How to Build A Cannabis Grow Room in a Garage

How to Build A Cannabis Grow Room in A Garage

Growing cannabis indoors comes with a lot of benefits. Apart from saving you money, you can be sure of the quality you’re consuming. Though you trust your dealer or the dispensary near you, anything grown commercially might forego the small, essential procedures— like proper drying and curing—that make the weed safe and potent. 


How to Build A Cannabis Grow Room in A GarageIf you have a family, growing weed in the same house can be a nightmare, even impossible when you can’t control the reach of children and pets. Most people resolve to using the garage for growing weed. Growing in the garage keeps everything in your control— the weed plants are out of reach of your children and pets, but also the eyes of the public can’t graze your thriving plants. 


It’s funny that states that allow the growing of recreational weed have strict laws on who spots your weed. For instance, in Nevada, you can grow weed, but the plants must be kept hidden from the public. Growing in the open is a felony in most states. So naturally, if you have a family, your weed growing endeavors will gravitate towards your garage. 


Growing weed in the garage is also cost-effective, especially if you’re growing just a few plants. 




When setting up a grow room in your garage, there are a few factors to consider. This article covers the obvious, the not-so-obvious, and seasoned grower secrets that will help you achieve a robust harvest.


A marijuana grow room is an interior space that you use exclusively for your cannabis plants. This room must be completely sealed off and have adequate ventilation and lighting for your plants to thrive.


If you’re building your grow room in a garage attached directly to the house, you risk taking up space intended for vehicles or equipment. It may also be insecure if your house has an adjoining door to the garage.


A detached garage gives you the benefit of a custom space for your grow room. If it’s blocked from public access, it gives you more control and saves you from making additional changes to the main house structure if you need to make any permanent modifications. Your grow room will also remain out of sight and smell to minors and visitors.

Cannabis Grow Room Size

The ideal cannabis grow room size depends on the number of plants you’re willing to grow. If you’re going to grow just a few plants for your consumption, 3x3x2.5 meters is enough. If you need more plants for commercial growing, you’ll need more space. 


The larger the grow room, the more expensive it gets— remember, fixed overhead lights can only serve a small area. You’ll need more lights and more fans if the grow room is larger.

How to Build A Cannabis Grow Room in a Garage
Cannabis plant basking in the light. Proper lighting is essential in your garage grow room.
Photo by Washarapol D BinYo Jundang from Pexels

Advantages of A Grow Room

Cannabis grow room gives you control and makes it easier to manage light, humidity, and temperature. Check out our beginner’s guide to learn more about the ideal environment for your plants.


It is also easier to manage the space economy and protect your young seedlings in a grow room. Your plants also experience better overall conditions, such as protection from bugs, harsh weather conditions, and physical destruction.

Building Your Grow Room

Installing your grow room is a significant investment. You will need enough space and all the essentials your plants need to thrive, including lights, ventilation, water, and nutrients. Check out our guide on how to take care of cannabis seedlings for more information on all the requirements.


If you are growing marijuana for medical use, consider the amount you need. Of course, there is no standard amount because each patient is different. According to ilovegrowingmarijuana, on average medical patients require 1-2 grams per day.


To ensure you have enough supply, you will need to pull almost 2 ounces a month. Considering the 60-day flowering period, you will need to harvest around 4 ounces a month.


Before you start your grow room set-up, consider the materials you will use. The best materials do not hold moisture and prevent moldy walls. If your garage walls are made of wood, consider changing them to concrete or any other material that does not retain moisture.


Your plants need adequate airflow to flourish. They need carbon dioxide too to make their food. You’ll need to install vents, windows, or exhaust fans to enhance the flow of fresh air into your grow room. Also, good airflow helps eliminate odors, prevent bugs, and boosts plant performance.

Electrical Source and Water Supply

Most garages will have an electrical outlet. If you do not have one, install a power source to ensure you can provide adequate lighting. Cannabis plants need water to grow and thrive. Please don’t keep them waterlogged as that makes them more susceptible to bud rot. 


To avoid cannabis root diseases, install a proper drainage system for the overflow. 

Setting Up the Grow Room

Setting the room right is essential in creating the right environment for your plants. From the floor plan to light installation, everything must be just right where it should be;

Floor Plan

You will need to map out the ideal areas in the garage for your plants, complete with accurate dimensions. Taking the exact measurements will help you figure out the right size of vents, lights, and fans to install.


As you draw the floor plan, detail the exact spots where your plants and lighting will go.

Insulate The Walls Of The Grow Room

Insulate your walls with highly reflective materials. We recommend using Mylar, which prevents moisture damage and is highly reflective, giving your plants adequate lighting. Highly reflective mylar also ensures light efficiency, further saving you money. 

Install The Lights

Depending on the number of plants you are growing, you will need 600-watt light every 5-6 feet. 


The more lights you have, the more heat is produced, so factor this in when choosing your extractor fan. Make sure all lights are secure and safeguarded from damage.

Exhaust and Intake Fans

A grow room needs lots of cool air, so you have to expel the hot air produced by the lights. Ideally, the extractor fan should be bigger than the vents. Place the ducts close to the bottom area and the extractor at the top to mimic natural airflow.


You can also position fans towards the lights to keep temperatures low. At this point, install all other devices such as hygrometers, pH meters, and thermometers.


Cannabis plants need water to thrive, but water them with moderation.

The more lights there are, the faster your cannabis plants will dry out. Connecting a water system will ensure your plants have enough moisture.


After setting up your grow room, you can set up the containers with the preferred substrate; like soil or coco coir, and plant your germinated seedlings.

In Conclusion

Setting up a grow room is an expensive venture. However, it is also very satisfying to grow your plants. If you are on a budget, consider using soil, compact fluorescent lights, and white paint instead of Mylar.


Ultimately, the location of your grow room has little effect on the crop itself. The internal conditions make a bigger impact on the quantity and quality of your cannabis. When you keep the internal environment to the optimum, your garage grow room can produce high-grade buds. Keep your grow room discreet and regularly clean it to prevent mold, fungus, and disease. We recommend disinfecting the grow room before and after each grow cycle.