How to design and build a marijuana grow room indoors

Grow room requirements

If you’re looking to build a marijuana grow room indoors, there are a few grow room design requirements to consider. In this article we’ll help you learn the basics of what you’ll need to set up your grow room to the proper environment to grow weed. Once your grow room plans are a reality, you can learn how to grow weed indoors here.

How much space does a weed grow room need?

Knowing how much space your weed grow room needs is the most important consideration. You’ll want to make sure you have an area large enough to accommodate not only your marijuana plants but to give you adequate room to work around them for pruning and maintenance.

Your grow room doesn’t necessarily have to be large. A small closet can be used to grow several nice plants, but a small bedroom or better yet a room in your basement would be best. Plan to size your lighting and ventilation in accordance to the size of the room you have.

With high wattage lighting such as 1000W sodium halide bulbs, you need to make sure you have lots of ceiling height. But with cooler lighting options, less ceiling height is needed. You can control plant height based on how quickly in vegetation cycle you flip to 12/12 lighting to initiate flowering. You can also train plants using stakes or screens to grow vertically which is useful in short grow rooms. Remember that during the flowering stretch your plants may grow up to double in height, so the more height in your grow room the better.

If you want to simplify things, consider a grow tent. If you have a spare closet, check out how to set up a closet to grow cannabis plants.

Learn how to build a grow room for marijuana.

Selecting the best location for a grow room


The best location to build a marijuana grow room is one that doesn’t allow any light penetration. Weed plants need complete darkness during the flowering cycle to develop properly, so make sure your location doesn’t leak in ambient light.

Temperature and humidity

It’s best to keep your marijuana grow room at a temperature around 70-75 degrees max, so building a grow room in your basement is ideal to help control temperatures. This is especially important in the summertime; if you’re growing in a sunny spare bedroom you’ll need to plan on air conditioning.

You’ll also need to keep humidity levels within proper range. Learn about the best humidity levels and temperatures for growing weed.


Designing your room to be close to windows or a place for exhaust ventilation to exit your home is important.


Access to a sink or water source is nice to have since you’ll constantly need water for your marijuana plants, regardless of what growing medium you grow your weed in: soil, soiless mediums, or hydroponically.


Selecting a subtle location in an unused portion of your home is still a best practice even though you’re growing in a state that has legalized pot. You don’t want to advertise that you’re growing, there’s enough people in this world looking for a free ride that they steal nickels from unlocked cars.  Don’t assume they won’t go after an obvious grow room. Play it safe and be subtle. Use carbon filters to remove odors, and choose a silent grow tent fan if noise is a consideration.


The amount of weed you produce in your grow room is largely dependent upon your lighting. Typically you can plan to harvest about 1/2 gram per watt with a good grow if using Metal Halide or High Pressure Sodium lighting. For example, a 600 watt HPS light could yield about 300 grams of bud if grown correctly.

The amount of light intensity determines how well your buds will grow.  Using a low-intensity light such as a flourescent or CFL light bulbs will yield much less than a high quality LED or MH / HPS bulb setup.

LED lighting is a bit more expensive up front, but has lower long term energy costs and doesn’t require yearly bulb replacement. The light quality from LEDs is very good, but avoid very cheap models which are underpowered and use cheap diodes. Find the best LED grow lights for weed.

If you’re looking to build a marijuana grow room in a small space or if you are using high-wattage lighting, heat output may be a concern. Using air-cooled light hoods and an adequate ventilation system should help alleviate this.  Choosing to build a grow room in an area with tall ceilings is a big plus, it gives you space for robust plants that stretch into the lights. Ventilation and air intake can resolve most temperature and humidity issues.

Make sure to cover the walls with flat white paint or reflective material to redirect additional light back onto your pot plants. There are a number of options available commercially, but flat white paint works really well and is much cheaper than reflective coatings.

Ventilation and Exhaust

You’ll need to make sure that you can design proper ventilation and exhaust in your grow room. Weed requires precise temperatures and humidity for best results. Proper grow room ventilation ensures that hot, humid air can be removed while introducing new air with a fresh supply of carbon dioxide.

You’ll need to run venting that connects your grow room to the outside world. Windows, installing dryer exhaust vents, and running ducting up old chimneys are all employed successfully to ventilate grow rooms.  It is better to run shorter lengths of ducting to maximize efficiency, so plan to build your marijuana grow room where it can easily run exhaust pipes.

Using a carbon filter will scrub the rich odor of flowering marijuana from the outside world. Your plants will stink especially during late flowering, sometimes even a carbon filter can’t keep up.

Learn more about finding the best inline fans for grow tent or grow room setups, or how to determine how much ventilation you need.


Knowing how to build a grow room for weed plants requires some planning. Find a subtle location offering total darkness, near a place to ventilate, with steady temperatures. Plant to have extra space around each plant for pruning and maintenance.  Make sure to have a water supply nearby.

Design your marijuana grow room with adequate lighting, ventilation, and circulation. Filter exhaust air to reduce the smell of weed coming from your grow room.