Build an indoor marijuana grow room

‘The Indoor Marijuana Grow Room’ is where it all happens. The germination, early growing, vegetation, and flowering stages of your beloved cannabis plants will all take place here.

Any problems you encounter and solutions you discover will occur here.

Whether your harvest is a success or failure will depend mostly on how you build a grow room.

There are plenty of factors to consider when first setting up or building your grow room. Some of these factors may be ones that you have never thought about before.

‘Outbuildings, garages, and barns not attached to homes are some of the worst places to grow cannabis. Thieves and law enforcement often do not regard entering a barn or garage as a crime, though they would not consider entering a home.’ ~ Jorge Cervantes

The aspects of grow rooms that are of the greatest importance will be covered here, so read on to understand what exactly you need to do and why you need to do them. This article will teach you how to build your own indoor marijuana grow room.

The marijuana grow room

Before you take any other steps towards growing and cultivating your own marijuana, make sure you have a plan for what you’re doing. You want to have the space you need, as well as all the requirements essential for indoor plant growth— lights, ventilation, nutrients, water, etc. Keep in mind that installing your own grow room is a large investment. That includes labor! You’ll definitely want to follow the “measure twice, cut once” policy.

building an indoor grow room

The size of your grow room depends heavily on how much marijuana you want and how much space you have available. It also depends on the type of cannabis you want to cultivate. If you’re growing for medical purposes, the amount you grow will generally be up to you. The sensitivity and type of illness of the person intending to use it determine the volume that should be grown. You don’t need to be an expert on medicine dosing to calculate the required amount of cannabis for your condition. Everyone can decide by themselves, how much weed they need.

Mini greenhouse alternatives
PLant House Indoor Grow Kit
Plant house indoor grow kit

A lot of medical patients’ average use comes out to between 1 or 2 grams per day. This means for personal use, you’ll need to be pulling in about 1 or 2 ounces per month. In theory, you could be harvesting every 2 months because there are around 60 days of a flowering period. If you want 2 ounces a month, you have to harvest twice the amount, in this case, 4 ounces of cannabis.

Cannabis plants growing in greenhouse

Location of the grow room

The location of your grow room matters for a number of reasons. First of all, you want to have some discretion and privacy for your growing operation. You’ll also want to be sure it’s a location you have control over. There’s no sense in trying to grow indoors if it doesn’t allow you to control the environment. Below we’ll list some helpful tips related to location and planning, before jumping into a couple of hypothetical options.

Choose a sensible area for your garden – someplace out of sight. A cellar’s perfect because it’s underground. The earth is naturally thermally stable, and it takes a lot more time to cool down or heat up than above ground. A cellar will be reasonably cool in the summer and keep out the frost in the winter.

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    If you are in an apartment, you want to keep the location of your Cannabis garden discreet. Therefore, it’s wise not to choose a spot next to the entrance but instead, somewhere at the back. Use an unused room, a special wall unit, or even a cupboard as your growing location. Avoid rooms with large south-facing windows, especially on upper floors, because you can run into issues with heat control. Believe it or not, the sun puts out a lot of heat.

    Most importantly, the grow room should be fit for the variety of cannabis that you are planning on growing.

    Grow equipment

    If you are using electrical products, you will need to meet local safety regulations. Make sure that the amount of power used is adjusted to a range your connection can support. Do not use a lot of shorter cables connected to each other to form one long line, instead use one long direct cable. This minimizes the risk of electrical breakdown.

    Control temperature equipment
    Control temperature equipment

    Ideally, your grow room should make it safe to have both water and electricity present without any risks. If you can set it up in a way that both are nearby, it will make it a lot easier on yourself.

    Do not underestimate water, it is very important for the life of cannabis plants. It’s required -on a daily basis – and in great amounts. You’ll spend a lot more of your precious time on watering if there’s no source of water near your grow room. If you’re in a bind locating good water sources, try connecting a pipe from the nearest faucet and run it into the grow room. Use a submerged pump if you use hydroponics to grow a lot of plants and you have to empty the reservoir.

    The area must be ventilated well. It can be enough to use a window, air duct, or even a chimney to ventilate the room, but you need to make sure there is good airflow. This is especially true if you aren’t using any other ventilation systems to help. Use ventilation pipes to bring in the fresh air and take out the used air if windows and chimneys are too far away from the grow room.

    Also, remember that air takes time to travel. If your fresh air has a long distance to travel to get to your grow room (because of unusually long and winding pipes or ducts), you’ll need to make sure you use fans to help circulate the air.

    You also want to make sure the space is clean. Clean your grow room on a regular basis. Start with the floor first and then work up to the walls and by cleaning the ceiling. After cleaning, put the plants back in their places.

    An asphalt or concrete floor is great for indoor growing, because it doesn’t allow hiding spots for tiny bugs and insects and it is easy to clean. If you can’t provide a tiled floor, then any floor covered with a thick plastic layer might work as well. If you use carbon dioxide (CO2), properly isolate your garden in order to prevent it from leakage.

    Once you’ve thought about all these potential issues and developed a well-constructed plan for your personal grow room, you are ready to start.


    There are a variety of ways to set up your grow room. Before choosing one, determine your needs and location requirements. For example, when growing marijuana indoors, you need to have plenty of light. Without enough light, the plant will not grow.

    indoor grow room set up

    If you are short on space, possibly the smallest space you could get away with growing marijuana in is a cupboard. In fact, a space of 3.2 x 1.6 x 6.5 feet (1 x 0,5 x 2 meters) is big enough to produce enough medicinal cannabis for a single patient. And because of its small size, a cupboard is appropriate for marijuana cultivation – it can be covered up very easily. You can also put a 250-watt HPS light in it.

    A wall cabinet

    Another type of grow room possible in small spaces is a wall unit or a concealed storage space. Here are some estimates for the lighting you’ll need in various wall cabinet sizes:

    Cabinet SizeLighting
    3.2 x 3.2 x 8.2 feet (1 x 1 x 2.5 meters)400 or 600 watt HPS lights
    3.2 x 6.5 x 8.2 feet (1 x 2 x 2.5 meters)2 x 400 or 600 watt HPS lights
    6.5 x 6.5 x 8.2 feet (2 x 2 x 2.5 meters)4 x 400 or 600 watt HPS lights
    6.5 x 9.8 x 8.2 feet (2 x 3 x 2.5 meters)6 x 400 or 600 watt HPS lights

    You should not forget that you also need some space to move and work in the grow cabinet. The measurements above only cover only the area for the marijuana. They do not include the space you will need to move around. Therefore, plan to add some space to the numbers above. Extra space of fifty centimeters around the areas will suffice. Best grow lights and other equipment available here

    Grow tent

    Grow tents are a very popular and smart solution and my favorite. A marijuana grow tent is a lightproof, rectangular tent where you place your containers with soil or hydroponics system. Usually, flood and drain systems or drip irrigation are used in a tent, they don’t work as well with nutrient film techniques.

    They are black on the outside and totally light-proof, lined with reflective material on the inside to utilize light more efficiently. Grow tents allow you to completely customize the environment your marijuana plants live in, including temperature, light intensity, humidity, and location. Tents are portable, durable, washable, lightproof, and waterproof, and come in a wide range of sizes to suit any hobbyist’s needs.

    Full room setup

    There are advantages to using a full-sized room for growing marijuana. One is that fans can be used to refresh the air. They can also be connected with outside air through, for example, a window. This can work in a cellar because a cellar is (usually) built underground in the earth. The Earth keeps the temperature stable, unlike above ground. This means a few fans will be all you need to keep the area cool.

    Download my free marijuana grow guide at this link for more growing tips

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      The attic, on the other hand, is not as good of a choice because it does just the opposite trait. The temperature is highly unstable; it will either be very cold or very hot – depending on the season. The same for rooms and/or wall units facing southward, especially if there are large windows or are on upper floors. During the summer, plants can get quite overheated. Here are some potential room measurements and the light requirements you will want in a room of that size:

      Room MeasurementsLighting
      9.8 x 9.8 x 8.2 feet (3 x 3 x 2.5 meters) 9 x 400 or 600 watt HPS light for a fixed system

      Remember, make sure your room is properly covered and insulated so that it stays dark during dark periods. You want to be controlling the lights, otherwise, you might end up with a sudden, untimely flowering.

      Building your indoor grow room

      Keep all of the walls of the grow room covered with something that reflects light, such as white plastic or white paint. The best material for this, however, is tightly drawn Mylar.

      Secure your grow room lights. Do this by connecting them to the ceiling with a hook, ring or pulley. Make sure the electric portions are securely connected and safeguarded from damage.

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      Next, install devices for air circulation. This could be an exhaust ventilator, an intake fan, or an outlet fan. Avoid long air channels that have curves; they negatively affect the capacity of the aeration. Try and keep the pipe short and straight as much as possible so that your air travels efficiently.

      It’s a good idea to install any other devices at the same time. Some examples are measuring devices such as a hygrometer or thermometer. You’ll also need to set up the substrate (your bottom growing layer) and decide whether you plan to grow in soil or install hydroponics. Hydroponics are way less susceptible to bacteria than soil, making them a good choice in some cases.

      Cleaning your grow room

      It is of great importance that your grow room is kept clean. If you don’t keep your grow room extremely clean, you put the plants at risk for fungus, mold, and disease. A disease can spiral out of control very quickly in the warm, humid environment you’ve created. It’s absolutely vital that you don’t let mold or dust accumulate in any out-of-the-way corners or worse yet, on the plants themselves.

      Also read How to setup a low budget grow room?

      Additionally, you want to be careful to keep any animals far away from your plants. While this might not sound like a difficult task, cats are very curious and tenacious creatures, and dogs love to get into trouble. Don’t let them ruin your crop! Besides causing trouble, animals can carry bugs and bacteria that have a high potential to ruin your harvest.

      Before and after you begin a new growing cycle in your grow room, it’s a good idea to disinfect. Clean the whole location with some sort of cleaning agent, just to make sure you won’t be dealing with any latent parasites or bacteria in future crops.

      Cropped Hands in black gloves trimming medical Cannabis Marijuana buds prepare for drying

      Cleaning up also means cleaning up the waste that your plants create themselves. Inevitably some leaves and foliage will yellow and die off. Make sure you remove these right away. If you do end up having problems with mold or fungal growth, you’ll likely have to abandon that crop.

      FAQ about indoor marijuana grow rooms

      What is a growing room?

      A growing room or growth chamber refers to an indoor room where you grow plants under controlled conditions.

      How much electricity does a grow room use?

      According to the Northwest Power and Conservation Council (NPCC), cannabis grow rooms can consume from 2,000 to 3,000-kilowatt hours (kWh) of energy per pound of product.

      Can I use my basement as a grow room?

      As long as you’re providing water, light, space, support structures, and nutrients to your plants, then you can definitely turn your basement into a grow room.

      Thanks for reading. Please leave comments or questions below and don’t forget to download my free grow bible


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      Robert Bergman

      Robert Bergman is an Amsterdam-based marijuana grow expert who has years of experience from small grows to massive operations. His passion for growing led him to develop his own Gold Leaf strain. Now, Robert is dedicated to sharing his knowledge with the world.... [Read full bio]


      marijuana grow bible
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