The enforcement of building codes as they pertain to greenhouses is quite variable across the U.S. In some communities, a hoophouse is not considered a permanent structure and thereby doesn't require a permit. In others, the grower is required to provide an engineer's seal that certifies that the hoophouse meets all the code standards. This may even require setting the foundation posts in concrete.
The International Building Code (IBC) has been developed to make code enforcement more uniform. However it allows considerable discretion by the local building official so it is important to find out what will be required.
In my dealings with a number of inspectors in the Northeast, I find that many of them have a limited understanding of greenhouse construction and environment control systems. Some of them have never been in a commercial greenhouse. Many of them spend most of their time dealing with residences and light industrial or commercial buildings. The interpretation of how the code is applied to a greenhouse is left up to the building official who frequently is overworked and doesn't have the time to work through the process.
Some states, such as New Jersey, have tried to help production agriculture enterprises by developing a farm building code. This gives construction code relief for farm buildings including greenhouses. It allows farm structures of unlimited area so multi-acre greenhouses can be built. It eliminates requirements such as fire separation walls, fire suppression systems and the need for lighted exit signs. It also exempts temporary greenhouses or hoophouses that are less than 31 feet wide, covered with a flame retardant film plastic, are not anchored permanently to the ground and are used exclusively for the production or storage of live plants.
The IBC code differentiates between a production greenhouse and a commercial greenhouse. The production greenhouse is for growing plants and is not accessible to the general public. The commercial greenhouse, or retail greenhouse as it was referred to in other codes, is used for display and sale of horticultural products and supplies to the public. It comes under the more restrictive Mercantile section of the code.
The building code was developed to protect the health, safety and welfare of the people that work in or visit the building. Besides the structural aspects of the building, it also covers the electrical, plumbing and mechanical systems. Permits are required for these and inspections conducted to see that they are safe.
The following are a few guidelines that I have found helpful in getting through the code process.
- Before starting the project, sit down with the local enforcement officials to discuss just what type of maps, plans and calculations will be required. This could save considerable time and expense especially if all they are going to require is a hand drawn sketch rather than a full set of sealed drawings.
- Before the building official can sign a permit several other signatures are required. If your community has zoning, the zoning officer will usually require a plot plan that shows the location of the greenhouse with relation to property boundaries and other structures. This plan should show setbacks from the property lines and separating distances.
- Most communities have a wetlands commission that oversees a regulated area around a wetland. Check with their officer if you are planning to build near a wetland as they may want to know how you plan to control runoff, what sedimentation and erosion control measures will be installed and what pesticides you will store and use. Some communities will allow greenhouse construction in the regulated area.
- Permits may also be needed for a new driveway entrance and for any sanitary facilities for restrooms.
- In most states the electrical, heating and plumbing work has to be done by a licensed person. The building permit usually requires the name and license number of the craftsperson be listed.
- Pick a manufacturer or erector that has a reputation for doing good work. Check with other growers in the area. I frequently hear complaints from growers who were not satisfied with the quality of work that was done.
- The building official's job is to see that your building is constructed to meet the code. It is not to help you with the design of the building or the heating system although occasionally they will give you a little guidance. Usually the design and specifications are your responsibility. Many states require that the plans be prepared by an architect or engineer licensed in the state where the greenhouse will be erected. Most greenhouse manufacturer's can provide this. The engineers seal takes the responsibility for design away from the building official who just checks to see that the building, when erected, meets code requirements.
- Building permits are also needed for structural changes to an existing greenhouse or the demolition of an old structure. A copy of the permit is forwarded to the local assessor so that an adjustment can be made in your tax assessment.
- Although you may not agree with the concept of getting a building permit, it is generally best not to start your greenhouse without one. If you do, the building official can make you remove the building or if not, interpret the code so that you will have to dot every "i" and cross every "t". This has happened to several growers and can prove to be very expensive.
In general, you will find that building officials are very helpful in getting you through the code process. Their job is to see that your greenhouse is a safe place for you, your employees and customers.
John W. Bartok, Jr., Extension Professor Emeritus & Agricultural Engineer, Department of Natural Resources and the Environment, University of Connecticut, Storrs CT – 2013