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Build An Indoor Marijuana Grow Room

Build An Indoor Marijuana Grow Room

'The 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 your 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.

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

The cannabis grow roomBefore 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.

Location of the grow room

Best location grow room cannabis

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 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 hypothetical options.

Choose a sensible area for your garden – some place 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.

Download my free marijuana grow guide for more grow room tips

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

Grow equipment cannabis

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.

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. Cleaned 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.

The cupboard

Cupboard grow room cannabis

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

Wall cabinet grow room cannabis

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:

3.2 x 3.2 x 8.2 feet (1 x 1 x 2.5 meters)  for 400 or 600 watt HPS lights

3.2 x 6.5 x 8.2 feet (1 x 2 x 2.5 meters) for 2 x 400 or 600 wattHPS lights

6.5 x 6.5 x 8.2 feet (2 x 2 x 2.5 meters)  for 4 x 400 or 600 watt HPS lights

6.5 x 9.8 x 8.2 feet (2 x 3 x 2.5 meters) for 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

Grow tent

Cannabis grow tent

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

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.

For the best grow tents check this link

Full room setup

Full room setup cannabis

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.

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:

9.8 x 9.8 x 8.2 feet (3 x 3 x 2.5 meters) for 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.

Building your indoor grow room

Install grow room cannabis

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

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

Cleaning your indoor cannabis grow roomIt 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. 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, its 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.

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


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Comment Section

31 thoughts on “Build An Indoor Marijuana Grow Room

By carebear on 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 be~

By Jennifer ILGM on 1 June 2015

Thanks for the tip!!

By robert Vavra on 11 June 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 strong can you tell me if I might have just got wrong seen in a batchand another thing I just germinated one and it popped up and it's looking retarded and has maybe 5 or 6 leaves going all different directions and it's about an inch tall is that a retard or something

By Jennifer ILGM on 12 June 2015

Hi Robert, Our customer service will contact you via email.

By Melissa on 20 November 2015

Can I use a product made for kitchen herbs, like the aerogarden? Or is the marijuna plant too large for that?

By latewood.ILGM on 21 November 2015


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 plant and trained it LST style; You may get a decent plant to finish. Happy growing 🙂

By B-Rad on 5 December 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 stems because iv broken 2 during mid veg!!! Thanks.

By latewood.ILGM on 9 December 2015


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 too strong.

If you are still training the plant, it must be fairly young. And younger plants should be more flexible, and are, until you give them strong nutrient solution, or fertilizer. It is OK either way, just giving you a little info. Peace

By Maxwell on 30 December 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 would be for it? I've read some type of formula to get an estimate before but I can't remember it.

By latewood.ILGM on 4 January 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 get good coverage with 2 600 watt lamps.

By John on 23 January 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 be enough one on each corner and one in middle ?I have been growing outdoors for many years .Last fall some one stole them .I am still a going to grow outdoors .But this time I am a going to start them indoors . THANK YOU JOHN

By Paul r on 25 January 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 4 inch Honeywell fan in the ceiling and can't get my temperature below 85 Is there a way to figure out how much intake and exhaust I need

By Paul r on 25 January 2016

4ftx4ftx5ft not 6 ft

By latewood.ILGM on 26 January 2016


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; What? There are many different lights; So merely stating a value of 300 watts does not tell me much.

Best thing for you would be to join our forum and start a grow journal. Many good members and Staff experts to help you out there. Hard to design and build a system for someone here in the blog.


By latewood.ILGM on 26 January 2016


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 fill out a "Support Ticket", and we can help you much more efficiently. 🙂


By james on 29 January 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.

By latewood.ILGM on 3 February 2016


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 res' might be good for veg' stage but, plant should be transferred for flower to a bigger res'

By Mike on 30 November 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.

By Mike on 30 November 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 glass, digital ballast.

By Mike on 30 November 2016

Single plant by the way, indica origins.

By latewood.ILGM on 1 December 2016


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 just fine with the vortex fan drawing out the hot air.

Now; If you have temp issues and are using the exhaust fan to only cool lamp. Add another 4" to a bottom port, or save a bit of $$$ by using a 6" inline booster fan. (these are available at any home store).

You should consider joining our forum where we have many helpful growers. 🙂

Happy growing, lw

By Kenny on 3 December 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.

By matt on 7 April 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 the cost roughly? How many and what kind of lights would you use? How many plants could I grow I that amount of space? Water and power is not an issue..ventilation is taking care of ( mountain air system)I've had it I wanna grow a super crop. Would you just grown one strain or a variety? Thanks in advance I'll probably have more questions down the road

By Matthew Baez on 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 and it’s the future of indoor gardening in upcoming days. Thanks for your pieces of information. They are really helpful to me.
I have written a similar article, have a look.

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