The following entry was made on July 7, 1958, in Eric Hoffer’s personal diary, which later became one of his published works, Working and Thinking on the Waterfront: A Journal, June 1958-May 1959. Hoffer was a longshoreman for more than 20 years in the San Francisco Bay area. From time to time, I think of the following passage and reflect on its content.
Same ship, same place. Six hours [worked]. In the morning I took the Key-System bus to Encinal. As I walked down the several blocks from the bus stop to the docks I was impressed by the gardens in front of the houses. The houses of average size, are fairly old, yet in excellent shape. The people living here are mostly workingmen. The sight of the gardens and houses turn my mind to the question of maintenance. It is the capacity for maintenance which is the best test for the vigor and stamina of a society. Any society can be galvanized for a while to build something, but the will and the skill to keep things in good repair, day in and day out, are fairly rare. At present, neither the Communist countries nor in the newly created nations is there a profound capacity for maintenance. I wonder how true it is that after the Second World War the countries with the best maintenance were the first to recover. I am thinking of Holland, Belgium, and Western Germany. I don’t know how it is in Japan. The Incas had an awareness of maintenance. They assigned whole villages and tribes to keep roads, bridges, and buildings in good repair. I read somewhere that in ancient Rome a man was disqualified as a candidate for office because his garden showed neglect.1
These are remarkable words. Although nearly 40 years have passed since his thoughts were committed to writing, much of the content of his message remains the same. The question of maintenance of building systems is covered in the following chapters, which explore such topics as general building systems, mechanical systems, electrical systems, and other major elements of a physical facility. The level to which facilities managers aspire to keep their existing inventory of buildings in good repair is the “best test for the vigor and stamina” of their college or university. Facilities managers should read, study, and enjoy the following chapters to the benefit of their institutions. Thousands of buildings exist on college campuses and all appear to be different. Their outward appearance is limited only by the designer and the builder. Buildings also vary according to their primary structure. The following sections describe these basic types of structures.
Building Framing TypesTop
There are five basic structure or framing types and an assortment of alternative structural systems: (1) wall-bearing, (2) reinforced concrete, (3) structural steel, (4) a combination of these types, and (5) tensile structures.
Wall-bearing refers to a building type that relies on masonry walls to support floor and roof structural members. Such structures generally are only one or two stories in height, but they can be higher if circumstances warrant. Before the widespread use of skeletal framing, it was not unusual for buildings to have many stories, but the walls at the first-floor level were necessarily thick (three or four feet) to withstand the unit pressures on the masonry. A typical one-story wall-bearing structure might consist of a 12-inch exterior wall made up of 4 inches of face brick and 8 inches of concrete block, with the roof framing constructed of steel open-web bar joists.
Wall-bearing construction usually is found in fairly simple structures in which no major modifications are anticipated. They are rather easy to construct, but their floor plans are typically not as flexible as other building types because of the heavy bearing walls and the difficulty and expense required to move them. Masonry construction is susceptible to inclement weather because masonry and mortar cannot be laid in wet weather or freezing temperatures.
Reinforced concrete framing differs from wall-bearing construction in several ways, but a primary difference is that it consists entirely of freestanding columns braced by horizontal beams at each floor level. Skeletal framing is necessary for high-rise construction, and the columns and beams can be designed to carry almost unlimited loadings from the dead load of the building weight and the live load of contents, occupants, and wind. Skeletal framing provides wide flexibility for future changes to floor layouts, as there are few, if any, solid masonry bearing walls to remove or relocate.
Reinforced concrete frames usually are formed on the job and are poured floor by floor as the structure rises. If beams are a problem, either functionally or aesthetically, a flat slab floor system can be designed that eliminates beams by thickening the floor construction.
Reinforced concrete is an ideal building material for structures, because it is naturally fireproof and does not require any additional fire protection measures. This is especially important in high-rise structures, where fire safety and exit codes are more stringent.
Precast concrete framing is preferred over cast-in-place concrete for some situations. The beams, columns, and even units of the floor slab may be cast in a factory and delivered to the job site already cured and ready for placement. Quite commonly, these units are prestressed with steel cables under tension to supply the required tensile strength for the floor units. The connecting joints are usually welded to steel plates embedded in the concrete. This technology has unlimited applications, but one of the most common uses of precast concrete structures is in the construction of multistory parking garages.
Fiber-reinforced concrete (FRC) is concrete containing fibrous material, which increases its structural integrity. It contains short, discrete fibers that are uniformly distributed and randomly oriented. Fibers include steel fibers, glass fibers, synthetic fibers, and natural fibers. Within these different fibers, the character of fiber-reinforced concrete changes with varying types of concrete, fiber materials, geometry, distribution, orientation, and densities.
Steel-framed buildings have characteristics similar to concrete-framed buildings in that the structural frame relies on a post-and-beam approach to design, and it is built as a free-standing structure before the exterior walls are placed. Steel can be erected faster than poured-in-place structures and also is easier to work with in harsh winter weather than concrete. Steel-framed buildings range from the relatively simple prefabricated metal buildings to the more complex and sophisticated “superdomes” for sports arenas and high-rise structures. Steel structures are shop fabricated and field erected using rivets, bolts, welds, or combinations of connection techniques.
Steel framing must be fireproofed for certain types of occupancies and for multistory construction. If a steel structure is not properly protected, it can suddenly collapse in a fire if the temperature of the steel rises above 1,000Â°F. This was graphically evidenced with the tragic events surrounding the collapse of the twin World Trade Center towers in New York in 2001. Steel construction typically is lighter in weight, is erected more quickly, and usually has lower initial costs than concrete framing. On the other hand, it requires the additional cost of fireproofing and does not provide the same degree of structural “rigidity” as concrete framing. Rigidity can be particularly important with some building types, such as hospitals, classrooms, or research labs.
Combinations of Types
Some of the simpler building types often consist of a combination of framing types. It is not uncommon for one- or two-story structures to have exterior walls that consist of wall-bearing masonry, while the interior supports are all steel columns with steel beams or trusses.
Some areas of the country are highly suitable for wood frame construction and wood siding. This is particularly true in California, Oregon, and Washington, where the native woods are abundant, and the products of the giant redwoods, firs, and cedars weather well.
Another framing system consists of structural supports of either steel or concrete covered by a tensile fabric system. The fabrics used in this type of system carry loads generated only from tension, while the structural supporting elements in the system carry all of the compression loads. Most tensile structures are supported by some form of compression or bending elements, such as masts, as in The O2, formerly known as the Millennium Dome, or compression rings or beams. Tensile membrane structures are most often used as roofs for large arenas or public spaces because they can economically and attractively span large distances.
Footings and FoundationsTop
Spread footings are simple concrete footings bearing on the ground to support concrete foundation walls or grade beams above them. They commonly are used on simple and low-rise structures, but they usually are not adequate for either tall buildings or for poor or unstable soil conditions. Taller buildings (more than three or four stories in height) create larger single point-loading pressures that spread footings usually cannot accommodate. Poor soils typically cannot safely support spread footings without potential settlement and cracking to the foundation system.
The most common and one of the best substitutes for spread footings are pilings. Pilings can be made of treated timber, steel, or concrete and are driven into the ground to support point-loading conditions. Concrete piles can be either precast and driven into the ground with a pounding force, or they can be caissons that are drilled in place and poured with concrete and reinforcing steel cages.
Piles are classified as friction or point-bearing types. Friction piles carry their loads from the friction generated along their surface between the pile and the surrounding soils. Point-bearing piles usually sit on a stiff stratum of shale, rock, gravel, or other bearing strata capable of carrying large unit pressures.
Piles usually are placed in groups and capped with a heavy concrete top. Some piles in each group are driven at a slight angle from the vertical to provide batter, thus creating more stability within each individual pile grouping. They are driven into the soil by a large free-falling weight or a double-acting hammer weight. The pile driver guides the pile downward as it is driven.
Poured-in-place piles (caissons) are created by drilling large holes into the ground and filing them with concrete after the bottom of the hole has reached a suitable bearing stratum. Pilings vary in diameter from 12 inches to as much as five or six feet and sometimes reach 60 feet in depth. In shifting soils or where water is present, the pile drilling may have to be lined with a steel casing as it is being drilled, and the hole may have to be pumped full of concrete as the steel wall is withdrawn.
Pilings are more expensive than simple spread footings, but sometimes they are justified because the footing is a critical part of the building design and must last for the life of the building. It cannot be revised, replaced, or even maintained without a huge expenditure of funds; thus, it is not an item to gamble with in the overall design of the building.
Many concrete framed buildings have concrete floor systems that are poured in place as an integral part of the overall structural system. This is referred to as a monolithic reinforced concrete system. Monolithic systems usually are solid and stable and tend to reduce sound and vibration transmission problems.
Many companies manufacture precast floor units that can be set in place by a crane and anchored to the supporting beams. Precast units have the advantages of quick erection in all types of weather, a higher probability of quality control because of their shop-based manufacturing approach, and the same solid noise-reducing characteristics as monolithic concrete floors. Some units are prestressed and may have hollow cores to reduce their overall weight. Prestressed concrete is a method and a product used to overcome the concrete’s natural weakness in tension. It can be used to produce beams, floors, or bridges with a longer span than is practical with ordinary reinforced concrete. Prestressing tendons (generally of high tensile steel cable or rods) are used to provide a clamping load that produces a compressive stress that offsets the tensile stress that the concrete compression member otherwise would experience because of a bending load. Precast units generally do not have the same degree of flexibility as poured-in-place concrete in the design of odd-shaped structures and special openings through the floor.
Steel systems consist of lightweight steel joists or trusses with steel decking spot-welded to them. Usually some steel-welded wire fabric is laid on top of the steel decking and a thin layer of concrete is poured on top of that to add strength and stability to the overall structural system, reduce noise and vibration transmission, and improve fire resistance.
Steel units can be erected quickly and usually are more economical than concrete systems. Many steel deck units are designed with compartments or cells to carry wiring for power, computers, telephones, and other equipment.
Many types of floor systems are on the market and in use today. One such system is called a composite system because it combines the use of steel beams for the main support with a concrete floor that is poured on top of the beams as a composite structural system. The concrete and steel are designed to act together as a single unit to carry the loads by rigidly securing the top flange of each beam to the concrete slab. This anchoring is achieved by a series of steel studs welded to the top flange of the beam and encased into the concrete when the slab is poured. This type of system is lighter in weight yet provides all of the advantages of a concrete floor.
Composite floors also can be constructed using a technique similar to the one described above. In this case, corrugated steel decking has pins welded to the top of the deck at specified intervals and then a structural layer of concrete is poured on the deck. The pins tie the concrete to the deck. Normally, a second pour is completed, called the topping layer, which brings the composite floor up to its final height.
In general, floor systems with greater mass reduce noise and vibration transmissions, while lighter floors tend to transmit sound and vibration in a more pronounced way. In some cases, specific design needs may have to be met by the floor system to accommodate specialized research equipment or other special circumstances. It may be necessary to locate some equipment on a slab-on-grade floor with an appropriately designed mounting pad or piling.
Exterior Wall TypesTop
Exterior walls composed of masonry units have been used for centuries. Still in common use today are facings of brick and native stone, with a backup material made of either concrete block or lightweight cinder masonry units. Steel reinforcing and concrete often are added to some of the vertical block cavities to strengthen their overall structural capacity. Such walls usually are 12 to 16 inches thick and are relatively easy to maintain. They have poor insulating values and should be insulated in the core or on the interior face with high-quality, permanent insulating materials.
Another common exterior wall system consists of an exterior wythe (facing of one thickness) of brick or stone masonry anchored to wood or metal stud framing behind it. This system can be heavily insulated in the stud spacing or on the face of the studs in the cavity space, but extreme care must be taken to ensure that the exterior veneer is solidly and permanently anchored and that water entering the core of the wall is swiftly and surely routed back to the exterior.
The term curtain wall is used to describe any exterior wall suspended from floor to floor on the structural frame of the building. A curtain wall system is exactly the opposite of a wall-bearing system in that it is supported by the structure and does not carry any dead load. One type of curtain wall, popular since the 1950s, is a system composed of metal (usually aluminum) extrusions anchored together to form an exterior grid of vertical and horizontal mullions. The spaces formed by these mullions are filled with windows and opaque insulated panels. The number of designs, shapes, colors, and materials are almost unlimited. Modern glazing products offer excellent insulation and U-Values that make this type of wall system an excellent choice. “U-Value” is an understood term in glazing and construction for light transmission and heat gain.
High-quality curtain walls are relatively easy to maintain and have performed well. The major concern involves keeping them well caulked to avoid leakage in heavy rains and strong winds.
Curtain walls faced with precast concrete units provide a good, permanent exterior building face. Concrete units can be formed into any shape and texture and are usually of a size that can be transported and erected easily. Steel anchors are embedded into the concrete units so that the units can be welded or bolted to the building structure. The precast units can be backed with steel studs and gypsum board for insulation. This assembly makes an excellent exterior wall and is used extensively for university building projects. The stone and brick industries have developed and promoted prefabricated panels of brick or stone that can be erected in large sections similar to precast concrete units. An advantage of this type of wall is that it can be fabricated off-site while the foundation is being constructed. Then the precast units can be brought in and erected quickly, making for fast construction.
Wood facades normally are used on wood-framed structures. Redwood, cedar, and fir weather well in their natural state and can be utilized in many shapes (e.g., lap siding, shakes, board-and-batten, tongue-and-groove, and shiplap siding).
Tilt-up wall construction is sometimes used for warehouses and other simple utilitarian structures. Tilt-up wall panels are made of concrete and are poured in a flat plane on the job site, preferably next to the wall location. After curing, each panel is tilted up into place and anchored to the building structure.
In regions that experience large deviations in temperatures over short periods of time, attention must be given to the expansion and contraction characteristics of the materials that are chosen. Widely varying expansion coefficients among materials that are not properly accounted for in the design will cause serious structural problems later. Sealants are used on some wall construction types, and these must be carefully chosen and properly applied so that they accommodate the expansion characteristics of the materials that they are joining.
Seismic design is another major consideration. Wall construction and its integration into the structure needs to meet appropriate seismic design standards and local building codes. These design standards vary substantially by state and will not be covered here, but the facilities manager should ensure that all design professionals working on the project are familiar with the applicable seismic design standards.
Nothing in the building industry has gained more attention than roofing and the problems associated with leaking roofs. Roofs generally fall into two basic categories: flat (or nearly flat) or sloping. Older buildings tend to have steep roofs or roofs with an adequate slope, whereas many newer structures, which generally accommodate larger floor plans, are often topped with dead-level (flat) roofs or roofs with negligible or very little slope.
Sloped roofs usually are made of shingles (slate, asphalt, wood, cement, or clay tile) or standing-seam metal sheets. Dead-level roofs are built up with layers of felt and hot moppings of asphalt or coal tar pitch, and they then are capped with a flood coat of the hot liquid material and an embedding of gravel protection as a walking and wearing surface.
A built-up roof is constructed by placing alternate layers of saturated felt paper and moppings of hot asphalt or bitumen; the roof is then coated with a poured layer of hot asphalt (flood-coated) on the top layer of felt with the hot liquid asphalt or bitumen. Rock or gravel aggregate may be embedded onto the hot pour to form a protective surface. Four or five layers usually are used, and such a roof is expected to last at least 15 to 20 years.
A built-up roof should have at least a 1/4-inch per foot slope to readily allow water drainage. Expect to receive at least a 15-year guarantee on the roof against leakage; some roofs will attain a 20-year guarantee. The guarantee should include the flashings and counterflashings in addition to the roof itself. Flashings and counterflashings usually are made from galvanized steel or copper, but sometimes they are made of the same bitumen products as the roofing membrane.
On older roofs with a slope of less than 1/4 inch per foot, it might be necessary to use coal tar pitch instead of asphalt. Pitch flows at a lower temperature and tends to seal itself in warm weather. Thus, it will flow off a steeply sloping roof in hot weather and clog the gutters and downspouts. Four grades of asphalt exist; their use depends on the roof slope, which can vary from almost flat to several inches per foot.
The installation of a built-up roof is extremely labor intensive in the field and requires strict control of workmanship and attention to the weather. Built-up roofs are flexible and can adapt to almost any near-flat roofing problem.
The term single-ply describes a factory-made sheet system from a single material or a laminated material. The sheets are shipped in a large continuous roll, are cut to fit field conditions, and then are placed over an insulating substrate on the roof. The top surface of a single-ply sheet may be factory coated or field coated. Single-ply roofs can be grouped into many classifications according to type of installation, material type, chemical composition, or manufacturing process. The most common types of material are EPDM (Ethylene Propylene Diene Monomer) and TPO (Thermoplastic Olefin). TPO has become more popular as it has a low albedo. The albedo of an object is the extent to which it diffusely reflects light from the sun and therefore better meets the requirements of LEED (Leadership in Energy and Environmental Design) certification as provided by the U.S. Green Building Council (USGBC). TPO also tends to have stronger seams. The usual installation types are adhered or externally ballasted. Joints between sheets are sealed with contact cements or welded using solvents or heat.
A fully adhered system usually is attached to the top surface of the roof insulation by contact cements spread by hand or sprayed. The partially adhered system uses mechanically attached plates spaced over the insulated roof deck or other types of individual mechanical fasteners. These mechanical fasteners can easily become a source of failure if not installed properly. Adhered sheets are fairly easy to maintain, as rips, tears, or holes are apparent and can be repaired.
Another type of installation method involves laying the single-ply membrane onto the roof deck without any direct adhesion except at roof edges or penetrations. The loosely laid membrane is then held down by rounded, smooth, clean rocks with a diameter of about 2 inches. Because the ballast tends to cover any problem areas, these roofs are less likely to be well maintained.
Other Roofing Types
Steep roof slopes are readily compatible with various types of shingles or with standing-seam metal sheets. Conventional shingles are composed of asphalt, clay tile, cementitious tile, wood, or slate. Standing-seam roofs are made of long, narrow sheets of metal and are joined by a raised, interlocking watertight joint (the standing seam). Also on the market are foamed coatings that spray on and provide insulation and waterproofing. These roofing types are usually used for re-roofing and not for new construction. Insulating Concrete Form (ICF) Decks for roof systems use insulating concrete forms and reinforced concrete to provide an insulating substrate for several roofing system types.
It is important to protect roofs from damage from pedestrian traffic. If equipment on the roof requires regular maintenance, roof walkways or stepping stones must be installed for maintenance access. Special units that are positioned on top of the roofing surface are made specifically for this purpose. In any case, the number of penetrations should be kept to a minimum and may require coordination with the mechanical system design.
The primary materials used for window frames are metal and wood, although new high-strength plastics are sometimes considered. The most popular windows for institutional buildings are constructed of aluminum or nonferrous alloys. They are long lasting, do not rust or rot, can be extruded into intricate shapes to receive good weather stripping, and require little maintenance. Factory-applied permanent finishes are popular because of their visual appeal and low maintenance requirements. The raw aluminum can be coated with several finishes, including a natural mill aluminum finish, a rich dark bronze color that blends well with brick and stone facades, or any number of colors. Many of these coatings are chemically or electrically applied and will last for many years.
It is important to compare air infiltration tests provided by the window manufacturers as a measure of the amount of tempered air within the building that may be lost to the outside on a windy day. Some of the more expensive windows provide a nonconducting thermal break barrier or joint built into the window to prevent frost buildup on the interior in extremely cold weather. Good windows should be designed to allow the installation of factory-sealed dual glazing, which can be 3/4 inches thick or even thicker for extremely large panes of glass. For multistory structures, it may be important to select a window that can hinge or pivot so that the exterior pane of glass can be cleaned from the inside of the building.
Wood windows require more maintenance, primarily painting, but some window manufacturers provide a factory-applied plastic facing for the exterior portion of the window that does not require painting. Wood windows conserve more energy than metal windows because of the difference in density and conductance between wood and metal. In addition, naturally finished wood windows contribute to the aesthetic beauty of a project. If wood windows are considered, it is important to select one of the better windows on the market, because they usually are made of better materials and hardware and have a more acceptable appearance and longer life cycle.
The insulating properties of windows can vary substantially. Metal frame windows should have thermal breaks to reduce the heat loss by conduction through the metal frame. Glass can have a variety of spectral characteristics that control the amount of solar gain and heat loss. For example, in northern climates, glass can be designed to allow the shortwave radiation of the sun into a space while keeping the long-wave radiation of heated interior surfaces from radiating out through the window. “Low E” glass has been specifically developed to have a low emissivity, which means that when it absorbs energy it does not reemit it. This reduces the energy emitted into the space from the heated glass of the window.
Doors and FramesTop
Doors and frames for institutions usually are made of wood or hollow metal. Hollow metal doors and frames are fabricated from sheet steel and are strong and durable. The doors and frames are reinforced to fit all types, styles, and sizes of hardware. They are custom fabricated and require a certain amount of lead time for shop drawings, manufacture, and delivery. Frames should be put in place before the masonry work is laid, so that the frame anchors can be built into the masonry joints. Special attention should be given to entrances with heavy traffic to make them sufficiently durable. Wood doors should be solid-core doors to withstand abuse, provide better fire protection and noise control, and serve as a substantial receiver of the various anchoring devices for hardware. The right mullion should be chosen to ensure that it can meet the traffic demands of the installation location.
Some doors and frames are integral parts of a fire-rated wall system required by building fire codes. In these cases, the use of “labeled” doors and frames are necessary to meet these requirements. These labels are attached to the doors and frames and indicate that the particular products meet the fire-resistive requirements established by Underwriters Laboratories.
The selection of high-quality hardware for lock sets, panic devices, closers, and butts is important to provide security and service and to sustain low maintenance costs. Institutions should select a good hardware company and use the same keying system for all buildings, if possible, to reduce the number of keys and master keys. Cheap hardware is quite costly to maintain over a long period of time.
Doors must meet certain Americans with Disabilities Act (ADA) requirements for swing, width, and side clearance, along with requirements for doors with automatic door closures and pressure requirements. Some of the challenges of door location and swing can be mitigated with automatic door openers.
Roof and exterior wall insulations are manufactured from many types of materials. They can be classified as loose fill, batts, boards, poured-in-place, or lightweight material. Hollow cells in masonry units usually are filled with a pourable, granular material that is delivered to the job in sacks. It is important to select only materials that will not settle or decay and will not be eaten by termites or rodents. Care must be taken when using these products to ensure that gaps in the mortar joints, which allow the granular fill to seep out, do not occur.
Insulation boards commonly are used as roof insulation and as the vertical joint between masonry wythes (vertical layers of masonry) in exterior walls. Again, this material should be permanent and not attractive to insects or rodents. Because many types of materials are available on the market, the services of an expert may be considered to ensure the selection of the proper board or plank insulation from the available organic, inorganic, plastic, and synthetic materials.
Some tapered roof boards are preformed to install on a flat roof to provide a sloping top surface. This requires special attention to the location and height of roof drains, curbs, scuppers, and flashings to make certain that the entire roofing system is a complete and integral installation. An option for roof board insulation is a poured-in-place, lightweight, concrete-like material that is flexible and can solve many roof slope problems. Care must be exercised to allow sufficient cure time for the wet materials before roofing or vapor barriers are installed, and sometimes it is recommended that these types of wet systems have appropriate vapor venting systems installed.
Batt insulation is quite effective in joist or stud spaces. It should be anchored permanently to avoid future slipping or sagging. Fiberglass material is common, but other good inorganic materials also exist in the market.
The resistance to heat flow is classified by the R-value of the material. The higher the R-value, the more insulation the material provides. Different insulating materials have different R-values and need to be selected based on their physical characteristics as well as their insulating value.
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Coduto, Donald P. Foundation Design: Principles and Practices. 2nd ed. 2001. New York: Prentice-Hall Inc.
Edward, Allen. “Fundamentals of Building Construction.” In 1988 Handbook of Commercial Roofing Systems. 1988. Cleveland, OH: Edgell Communications, Inc.
Fleming, W.G.K. et al. 1985. Piling Engineering. Baltimore, Maryland: University Press.
Hunt, R.E. Geotechnical Engineering Analysis and Evaluation. 1986.New York: McGraw-Hill.
Longworth, Jim. “Precast Concrete Station Buildings in New South Wales.” Australian Railway History,163-185. May 2005.
Naval Facilities Engineering Command (NAVFAC). DM 7.02 Foundations and Earth Structures. 1986. Washington, D.C.: U.S. Naval Facilities Engineering Command.
Rajapakse, Ruwan. Pile Design and Construction Guide. 2003. Sri Lanka.
TEK Information Series. Herndon, VA: National Concrete Masonry Association, 1995. This series of newsletters is distributed by the National Concrete Masonry Association, and information on specific topics can be obtained by contacting the association.
Tomlinson, P.J. Pile Design and Construction Practice. 1984. New York: Taylor & Francis.