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What Building Codes Apply to a Tiny House?

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The Tiny House movement has been pressing forward very quickly yet many people seem to hit a road block when they come across building code regulations since Tiny Houses have not been addressed in the Building Code, until now…

The newest edition of the 2018 International Residential Code has finally addressed the Tiny House issue. Up until now the building code regulations for Tiny Houses have been left up to the local jurisdictions and typically the code sections that pertain to your traditional dwelling does not really reflect the intent of a Tiny House.

The International Code Council has newly published Appendix Q, titled “Tiny Houses” within the 2018 International Residential Code. This Appendix lays out the building code requirements for Tiny Houses with the intent of establishing the minimum standards to safeguard health, safety, and welfare to the user.

To best understand how this Appendix applies, let us look at the definition of a Tiny House since it now has been defined by the code.

Tiny House Definition

Per Section AQ102 of the 2018 International Residential Code :

A Tiny House is considered a Dwelling that is 400 square feet in floor area or less, excluding lofts.

While we’re defining words lets look at a few more…

A Dwelling is any building that contains one or two Dwelling Units intended to be used and occupied for living purposes.

A Dwelling Unit is a single unit that provides complete independent living facilities such as living, sleeping, eating, cooking and sanitation.

Therefore a Tiny House has everything a traditional home does except that now the size has been defined.

It is important to understand that in previous code cycles the minimum room sizes and ceiling heights required by code for a dwelling unit made it difficult to achieve the intent of a Tiny House, but now with specific language defining what a Tiny House is, it makes building one much more achievable.

With that said lets dive into those important building code regulations…

Tiny House Regulations per Appendix Q of the International Residential Code

Tiny House Ceiling Height

Section AQ103.1 outlines the minimum ceiling height required for a Tiny House. This code section outlines the ceiling height requirements for 3 main areas within a Tiny House.

1. Habitable spaces and Hallways shall not have a ceiling height less than 6 feet 8 inches.

2. Bathrooms, Toilet rooms, and Kitchens shall not have a ceiling height less than 6 feet 4 inches.

3. Lofts are permitted to be less than 6 feet 8 inches. No minimum stated.

Since we are here lets define a few more words to better under these code sections.

A Habitable Space is considered any space within a building that is used for living, sleeping, eating or cooking. Spaces such as bathrooms, toilet rooms, closets, halls, and storage spaces are not considered as habitable spaces.

A Loft within a Tiny House is defined as a floor level that is located more than 30 inches above the main floor, open to the main floor on at least once side with a ceiling height less than 6 feet 8 inches and used as a living or sleeping space.

The Loft ceiling height is more of an exception since the use of one is considered a habitable space, however if the ceiling height is less than what is required for a habitable space and the floor elevation is more than 30 inches, then it is considered a Loft and the ceiling height can be less as defined for a loft.

Ceiling heights for a Tiny House differ from the general requirements for ceiling heights of a standard dwelling.

Want to see what the ceiling height requirements are for a traditional dwelling unit, check out this Post about Residential Ceiling Heights Per Code.

Tiny House Loft – Minimum Required Area

Since the code excludes the Loft area from the maximum floor area of a Tiny House, it does define the minimum floor area and dimension that a Loft must be if it is being used for sleeping or living.

Section AQ104 outlines these minimum requirements for Lofts.

Lofts shall have a minimum floor area not less than 35 square feet.

Lofts shall not be less than 5 feet in any horizontal dimension.

That which is defined as a Loft must comply with these requirements, however there can be portions of a Loft that are not considered to be contributing to these minimum floor area and horizontal dimension requirements.

Portions of the Loft with sloped ceilings that measure less than 3 feet from the finished floor to the finished ceiling do not contribute to the minimum required area for a loft.

Tiny House Loft Access

A Loft must provide a minimum level of access and egress to and from the space, such as stairways or ladders. These requirements are outlined in Section AQ104.2.

TINY HOUSE STAIRWAYS

The clear width for stairways above the handrail height shall not be less than 17 inches and not less than 20 inches in width below the handrail.

Headroom for stairways accessing a loft shall not be less than 6 feet 2 inches.

Risers shall not be less than 7 inches and not more than 12 inches in height.

As for the Tread depth, there’s a formula involved which factors both the tread depth and riser height to determine compliance. Both the tread depth and riser height shall be calculated by using one of the following formulas:

1. Tread depth shall be 20 inches minus four-thirds of the riser height.

2. Riser height shall be 15 inches minus three-fourths of the tread depth.

The top tread and riser of the stairway accessing the Loft shall be built as a landing platform. The landing platform shall be 18 inches to 22 inches in depth when measured from the nosing of the landing platform to the edge of the Loft and 16 inches to 18 inches in height when measured from the landing platform to the loft floor.

As for Handrails they must comply with the same code sections used for your traditional home. This is found in Section R311.7.8.

Same goes for stairway guards. These too must comply with the same code sections used for your traditional home. This is found in Section R312.1.

Stairway codes applying to a Tiny House differs greatly from the general requirements for stairways of standard dwellings.

Want to see what these Residential Stair Code requirements are for a traditional dwelling unit, check out this Post about Residential Stair Codes.

TINY HOUSE LADDERS

Ladders used to access a Loft shall have a rung width of not less than 12 inches with a 10 inch to 14 inch spacing between rungs.

The ladder shall be capable of supporting a 200 pound load on any rung and the rung spacing shall be uniform within 3/8 of an inch.

Ladders shall be installed at a 70 to 80 degree horizontal incline.

Alternating Tread Devices and Ship Ladders can also be used but must have a clear width of not less than 20 inches measured below the handrail height.

Loft guards shall also be located on the open side of the loft. Similar to a guard rail for a bunk bed, you don’t want to roll off of one in your sleep!

Loft guards shall be either minimum 36 inches in height or 1/2 the clear height to the ceiling, whichever is less.

Tiny House Emergency Escape and Rescue Openings (Egress)

Not much has changed here from the general requirements for Emergency Escape and Rescue Openings as outlined in Section R310 other than the fact that windows in Lofts used as a sleeping room shall be considered to meet the requirements of Section R310 as long as the bottom of the opening for the window is not located more than 44 inches above the floor of the Loft, provided that the window complies with the minimum opening area requirements of Section R310.2.1.

Want to see what these requirements are along with a visual guide, be sure to check out this Post about Egress Window Requirements.

Only other addition here to note is that the code as added the term “Egress Roof Access Window” to the definitions for a Tiny House and it is basically a skylight or roof window that satisfies the emergency escape and rescue opening requirements of Section R310.2.

So this basically sums up the general code requirements for a Tiny House. For more information, see Appendix Q of the 2018 International Residential Code for a more in-depth look at building code language for Tiny Homes.

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Reference Source – 2018 International Residential Code – [Buy on Amazon]

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