An Education on Masonry: Designing schools with the construction process in mind

by Katie Daniel | May 4, 2015 11:05 am

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by Joe Noser, PE
Masonry may be one of the oldest construction methods, but it maintains its viability in the modern world, offering durability combined with low maintenance needs. Various building types use masonry as their primary method of construction, and even for those that do not, the serviceability of Division 04 materials makes it a popular choice for areas such as stair and elevator shafts and foundations. Where lifecycle considerations are critical, masonry construction is an attractive option for the entirety of a structure. For schools, in particular, masonry remains a go-to material.

Buildings serving kindergarten through 12^th grade are required to have long lifespans, frequently being expected to last 100 years or more. They also need to withstand a certain amount of abuse. Masonry is a relatively impervious substance and it offers a competitive cost, especially factoring in the life of a structure and low maintenance budgets. Additionally, masonry provides mold resistance, high thermal mass, and fire protection. Architectural masonry units are produced in a wide range of shapes, sizes, colors, and textures, so construction can result in attractive building designs.

Multi-story student housing also commonly employs masonry construction, although changes in campus housing trends are shortening the expected lifespans of these structures. Updated housing can be a real selling point for an institution of higher learning, especially in today’s competitive market, so cheaper materials may be chosen with the intent to achieve greater flexibility for future renovation or even to tear down the facility in the comparatively near-term. However, the same benefits of masonry making it attractive for schools also deem it desirable for student housing design.

When used in schools and dormitories, masonry often provides the load-bearing structure and is the main element of the building façade. This means, in addition to providing designers with a serviceable material option, it becomes a prominent design element. In addition to the availability of aesthetically pleasing architectural masonry units, the building method offers a great deal of design flexibility. However, it also has limitations. Building with masonry has the best outcomes when construction material choices and constraints are considered at a project’s outset.

With school facilities representing a large market for masonry construction, it is prudent to become familiar with the particular issues encountered when building masonry schools. This is especially true in light of the fact stringent governmental standards often regulate school construction. It is not unusual for these standards to involve competing, even contradictory, requirements.

Fulfilling many criteria
One of the main factors to take into account when designing a masonry structure is the speed at which it can be constructed. Building with masonry requires a high degree of coordination between trades.

For other structural systems, this is not necessarily the case.

For example, the erection of steel framing can be performed as an isolated activity. A typical brick or concrete masonry unit (CMU) school building, on the other hand, will require the masons to build a structure up to the second story, then stop working to allow the steel erector to place the second floor framing. This process occurs at each floor of the building, and work stops again when the mason comes to the roof elevation. Similar coordination has to be accomplished between the masons and electricians, who need to run conduit and place outlets in the walls. The cumulative effect of these stoppages on the project schedule can be quite significant. When designing a several-story building with masonry, it is therefore advisable to take these coordination efforts into consideration early on.

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Further, local government standards may have stringent requirements for school building construction. Ohio has a set of standards intended to ensure quality and consistency in public education facilities. These standards strive to address many factors, ranging from student health and wellness to environmental sustainability. Working to meet such a diverse set of goals, however, can complicate the design process.

Ohio also leads the nation in the construction of green schools, with more than 150 Leadership in Energy and Environmental Design (LEED)-certified public schools. State-funded schools are, in fact, required to attain at least LEED Silver certification, with projects being encouraged to attain Gold. Considering schools have an important role to play in the health and wellness of their student bodies, earning the LEED points awarded for daylighting is a priority.

According to the Rensselaer Polytechnic Institute, research funded in part by the U.S. Green Building Council (USGBC) and a grant from a Trans-National Institutes of Health Genes, Environment and Health Initiative (NIH-GEI) quantified the impact of daylight design on students’ well-being and performance in K−12 schools. Researchers also investigated the underlying biological mechanisms involved in the students’ response to natural light.

Mariana Figueiro, program director of Rensselaer’s Lighting Research Center (LRC), says the study found “today’s rigid school schedules requiring teenagers to be in class early in the morning cause them to miss the essential morning light needed to stimulate the circadian system, which regulates body temperature, alertness, appetite, hormones and sleep patterns.” Subsequent to the research, LRC developed a daylighting design guide that “balances the photobiological benefits of daylighting with well-known daylight design techniques that can be applied in schools,” according to the news release.

As ample natural light can reduce dependence on artificial lighting, designing in daylighting also helps schools meet the state’s stated preference LEED points be earned in the Energy and Atmosphere (EA) category. According to the U.S. Green Building Council (USGBC), the daylighting requirement as defined in LEED v4 is “to connect building occupants with the outdoors, reinforce circadian rhythms, and reduce the use of electrical lighting by introducing daylight into the space.”

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To meet this standard, as well as to enhance the aesthetic quality of a school building’s façade, architects frequently design large window openings. As windows get bigger, however, the lintels required to span them also get bigger. So, while a mason can easily lift and set a steel lintel in
a small window opening, placing a larger lintel requires the intervention of a steel erector. Lintels can become so large steel columns are needed at the window jambs, which also requires a steel erector.

Again, the solution is to consider the building material’s limitations while still in the project’s design phase—it is sometimes possible to obtain the desired visual effect and daylighting goals by separating a design scheme’s large window openings into smaller, separate windows that have masonry piers between them to provide structural support.

Masonry in Correctional Applications

In addition to schools, masonry’s attributes can make it a good choice for prisons. For lower-security facilities, such as juvenile detention centers, clay brick and concrete masonry units (CMUs) can provide the feel and look of a more standard institution such as a school or dormitory. However, it can even meet the needs of maximum-security facilities, satisfying stringent security requirements when extra reinforcement is added into wall cavities (to prevent deliberate breaching on the part of inmates).

Often, another goal of school design is the finished building be flexible enough in order to accommodate future renovation. Typically, such renovation entails the alteration of classroom and hallway walls. If these are bearing walls, removing them is difficult and uneconomical to do in masonry construction. At the same time, the interior walls of a school meet programmatic requirements better if they are of a hard, durable material. In fact, Ohio guidelines specify both hallway and classroom walls be of a durable material and be non-loadbearing. Owners in many other parts of the country may mandate this kind of dual focus.

A recent project completed in Lancaster illustrates the complexities involved in fulfilling these competing criteria. State of Ohio guidelines were strictly enforced, which led to the building being built with two systems: steel for structural framing and masonry for wall surfaces. The team designed a structural frame that used 178-mm (7-in.) columns for structural support; masonry units were then pieced together around the columns to create a continuous wall surface.

Any column or vertical steel member that has a depth less than or equal to the 203-mm (8-in.) nominal thickness of the masonry unit can be concealed within or mounted flush with the masonry wall. Exposed steel can be mostly camouflaged—or articulated, if so desired—using paint. For the Lancaster project, because the school system did not have money in the budget for the redundant steel building frame, costs were recouped by value engineering elsewhere in the project. As the situation was recognized early in the design process, owners and designers were able to proactively address it, and project costs and schedule remained on track.

Further advantages
The use of masonry also provides additional dual benefits to the design of the building. Load-bearing walls also serve as shear walls to resist lateral loads. If the site location and seismic requirements do not require special detailing in the masonry, little additional reinforcing is typically needed for this to happen.

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In buildings that use other structural systems, such as structural steel, masonry shaft walls or strategically placed masonry walls in areas of the building such as mechanical spaces can be used as shear walls. In structural steel systems, the typical lateral-load-resisting systems used are steel braced frames, steel moment frames, or shear walls.

Braced frames are an economical system, but they are not always compatible with the building design and they can be limiting if future flexibility of the interior spaces is needed. Moment frames result in heavier steel members and more expensive connections. Masonry shear walls, therefore, can be the most practical and economical lateral load-resisting system.

Public perceptions of building materials
Schools are particularly subject to the scrutiny of the taxpaying public. Done well, they can help broadcast a positive message that tax dollars are being wisely spent. The benefits of masonry are fairly well known—a fact helpful to the public entities that have to satisfy taxpayer interests. However, as with any material, there can also be negative opinions to address.

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There is often a public perception masonry can be expensive. Usually this can be countered by more thoroughly communicating the ways in which upfront costs are recouped in the form of lower maintenance costs during the lifecycle of the building. Frequently, too, the impression masonry is a slow building method may be exaggerated.

However, it is true masonry is a somewhat temperamental building material. If construction
is underway in the winter, care must be taken so the water in the mortar does not freeze. To ensure this, areas in which work is being performed may be tented with plastic sheeting and heated with space heaters. However, given the fact most school construction is timed to occur, to the extent possible, in the summer months between school years, this problem is partially offset.

In warmer months, rain can wash out mortar, which also requires extra care to be taken on the jobsite. As with the work slowdowns attributable to coordination between the trades, these logistics problems can be partially alleviated by careful upfront planning—a fact that should be communicated to the taxpaying public.

The benefits of masonry are likely to ensure its continued use. Since a key part of design is to anticipate and respect construction processes, architects and designers are responsible for early analysis of any chosen building material or system. By addressing issues early, any constraints that masonry may impose on the jobsite can be greatly reduced.

Joe Noser, PE, is the director of structural engineering for Columbus, Ohio-based firm, SMBH Inc. He is active in the Structural Engineers Association of Ohio (SEAoO) and American Society of Civil Engineers (ASCE). Noser can be reached at jnoser@smbhinc.com.

Source URL: https://www.constructionspecifier.com/an-education-on-masonry-designing-schools-with-the-construction-process-in-mind/

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