AUTHOR: Valerie Ziavras

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How to Calculate Occupant Load

A fundamental concept of model building codes, fire codes, and life safety codes is that a means of egress is designed to accommodate all occupants of a building. Knowing how to determine the total occupant load of a building is an integral part in determining if the building meets that basic concept. It can be difficult to estimate how many people are going to use a space within a building so most model codes that address egress design will provide requirements for how to estimate this number. If you are working with NFPA 101, Life Safety Code, Table 7.3.1.2 provides occupant load factors for different uses found in a building. Occupant load factors are chosen based on how the space is used and not the occupancy classification of the space. For example, it isn't uncommon for a business occupancy to have spaces that would fall under “business use”, as there will almost always be spaces used for non-business purposes also within the building. A conference room within the business occupancy wouldn't be considered an assembly occupancy unless it was determined to have an occupant load of 50 or more people. For the purposes of determining the occupant load, that conference room has an assembly use. Once the occupant load factor has been determined based on the use of the space, it is then used to calculate the occupant load of that space. Calculating occupant load can be thought of in three steps: Select an occupant load factor Determine the size of the room Apply the occupant load factor to the space There is a common misconception that the calculated occupant load is the maximum number of occupants the space can contain. Instead, the calculated occupant load is actually the minimum number of expected occupants. If the designer, building owner, or other involved party knows the expected number of occupants may be higher than the calculated number of occupants, then that number should be used as the occupant load. If, for example, the building owner knows there will be 5 people working in a storage room that has a calculated occupancy of 3 people, the design needs to be based off of the expected occupant load (5 people). Now, if the building owner says there will only be 1 person in the storage room that has a calculated occupancy of 3 people, the design needs to be based off of the calculated occupant load (3 people).   For a detailed step-by-step explanation of calculating occupant load and to learn about changes to some of the occupant load factors for the current edition (2018), download your free fact sheet! 
Tiny home

Is a tiny house safe? Codes and issues facing tiny houses

What is a tiny house? While the definition varies depending on who you talk to, typically it is considered any house under 400 sq ft. You could fit 6.5 tiny houses inside the average American home (which is around 2,600 sq ft). The tiny house movement is quickly spreading across America. For some buried in student debt, it is viewed as the only way to achieve the American Dream of owning your own home and for others, it is about getting rid of the excess and living more simply. Whatever the reason is, are they safe? Some tiny homes have foundations or are built off-site and tied down to a foundation. Since these sit on a foundation, these have to meet local building code requirements. Safety concerns are related to the large number of tiny homes being built on wheels. You'll see these referred to as THOWs (Tiny Houses on Wheels). These are presenting a problem for AHJs. Local building codes are not enforceable because they aren't built on foundations. Although you might think they should be considered RVs, they are not. The RV standards make it very clear that RVs are only meant for temporary living, not permanent. These tiny houses seem to have created a large problem in the codes and standards world. Many in the tiny house movement like that they are living "outside the law". People build their own tiny homes with their needs in minds. This allows for arguably the most efficient use of space. But, they are technically illegal. While I'm not sure I'm ready to trade in my "large space" for a tiny home, I see the potential. Many have suggested using them to house the homeless or as women's shelters. I've even heard of military families using them. Before we consider using them for such great causes, we need to know they are safe. Some of the major concerns with THOWs: Required number of means of escape Use of ladder in the means of escape Size of windows if they are provided as a means of escape Requirements for smoke alarms and sprinkler systems Lack of foundations Minimum room sizes Plumbing requirements (many THOW owners want to use composting toilets which are largely illegal) Are you ready to trade your "large home" in for a THOW?  Have you seen these in your communities? This seems to be a movement that isn't going anywhere. What safety concerns have you heard regarding these tiny spaces? Picture Credit: The Move | A Tiny House on the Prairies

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