What Permits Do You Need?
When investing in a greenhouse, a common question that comes up is permitting. The best way to handle that question is to call the county building department and ask them. In some cases you might be required to give your job site address.
Here’s one way to ask the county and stay anonymous: Hello, Building Department! I am zoned ag and I’m considering putting up a non-code temporary ag structure that does not require footings or a slab. Is that ok?
They might ask what type of ag structure and if you are using electricity. In some cases they may ask for an engineered electrical plan. Typically “residential ag” and “commercial” zoned properties end up needing a permit. The other permit that might be required is a grading permit. Typically, if you move more than 50 yards of material, you need a permit to grade.
A Potential Challenge
If you do need a permit, the county will tell you everything you need to know. One hurdle I see as a challenge is that regulators and licensing authorities for cannabis want everything to be permitted but if the building department doesn’t require one, then how can the licensing authorities for the crop require one? I believe it’s a confusion or interpretation problem that arises from licensing indoor operations. Indoor and outdoor cannot be mixed, joined or compared for licensing and permitting issues.
Site Prep and Installation
Once all the permit issues are dealt with, we can actually prep the site and begin the install. The first step is clearing the land and grading a level spot. Make sure drainage and proper erosion controls are followed.
One of the most common mistakes in prepping the pad is putting down gravel first. Gravel will ultimately get contaminated with soil when you dig through it. Before we add gravel we need as much digging and trenching done as possible. Water lines, power, propane etc. The pad should be laser leveled within an inch variance if possible. A 4-foot difference in elevation from one end of the pad to the other does not qualify as level.
After the pad is cut, leveled and compacted, we can set the strings and mark the holes. The holes are augured with a 12-18-24″ bit depending on the structure. It’s easiest to have a concrete truck drive right onto the pad and fill the holes with the chute off the back. Once the mud sets and is dry, we can call in the gravel. I like to use 3/4 crushed base rock (he same stuff you see on driveways). There are small fines mixed in the rock so it’s easy to compact. Washed rock does not compact well and will end up feeling like loose marbles when you walk on it.
The end wall columns on our greenhouses are 10′ apart so a dump truck can barely fit inside and dump right on the pad. I typically spread a 6′ layer of gravel throughout the greenhouse. It’s also a good idea to keep moisture in the rock and compact it. In some cases, you can get the gravel to be compacted and smooth like concrete.
The next step is to address erosion control. Spreading straw over the areas of land that were disturbed is one of the easiest and most affordable ways to repair the land. Grass seed and even filter fence or straw waddles might be required for cut and fill slopes to avoid sediment run off and landslide protection.