Older buildings have a history and surprises. Demolishing an old building is not just a demo crew with brute force, it is a complicated process that takes history into account to protect people, neighbors and the environment. This article outlines why experienced crews take a different approach to progressing demolitions, and how thoughtful planning can preserve what is worthwhile.
What Makes Historic Buildings Different?
Historic buildings were built with materials/methods that do not always translate with modern standards. Lime mortar, hand fired brick, balloon framing, and early concrete mixes age differently, so loads, or demolition, can be unpredictable. There may be layers of additions, repairs or improvements that were completed at different times that create load paths and connections that make no sense at first (and may look as if they were not done well). Understanding connection and load paths must be done before anything gets taken down.
For this reason, professional teams will often rely on “selective” demolition method rather than an “all-at-once” method, or what my good friend likes to call “the big pop of the demo”. With the selective demolition method, crews leverage an on-site investigation as unnecessary finishing and non-structural elements. Once the framing, masonry (and possibly the connection to other adjacent buildings) is visible and exposed, they can verify their assumptions. If they do discover unsafe or necessary unsafe structural area, they can begin to modify their demolition plan.
Not only will selective demolition protect particular architectural features worth saving but will also reduce the likelihood of an unsafe and uncontrolled collapse by sequencing the removal of the framing and support systems. Thoughtful planning will also help if the owner decides that elements/parts of a structure may be saved for reuse in any restoration projects or as artifacts for a museum.
Common Risks with Older Structures
Sometimes buildings don’t look terrible from the street, but age and undocumented repairs often create unsafe scenarios. Engineers and demolition superintendents start with a built-in protection of structures through structural assessments, documents and archival research and intrusive investigation of the structure. They also work with the local government for permits and historical status checks, and utility records going back decades. Only then can a safe step-by-step plan be developed.
Some items for hazards that crew members think about in their planning include:
- Unreinforced masonry that is brittle and may shear or “zipper” if cut without shoring.
- Balloon framing created vertical voids that can allow fire or dust to travel quickly through the structure.
- Hidden pocketed beams, deteriorated sill plates, or corroded steel that no longer have a load path.
- Unknown modifications (for instance, partitions removed decades ago) that have changed the load path of the building.
- Legacy hazards like lead paint, asbestos-containing materials, including knob and tube electrical work. Check here for more details.
How Crews Protect Nearby Properties
Demolishing buildings in tight urban blocks or beloved neighborhoods requires extra courtesy and control. Crews establish exclusion zones, protective scaffolding or debris netting, and sequence the work to pull material up and in versus down and out towards sidewalks or party walls. To measure vibration, crack gauges monitor adjacent buildings, water misting and negative-pressure containments help control dust from being released.
Communicating with neighbors is equally as important as the engineering. Pre-demolition condition surveys as documentation of adjacent façades, windows, and landscape features, daily briefings and signage before work starts managing expectations around noise, traffic, and work hours. For reference on local customs and reputation regarding commercial building demolition Spokane, many people refer to well-known companies like JTC Demolition Spokane, shown below:
Dust control accompanies good logistics: visible haul routes, flaggers, and timed truck dispatch keep the streets mannerly and safe. Each salvage crew can break apart brick, timber, and metals from the structures early on, while roll-off container staging means debris can be loaded efficiently and without blocking their vehicle access.
Handling Lead and Asbestos Safely
Legacy contaminants are likely one of the big reasons the protocol for demolition of old and/or historic buildings is dissimilar. Before any work can disrupt the building’s fabric, certified inspectors can survey for lead-based paints, asbestos products, mercury switches, PCBs, and old refrigerants. Abatement staff then address hazards in accordance with a legal protocol in a contained workspace—typically weeks before heavy demolition begins—so that no hazards contaminate the mixed waste stream.
The best practice then follows usually looks like:
- Using licensed abatement teams to remove and package regulated material under negative pressure and HEPA filtered air (https://www.epa.gov/indoor-air-quality-iaq/what-hepa-filter).
- Following the permits and chain-of-custody manifests so that tonnage of hazardous waste has a record each pound from its point of waste to disposal.
- Coordinating schedules for debris haulers and use of only dedicated containers so clean waste does not mix with the regulated materials waste.
- Lining or covering the containers if waste of the regulated materials are in loose bulk, and as a reminder the misting of work to reduce fiber releases, then booking roll-off dumpster rentals for use during both the demolition and the later structural tear-down demolition phases.
Balancing Preservation with Progress
Thoughtful demolition is partly archaeology and partly engineering. The demolition crew considers the value of the items, but must balance community safety, funding, and current community need. In some instances, the façade or defining elements, such as terra-cotta cladding, mill-work, or iron storefronts, can be braced and preserved while the structure behind can be demolished and replaced. In other examples, modelling the site with measurement, photography, and salvage of the materials depicts the history of the building even when weathered decay was irreparable condition resulting in all materials being demolished and removed from site.
Respecting the building does not end when the last wall comes down. A responsible contractor would value and plan for how the site cleanup would be based on the same considerations as with the demolition—by stabilizing the soil beneath; removing above ground trip hazards; limiting run-off; and leaving a cleared site ready for the start of the next place experience. Once communities see that attention to detail, from an early layout of site for survey needs to the final clearing of the last contaminant, they imagine that even old buildings can be professors, informing new actions and strategies for safety, smarts, and all manner of respectful treatises on how we act within place in future planning.
