How Does Zoning Affect My Greenhouse Construction?
Local government will determine the necessary permits, licenses, and zoning standards that will apply to a greenhouse. At a minimum, a Certificate of Occupancy and business license will be required. At this time the International Building Code (IBC) has been adopted almost universally in some way. Interpretation and enforcement of the code varies, but inspectors will likely look at factors such as wind load, snow load, coverings, building size, and fire hazards.
Historically, hoop houses and temporary greenhouses have not needed building permits. In some states, waivers for temporary agricultural structures may still exist, but a commercial greenhouse is likely to need building permits and zoning approval. States like New Jersey have adapted special agricultural building codes that are more lenient than regular building codes for retailers or residences. The application of a more lenient code for an agricultural production greenhouse may not apply if the greenhouse contains a retail space.
Building Code Basics
- Wind Load Requirements
- Snow Load Requirements
- Fire Safety Requirements
- Size of Structure Allowed at Location
- Type of Covering Permitted
- Energy Efficiency and Sustainable Construction
- Type of Foundation Required
- Electrical, Plumbing, and Mechanical System Requirements
Before building and designing the greenhouse you should meet with local building code enforcement officials and find out what requirements will apply to you. Things like building plans may require only a simple hand drawing or plans that have been sealed and approved by an engineer. They can also let you know if the site has zoning requirements that will require inspection and approval. Ensuring that you know the requirements for building in your locality will prevent potentially costly mistakes and fines and help guide the construction of your greenhouse.
Greenhouse Wind Loading
The influence of wind on a greenhouse depends on the wind speed and factors of the greenhouse design and site location such as the orientation of the greenhouse, windbreaks on the site, greenhouse style and shape, and ventilation. When wind passes over a greenhouse it creates a pressure differential that is strong enough to cause damage to the building. Wind can also produce a lifting effect strong enough to lift the greenhouse off the ground. Wind loading, the practice of engineering buildings to withstand the effects of wind, ensures that structures are built strong enough to resist this kind of damage. Here are some examples of how wind loading is considered:
An 80 mph wind can produce 16 pounds of pressure per square foot. A 10’ x 100’ gutter connected greenhouse sidewall would need to be strong enough to withstand this force.
An 80 mph wind blowing perpendicular to the side of a hoop house can create a lifting force of 220 pounds per foot of hoop house length. For a 28’ x 100’ hoop house, that is a total lifting force of 22,000 pounds, enough to lift the entire structure. If the hoop house is about 6,000 pounds, the foundation where the posts are anchored must have a withdrawal resistance of around 300 pounds each.
Greenhouse Snow Loading
Snow can have a water equivalent of 1-inch of rain per 12-inches of snow when it is light and fluffy. When snow is wet and heavy it can take only 3-inches of snow to reach an equivalent of 1-inch of rain. Snow can weigh as much as 100lb per square foot in some regions such as Northern Maine. The snow that accumulates on a greenhouse puts a significant amount of weight on the structure. A 1-inch rain equivalent of snow loads a greenhouse with 5.2lb per square foot, which can be as much as 6.5 tons on a 25’ x 96’ greenhouse. Building codes in a locale will generally specify the snow loads a structure must be able to withstand. Semi-gable or gothic greenhouses will be best suited to shed snow.
Building Tips for Snow Loading
- Foundation posts/piers large enough to support the weight of the building
- Diagonal bracing on frames or truss reinforcement
- Adequate number of bolts on collar ties and post connections
- Gothic and semi-gable greenhouse designs shed snow best
- 2"x4" posts installed every 10-ft under the ridges of a hoop house can be installed when snow is predicted
- Multiple greenhouses should be at least 10-ft to 12-ft apart
- Heating systems should be large enough to maintain an indoor temperature of 60°F for melting snow and ice (250 BTU/hour per square foot of glazing can melt 1 inch of wet snowfall per hour)