Dear Builder’s Engineer,
The house plans called for a footing nine-inches tall, which is how I formed it. The building inspector came along and rejected it saying it had to be 12-inches tall, minimum. So I had to change it. These plans were engineered; can he legally do that?
Alonzo, Tracy, Calif.
In a word, maybe.
The first question to be answered is: What does code require? In the old days that was a pretty straightforward question. No longer.
To my knowledge, all of us in the U.S. must adhere to the International family of codes, specifically, the International Building Code (IBC) or, optionally for residential construction, the International Residential Code (IRC). Both specify minimum requirements, meaning you can build stouter if you wish but not to a lesser standard.
Certain jurisdictions possess their own amendments to the International codes. For example, California has its own code, the California Building Code (CBC), which supersedes certain parts of the International codes. So all builders, engineers, and architects in California must know and adhere to two sets of codes.
But wait, to make matters worse, certain cities and counties have their own versions of codes and ordinances that supersede both the International and state codes. How in the heck is a person supposed to know all those codes—particularly considering that the International codes adopt by reference some five hundred other industry codes, regulations, testing results, etc.? (I tried counting them once but fogged over at 314.) Does any human, living or dead, happen to own, know, or even have a vague awareness of all the above? Show me that man and I’ll show you a liar.
What is the minimum thickness of a footing per the IBC? I don’t think there is one. Notice I said "think." While I’m fairly handy with the IBC, I’m quick to admit that I don’t know all 500+ codes, regulations, ordinances, etc. Thus it is possible that there’s a footing thickness rule lurking somewhere I haven’t looked. I do know there’s a minimum width, 12 inches (IBC, 1809.4). And there’s a table that allows various minimum dimensions for light framed construction (IBC, Table 1809.7). But I don’t find a specified code minimum thickness. Interestingly, Table 1809.7 allows 6-inch-thick footings for one or two story stick-framed construction.
Alonzo’s footing was 9-inches thick. He said "engineered," which indicates to me that a licensed engineer used science to determine that size. I’ve personally designed many hundreds of footings and can attest that 9 inches thick for residential and light commercial construction is not unusual.
So what we
believe strongly is that the building code does not prohibit a 9-inch-thick footing and such thickness is normal for residential construction. What we’re unsure of is whether the local jurisdiction has an ordinance that supersedes the IBC. The best way to find that out is to ask the building official.
Here is where things get sticky. Should Alonzo ask the question and risk provoking the building official? Find out next week in Part Two.