Settlement in structures of all types is a problem which we often see here in the northwest, and various locations across the country. Structural settlement has been a cause of structural damage and failures since man has been building on the ground. Settlement can affect any type of structure, and can develop over many years. At other times, it can happen in an instant when just the right conditions are reached within soils or other supporting materials.
Settlement can occur in about any type of structure. Residential and commercial foundation systems, decks, porches, and cabins are some of the types of structures with which we typically see settlement problems. We see many residential structures with settlement issues, particularly those which were built more than a few decades ago, when building codes were minimal or nonexistent.
Older structures often have little or no steel reinforcement in concrete footings and walls, which can contribute to settlement issues. In addition, engineered designs for many smaller structures such as residences and accessory buildings were not as common decades ago as they are now.
Design flaws which are usual suspects in causing settlement include undersized footings (or total lack thereof), poor soils including those with organic or expansive materials, groundwater and drainage issues, and steep sloping soils.
Most, yes, most, of the problems we typically see could have been prevented with proper construction methods. Rushing to meet schedules or reduce labor costs, as well as a general lack of understanding and appreciation for the importance of a solid foundation, are probably the two main types of reasons for these types of construction related settlement issues.
Preventing structural settlement is primarily accomplished before and during construction. Before turning a shovel, it just makes good sense to investigate the composition, and maybe even the history, of your construction site. It's all too common that we see structures with settlement problems caused by 'unknown' factors that could have been 'known', with a little research. Residential structures, particularly those built pre-1960's or 1970's, seem to be the type of structure we find ourselves getting the most calls on when it comes to settlement. Not only was rebar not very popular back then, but we also have to remember that back in those days, it was more common to see owners building things on their own, maybe without engineering, and maybe even without plans!
Of course, as any old contractor worth his salt will tell you, a lot of buildings that don't seem very well-built have been refusing to fall down for many a winter, and many a windstorm. This doesn't change the fact that some of those old buildings actually DID fall down, and some of those that didn't were just plain lucky.
If you find yourself investigating structural settlement, it's helpful to have expertise in structural design, geotechnical engineering, and construction methods. It's particularly helpful to have experts who have been around long enough to have seen how things were built in the past, as well as today. Consider things like soil type and moisture content, recent water leaks or broken pipes, drainage issues and recent weather patterns including abnormal precipitation. Design flaws and maintenance and upkeep should also be taken into account. We find that interviewing people and getting all the information we can, from all parties involved, always pays off in the long run.
Don't be intimidated by settlement investigations. Like most origin and cause investigations, the evaluation of settlement cases take diligence, expertise, and the use of engineering common sense.
When a lawyer or an insurance company adjuster decides it is time to look for an expert, the tendency is to find that very particular expertise that fits narrowly within the parameters of the case at hand. A large crane failure? It then becomes essential to find an engineer with that very particular expertise on that particular crane. A valve failure at a refinery leads to the leakage of thousands of gallons of fluid? Well, the search begins for an engineer who has spent a lifetime designing these particular valves for this particular service.
Yet, the courts have shown that just because you call yourself an expert, means nothing if the scientific method is not followed. If a shipment of bath toys from overseas becomes damaged in transit, who do you call? Is it a mechanical problem? A shipping problem? A chemical gel problem? A packaging problem? Do you make a quick call to your local bath toys engineer? No. You need an experienced engineer who has handled numerous investigations throughout their career, across a broad spectrum of investigations. Many times, a combination of disciplines are needed, since the cause of the failure may be the result of a series of interactions that is multi-discipline in nature. You need a forensic engineer, and one who is inquisitive enough to get to the bottom of the failure.