Build An Indoor Marijuana Grow Room

March 9, 2021

‘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 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.

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.

If you don’t want to build a grow room, check these plug & play options

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

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 then above ground. A cellar will be reasonably cool in the summer and keep out the frost in the winter.

Learn to harvest marijuana and build your own grow room in my downloadable Harvest Guide!

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.

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.

Get the best grow equipment at this link here

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 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 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 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 or 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.


indoor grow room set up

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.

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. An extra space of fifty centimeters around the areas will suffice. Best grow lights and other equipment available here

For the best grow tents check this link

They are black on the outside and totally light-proof, lined with a 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

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

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

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 the dark periods. You want to be controlling the lights, otherwise you might end up with a sudden, untimely flowering.

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 then 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.

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.

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 indoors 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


The founder of I Love Growing Marijuana, Robert Bergman, is a marijuana growing expert that enjoys sharing his knowledge with the world. He combines years of experience, ranging from small-scale grows to massive operations, with a passion for growing. His articles include tutorials on growing... [read more]


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  1. By carebear ,29 May 2015
    hey dude ... I had a moldy crop last year... u wash them wit water n peroxide... 1 cup to 4 gallons of water....let dem dry by the fan..... awesome killin mold.... n its still great weed!!!!!!!!!!! peace n blessed […]Read More
  2. By robert Vavra ,11 Jun 2015
    hi I have a question I bought 10 seeds from you guys white widow and I noticed one seems to be more green and rounder Leafs and the other ones or more straighter. The year and theOddOne doesn't smell is […]Read More
    1. By Jennifer ILGM ,12 Jun 2015
      Hi Robert, Our customer service will contact you via email.
    2. By Cheezy0220 ,22 Jan 2021
      It's not retarded. It's special! Jk!
  3. By Seeds Or Clones? How To Start My Indoor Marijuana Grow ,17 Jul 2015
    […] the article How To Build A Grow Room for more […]
  4. By Indoor Marijuana Growing Systems ,18 Aug 2015
    […] Additionally, tall windows in a small apartment can actually be close to ideal. If the windows reach down to the floor, the plant itself can be placed on the ground. This is better than raising it up since it […]Read More
  5. By Advantages Of Growing Marijuana Indoors ,23 Oct 2015
    […] When cannabis is cultivated with medicinal function in mind, it needs to be completely free of germs, fungus, parasites or any other microscopic organisms that can cause illness. People with weak and sensitive immune systems or breathing systems need […]Read More
  6. By Melissa ,20 Nov 2015
    Can I use a product made for kitchen herbs, like the aerogarden? Or is the marijuna plant too large for that?
  7. By latewood.ILGM ,21 Nov 2015
    Melissa, You can grow Cannabis in any system; You could use the aerogarden,, but you would have to temper expectations in relation to yield. I researched it years ago, and decided it was too small, but if you tried one […]Read More
  8. By Stop Spider Mites On Marijuana Plants Now! ,01 Dec 2015
    […] also shouldn’t allow old, dead leaves to sit in your marijuana grow room – ever. Pick up any dead leaves on a regular basis and put them in a totally new location. […]
  9. By Advantages of Growing Marijuana Outdoors ,01 Dec 2015
    […] why is this height difference an advantage for marijuana plants grown outdoors compared to indoor cannabis gardens? The answer is simple: it’s a difference in efficiency. Indoor plants are usually smaller so for […]
  10. By B-Rad ,05 Dec 2015
    Very useful & informative chapters in these articles. Q: When poking the stretching tops back under your screen, should you pinch the stems before tucking them, or will this stress them in this stage? My plant seems to have brittle […]Read More
    1. By Anthony ,19 Oct 2020
      I'm planning to grow my own marijuana in a small grow room, how do I boost up the THC content in my plants, thank you.
  11. By latewood.ILGM ,09 Dec 2015
    B-Rad, You can do it either way. Pinching the stems will create some more bud sites, and it might make the stem more manageable. If your stems are that hard, it is possibly due to your nutrients being a little […]Read More
  12. By Maxwell ,30 Dec 2015
    I'm setting up a sog system with a 3×3 mother room, a 7×7 veg room and a 10×10 flowering room. Would 3 600w lights on movers to be sufficient for the flowering room? What do you think the average yield […]Read More
  13. By latewood.ILGM ,04 Jan 2016
    Light movers are 6" long max. So you might bbe able to use 2 600 watt lamps . I would have my footprint in flower room no bigger than 8'x8'. This gives the plants room to breathe and you can […]Read More
  14. By John ,23 Jan 2016
    I am fixing to start my first grow room .What would be my plant to start out with ?I am a going to make it 8x8x8 .How many plants can I get by with and would 5 300 watt lights […]Read More
  15. By Paul r ,25 Jan 2016
    Need some help am building a 4ftx4ftx6ft high grow room am running a 400 watt mh with a switchable ballast .I'm running a 4 inch intake fan and a standard bathroom exhaust fan in the ceiling am also running a […]Read More
  16. By latewood.ILGM ,26 Jan 2016
    John, 8'x8'x8' room can hold 12-16 plants comfortably but, a bit crowded. You need good air circulation and the ability to move from front to back. So 12 is probably the best number. In regards to your lights; 300 watt; […]Read More
  17. By latewood.ILGM ,26 Jan 2016
    Paul. Without more information as to the temps in your room, outside the tent, it would be hard to guess. 1st thing you should do is to get adequate ventilation fans all around. Please join our forum where you can […]Read More
  18. By james ,29 Jan 2016
    I got a 1ft deep by [email protected]/2wide & 4ft tall Box with 1 & 1/2 GL reservoir. Well the Roots out grow the reservoir. Thanks James. Love your seeds got them fast.
    1. By latewood.ILGM ,03 Feb 2016
      james, It is possible that the roots could outgrow your reservoir. I can only assume that your talking DWC??? You did not give good info. I use a 5 gallon reservoir or bigger when using the DWC method. That size […]Read More
  19. By LED Lights For Growing Indoor Marijuana – I Love Growing Marijuana ,15 Apr 2016
    […] creating an indoor setup for growing marijuana, one of the most important decisions is what kind of lights to use. In this article, we’ll […]
  20. By Mike ,30 Nov 2016
    Will a 2' x 3' x7' room work with a 400 hps light? And how strong a fan should I have top and bottom, using a full box shroud with glass, digital ballast.
  21. By Mike ,30 Nov 2016
    Havent grown indoors on a small scale in FOREVER, question: Will a 2' x 3' x7' room work with a 400 hps light? And how strong a fan should I have top and bottom, using a full box shroud with […]Read More
  22. By Mike ,30 Nov 2016
    Single plant by the way, indica origins.
  23. By latewood.ILGM ,01 Dec 2016
    Mike, That is a perfect tent for 1-2 plants. A 400 watt hps will do great, and you should invest in a 4" vortex style fan and carbon filter. No fan will be needed for intake. Passive intake will do […]Read More
  24. By Kenny ,03 Dec 2016
    Did not receive my first order of seeds but once notified a replacement order was sent. Received after 14 days. One happy Aussie thank you.
  25. By matt ,07 Apr 2018
    Question for a master grower! I wanna turn my shop into a huge grow room, my shop is 42x38 with 15ft ceilings with a petition off centered a couple of feet How would you set this up? And any idea […]Read More
  26. By Matthew Baez ,11 May 2018
    I personally know some guys who have tremendous success using grow tents. I think more people will use grow tents now than past. Because the Brands are adding more options and features day by day. Lots of benefits out there […]Read More
  27. By Vincent ,11 May 2019
    You can transform the walls of your grow room into a permanent air ionization system. Eliminating any potential contamination from Powdery Mildew-Botrytis-Gray Mold-Bacteria-Viruses-Mold Spores. Simply mix the ionic paint additive with interior house paint and apply the blended mixture to […]Read More
  28. By Domino Bet 88 ,04 Sep 2019
    I like this website very much, Its a really nice situation to read and get information.
  29. By Best Grow Room Temperature For Marijuana Plants (According To Science) ,29 Apr 2020
    […] Aside from that, the size of your room, the airflow, the number of lights and the extraction rates play an important role. Keep this in mind when building your grow room. […]
  30. By Rhyse ,18 Jun 2020
    Hi I have a long narrow room that's approx 27 square feet 9.2 feet long by 2.8 feet wide at a height of 7.3 feet high Its enclosed with concrete floor inside my home Like a storage space. Is this […]Read More
  31. By Arthur ,19 Oct 2020
    I am a subscribed member to the Lab and yet for some reason, I have lost access. What is the problem with my subscription and when can I expect it to be resolved?
  32. By Dale ,20 Oct 2020
    I'm wondering what's going on I ordered 15 seeds I got 14 and only 10 terminated and to make things worse one strain was supposed to be Train wreck and 2 of the 5 supposedly train wreck plants are nothing […]Read More
  33. By Ken ,20 Oct 2020
    How much light for new seeds 1st, 2nd week?
  34. By Terry ,05 Nov 2020
    I want to try an auto flower set up, do you have a kit or suggestion on lights and equipment and a ball park figure on a price to get started. I have plenty of room but would like to […]Read More
  35. By Tim ,10 Dec 2020
    Hello I'm looking for idvise on what watt LED light I need to get seeds started and big enough to transplant out doors
  36. By Howard ,21 Dec 2020
    Awesome reading if you want to do it right . Thanx Robert
  37. By Andrea ,27 Dec 2020
    I now understand why my downstairs stinks. I do not smoke. But the fumes are making me sick and I hate it. But I learned allot from you and thanks so much. It was very informative.
  38. By Francisco ,01 Apr 2021
    How tall should I grow my plants before putting them to flower if I'm growing indoor in 5×5 tent
  39. By Shirley ,06 Apr 2021
    Yes I have a 9 by 14 grow room is it best to Bud under the colored LEDs or can you use the white LEDs

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