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Cannabis Farms


According to a report published in 2018 by the Institute of Economic Affairs, the black market in cannabis in the UK is estimated to be worth £2.6 billion per annuum, with 255 tonnes sold to over three million users.  Against this background, recent years have witnessed an explosion in the number of clandestine, indoor cannabis growing operations being established.



The type and scale of the premises in which illegal cannabis farms are established for commercial or personal use vary considerably, ranging from converted rooms in residential buildings, through to large scale production in unoccupied commercial or industrial properties. Premises known to have been converted for cannabis production have included shops, offices, public houses, restaurants, former mill buildings and even a nuclear bunker and a leisure centre. Unsuspecting property owners often do not know that their premises have been used for the purposes of cannabis production until after extensive damage has occurred and the operators have fled. 

In all cases, illegal cannabis cultivation presents a significant risk of damage and costs to the property owner from fires, explosions, escape of water, structural damage and, in some occasions, asbestos contamination. Rot, mould or infestation damage can also occur arising from moisture from irrigation systems. Clear up and repair costs in the aftermath of a cannabis farm can be considerable involving serious loss of rent.


Particular hazardous features associated with illegal cannabis cultivation include:

  • Electrical fire hazards arising from the use of temporary electrical supplies often bypassing the electricity meter (cases have been recorded of digging underground to connect into street lighting).

  • The use of high-powered lighting, heaters and other electrical equipment, temporarily installed with little recognition to safety.

  • Bypassing of gas meters to provide natural gas for use in CO² generators to assist the growing process.

  • Explosion hazards arising from the use of butane gas in the production of Butane Hash Oil

  • Compromising structural fire safety design by the removal or breaching of fire compartmentation.

Commercial cannabis growing has strong links to organised crime, use of firearms, illegal immigration, modern slavery and the exploitation of vulnerable adults and children. Many employ Vietnamese nationals who are forced to work in cultivation in order to pay off debts

to people traffickers.

Under section 8 of the Misuse of Drugs Act, 1971, property owners that knowingly allow a property to be used for the cultivation or supply of cannabis, face prosecution and possible imprisonment.  



Warning signs that a property is being employed for illegal cannabis cultivation, or are intended for this purpose are numerous and can include:

  • A tenant wishing to pay for several months’ rent in advance, in cash.

  • Sudden heightening in the fortification of the premises.

  • Requests not to visit the premises.

  • Evidence of the tampering of the electrical installation.

  • Windows shuttered, blacked out or otherwise obscured.

  • Powerful interior lighting in operation 24/7.

  • A sudden rise or fall in electricity consumption.

  • Constant whirring of ventilation fans and presence of ducting protruding out of walls and windows.

  • Evidence of a pungent and sickly-sweet smell within or emanating from the property.

  • Little evidence of movement in or out the property, or visits made during unsociable hours.

  • External accumulation of bagged rubbish, particularly potting soil, plant fertilizers and insecticides packaging, and spent vegetation.

  • Rapidly melting snow on roof surfaces, or birds gathering on the roof in cold weather arising from escaped heat from cannabis cultivation. 

It is important to recognise that no single one of these signs provides conclusive evidence that illegal cannabis cultivation is being undertaken, but several may be enough to sound an alarm.

In cases of genuine concern, property owners or their agents should immediately contact the Police or Crimestoppers, refraining from tackling the occupants personally.



In an effort to mitigate the ever-present risk of premises being taken over for illegal cannabis production, property owners should consider the following measures as recommended best practice:

  • References should be obtained for all persons named on the tenancy agreement. These should come from an employer and a previous landlord (if applicable), or a Tenant Referencing Service. References should always be requested in writing and should be followed up to confirm their legitimacy.

  • Avoid taking payment for deposits and advanced rent in cash, insisting that payment is made by cheque or bank transfer.

  • Specify in the lease that inspections of the premises are carried out following initial occupation and at least once every three months thereafter.

  • Wherever possible, get to know the neighbours and ask them to keep an eye out for anything suspicious. 

  • Avoid sub-letting.

  • Pay close attention to the security of vacant buildings for which a range of products and services are available, such as perimeter protection, security door and window screens, manned guarding, wireless monitored intruder alarms, CCTV towers, vacant property inspection services, live-in guardians etc.… In many cases it will be advisable to consult a specialist company providing vacant property risk management services and which is a member of the British Security Industry Association.

Details of these organizations can be found at 



Quoting from the website of the National Landlords Association, Richard Lambert, CEO says: “Cannabis farms are a continual threat to landlords and despite carrying out the necessary checks, we regularly hear of cases where landlords’ properties are used for illegal purposes.

To help limit the risk of rented properties being used as cannabis factories, the NLA advises landlords to take full references from their tenants, avoid taking long term rents up-front, check on the property often and get to know the neighbours in the area and encourage them to report anything suspicious.

The risk of premises being taken over for the illegal cultivation of cannabis, resulting in significant property damage and loss of rental income should not be under-estimated. To counter this threat, it is recommended that property owners take on board the advice of this risk bulletin as part of a risk management programme. It is also recommended that this document be made available to companies involved in letting or property management, in order to increase their vigilance in this critical area. 



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