ZACK HOOPES ¦ Staff Writer
(Sept. 28, 2012) After a flurry of concern last week, The Ocean City Council moved unanimously Tuesday to adopt the State of Maryland’s revised building codes, particularly as they pertain to wind and hurricane impacts.
During a meeting some weeks ago, City Engineer Terry McGean had submitted to the council Maryland’s updated codes for structural weather-preparedness. Although the revised requirements included dozens, possibly hundreds of line changes, the major alteration that the city had been advised of was that the new hurricane mapping methods excludes large parts of the island from the “windborne debris region,” where impact-resistant glass glazing is required on all windows.
But Councilman Doug Cymek, who works in the construction and contracting industry, said it was his impression that there were other changes that the city was unaware of that could have an impact and that he would like to see a more full list of the state’s points.
Cymek’s concerns seemed to be backed up by David Barnes, president of Viwinco, a manufacturer of impactresistant glass.
“I’ve been following this action because we are extremely involved with building codes,” Barnes said last week. “I would just ask that the council get all their homework done. Some states have had problems with insurance companies.”
“It’s not like it [hurricane risk] has gone away … you’re still so close to the wind line on the map, it’s not just debris but it’s also water penetration that causes mold and other things,” he continued.
This week, McGean made a full presentation along with city Chief Building Inspector Kevin Brown on their impressions of why some contractors seemed to think that the new wind and impact designations were inconsistent and could present liabilities.
The story, however, was not easy to digest for the layman, causing McGean to preface most of his comments and answers to the council’s questions with, “Wow, this is really complicated.”
“There’s really only a few people you can find who actually understand this, and Terry is one of them,” Brown said. “He’s way smarter than I am.”
In brief, McGean explained that the two building codes that the state – and almost every jurisdiction the world over – adopts are the International Building Code [IBC] and the International Residential Code [IRC]. While the IBC is broader in scope, covering all types of buildings, it is performance-based, meaning that it requires buildings to meet certain thresholds when it comes to physical loads and forces. It does not, however, prescribe specific methodologies on how to achieve this. The construction details are left up to the architect or engineer.
The IRC, on the other hand, applies only to one- and two-family homes. But while narrower in scope, it goes the extra step to prescribe specific construction methods that must be used.
“The fact that this is a prescriptive code is why you don’t need an engineer or architect to seal the drawings on a single-family home … because our inspectors are looking at the construction method to make sure it meets exactly what is in the code,” McGean said.
But the difference between performance and prescriptive codes also means a difference in how the stress and load of wind forces are calculated. Ocean City lies, according to hurricane maps, in a high-wind area. But in order to compensate for the fact that it is less of a debris risk, the wind speed tolerances are lowered in the IRC, putting the resort in a 100 mph zone.
By the same token, the IBC – because it is not prescriptive, and must allow for a multitude of materials – uses a different methodology. In that code, the tolerances of the materials themselves are lowered and wind loads are kept at an unadjusted level.
This means that Ocean City’s load is rated at 128 mph under the IBC. But because it assumes less material strength, it equals out with the IRC.
“If you take the 128 and apply the allowable stress method, it’s the same as the 100 mph requirements,” McGean said. “It took us a while to figure out what they were doing … but what I’m trying to point out here is that they are exactly the same.”
McGean also said that he had spoken with Barnes, who seemed satisfied that the new codes would not actually, in total, create any change or inconsistency.
“When I explained to him that we were not changing the design pressure rating, he calmed down,” McGean said.