B-45 2020-Current: Hoop House Membrane Structures for Cannabis Cultivation

The purpose of this technical bulletin is to clarify the permitting and construction requirements for both temporary and permanent membrane structures for Group U (Utility and Miscellaneous) occupancies used for cannabis cultivation.  Hoop house membrane structures are used to extend the growing season by creating a protected interior environment.

This technical bulletin is not intended to address temporary or permanent membrane structures used for Group A (Assembly) occupancies, typically associated with events, such as winery events, weddings, etc.  This technical bulletin is also not intended to address membrane structures used for other occupancies such as an agricultural employee workstation, area of employment, or any other cannabis-related purpose such as cannabis sales, drying, trimming, and/or extraction where the occupancy classification of M (Mercantile), F-1 (Factory Industrial Moderate-hazard) or F-2 (Factory Industrial Low-hazard) or other classification is more appropriate.

Version: 09/12/2022

1. Greenhouse: includes glasshouses, conservatories, hothouses, or similar structures for the covered propagation and growing of plants, constructed with a translucent roof and/or walls. A greenhouse is considered to be a permanent
2. Hoop House or Temporary Membrane Structures: means a membrane-covered frame structure erected for a period of less than 180 days within a 12-month period.
3. Permanent: means a building or facility is intended to be used for periods longer than 180 days within a 12-month period.

1. Greenhouses are permanent structures that typically have a foundation, solid support framework, and durable coverings made of plastic sheathing, rigid polycarbonate, or glass. Greenhouses have full protection from the weather, rodents, disease, and other detrimental conditions and are generally completely enclosed.  A greenhouse typically has electrical serving exhaust fans, coolers, heaters, and lighting systems used to provide environmental controls.
2. Hoop houses/temporary membrane structures are traditional agricultural construction methods using a series of flexible or rigid support materials (generally PVC or similar lightweight prefabricated materials) bent into a semi-circle and used as a framework to support plastic sheathing.
   
   The system is placed under tension by staking or otherwise anchoring the structure to the ground at regular intervals to maintain its shape. The structural design and materials used are not tested, listed, or approved as conventional construction methods or materials.  Structures built in this manner are extremely lightweight and generally represent a low fire/life/safety risk if designed within defined size and material limitations.
   
   Hoop houses have no electrical and have passive lighting, air circulation, and moisture controls, typically by opening or closing the ends or sides of the enclosure.

1. Green Houses – Building Permit/ Demolition Permit: a building permit shall be required for any greenhouse exceeding 120 square feet, or that includes any improvements such as mechanical, electrical or plumbing that would normally require a permit. A demolition permit will be required to remove a greenhouse exceeding 120 square feet and any associated mechanical, electrical, or plumbing improvements.
2. Hoop Houses - Temporary Membrane Structures: Permits for temporary membrane structures will be issued and monitored by the Code Enforcement Section in cooperation with The Division of Fire Prevention and Hazardous Materials.
   
   A temporary membrane structure will not be required to obtain a building permit or demolition permit provided all required cannabis cultivation Use or Zoning permits have been approved and all the following conditions for the structure are met:
   1. used exclusively for the growing of cannabis
   2. meets required setbacks from property lines, other structures, residences, schools, and businesses
   3. 400 square feet or less in size
   4. erected for less than 180 days in a twelve-month period
   5. is detached and free standing from any other structure or object
   6. does not have a permanent anchoring system or foundation/footing
   7. does not have an impermeable floor
   8. structural members that are made of flexible and somewhat rigid construction materials, typically PVC pipe or similar material or light-weight pre-formed metal framing.
   9. less than 12 feet in height with not greater than 6 feet vertical sidewalls
   10. the material covering the structural members is readily removable
   11. the material covering the flexible frame is a max. 10 mil plastic or cloth
   12. contains no ventilation, heating, artificial lighting, or any electrical components including electrical conduit
   13. shall not be used for storage of combustible materials
3. Hoop Houses - Temporary Membrane Structure Permits Required:
   1. Building and/or demolition permits are required when:
      1. electrical is supplied to the temporary structure from a service utility or solar array
         1. use of portable generators is prohibited
         2. use of extension cords as electrical conductors is prohibited
   2. A temporary membrane structure containing any of the elements required for a permit shall require a building permit to install and a demolition permit to remove.
   3. No portion of a non-exempt hoop house/temporary membrane structure may be erected prior to the issuance of an appropriate temporary/building permit.
   4. No portion of a non-exempt hoop house/temporary membrane structure (including framing members or foundation elements) shall remain in place after the approved temporary period or longer than 180 days.
   5. Multiple non-exempt temporary structures will not be permitted under a single permit.

When erected, temporary hoop house structures, and all related improvements shall conform with permitting and construction requirements of the California Fire Code and the California Building Code.

Using all available information including verbal disclosures, aerial photography, permit history, methods and materials of construction, etc. staff shall make a determination if the framework supporting the membrane has been in place for over 180 days.  The membrane itself may or may not be present and is not required to make this determination.

Temporary Structures: Membrane structures erected for less than 180 days with a floor area of greater than 400 square feet are subject to the permitting provisions of the California Fire Code for temporary structures.

Permanent Structures: All structures erected over 180 days and/or greater than 120 square feet of floor area are considered permanent and are subject to the provisions of the California Building Code.  A building permit is required to construct, and a demolition permit is required to remove.

In all cases, a building permit is required for the installation of any electrical, heating, plumbing, or mechanical systems serving a membrane structure.  A demolition permit is required to remove these systems.

1. Permit Sonoma Fire Prevention Division – Cannabis Hoop Structure Permit Application
2. Permit Sonoma Fire Prevention Division – Site Plan with Setbacks