Preserving History: The Unique Challenge of Maintaining Aged Buildings
Preserving History: The Unique Challenge of Maintaining Aged Buildings
Feb 19, 2019 by Lauren Norris
Whether you buy a historic manor or one of your city’s first buildings it’s important to understand the challenges that come with maintaining aged and historic buildings. The architectural features of historic buildings can fill you with awe, especially those with intricate designs. They can also evoke a sense of reverence, whether you’re viewing an art gallery, town hall, museum, library, campus hall, ski lodge, or mansion.
Visitors, students, and patrons can appreciate the history these buildings portray. Yet the effort required for their upkeep isn’t widely known. Few entities share this awareness, such as building owners, historical societies, and real estate professionals like yourself.
This article broaches four maintenance challenges, along with how to surmount them. You’ll also gain a deeper realization of why historic preservation is economically sound.
1. Unstable Foundations
Over time, all buildings gradually settle. However, uneven or drastic settlement results in “foundation failure.” A building with weak ground support isn’t safe for occupation. A sinking foundation leads to tripping hazards and equipment malfunction. Unsightly cracks further undermine real estate value. The longer a foundation failure persists, the more structural damage it breeds.
Foundations can become unstable for many reasons. For most buildings, the problem is traced to loose or clay soil. Varying moisture levels cause soil to shrink or swell, shifting the foundation above. Other sources of instability include:
inadequate landscape drainage
broken sewer and rainwater pipes
vibrations of heavy machinery
earthquakes and seismic activity
Additionally, when nearby tree roots spread beneath a building, they extract water from foundational soil. Thick root networks can render parched, desert-like conditions. Prolonged drought can do the same. Clay soil is especially prone to shrinking when it dries.
Conversely, ground heaving results when earth is too saturated, making it swell. In that case, the pushing force lifts the foundation. Again, clay soil may be at fault since it expands when soaked with water.
Seismic activity triggers soil liquefaction, with earth acting like a liquid. Roughly 60 percent of structures built on unstable soil eventually suffer foundation failure.
A distressed foundation gives warning signs. A building exterior may display wall warping, gaps around windows and doors, and cracks in bricks and foundation cement.
Hairline cracks occur with normal settlement. However, fractures wider than 1/8th inch are red flags for foundation distress. Usually, vertical cracks signal downward settlement. Clefts that are horizontal, jagged, or angled 45 degrees indicate lateral soil shifting.
Inside, you may see uneven floors, displaced moldings, sheetrock and floor cracks, and misaligned windows and doors, not closing properly.
To restore a firm foundation, start by hiring a structural engineer, who will identify the causes of instability. Then, building contractors can use various methods to correct the issues.
For instance, tree removal eliminates the problem of invasive, thirsty roots. Installing drains and mending pipes improves drainage.
Through a process called soil grouting, contractors stabilize shifting soil. This technique entails injecting soil with polyurethane grout. Structural resins in the grout produce chemical reactions that rectify soil imbalances.
As a result, loose soil gains strength and density. Clay soil becomes more homogeneous and permeable, resolving shrinking and swelling. The pressure exerted by polyurethane grout lifts and levels a failing foundation.
For buildings shaken by earthquakes, contractors use computers to direct grout injection. Grout ports are placed strategically, over large sections of foundation, with the resins delivered in rapid succession. Then, the combined hydraulic forces boost a building back to its correct level.
Once a foundation is firm, contractors can proceed to fix related damage to other building features. With restored footing, you can almost sense a building sigh with relief!
2. Artifact Protection
The collections and displays housed by historic buildings are vulnerable to environmental harm. Most vintage structures lack the vapor barriers and insulation of modern buildings. Consequently, artifacts featuring paint and decorative finishes can be marred by changes in relative humidity and temperature.
Environmental conditions are effectively controlled by systems for heating, ventilation, and air conditioning (HVAC). However, their installation can leave structural scars. For example, to conceal pipes, ducts, and equipment, contractors must cut and patch building materials.
In the US, the National Institute of Building Sciences has created guidelines to prevent structural damage to historic buildings. HVAC recommendations are contained in a dedicated chapter of a handbook by ASHRAE, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers.
This chapter addresses HVAC design for galleries, archives, museums, libraries, and other historic structures. It also advises that HVAC systems need upgrading or replacing every 15 to 30 years.
One ASHRAE recommendation is that institutions conduct an Environmental Monitoring Program one year before adopting a new HVAC system. Monitoring involves establishing baseline building performance data, which is then measured with hygrothermographs. After HVAC installation, the new data is compared to the baseline, noting how the system affects building structure and operations.
Performance data includes relative humidity and temperature set points, based on whether the system should protect artifacts, display collections, store non-sensitive materials, support computers, or promote human comfort.
To determine ideal operating conditions, the National Park Service urges forming a team of experts, with current knowledge of building codes. The team should include a preservation architect, structural engineer, electrical engineer, mechanical engineer, and preservation specialists. Working together, they can tweak a new system, ensuring that collections are protected while building structures remain intact.
This preservation brief by the National Park Service outlines planning steps for choosing a new HVAC system. Additionally, expertise in preserving artifacts is available from the American Institute for Conservation of Historic and Artistic Works.
3. Matching Materials
Frequently, modern materials aren’t compatible with those of vintage structures. In the past, builders chose products based on availability, efficiency, and cost. Now, some of those sources no longer exist. Plus, new materials may be tough to blend. Here are some building features that pose difficulties, along with management solutions.
With time, the mortar used for masonry has improved. Lime mortar is commonly found in older structures. However, replacing it with modern cement causes brick deterioration. Repairing mortar joints, called repointing, should only be done where mortar is crumbling.
Lime mortar has a soft texture, so it should be removed with pneumatic chisels or manual grinders. Since these tools must be handled skillfully, have mortar repair done by a masonry restoration company. Their staff can deftly match historic mortar, based on its color, composition, texture, strength, and aggregate distribution.
Matching brick isn’t a problem, but customizing it requires additional time. So, when scheduling brick repair, allow extra time.
In the past, terracotta units were produced with salt glazing. Now, anti-pollution laws have banned this process. To match new terracotta to existing clay, the units may need special coating, supplied by modern terracotta manufacturers.
Stone can be hard to match, especially when an original quarry source has since closed. Contractors are tasked with lining up stone graining between the new and old. Otherwise, as the new stone weathers, it won’t blend with the original.
One way around this dilemma is using fiberglass, matching easily. Additionally, fiberglass is lighter than stone. Another replacement option is cast stone, a type of molded concrete, which is less expensive than quarry stone.
Certain types of substitute woods are prone to decomposition, making them unsuitable for outdoor porches, shutters, handrails, decks, trim, and siding. To skirt this problem, some contractors use Radiata pine, treated with acetic anhydride, a vinegar-like compound. Known as acetylated wood, such resistant pine stands up well to moisture and insects.
Another wood alternative is fiber-cement. Although thinner than traditional wood siding, it matches well. Additionally, many US cities use cementitious wood to repair historic buildings.
Roofs are tricky to replace since you must consider roof height and shape, along with material color, pattern, texture, and configuration. Frequently, contractors use ceramic tiles as a slate replacement. In historic districts, many commissions approve faux slate.
In case this term is unfamiliar, cladding is material layered over exterior walls to improve weather resistance or aesthetics. In the past, builders have used various types of cladding, reflecting a particular architectural style or historic period. These materials include stucco, tile, pressed metal, shingles, and clapboard.
Cladding must be regularly inspected and promptly repaired. Otherwise, deterioration can rapidly become widespread. Depending on the original material, cladding may be restored with caulking or painting. Alternatively, you can replace cladding with shingles and clapboard.
4. Exterior Cleaning
Cleaning some historic materials is risky since it can destroy their lovely patina. Also prone to damage is old masonry. Generally, cleaning should only be performed when architectural features are obscured by dirt or debris.
Avoid using acidic and highly alkaline cleaners, the most harmful type. Instead, choose detergents with a neutral pH. If cleaning is done with brushes, make sure they’re non-metallic. If pressure washers are used, water pressure should be kept under 200 psi. Never allow the use of sandblasters or grit blasting.
Before initiating a restoration project, ask the building owner if a Historic Structure Report (HSR) is on file. This type of document provides background information on original construction, such as materials, finishes, drawings, and photographs. By reading the HSR, you’ll learn the building’s defining and historical features.
Typically, HSRs are the fruit of archaeological surveys, physical inspection, and extensive research. Frequently, they include recommendations for handling prospective maintenance problems. Following these suggestions can facilitate your efforts to restore, repair, and preserve a building.
If an HSR doesn’t exist, you can have one compiled by a team of preservation specialists. One professional resource is the Association for Preservation Technology International. Members of this organization include engineers, architects, and planners. Another source of preservation architects and guidance is the American Institute of Architects’ Historic Resources Committee.
If your building is a National Historic Landmark or listed with the National Register of Historic Places, obtain the nomination form. It should highlight the building’s key architectural and historical features.
Additionally, the National Park Service has written 50 preservation briefs, offering tips for historic building restoration. Among the topics are Improving Energy Efficiency, The Use of Substitute Materials, Making Historic Properties Accessible, and Rehabilitating Historic Storefronts. Here you can access online versions of all 50 preservation briefings.Restoration Benefits
By taking a vintage building under your wing, you’re preserving insights into human history that can enhance our lives now. You’re also paying tribute to the inspired vision of architects and the craftsmanship of former builders. In historic districts, your restoration efforts will boost commercial value by drawing visitors and patrons.
Plus, building repair is often cheaper than new construction regarding labor and energy costs. Repair generates less debris than demolition and construction. By using an existing building versus starting new, you’ll secure occupants more quickly.
Maintaining a vintage building is a worthwhile investment. Yes, there are challenges — fixing foundations, protecting artifacts, matching materials, and cleaning building exteriors. Still, you have many resources to streamline upkeep, such as Historic Structure Reports, preservation briefings, and professional organizations.
When veteran structures are demolished, giving way to malls, condos, and parking lots, we lose part of our valuable heritage. Thank you for the willingness to keep our history alive. You’re bound to reap great rewards.
Kara Masterson is a freelance writer from Utah. She enjoys Tennis and spending time with her family.