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Johnston County Inspection Hours Mon - Fri 8:00 am - 5:00 pm  Mon - Fri 8:00 am - 5:00 pm  
Johnston County Inspection Phone 919-989-5060 919-989-5060

Johnston County Inspection Address 309 E. Market Street - Smithfield NC 27577 309 E. Market Street - Smithfield NC 27577  309 E. Market Street
Smithfield NC 27577 

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Residential Sun Room Addition Requirements

The requirements for Sunroom additions vary and are dependent on the type and method of construction.

Three of the most common methods are:

  1. New construction from the ground up,
  2. Construction upon an existing structure such as a deck,
  3. An engineered pre-manufactured system/unit.

Definitions/Descriptions as found in the current edition of the NC Residential Code:

Addition: an extension or increase in floor area or height of a building or structure. For energy purposes, an extension or increase in the conditioned space floor area or height of a building or structure.

Roofed Porch: described in Appendix M as being open or screened in and may be constructed to the provisions of Appendix M.

Sunroom: a one-story structure attached to a dwelling with a glazing area in excess of 40 percent of the gross area of the structure’s exterior walls and roof.

Glazing area: the interior surface of all glazed fenestration, including the area of sash, curbing or other framing elements, that enclose conditioned space. Includes the area of glazed fenestration assemblies in walls bounding conditioned basements.

Deck: an exterior floor system supported on at least two opposing sides by an adjoining structure or posts, piers, or other independent supports.

General Construction Knowledge

Decks and Porches are constructed in accordance with Appendix M of the current edition of the NCRC Wall erection creates a wind load thus construction requirements are found in the body of the NCRC as an addition.

New construction additions must be constructed on a permanent masonry foundation as per NCRC and comply with trade provisions pursuant to Certificate of Occupancy.

Construction on an existing structure can be done via one of two options:

  1. install new footing/foundation providing existing floor system can carry anticipated loads
  2. provide a detailed structural analysis report from a professional engineer in regarding the existing system.

Engineered pre-manufactured sunroom plans shall include information regarding Energy Code compliance. Construction supported by piers only shall provide provisions for insulation and duct protection. If protection is achieved by closing the crawl space area, ventilation details shall be provided.

Sunroom additions shall maintain thermal isolation; and shall be served by a separate heating/cooling system, OR be thermostatically controlled as a separate zone of the existing system provided the existing system is capable of carrying the extra square footage.



Page last updated: January 19, 2024

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