August, 2010
Inspection News and Views from the American Society of Home Inspectors

Marijuana Grow Operations – The Challenge for Home Inspectors


Homes used as marijuana grow operations, commonly referred to as “grow-ops,” may suffer significant damage. While it’s easy to identify existing grow-ops, this article will focus on the less obvious situation: homes that have been grow-ops in the past. We’ll discuss clues to watch for and what to say in your report. Reporting on these homes can be even more challenging than inspecting them.


Grow-ops are illegal enterprises that often are set up in single-family homes to avoid detection. It is estimated that in some parts of America, as many as one in 150 homes has been used to grow an illegal marijuana crop. Damage to the home can  occur through building modifications and as a result of high humidity levels.

What to look for

While it often is difficult to identify homes that have been used as grow-ops, there are clues.

• Not your average home wiring setup!
    Photo 1

– Damage to the electrical service entrance from tapping into the system upstream of the meter—stealing  electricity.  Photo 2


– Patched holes in the foundation, often covered over, that were used for tapping into the electrical service below ground, before the meter.

– Evidence of non-standard electrical work: wires, fixtures, receptacles, transformers, etc. Photo 3


• Evidence of temporary ductwork    Photo 4


– Repairs to wall, floors and ceilings where ducts were run into the attic or outside.   Photo 5


– Remnants of ductwork connected to roof vent.   Photo 6


– Abandoned attic ductwork and evidence of extra roof vents in the attic.

– Patched damage near fireplaces where ductwork has been run through, often visible from below.   Photo 7


– Cut framing members to accommodate temporary ductwork.

– Stud cut to accommodate duct.  Photo 8

• Plumbing modifications

– Valves added to plumbing supply lines.   Photo 9


• Specific type of damage to walls, ceilings and floors

– Staples around windows and openings for temporary coverings to provide privacy and light control.

– Staples on ceiling, often in patterns, for example, around windows. Photo 10


• Lots of mold
– Mold from the high humidity levels, often on lower floors.   Photo 11


Depending on the community, the buyer may be able to check a registry of homes. Some communities keep a public list of grow-op homes.

What to say

The ASHI Standards of Practice does not require us to identify grow-operations, although we should identify the performance issues listed above. Yet, we know the media and the public expect home inspectors to identify many issues beyond the scope, including homes that have been a grow-op. Because the public expects home inspectors to address any and all home-related issues, we must adjust those expectations or we may find ourselves responsible for things well beyond our intended scope. In my opinion, home inspectors have to meet broad and reasonable consumer expectations or work hard to adjust those expectations.

Here are two questions:

“Should I be expected to identify ex-grow-ops?”

“If yes, what do I tell customers?”

If you want no part of identifying grow-ops, add it to your list of exclusions with your attorney’s assistance. It is perfectly acceptable to say that identifying marijuana grow operations is beyond the scope of a home inspection, and that advice should be sought from those with an appropriate background. This helps, but people still may come after you.

You may suggest customers engage a specialist if they have concerns, or you can offer it as a separate service — for a separate fee. The service may include special equipment,
invasive testing and air-quality testing. If you choose this path, make sure you become the specialist first.

If you decide you will report on grow-ops, understand this is a significant issue that will change many people’s minds about buying a home, and may make a home very difficult to sell. Raising this topic will usually create a strong reaction.

You may see convincing evidence of a grow-op, or you may see subtle clues that leave you unsure. In either case, you can document the evidence and recommend further evaluation. If you are sure it was a grow-op, the evaluation will be to determine whether there is any concealed damage. You may advise customers that while grow-op homes often result in health, safety, performance and durability issues, most can be repaired.

Leave the issue of a stigma to the real estate professional. If you are not sure, again, document what you have seen and recommend further evaluation, which, in this case, is to first determine whether the home has been a grow-op, and second, whether there is concealed damage.

The legal counsel for one home inspection association has suggested wording similar to the following:

“During the inspection, the following items were found: [list the clues]. It is not possible to verify why, how or when these items occurred, but they have been known to be associated with marijuana grow operations. You should seek advice from your real estate professional, the sellers, municipal and/or police records, and if you decide it’s necessary, contractors or engineers, to determine if these items were associated with a marijuana grow operation or not.”

(Note: Wording revised by author. Seek legal advice before using this wording.)

We walk a fine line — we cannot pretend to be experts without the proper background, but often are expected to identify issues that others will identify.


In some areas, marijuana grow operations are a significant issue for homebuyers. Approach the issue as you see fit, but we encourage you to be proactive rather than surprised by a call from an unhappy customer.

Thanks to James Dobney for contributions of both content and images. James Dobney is president of James Dobney Inspections, which has been in operation since 1986 in Greater Vancouver and currently employs 11 inspectors.

He is a founding member and past-president of the Canadian Association of Home Inspectors (British Columbia.) In 1992, he received the Stephen Greenford Award from the CAHPI for dedication to the advancement of the home inspection profession in Canada. Dobney has served on the ASHI and the CAHPI Board of Directors.

All photos in this article Copyright © James Dobney and Associates.

ASHI Past President Alan Carson has been a pioneer in home inspection since 1978. His work includes home and commercial building inspections, inspection training and the HORIZON report writing systems. He has developed many educational programs, most significantly the ASHI@HOME training program.