Vibration Damage
Every year there are construction projects large and small. Recent examples or larger projects include the new Herb Grey Parkway (aka Windsor-Essex Parkway) and Kitchener-Waterloo LRT. Smaller examples are typical roadway or building construction projects – a new highrise building in the downtown, new road services, etc.
Whether large or small in nature, all of these types of projects produce vibrations in the soil. The magnitude of these vibrations depends on what type of project and what equipment is being used. The larger the equipment, the more vibrations. For example – blasting will produce a much higher vibration than a vibratory pile driver, which will produce a much higher vibration than a jack hammer.
How that construction vibration affects people and buildings has been the subject of many studies. We hear almost universally from homeowners that their building was shaking, the noise was deafening, things in their house were rattling (e.g. pictures, windows), they could see trim moving. They start looking around their houses and finding cracks at various locations and think the worst: “Oh no! All this construction has damaged my house!” or the even worse conclusion that their house is no longer safe.
The majority of the time we find nothing structurally wrong with these homes. “But how can that be?” people ask. The answer is that soil is able to dampen (reduce) vibrations very well. As the vibrations travel through the soil, they dampen very quickly. And when they do reach the structure, they dampen even further. They require direct load transfer paths through a structure to damage anything at the interior of the structure.
This seems strange to people, because they say, “But I heard and felt the vibrations in my home. They were awful! And I could barely hear the TV over all the noise”. This is the second point, that vibrations are far more disturbing to people than structures. There has been a lot of research done with respect to this.
Construction Vibrations: State-of-the-Art by John F Wiss (Published in the Journal of the Geotechnical Engineering Division in February 1981) through to the more recent Transportation and Construction Vibration Guidance Manual (published by the California Department of Transportation – aka CalTrans – September 2013) have had similar findings. While vibrations produced from construction activities can be “disturbing” to people, these same vibrations are often insufficient to cause damage to structures, including fragile older historic buildings, let alone newer more resilient buildings.
Does this mean we never see vibration damage to structures as a result of vibrations/construction activities, then? No, it doesn’t. We have seen foundation walls collapse inwards as a result of nearby construction activities, as well as other less severe damage. For significant structural damage to occur, the source of the vibrations must typically be very close to the structure in question.
Your next (logical) question will be, “What distance is a safe distance?” That’s not something with a straightforward answer. Obviously, you can use a jack hammer much closer to a structure than you can use dynamite without causing damage to a building. It becomes important to know what type of equipment was used and how far away it was used, so that this can be analysed and determined. It is also important to look at the quality of the structure in question – is it an older structure in poor condition or a new commercial building? Obviously, the new building can sustain higher loading from vibrations without sustaining damage as compared to an older structure in poor condition. These are all factors that come into consideration when we assess a building, as each building and construction situation is unique.
And of course, there is always the question from the homeowner, “But how can you say my building did not sustain any damage when I have found cracking all through my entire house?”. This is often the most difficult part to deal with. The problem is that people start walking through their house with a critical eye, and issues that may have been there for years are now being seen for the first time.
Depending on the type and source of vibrations, maybe there are new cosmetic damages and maybe there aren’t. Building finishes such as drywall are more brittle than the wood framing behind. For this reason, cosmetic damages are not necessarily indicative of structural damage. It takes little force to worsen cosmetic damage. For example – that crack above your door that has been there forever just doubled in length.
Assessing the cosmetic damage can often be the most difficult part of these types of claims. But the general rule of thumb is that if there is any cosmetic damage, it will be most significant at the exterior wall that is facing the source of the vibration. If you are seeing a high amount of cosmetic damage at the back wall of the house, but none at the front wall of the house, yet the construction was in front of the house, then it is likely that these cosmetic damages were not related to vibrations.
All situations are unique and there are several factors in each situation that need to be considered and assessed to determine if observed damage was caused by construction vibration. Key variables are magnitude at source, distance to structure, condition of building, and the damage pattern observed. Other variables are soil type, duration of exposure, saturation level of soil, and continuous verses intermittent loading.
We are happy to help you sort through these factors and determine what, if any, damages were sustained as a result of vibrations.
