Your Demolition Questions Answered
- By texcon
- 9 Feb 2018
Demolition is a very interesting process. It takes days, weeks or months to build something, but sometimes only a matter of seconds to tear it down. Our clients are often curious to know more about demolition, so we wanted to take the opportunity to share some information about a task that is both rough and delicate.
What Is Demolition and Why Is It Necessary?
Demolition is the process of dismantling a building until there is no trace of it left. It is often called “construction in reverse”. There are several methods that can be used, which we will outline below. Demolition sometimes occurs when a building has become unsafe and must be torn down before it collapses on its own. These so-called “condemned” buildings are not only a safety hazard, but make it harder for the property to be sold. A vacant lot is often more appealing than one with an unusable building.
But a more common reason for demolition is that a new owner has bought the property and wants to use it for a different purpose. For example, an old strip mall might be demolished to make room for medical facilities or apartments.
Small-scale demolitions can also occur within an existing building when remodeling is desired. For example, non-load-bearing walls might be removed for a more open format in a renovated office building.
Is “Deconstruction” Just Another Word for Demolition?
Demolition and deconstruction are two different things that go hand-in-hand. It’s virtually impossible to talk about one without talking about the other.
Deconstruction is the “delicate” portion of demolition. Whereas you might have in image in your mind of buildings being imploded or knocked down with a wrecking ball—all very rough-and-tumble procedures that generate a lot of dust and debris—deconstruction is performed with great care.
Crew members go into the building to remove reusable or recyclable elements by hand during the deconstruction process. It’s worth taking the time to perform deconstruction because it is inherently valuable. The things that are removed from the building can often be resold, allowing the owner to earn some cash back. Sometimes building materials are in excellent shape and can be reused in the new construction.
It’s also more environmentally friendly to remove various materials for recycling. Even the concrete rubble can be recycled; the concrete is ground up into aggregate to be used in new concrete mixes. When the debris is not littered with pipes, wires, bricks, wood, glass, etc., it is easier to haul the concrete away for recycling. Think of deconstruction as pre-sorting your recycling. It’s just easier to do when the building is still intact rather than sifting through a pile of rubble. Plus, many of the recyclable or reusable materials, like sinks and window panes, would break in the demolition process.
There’s one other primary reason for deconstruction, and that is for historical preservation. Sometimes it is safer, easier and more economic to rebuild a historical building than to attempt to restore it. Historical societies take great pains to ensure that a rebuilt historic building maintains as many of the original elements as possible.
Sometimes even the original building techniques are used in order to preserve authenticity. This means that original wood panels, flooring, doors and door frames, windows, fireplace mantles and bricks, light fixtures, cupboards, stoves, plumbing, faucets, and any decorative elements are all removed with the aim of reinstalling them in the new building whenever possible.
After deconstruction, all that is typically left is the shell of a building. Deconstruction may not be possible in a building that is condemned and deemed unsafe to enter.
Is Demolition Environmentally Friendly?
It’s easy to assume that demolition is not environmentally-friendly because an entire building is knocked down and a brand-new building will take its place. If you’ve ever seen a demolition in progress, you know there is quite a bit of debris, and all of this is hauled away. Imagining all of that in a landfill is a sad thought indeed.
Fortunately, demolition often results in over 90% of building materials being reused or recycled. Very few materials end up in a landfill when the demolition company is environmentally conscious. There is often money to be made in reselling or recycling these materials, so most companies do choose that route.
What Are Some Common Demolition Techniques?
There are several different ways to demolish buildings, and the chosen method depends on the location of the building, its proximity to other buildings, the type of material that the framework is composed of, the building’s dimensions, etc.
- Implosion. You might have seen videos online of this demolition technique, because it is astonishing to watch. After the blueprints are analyzed and the main structural supports are located, explosive devices are set to destroy these supports.
Once those structural supports are gone, the building collapses under its own weight. From there, it’s just a matter of using bulldozers and dump trucks to clean up the debris. Sometimes a portable concrete grinder is also brought in to recycle concrete on site.
There should be little to no outward blasting of materials; in other words, the building does not burst apart like what you might see in Hollywood movies, but there will certainly be a large dust cloud as the building falls. When space is available, the building can be made to fall sideways with the use of steel cables to direct its route. Otherwise, buildings fall onto their own foundation and are largely self-contained. Still, nearby streets are closed and buildings are also often evacuated, just in case.
- Ball and crane. A wrecking ball can weigh over 6 tons! It is methodically swung into the building or dropped on top of it in order to break through the strong concrete and steel materials. The wrecking ball is suspended via a crane machine, and a second machine is used to pull the wrecking ball back with a steel cable. The cable is then separated from the ball, and the ball swings into the building. This process is repeated from different angles until the building has been smashed to pieces.
This demolition method is not suitable for all scenarios. Most notably, there must be enough room for the ball and crane to operate without causing damage to neighboring buildings. It also can be a more time-consuming method compared to more modern processes like implosion or a high reach excavator.
- High reach excavator. A high reach excavator is essentially a bucket head on a very long arm. In fact, high reach excavators can be used to demolish buildings multiple stories high. “Ultra high reach demolition excavators” (shortened to UHD) can reach over 200 feet, although these machines are somewhat rare. The excavator destroys the building from the top down, scraping away the building materials until nothing is left.
- Regular excavators and bulldozers. For smaller buildings, a regular excavator is big enough to push and scrape materials, and bulldozers can also be rammed into small walls to break them down. The size and power of these machines allows them to bust through heavy materials like concrete and steel.
- Hand tools. Often used for small buildings with wooden frames, hand tools such as sledge hammers are also part of a demolition crew’s tool box. Jackhammers are also used to break up concrete foundations once the building has been razed, but dropping a wrecking ball serves the same purpose.
Is Demolition Safe?
Contractors take great care to ensure the safety of their own crew members, as well as members of the general public when performing a demolition. For example, any hazardous materials within the building, such as asbestos, are removed and disposed of using safe methods that meet all state and federal standards.
When an implosion takes place, there is a designated “evacuation zone” to protect the people who live, work and shop in nearby buildings and travel on the surrounding roads. There’s always a risk of flying debris damaging neighboring buildings or flying through a window, and of course there cannot be anyone walking on the sidewalk or driving on the street when the building tumbles down.
Demolition crews wear safety gear such as hard hats, gloves, protective glasses, ear plugs and dust masks when demolition is in progress. All team members are trained in safety protocols and are aware of the hazards that are both common and rare among demolition.
Power lines and underground utilities are identified in order to avoid electrocution or damage to, for example, natural gas lines that could cause a gas leak.
When proper preparation is undertaken and crew members are adequately trained, demolition is as safe as any other construction task.
What Happens to the Rubble After Demolition?
Because the deconstruction process strips most of the other materials out of the building, what’s often left is concrete, rebar and steel. Immediately speaking, this debris is typically loaded into dump trucks via excavators and bulldozers. Then, it is taken to a recycling plant that handles these industrial materials.
Steel can often be melted down to make new steel, and concrete is ground to make coarse aggregate. When combined with Portland cement, this aggregate is used to make new concrete mixes. Crushed concrete can also be used as gravel for a variety of projects.
Sometimes concrete can be ground on site, which allows the clean-up crew to make fewer dump truck loads, because more concrete can fit in the truck. In this case, the demolition company often sells the crushed concrete directly to commercial buyers.
Although the immediate aftermath of demolition makes it look like there is a lot of material going to waste, much of the rubble is recycled. Only materials that are too contaminated to be recycled or reused end up going to the landfill. Some demolition companies achieve a recycle or reuse rate of 98%.
How Long Does Demolition Take?
Depending on the method, the demolition itself can take a matter of seconds (in the case of implosion, for example). But there is a lot of work that leads up to that moment.
Permits have to be obtained and blueprints must be analyzed. Of course, the deconstruction process can take a significant amount of time in a large building because everything is removed by hand. An evacuation must be coordinated in some circumstances. And once the building is reduced to rubble, all of that debris has to be loaded into dump trucks and hauled away.
The short answer is: it depends. The longer answer is that it can take anywhere from a few weeks to a few months for demolition to be completed, start to finish. The timeline directly relates to the size of the building and the method of demolition that is used.
Contact Tex Con Construction With Additional Questions!
We hope that these answers have given you confidence in your understanding of the demolition process. But reading this may have raised additional questions.
If you have additional questions about the demolition process, do not hesitate to contact Tex Con Construction. Our knowledgeable team members can discuss the methods we use, our safety protocols, typical timelines, recycling practices and more.
As a premier Houston site work, utility and dirt work company, Tex Con Construction has the tools and knowledge to make demolition a breeze. And once all the debris has been cleared away, you can save time by having the very same team prepare the site for a new construction with land grading, excavation, utility repair and more.