Landlords have been warned that cannabis farmers who pose as ordinary tenants could cause extensive damage to their properties.

Insurance company Norwich Union said it had paid more than £1m to 60 landlords who claimed under these circumstances in 2007.

It said houses were likely to be damaged by water, condensation and holes drilled in walls.

Among tell-tale signs were a "pungent smell", often noticeable next door.

"We have had regular warnings from some police authorities," said Ian Potter of the Association of Residential Letting Agents (ARLA).

Police statistics showed that the number of cannabis seizures rose by 34% in the year to 2006/07.

Tenant vetting

Norwich Union said its claims experience showed that severe damage could be caused by the irrigation systems used to grow cannabis plants.

Holes were often drilled through walls to allow electricity cables to be passed through from one room to another.

And high-powered lighting was often rigged up to illegal power supplies that bypassed normal meters, sometimes causing fires.

"They [landlords] may not be aware that if their property is damaged by tenants using it for the production of cannabis, they may not be covered if they haven't taken 'reasonable precautions' to prevent it happening," said Mike Colmans, an underwriting manager at Norwich Union.

"Vetting the tenant is essential as is carrying out extensive background checks, including checking bank details and references.

"Don't accept payment for rent in cash but, instead, insist it is paid through a bank," he added.

Inspection

The insurer said that cannabis plants were usually grown in pots in every room in a house, with their walls, doors and ceiling lined with polythene.

The plants were typically irrigated with pump spray guns under special lamps, which led to considerable condensation.

Landlords usually do not have right of immediate access to their properties and have to make appointments with their tenants for an inspection.

Mr Potter at ARLA said repeated refusals by a tenant to let their landlord in should be taken as a good tell-tale sign that something suspicious was going on inside.

"One answer is to have a regular pattern of visits to a property, and if a tenant refuses entry do a drive-by to make sure there is no sign of criminal activity," he said.

Article Source: BBC News Website. 16th February 2009.