Structural PSA #6: Live in a Condo?

If you live in a condo building where you are responsible for your exterior windows and doors, make sure to determine what type of demising wall (wall in common with the units next to you and the hallways) you have. The problem with protecting a condo unit, individually from your neighbor and the building as a whole, is that typically the demising walls and entrance doors are designed as interior walls & doors and are not adequate to sustain strong forces. That is, unless your demising walls (such as in some townhouses) are a structural fire wall or shear wall. Therefore, if you protect your unit with impact windows and your neighbor does not, more than likely your demising wall in common with them will fail, as well, should they lose a window or door in the storm. The interior walls are designed to support only 5 pounds per sq. ft. whereas wind forces for a condo can be in the order of 50 to 130 pounds per sq. ft. If your neighbors windows fail that would introduce large positive pressure, debris and water which will affect everyone on your floor and most likely introduce water to the units below. Should this happen, the safest place in the building would be the stairwell which is typically solid concrete or masonry all around. I would not worry about the roof, per se, as flat roofs in condos are typically of reinforced concrete. Condo buildings need to design for such occurrences holistically and protect the entire envelope. Do not think just because your unit is protected with impact windows and doors, that you are safe during a strong storm.

Structural PSA's Before, During and After Hurricane IRMA

Structural PSA #1:

Products ARE NOT designed for wind speeds, that is a commonly repeated false statement. Products are designed for pressure. Buildings are designed with wind speed as one of the factors of their design pressure. Design pressure is based on wind speed (squared), roof type, height above grade, surrounding terrain, etc. Then, a factor is placed on the design load based on building essential value to recovery or shelter. All of these factors affect the pressure that a storm imposes on a structure or that a product is designed for. A single family residence products are designed to sustain forces in the order of 40 pounds per sq. ft. A high rise products are designed in the order of 85 pounds per sq. ft. In summary...Don't be fooled by people who tell or sell you that a window can sustain X mph winds, that is impossible to tell. Windows can sustain pressures. The same wind speed can produce radically different pressures. You need to know your unique design pressure before you buy your windows.

Structural PSA #2:

The impact force is a different story. Products are designed to sustain two different types of missile impacts based on height above grade (over 30 ft or below 30 ft). The design standard for products below 30 ft (large missile) is a 9 ft long, 9 pound 2x4 shot from a laser guided cannon at 50 ft per second at three locations. Above 30 ft, the design criteria is ball bearings, 30, shot at the product in three groups of 10. Products must sustain theses loads and then are subjected in the lab to 9000 wind load cycles at the design pressure, 4500 cycles in the positive direction and 4500 cycles in the negative direction. Our products are VERY STRONG if installed properly.

Structural PSA #3:

Impact windows versus shutters. It is a matter of cost vs convenience. Impact windows will protect you equally, they are both designed for the same criteria/pressure. The difference is shutters can be opened and removed and than reused. Impact windows provide you the convenience of not having to board up or put up your shutters but broken impact windows must be replaced. If you can afford the cost and prefer the convenience, impact windows are the option for you. If you cannot afford the cost to replace your windows shutters are your best option.

Structural PSA #4:

We are all told that the state of Florida has one uniform building code as a result of lessons learned from Andrew. However, while on paper we all follow one code BOOK, the actual specifications and requirements for hurricane design in the code are in fact separated into two distinct sections. The general code and the High Velocity Impact Zone (HVHZ) which by definition includes Miami-Dade and Broward counties ONLY. The HVHZ is the stricter code. The reason for that is....(too political and lengthy to discuss on FB)

Structural PSA #5:

PLEASE do not be fooled by IRMA's effects on Florida (Exception: The Florida Keys). Do not say your house "Survived IRMA therefore it can survive anything" when another storm threatens us in the future, and it WILL. Certainly there is a lot of suffering and it is not my intent to minimize it (loss of power, downed trees, some structural damage and lots of water infiltration) IN MY OPINION, this was nothing but a strong tropical storm event for us in Miami-Dade and Broward counties and a CAT 2 for North Florida. Nowhere near a "code testing" event. For the true impact of IRMA you only need to look at the Caribbean and the Florida Keys. I made a very controversial post about a week away from what was expected to be a monstrous category 5 hurricane with winds of 185 mph that I immediately took down for fear of panic. I advised not to try and ride out IRMA at it's present wind speeds. I myself considered leaving until the winds lowered to below code level speeds. What I should have written was to not try and ride out IRMA (at 185 mph) in a single family residence and instead seek a proper shelter. Have a plan, in the future, for a code level event, in my opinion 150 mph or less (we design for 175 mph, but my faith in plans review, installations and inspections of very well designed and tested products is very poor based on experience) and then have a plan for the monster storm 151 mph plus. As I posted previously, the wind speed causes the pressure to exponentially increase or decrease with each mph which is the true measure of a building or product's strength. In fact, I am VERY concerned that with such a minimal wind event many are praising our preparedness and our ability to survive a code level event especially considering the enormous loss of power after tropical storm force winds.

I AM CONCERNED THAT WE, AS A COMMUNITY, WILL HAVE A FALSE SENSE OF SECURITY AFTER THIS.

WE HAVE A LOT MORE TO DO FOLKS TO BE PREPARED FOR A POWERFUL STORM SUCH AS IRMA...AT IT'S PEAK WINDS.

WE DODGED A BULLET.