Marijuana Grow Rooms

Carl Brahe, Guest Author, Certified Home Inspector,  CCI

Growing marijuana can be legal in Colorado but it raises more home inspection issues.

Growing marijuana can be legal in Colorado but it raises more home inspection issues.

As medical marijuana becomes legal in more states like Colorado, it also becomes legal to grow at home for certain people. The number of houses and commercial buildings that are used for growing marijuana is increasing. Grow rooms are becoming more common and can cause great damage if improperly built or operated.

Poorly wired or overloaded circuits can result in fire, shock or damage to electronic equipment. A common danger for grow rooms is overloading the circuitry. An average bedroom may share a 15 amp circuit with another room. This means that the wire is able to safely handle 15 amps of electricity at a time. To keep the wire from overheating from too much electricity flowing through it at one time a circuit breaker, or fuse, is wired into the circuit to stop all electricity flow if it gets to be too great. If the wire overheats a fire can result.

If a grow room is made inside this average room a 1000 watt grow light will require a little over 9 amps to operate. That leaves only 6 amps for all other equipment. Add in 100 watts for a circulating fan and 60 watts for an external light source. That consumes your entire available 15 amps. (amps = watts/110 volts)

A larger circuit breaker/fuse might be used to stop power interruption, but that drastically increases the fire hazard. The wire, and outlets,  can only handle so much electricity at a time. Increasing the size of the fuse or circuit breaker will not increase the capacity of the circuit. It will increase the temperature that the wire and outlets might be allowed to reach. In most cases additional circuits can be easily added by a licensed electrician.

Wiring type and quality as well as the kind and condition of breaker/fuse boxes and fixtures should be inspected by a professional. Aluminum wiring and certain breaker boxes increase the likely hood of fire. The cost is little compared to fire and what goes along with it.

Poor quality electrical work may not only endanger your life and property but may also lower resale value. No one objects to having extra, or larger, electrical circuits. It’s a plus, but handyman quality, or worse, wiring makes a house harder to sell. It will probably sell for less.

Inadequate ventilation can cause several problems. If humidity is allowed to get too high, or if ventilation exhausts in improper places, like attics, chimneys or crawlspaces, mold, wood rot and mortar damage can result. Once moisture content reaches about 19% in building materials for 48 hours mold and rot will grow to begin digesting the building materials. An average cubic foot of air on earth has around 100,000 mold spores. When sufficient moisture is available mold grows.

Ventilated into chimneys the excess moisture can combine with creosote to produce acids that dissolve mortar. Exhaust fumes can then leak into living areas. As mortar crumbles bricks/stones are displaced and can fall out.

Growers require ventilation to exhaust heat, moisture and odor, and to bring in fresh air, in most cases. Some growers opt for a completely sealed room with no ventilation. A sealed room presents even more dangers to building and occupants.

A sealed room may require a dehumidifier to keep moisture levels in the healthy range. This consumes more electricity. Materials to cover walls to attempt to keep moisture from the building materials may be used. Failure to control humidity can result in portions of the building requiring gutting to correct moisture, mold and wood rot problems.

Legal marijuana in Denver ColoradoPlants require CO2 to breath.  Without it they die. If a room is sealed the CO2 is consumed by the plants and must be replenished. Propane powered CO2 generators may be used introducing the possibility of gas  leaks and explosions. Where industrial propane burners are used to create CO2 to boost production ultra fine particles and CO can accumulate to lethal levels.

Another method is to vent furnaces and water heaters into the room. This probably works fine for the plants, but put all animals and humans at risk for gas poisoning. Besides CO2 which is fairly harmless to humans gas burning appliances produce carbon monoxide which is deadly and sulfur dioxide which is highly corrosive.

These vents are designed and installed specifically for the appliance. If the venting is altered toxic gases may leak into living areas. If vent gases are allowed to cool too much sulfuric acid forms and damages vent pipes and appliances. Hot vent gases can cause fire.

Excess humidity can cause burners, vent pipes and cabinets of water heaters, furnaces and boilers to rust. Moisture vented into areas with gas burning appliances or not vented from room with furnace air returns, can also cause this.

Another result of excess humidity is the growth of insects and rodents to eat them. The most common things that are hazardous to your property or that create an unhealthy environment in your home usually involve too much water.

Structural damage has been found in illegal grow houses resulting from cutting holes in improper places through joists and foundations. Holes are cut to provide ventilation or electrical access. Building codes provide detailed information about how and where joist may be cut. If these guidelines are not followed floors, roofs, ceilings and walls can break under the load of the building.

It is never a good idea to cut holes in a foundation. The entire building and all of its weight rest on the foundation. Any alteration to the foundation will affect everything above.

Most grow rooms and even commercial grow houses probably pose few threats to future buyers and residents. People growing medical marijuana for their own use, in their own homes are probably not as likely as large scale illegal growers to damage their own living environments. Ignorance may be the biggest threat to these home growers and the people and property around them.

Industrial Hygienist Caoimhin Connell writes: “Remediating a grow house is not difficult and does not usually require gutting the property. The biggest problem in remediating a grow house is getting rid of the odor of marijuana; that can be very difficult.”

As an afterthought Mr. Connell warns that the airborne levels of THC are high enough that any person living in a grow house, or in an adjacent living unit, will test positive in a urine analysis without actually consuming the marijuana. People in positions that require UAs, such as airline pilots and professional drivers, may be fired or prosecuted as a result of a positive test. All residents of multi unit buildings can be adversely affected in this way.

Carl Brahe, Certified Home Inspector, Certified Commercial Inspector

Inspection Perfection Inc: prompt service; honest, thorough inspections; highest quality reporting – on site walk through and written.

For many more resources for property owners/buyers/sellers and professionals go to:

Inspection Perfection, Inc – 303-816-5556


    • Surviving Cancer says

      Where is the danger in maintaining a legal grow room wired by a licensed electrician, using entirely organic nutrients to produce holistic medicine for cancer patients. it may just be me but this seems to be a world away from the danger of producing a drug designed to “EAT AT” your brain.

  1. says

    Other code violations can be probably be found in ventilation and AC systems causing poor air circulation and growth of mold spores. A good inspection is vital to prevent walking right into a ‘sick building syndrome’ situation.
    Orlando Lamas

  2. says

    These types of systems can be very dangerous and hard to maintain. We need environmentally friendly solutions, such as low watt bulbs and fixtures that use less electricity, produce little or no heat, and new types of aeroponics systems that reduce the use of water. HID (High Intensity Discharge) systems need extra ventilation, temperature control systems, ect, these can be eliminated or reduced significantly if you use a new type of system. New developments in flourescent and LED light technology can save thousands and reduce the threat of damage and make it easy and even fashionable to grow. I am colorado based and use a system that grows 75 plants, yielding 4-6 ounces per plant 4-5 times per year. The system uses less than 400 W and only 20 gallons of water which is less than the average fish tank. It has to be the simplest system to use and I have had no problems. The system can be moved (portable) in a matter of minutes if needed.

    • Paul says

      I like your approach to truly green indoor growing. Perhaps you could steer me to a few places to educate myself for a larger grow room. (12′ x 12′)

  3. why says

    lighting a few candals inside of ceramic enclosures or even oil lamps witch have been used safely in the early 1900s and before

    just keep the area around the lamp clear maybe mount it on a wall lined with bathroom tile why not line all the walls with tile

    as far as the thc lite a bond fire behind the police station or near the air intake of a school

    drug testing has so many flaws for false positives bring it to a new level and see if it is still accepted

    last i checked having popi seeds on your bagel can cause a false postive thc has so many valid medical uses such as pain relief just mix it with rubbing alcohol and its instant relief in a topical liquid among other uses

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