It's not rocket science...Metro-dome Collapse

Why did the Metro-dome roof collapse – shouldn’t it have been designed to withstand a build up of snow?

“Non Engineer” Answer: Yes, it should have.

Explanation: While the Metro-dome should have been designed to withstand a build up of snow, it may have been poorly designed or constructed OR perhaps it just snowed too much. As much as we would like to believe that buildings are designed to be invincible to natural occurrences or other disasters, it’s just not so. When looking into why a building or building component fails, there are several possible contributing factors to consider:

Was this a “design event”?
Was there a “design deficiency”?
Was there a “construction defect”?
What is the “life expectancy” of the building or building component?

A design event occurs when an extreme event subjects the structure to intense loads possibly greater than the building was designed to withstand.

A design deficiency occurs when a building or building component has not been designed to satisfy Code requirements or meet the strength requirements needed to withstand anticipated loads.

A construction defect occurs when a building or building component has not been built the way that the designer intended or the manufacturer requires.

Life expectancy is simply how long a structure is expected to stand and/or remain serviceable.
In order to determine why the Metro-dome roof failed, the engineers tasked with the analysis would need to compare the load that the roof was designed to withstand to the load that caused the roof to fail. Then they will need to review the debris so as to determine the existence and or contribution of any design or construction defects.

Commentary: Without investigation, there is no way to be sure what the cause and/or contributing factors of the Metro-dome collapse was. It is important to note, however that there are times when structural systems can be completely up to Code and built to spec, but still fail when exposed to unlikely, extreme circumstances.

It's not rocket science... Sinkholes

If my neighbor just had their home repaired for a sinkhole, does that mean I have a sinkhole under my home too?

"Non Engineer" Answer: No.

Explanation: While there may be potential for your home to be affected by a sinkhole if there is activity in the area, it does not necessarily mean that you have a sinkhole or will have one in the future.

Unless you have legitimate concerns for damage there is no reason to believe that you would have sinkhole activity under your home. Legitimate concerns for damage resulting from sinkhole activity can include noticing doors or windows that are "out of square", noticing a slope in your floor where it was once level, or noticing cracks in your walls that you have had previously repaired.

A diligent home owner will take note of differences in his or her house observed over time. One way of doing this is to mark and date a crack that you believe to be recent. Another way of monitoring a crack is by measuring its size and periodically checking to see if the size of the crack has increased. If you notice the crack getting larger with time you may want to consult a qualified, licensed professional.

Commentary: Without a proper investigation by a qualified Structural Engineer or Geo-technical Engineer there is no way of knowing for sure if there is sinkhole activity beneath your home. If you begin to become concerned about changes in your home, a Home Inspector might be able to offer an opinion on whether or not the damage in your home is frequently observed or "normal", or if there is cause for concern and a second opinion is needed. This is an inexpensive, unobtrusive option before embarking upon a full blown investigation.

While a Home Inspector can not opine on significant structural deficiencies, or if a sinkhole exists, they will at least be able to offer the knowledge of what they see in homes throughout the community. For a reputable Home Inspector visit the American Society of Home Inspectors at http://www.ashi.org/.

It's not rocket science... Cost Estimating

How does construction cost estimating work? Do contractors pull the numbers out of thin air or is there an actual method they use to get the numbers to repair my house?

"Non Engineer" Answer: Yes, there is a method to the madness.

Explanation: A construction estimate is based on the cost of materials, equipment and labor used to complete a project. Estimates can be reached by calculating these numbers by hand, or by using construction estimating software such as Xatimate.

Professionals who choose to calculate construction estimates by hand do their own research by checking prices of materials and equipment locally and reaching an average cost of each. For example, if the cost of (1) 2x4 is $2.97 at the local Home Depot, the professional will use that and multiply it by the estimated number of 2x4s needed to complete the job at hand and so on. Labor costs are typically based off of what an individual company charges hourly for their workers to perform tasks at hand and multiplied by the number of hours expected to complete the job.

Using software like Xatimate can speed this process up by allowing the estimator to put in specific information about the project and then let the software calculate a construction estimate for the user. Estimating software companies have a team of their own professionals that gather averages in specific regions so the cost estimates are based off of regional averages for materials, equipment and labor.

Commentary: It is important to remember that whether your construction estimator uses estimating software or crunches numbers themselves, getting a second and third estimate is always wise to guard against unscrupulous individuals. And always make sure that your contractor is properly licensed and insured (as previously discussed).

It's not rocket science... Hurricane Damage

Why do some houses display more damage after a hurricane than other houses?

"Non-Engineer" Answer: Because of differences in the age of the houses and the contractors used to build the houses.

Explanation: The reason that your house may have experienced minor damage while your neighbor's house may have experienced substantial damage does not always involve luck. A difference in the age of the houses can play a role in the amount of damage one house may experience compared to another. Specifically, if your neighbor's house was built in the 1980's, then it would have been built according to the Southern Building Code. Whereas, if your house was built in 2002, then it would have been built according to the Florida Building Code, which is more stringent. Like everything else, the building code has improved through time, just as technology and research have also improved. Through research and past experiences, the newer codes account for potential catastrophes such as hurricanes and require that the houses be designed and built to withstand these catastrophes.

In addition to the differences in the time the houses were built, the individual responsible for building the home can also affect the outcome. While we would hope that all contractors, engineers and architects responsible for the design and construction of your home would be reputable individuals, the reality is that not all are and some take shortcuts. A home built with construction deficiencies, (i.e. improper fasteners, incorrect installation of components or the use of wrong materials during construction) could also affect the performance of your home during a hurricane.

Commentary: While no building is ever designed to withstand every type of natural disaster it is possible to safe-guard yourself against hurricanes. One way of safe-guarding your home is to hire a professional such as an engineer, architect or building inspector to inspect your home for hurricane readiness. The professional can look for unnoticed damages and construction deficiencies that could possibly compromise the structure.

It's not rocket science... Safest Place During a Building Collapse

Where is the safest place to wait for help in a building during a building collapse or other disaster?

“Non-Engineer” Answer: The stairwell

Explanation: According to chapter six of the book “Design against Fire” entitled “Fire Escape in Difficult Circumstances” the stairwell is often the safest place in a building to be during a collapse or other hazards such as smoke or fire. Some buildings have “Safe Havens” that are reinforced to protect evacuees during a structural collapse. More often than not, the stairwell can be used as a safe haven. During the investigation outlined in this chapter, the independent variables during a building evacuation which included the complexity of the building and movement ability of the evacuees were tested. It was noted that during an evacuation the strategy of the evacuee changes from that of “fast egress” to “slow egress” and “move to a safe place inside a building”. Safe havens (such as a stairwell) are often where evacuees with limited mobility are requested to stay until emergency rescue personnel can respond.

Commentary: During a building collapse or any other type of structural hazard it is important to remember to stay calm and try to exit the building as quickly and safely as possible. As discussed in a previous blog, The U.S. requires buildings to have stairs as a means of evacuation and elevators are inoperable and should not be considered during an evacuation.

http://en.wikipedia.org/wiki/Emergency_evacuation

It's not rocket science... Tile Delamination

Yesterday, sitting around drinking coffee, I hear what sounded like a small animal walking around on my ceramic tile floor or someone pouring rice on the floor. I later checked and of all those tiles in that area sounded hollow. The tile have been down for 9 ½ years and we’ve had much colder weather. Have you ever heard of this happening?

"Non-Engineer" Answer: The cold was the final straw

Explanation: We encounter what you described quite often and especially around the first major temperature drop each season. Why now after several years? Delamination is a result of a build up of stresses between the tile and its substrate. These stresses build as a result of continued slab shrinkage and tile absorbing moisture resulting in expansion over time. Eventually the build up of stresses overcomes the ability of a thinset to resist and the tile delaminate. This delamination often occurs during the first major cold snap each year since the change in temperature also adds stresses that act as the final straw.

Commentary: What to do about it? If the tile delaminate cleanly and the thinset remains bonded to the slab, simply clean the slab and reset the tile using an adhesive mastic or polymer modified thinset

It's not rocket science... Which weighs more?

Which weighs more - A bridge full of people or a bridge full of cars?

"Non Engineer" Answer: A bridge full of people.

Explanation: An average car will weigh between 3,500 and 7,000 pounds and will take up an area of roughly 150 square feet (or 8 feet wide by 18 feet long). This equates to between 25 and 50 pounds per square foot. Whereas the average person will weigh between 120 and 240 pounds and will take up an area of roughly 2 square feet (or 1 foot long by 2 feet wide). This equates to between 60 and 120 pounds per square foot. Therefore, a bridge filled with people will weigh more than a bridge filled with cars.

Commentary: Not to worry though, bridges are designed for much more than just cars and much more that an average static load spread out over its surface. Either way, you will not catch me on a bridge filled with fully loaded concrete trucks.

It's not rocket science... Licensed?

How Do I Verify If An Engineer is Licensed?

“Non-Engineer” Answer: Check with your State’s engineering licensure board

Explanation: Nearly every state has an on-line method of looking up and/or verifying those engineers licensed to practice in your state. If after searching, the individual does not appear then chances are they may not be licensed to practice in your state. Always take that extra step to verify that your engineer is licensed to practice in your state.

Commentary: Engineering may employ science and physics but as a profession it is regulated at a state level. As such, you can not assume that because an individual is licensed to practice in one state, they are licensed (or allowed) to practice in another state.

It's not rocket science... Mezzanine

What is a mezzanine?

“Non-Engineer” Answer: A Mezzanine Is A Landing Or A Partial Floor Between Floors

Explanation: A mezzanine is not counted as its own floor and does not add to the total number of floors within the building when it meets certain criteria .

Commentary: The criteria that allow for a mezzanine requires that it be constructed of the same type of materials and fire resistance rating as the the building in which it's locatred. Building codes limit the total floor area of a mezzanine to no more than 1/3 to 1/2 of the floor area that the mezzanine looks down upon , and require it to be open to the floor below except for walls not more than 42" high. This last requirement has been relaxed and full height walls are allowed if the occupant load is less than 10 or in some sprinklered buildings meeting specific egress criteria.