefully. The precast manufacturers have extensive experience with this from commercial construction. They should be involved by the builder at a very early stage in order to avoid any design or construction site conflicts. This method requires the use of integrally-insulated panels. The second method is to install the utility systems on site and is typically done when solid panels have been used. A surface mounted metal pipe conduit and surface mount boxes may be used. If the interior holds furring and insulation, the electrical system typically runs in the bays between the furring much as it does between conventional framing studs. On occasion a planning error will make it necessary to cut directly into an insulated concrete panel on site. Cutting openings on site must be approved by the precast engineer because panels are engineered to support and transfer various loads. Making an opening which is not accounted for in the engineers design might compromise the structural performance of the building. Typically, openings are cut in the field after the panels have been placed and grouted together. This provides support to the panel that will be cut. It also minimizes the risk of breaking the panel during its placement or during the installation of adjacent panels or components.

Precast Housing “Design Project”
Project Description Expansion of existing housing community in urban setting. New structures to be built on a one-acre lot near three existing five-story yellow brick apartment buildings (existing 120 units were recently converted to condos). [The Precast Housing Design Challenge is an opportunity to engage your students and encourage participation as you walk through a real-world design challenge.] Now let’s apply what we’ve learned to an actual precast housing project. Here’s the broad description of the project.

Project Goals Homes for 38 mixed-income families New buildings must complement architectural features of existing apartment buildings (yellow brick and decorative cornice) Green space Parking for 2 cars per family Balconies and large rooms Easy to decorate walls, hang heavy art, mirrors, etc. The client has provided these six goals. How can you use precast to meet these goals? What issues must be addressed? Of course, before you begin the design, you’ll need to get the precaster involved. The precaster can advise you on both aesthetic and structural options and will work with you to meet the clients goals economically. For example, you’ll save money if you can take advantage of the precaster’s existing form liners for panels or plank. Let’s look at each goal individually…

Goal #1: “Homes for 38 mixed-income families” What types of housing structures could achieve this goal? (And what factors should be considered?) The first question to ask is, “What type of housing structure should we build?” [Presenter should solicit answers from participants] Model answer: Factors to consider: project footprint (how much space available) cost limitations (low income, affordable, or market priced or a mixture of all) green space (common areas or utilizing roof top as a green space) parking (private, inside or open adjacent to building) Obviously there is no single correct answer for type of housing structure. With the limited space available (1 acre) for so many families (38)., we can rule out detached single family homes. We could build one or two condo buildings similar to the existing buildings. Town homes are also a possibility, but they probably would need to be attached and at least three stories high to maximize our green space and parking options. For the purposes of this design challenge, let’s assume town homes would have more appeal to the prospective customers, so let’s proceed with a town home solution.

Goal #2: “Complement or match the architectural features of the existing apartment buildings” What are the precast options for complementing the existing yellow brick and stone cornice? The client wants to match or complement the brick and stone cornice of the adjacent buildings. What are some possible solutions using precast? [Presenter should solicit ideas from students.] Model answers: Brick: The most economical precast solution is to use a form liner to create a panel that simulates the texture of brick. The panel could be either colored with pigment during casting or stained after casting. Thin brick cladding is another possible solution. A close color match is possible, and it would be much cheaper than using actual brick. Two or three different shades of yellow thin brick could be used to help differentiate the townhouse segments. The savings are achieved through the use of less material, less transportation cost, and quicker construction. Cornice: The cornice could be replicated in precast using a custom-designed form, and integral to the panel. Alternately, cornices could be after market composite pieces attached after building is erected. [See next slide for thin brick examples]

Thin Brick Textures and Colors This is just one example of of a product sheet that shows the various textures and colors available for thin brick. Your supplier will have many more options.

Form Liners Form liners can be used to create textured and colored precast panels that satisfy aesthetic goals within strict budget limitations. If the budget is too small for even thin brick, an alternative precast solution is to use a form liner with yellow pigment to simulate the brick, or a different texture altogether. All of the exteriors in this example were created with form liners. Two different textures are use: simulated brick for the façade and simulated stone for the side wall. Precast concrete two-family housing

Goals #3–5: “Green space” “Parking for 2 cars per family” “Balconies and large rooms” How can precast or prestressed concrete help achieve these goals? What are the important considerations and possible trade-offs? How can precast help achieve these goals? [Presenter should solicit answers from students] Model answer: You get the green space by building high (or deep). In this case, we can go only three stories high, so building the homes attached and back to back helps us maximize the surrounding green space. Precast wall panels of appropriate strength can support the load of three stories. Specifically, a possible precast solution would include integrally-Insulated panels for exterior and shared walls (with a 4 hr fire rating) and solid precast panels for interior walls. In addition to choosing the type of wall panel, insulation options, and utility openings, it is extremely important to coordinate the panel design closely with the precaster so that architectural details like window openings and sills are taken into consideration. One potential trade-off is not being able to get the architectural details you want because the budget doesn’t allow for customization, forcing you to use the precaster’s standard framework. Precast hollowcore plank or hybrid flooring systems, with their long span capabilities, make it possible to design very large rooms and ground-level garages with no obtrusive columns. Hollowcore plank is ideal for the balconies. The main considerations are thickness and connection options.

Goal #6: “Easy to decorate walls, hang heavy art” How can you meet this goal in a home with concrete interior walls? Drilling into concrete to hang heavy objects is nearly impossible without specialized tools that most homeowners do not have. [Presenter should solicit answers from students] Model answer: You always have the option to add first attach furring strips and wallboard to the interior of a precast wall. If a concrete wall is left exposed (I.e. no wallboard), the tenant can use self-adhesive hangers available at a hardware store to hang lighter items.

Summary Compared to conventional housing structures, precast/prestressed concrete housing … can be equally attractive is more fire resistant is more weather and insect resistant can provide better acoustical/vibration control can provide better indoor air quality can be more economical

PCI Resources PCI provides ongoing industry support with its many resources: Publications Design handbooks Technical literature Guide Specifications PCI JOURNAL ASCENT Website – Designer’s Knowledge Bank

Questions? This concludes the American Institute of Architects Continuing Education Systems Program. Thank you for your time! For more information or to find the location of a PCI-Certified precaster in your area, contact the Precast/ Prestressed Concrete Institute as noted here. The precaster will help you determine how you can best take advantage of the inherent benefits available in precast concrete hollow-core components and how to realize the maximum cost savings to create an aesthetically pleasing and cost-effective design. Thanks for your time; what other questions can I answer for you?

Precast Housing Structures

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