Ch.8 - Plumbing and Mechanical Requirements

Delia Tacheny
Reading: The Codes Guidebook for Interiors

INT 324 - Building Codes

Keywords:

• Drainage System
• Water Supply System
• Plumbing Fixtures
• IPC (International Plumbing Code)
• IMC (International Mechanical Code)

This week we read about Plumbing and Mechanical Requirements as they pertain to interior projects. Plumbing and Mechanical codes are concerned more with health and welfare, rather than life safety. Additionally, the plumbing and mechanical requirements on a project will almost always be handled by an engineer and or a plumbing/mechanical contractor. However, as Interior Designers, it is important for us to converse and coordinate with all workers on a job, so it helps to have a foundational knowledge base of all components of a project. 

Plumbing

There are three main components to a plumbing system: Drainage System, Water Supply System, and Plumbing Fixtures. 

One of the biggest plumbing factors that affects designers, is the number of fixtures required in a space/ building. "The code indicates when water closets (toilets), lavatories, bathtubs or showers, drinking fountains, and other miscellaneous fixtures, such as service sinks and washing machines, are required by the codes. Typically, every floor in a building will require at least one toilet, but the actual number of fixtures depends on the type of occupancy and the occupant load." While the codes require a minimum number of fixtures, some projects and/ or clients may request additional fixtures such as a private office bathroom for the executive. 

When determining the number of fixtures needed, the total occupancy load is usually split 50/50 to account for males and females; however, some projects may necessitate a different ratio if the intended use of the space is proven to accommodate one gender more than the other. The IPC (International Plumbing Code) contains a chart for the required number of fixtures per occupancy and gender. 

All required fixtures must be publicly accessible. Fixtures may be grouped into common toilet facilities, typically separated male and female (though some ungendered spaces are becoming allowed.) Certain occupancies require family/ assisted single-use bathrooms for families with small children or those that are elderly and disabled and may require assistance. Toilets must be provided for customers and employees which may be combined or separated depending on the facility. It's important to understand that the codes do limit the travel distance to a toilet; typically, the path cannot be more than 500 feet, and in malls, it cannot be more than 300 feet.

Once the number of overall fixtures has been established, designers must apply ADA accommodations. Typically, all the components of a single-use bathroom, and 5% (at least 1) of all other fixtures must be accessible. In regard to bathrooms, space/pathways for wheelchairs, heights of fixtures, and the addition of grab bars are usually the primary changes for accessibility. ADA accommodations will vary by occupancy as always. 

Fixture Requirements

"The code requirement that is common to all plumbing fixtures is that each fixture must be durable and finished with a smooth, impervious material to be cleanable and sanitary. For each typical material whether vitreous china, stainless steel, plastic, or other material, there is a standard to judge the quality of the product. For example, vitreous and non-vitreous china fixtures including toilets and urinals must meet the ASME A112.19.2 standard. Although most fixtures are fabricated by the manufacturer to be compliant, meeting the appropriate standard might be a concern when specifying, retrofitting, or designing custom plumbing fixtures."

Water Closets (Toilets)

• elongated bowl and a hinged seat with an open front
• min. of 15" from center of bowl to any side wall/partition/vanity (16"-18" for ADA)
• min. 21" clearance in front of bowl
• if enclosed, compartment cannot be less than 30" x 56-60"

Urinals

• *not required by code for most occupancies, but can be substituted for a percentage of the required male fixtures as indicated by the IPC

Lavatories (Hand-washing Sink)

• 
  must be provided wherever a toilet is required, but not necessarily by a 1-1 ratio
• centerline of lavatory to water closet and/or another lavatory must be at least 30" 
• typical clear floor space must be 30" x 48" or 30" x 52"
• clear floor space must extend 17"-25" underneath the lavatory to allow for a forward approach

Sinks

• *In the codes, a sink refers to a container to hold water for washing
• 
  Ex. service sinks, utility sinks, and laundry basins...

Drinking Fountains

• cannot be stored in a public toilet room or vestibule leading to toilet room
• cannot protrude into an accessible path of travel
• IBC and IPC require two types of drinking fountains: one wheelchair accessible and one standing height.

Bathtubs/ Showers

• mostly provided in residential/ institutional occupancies

*Additional restricted facets of plumbing design to be aware of include, finish requirements, grab bars, accessories, signage, and water flow (sustainability concerns)

Mechanical Requirements

"Mechanical systems provide ventilation, regulate the interior temperatures, and improve air quality in a building so that occupants are comfortable and healthy while indoors."

Mechanical systems are typically combined and stored in mechanical rooms including furnace/ boiler rooms, fan rooms, and refrigeration rooms. The size of the room will be affected by the heating and cooling needs. Heating and cooling loads refer to how much energy is required to heat or cool a space to a comfortable environment; these depend on the occupancy, capacity, use of the space, and any pieces of equipment and light fixtures that give off heat (measured in BTUs). Usually, the most efficient design of HVAC is to separate the building into zones with individual thermostats to accommodate for varying needs of temperature and environment.

The codes require varying degrees of exhaust and ventilation requirement to protect indoor air quality. Return air can be vented through either a plenum or duct system. A plenum system has more restrictions; it must be limited to single fire areas within a building. 

The IPC and the IMC (International Mechanical Code) both produced by the ICC will typically be the required code references in regard to plumbing and mechanical systems. 

Source(s):

Kennon, Katherine E., and Sharon Koomen Harmon. “Ch.8: Plumbing and Mechanical Requirements.” The Codes Guidebook for Interiors, John Wiley & Sons, Inc., Hoboken, NJ, 2022.