Breaking Down Demolition Basics

By Chance Warren

Before you can build your client’s vision, it’s sometimes necessary to deconstruct what is presently on the property. Generally, this involves one of two types of demolition: major demolition, meaning bringing the entire structure down, and selective demolition, wherein the super-structure remains intact but demolition takes place within the building.

MAJOR DEMOLITION

Work on a major demolition project begins well before the building comes down. Although the details covered in this article refer to a demo performed with machinery, many of the same principles would apply to an explosive or implosive demo situation. Planning is an essential part of any construction project and is especially pertinent to demolition.

Mitigation

There are several fundamental actions that must occur before demolition begins. The first step is to obtain certification that the building is asbestos, lead and mold free. Asbestos can be found in thousands of building materials, and the hope is that the owner will already have completed a survey. If there is no survey, no work can move forward until one is performed. If any of these contaminants are detected, they have to be mitigated before proceeding. Some general contractors do this themselves, but often a third-party specialist is brought in.

Authorities Having Jurisdiction

Now come the governmental agencies, and several things happen here nearly concurrently. Once the building is verified to be free of toxins, a written letter stating that fact is required. Next is the process of obtaining a demo permit from the state. This can vary by jurisdiction, and the National Demolition Association is a good resource if you have questions. The subcontractor company who is physically performing the demo needs to procure the permit from the state. A step that is often overlooked is notifying the local police and fire departments that the building will be demolished. Many times, these organizations like to use building for training exercises before it’s taken down. Once the state demolition permit is obtained, and fire and police departments have completed their training exercises, demo can begin. It’s important to remember that the demolition permit must be physically onsite throughout the duration of the demo.

Utility Locates

Be sure to verify in writing that the pertinent utilities have been shut off at the main. The caveat here is that you will want a major water source, whether from water trucks or utility, to provide dust control and mitigation. Natural gas/propane, electricity and steam are all major safety concerns and should have lock-out/tag-outs by the utility companies. Steam is often overlooked as it is not that common and found mainly on college campuses. Sewers should be abandoned back to the nearest manhole or grouted solid (filled with concrete), unless being reused.

Recycling

Many times the building materials recovered from a demolition can be recycled, or in the case of items like windows and doors, reused. If working on a LEED project, this is nearly a certainty. Considering in advance which materials will be recycled and how they will need to be sorted can save time in the long run. Metal, wood, concrete and CMU/brick veneers are all good candidates for recycling. Check with your recycling site; in some cases, you may need to separate the rebar from the concrete.

Total vs. Partial Foundation Demo

The general contractor’s preconstruction team will have determined if the demolition will encompass taking out the entire foundation or if the foundation will be cut off about a foot below what will be the finished grade (always determine height from finished grade, not existing grade). The majority of the time, foundations are concrete, which leads to a slew of safety and logistical considerations if it is a total foundation demo. Silica is a safety hazard that can cause serious health issues if not approached properly. Within the last couple of years, OSHA has released new safety standards regarding dealing with silica that are much stricter and protect workers. Haselden has videos in both Spanish and English—all of our safety training is provided bilingually—that provide silica safety training and any company is welcome to incorporate them into their own training program. Another issue that arises with a total foundation demo is: What do you do with the concrete? If you haul it to a dump site, can that site handle that amount of concrete? Haul routes through cities and towns will need to be determined—sometimes roads in smaller municipalities can’t handle the weight of the large trucks needed to haul that volume of concrete. An alternative is to grind the concrete onsite and use for crane pads, temp roads, etc.

SELECTIVE DEMOLITION

Selective demo can encompass a building from one existing exterior wall to the opposite existing exterior wall (a complete gut) or simply removing a section of wall to add a door in an existing partition. As long as the super-structure stays intact, it would be considered selective demo. The roof structure usually stays put, although it can be replaced as part of a selective demolition project.

Safety Considerations

Though generally smaller, there are still numerous safety considerations with selective demo. As with major demolition, there must be written verification that an industrial hygienist has surveyed the building and the property is asbestos, lead and mold free. If the owner has not had a survey done to determine this, stop work until the survey is completed. Because only a portion of the property is being affected, it’s also imperative to verify with the structural engineer that what is being demoed is not structural. If it is, shoring may be required.

Overhead and In-Wall Utilities

Working with utilities during selective demolition can be tricky as many of them need to remain active to service the functioning part of the building. Medical gas and steam lines are usually located in the ceiling  and must be handled especially carefully; they are under extreme pressure and the slightest rattle, shake or impact can cause a break. Fire protection (sprinklers) and fire detection (smoke alarms) are often kept live as long as possible, however if you choose to do this, be sure to take appropriate steps. Contacting the fire detection monitoring company twice daily—once just before work begins to take them offline and once just after work completes to bring them back online—is a wise strategy. Sprinkler head protectors are also a good investment. Bumping one can cause a litany of issues, including a false alarm. If a fire truck is dispatched to the site for a false alarm, there is usually a monetary penalty. Establishing a prior working relationship with the local fire department and communicating the steps your crew is taking with the fire detection/protection systems may help mitigate penalties if a mishap does occur. If you choose to take the system offline entirely, be aware that you will have to implement a fire watch (someone walking the building at least every hour to ensure there is no fire). This must be communicated with local and state jurisdictions and often requires a state fire watch permit.

Establishing a system to ensure the utilities that will be involved in the demolition are safely readied is vital. One method is to use a color-coding system wherein each trade is assigned a color and, once their foreman is confident their system is dead in the wall set for demo, they paint their color on that wall. Once the GC sees all colors accounted for and double checks, that superintendent paints the wall their designated color, indicating it is ready for demo. This color-coding system provides an immediate visual cue and overcomes any language barriers.

Occupied Building vs. Non-Occupied Building

Clearly, a non-occupied building is more straightforward than an occupied building. You probably won’t have to keep as many utilities turned on or build barrier walls or provide signage with detour routes. Occupied spaces, however, can provide a bevy of issues. If working in a healthcare setting, you’ll likely be dealing with Infection Control Risk Assessment standards, such as negative air machines.

While having a defined method of procedure is important in any job, it is especially crucial during selective demolition of an occupied building. Having a set MOP that outlines, step by step, how the demolition process will proceed, including all system shut-downs, detours, etc., is paramount to the success of this type of project. The MOP needs to be reviewed and signed off by all parties—owner, subcontractors, demolition companies and general contractor.

 

Whether you plan for a major demolition or a selective demolition, if the necessary proactive measures are taken, you mitigate the inherent risks and set yourself up to successfully deliver your client’s vision. A win-win for all involved.

Chance Warren is a superintendent at Haselden Construction.