---
title: "How to Build a Greenhouse: Site, Frame, Glazing, Heat, Permit"
description: "How to build a backyard greenhouse step by step: site, size, frame and covering, anchoring for wind and snow, heat and ventilation, then the permit rules."
url: https://yespermit.com/how-to-build-a-greenhouse/
updated: 2026-10-13
language: en-US
---

# How to build a greenhouse

Put the greenhouse on the south or southeast side of the house, size it about a third larger than today's needs, choose a frame and a covering such as polyethylene, polycarbonate or glass, anchor it against wind and snow, then plan ventilation and heat. Check your city's size line and setbacks first: utilities often require a permit.

*Updated October 13, 2026. Every regulatory fact below links to its official source.*

## Key facts

- A freestanding greenhouse stands on its own, usually with a symmetrical roof.[^1]
- In Park Forest, Illinois, greenhouses are allowed only in the interior side and rear yards, at least 5 feet from the rear lot line and 3 feet from an interior side lot line.[^4]
- Purdue Extension warns that wind can carry the structure away if the wind lift is greater than the dead load, and that the wind lift should not be more than two thirds of the dead load.[^2]
- Humboldt County, California, keeps its greenhouse exemption only up to two hose bibs, two light fixtures, two outlets and a 100-amp subpanel, with no separate electrical service.[^5]
- The model International Residential Code exempts one-story detached accessory structures of 200 square feet or less from a building permit, but your city may draw the line lower or require a permit for every greenhouse.[^3]

**We handle the permit. You build.** All-in, until approved: $399 (Fall 2026 launch price, valid through November 30, 2026; regular price $499), approved or your money back ([conditions](https://yespermit.com/guarantee/)): [order](https://yespermit.com/all-in/). Prefer to file it yourself? [Permit Kit](https://yespermit.com/permit-kit/), $349.

## Choose the type

There are two families of backyard greenhouses. An attached greenhouse leans on the house: a lean-to, an even-span attached at one gable end, or a small window-mounted unit. A freestanding greenhouse stands on its own, usually with a symmetrical roof[^1].

- **Lean-to.** Benches in one or two rows, a total width of 7 to 12 feet, and close to the house's electricity, water and heat[^1].
- **Freestanding.** Easier to place and shape as you like, and it gets more light, but it needs more heat at night because of its larger surface[^1].
- **Hoop or Quonset.** Usually a frame of pipe bent into an arch, easy to build and cover, ventilated by fans at the ends[^1].

## Pick the spot

Light decides everything. The University of Georgia Extension puts the best site on the south or southeast side of the house in a sunny location, where it catches the most sun from November to February; the east side is second best, then the southwest and west; the north side is the least desirable[^1]. For a freestanding greenhouse, it notes that research found a building laid out lengthwise north-south gets less shade than one laid out east-west[^1].

Then check the rules for that spot, because the best sunny corner is often inside a setback. In Park Forest, Illinois, greenhouses are allowed only in the interior side and rear yards, at least 5 feet from the rear lot line and 3 feet from an interior side lot line[^4].

## Size it

Count your plants. A 6-inch pot plant needs at least 1 square foot of bench space, and usually two thirds of a greenhouse is bench and one third walkways and aisles[^1]. The Georgia guide advises building 25 to 50 percent larger than your first estimate, because collections grow[^1]. Then compare with your city's permit line: a greenhouse just under it can save you a building permit, and one just over it cannot.

## Step by step

### 1. Prepare the floor and the base

Level the site and plan the floor. Paths and floors can be gravel, cinders, crushed stone, concrete or brick; a hard surface is cleanest and easiest to walk on, while a loose surface absorbs moisture and helps keep humidity, and the areas under the benches should always absorb water[^1].

### 2. Build or assemble the frame

Frames are made of wood, aluminum, iron or plastic[^1]. The Georgia guide notes that most greenhouses built today are double-layer polyethylene Quonset houses on metal conduit, which blocks less light than wood and lasts longer, since wood rots easily[^1]. Kits come with their own instructions: keep them, because some building departments ask for them.

### 3. Anchor it for wind and snow

A greenhouse is light and catches the wind like a sail. Purdue Extension warns that wind can carry the structure away if the wind lift is greater than the dead load, and that the wind lift should not be more than two thirds of the dead load[^2]. Snow adds weight fast: 3 inches of snow can add 5 pounds per square foot, and Purdue estimates the ground snow load in the U.S. Midwest at 15 to 30 pounds per square foot[^2]. Park Forest requires sheds to be anchored so wind cannot move them[^4]. If you live where snow or wind loads are high, have the design checked; we prepare permit drawings, not structural calculations.

### 4. Choose the covering

| Covering | What to know |
| --- | --- |
| Glass | The traditional choice, needs no replacement, but breaks easily, costs more and needs stronger construction[^1] |
| Fiberglass | Lightweight, strong and practically hail-proof; poor grades discolor and cut light[^1] |
| Polyethylene film | Low cost and light; lasts 1 to 3 years depending on the type; UV-inhibited film lasts longer[^1] |
| Polycarbonate | High impact resistance and service temperature; can yellow and scratch[^1] |

Polyethylene loses heat faster than glass, an advantage on sunny days and a drawback at night[^1].

### 5. Plan ventilation and cooling

Ventilation and cooling matter as much as heat, especially in southern climates; systems range from manual vents to fully automatic ones driven by a thermostat[^1]. Automatic controls for temperature, light, watering, humidity and ventilation cut daily chores to a few hours a week[^1].

### 6. Plan heat

Small greenhouses are often heated with space heaters and a fan to spread the warm air[^1]. If you burn gas, oil or coal, the Georgia guide warns to provide fresh air and an unobstructed chimney so carbon monoxide cannot build up[^1]. Set the thermostat around 40 °F for frost protection only, higher if you want to grow warm-season plants[^1].

### 7. Bring in water and power the right way

The Georgia guide recommends that plumbing and electrical work be done by professionals in accordance with local codes[^1]. This is also where permits come in: Humboldt County, California, keeps its greenhouse exemption only up to two hose bibs, two light fixtures, two outlets and a 100-amp subpanel, with no separate electrical service[^5].

## Do you need a permit to build a greenhouse?

The model International Residential Code exempts one-story detached accessory structures of 200 square feet or less from a building permit[^3], but your city may draw the line lower or require a permit for every greenhouse. Park Forest requires a building permit to install or replace one and caps it at 120 square feet in its residential districts[^4]; Santa Clarita, California, requires a permit for greenhouses over 120 square feet[^6]. The Georgia guide sums it up: usually a building permit is required to erect a greenhouse[^1].

Skipping it is a risk you carry until you sell. Santa Clarita can issue a stop work order for unpermitted construction, and if work continues, the owner faces fines and a lien on the property[^6].

> **We prepare the file, you build the greenhouse**
> The All-in offer checks your city's rule for your address, draws the site plan with the distances to every line, prepares dimensioned drawings or assembles your kit's documents, fills in the forms and answers the city until approval. We are not engineers and the city decides.

## Common questions

### Which direction should a greenhouse face?

The University of Georgia Extension says the best site is the south or southeast side of the house, in a sunny spot, then the east side; the north side is the least desirable. For a freestanding greenhouse, it notes that research found a north-south lengthwise layout gets less shade than an east-west one.

### What is the cheapest greenhouse covering?

Polyethylene film. It is low in cost and lightweight but breaks down in sunlight and must be replaced; the University of Georgia Extension gives one to three years depending on the type, and says ultraviolet-inhibited film lasts longer.

### How big should a backyard greenhouse be?

Count your plants. A 6-inch pot needs at least 1 square foot of bench, about two thirds of a greenhouse is benches and one third walkways, and the University of Georgia Extension advises building 25 to 50 percent larger than your first estimate.

### Do I need a permit to build a greenhouse?

Often, yes. The model code exempts detached one-story accessory structures up to 200 square feet, but many cities use a lower line, Santa Clarita, California, requires a permit above 120 square feet, and wiring or plumbing usually needs its own permit.

## Get it done

**We handle the permit. You build.** All-in, until approved: $399 (Fall 2026 launch price, valid through November 30, 2026; regular price $499), approved or your money back ([conditions](https://yespermit.com/guarantee/)): [order](https://yespermit.com/all-in/). Prefer to file it yourself? [Permit Kit](https://yespermit.com/permit-kit/), $349.

## Sources

[^1]: [University of Georgia Cooperative Extension, Bulletin 910, Hobby Greenhouses (minor revisions November 17, 2023)](https://fieldreport.caes.uga.edu/publications/B910/hobby-greenhouses), checked October 13, 2026.
[^2]: [Purdue Extension, Greenhouse Construction (HO-346-W, January 2026)](https://edustore.purdue.edu/media/wysiwyg/downloads/pubs/HO/HO-346-W.pdf), checked October 13, 2026.
[^3]: [City of Federal Way, Washington, Residential permit exemptions (International Residential Code, Section R105.2)](https://www.federalwaywa.gov/page/residential-permit-exemptions), checked October 13, 2026.
[^4]: [Village of Park Forest, Illinois, Building Department, Accessory Structures, Greenhouse or Shed (Chapter 118, rev. 3-2018)](https://villageofparkforest.com/DocumentCenter/View/3133), checked October 13, 2026.
[^5]: [County of Humboldt, California, Planning and Building Department, Residential Accessory Greenhouse Exemption Form (revised 10/2/2020)](https://humboldtgov.org/DocumentCenter/View/116674/Residential-Accessory-Greenhouse-Exemption-Form-PDF), checked October 13, 2026.
[^6]: [City of Santa Clarita, California, Building and Safety, Stop Work Order Information](https://santaclarita.gov/building-safety/?p=1012), checked October 13, 2026.

---

Source page: https://yespermit.com/how-to-build-a-greenhouse/ · YesPermit, sold by LACANGEL GROUP SAS, 1 rue Marguerin, 75014 Paris, France. Prices in US dollars, taxes included. YesPermit prepares permit applications; it is not an architect, engineer or law firm, and the city or county decides on every permit. Site summary for AI assistants: https://yespermit.com/llms.txt