how to spot a grow house

How to spot if you have a cannabis farm next door

A cannabis farm uncovered by police in Woolwich in south-east London. Photograph: Glenn Copus/PA

A cannabis farm uncovered by police in Woolwich in south-east London. Photograph: Glenn Copus/PA

I n the course of making a film about Britain’s cannabis industry, I have learned a lot about how to spot a cannabis farm. I have been schooled by policemen who raid them, gangsters who rob them and growers who set them up and produce more than 80% of the cannabis smoked in the UK today.

The latest Independent Drug Monitoring Unit report suggests there are now as many as half a million people growing cannabis in the UK, which equates to roughly one on every street. So how can you spot the cannabis farm next door to you?

Smell Follow your nose. A cannabis crop takes about three months to produce. During the final four weeks, the plants stink. Earlier this year, Crimestoppers helpfully issued cannabis-farm scratch-and-sniff cards to 210,000 homes in the UK to help you identify the exact bouquet.

Light Growers can’t get away from the fact that internal farming requires a lot of it: 2,000 watts running 12 hours a day in a small bedroom looks a lot like the sun, so look out for windows that are constantly blacked out to cover that up. Cannabis farms in spare rooms will have the tell-tale sign of curtains that never open.

Heat Those lights also give off a lot of heat, so the old theory was that the house growing cannabis in the loft would be the one with no snow on the roof in winter. But nowadays growers use internal tents, that isolate a lot of the heat. This makes farms harder for police to spot using their infra-red cameras.

Ventilation Growers need to ventilate the plants with large extractor fans, which generally emit a low hum. If every morning, at exactly the same time, it sounds as if someone next door is starting up their hovercraft, then it’s probably a cannabis farm warming up for the day.

Security Growers live in a paranoid world, always wondering when their door is going to get kicked in – not only by the police but by “enforcers”, violent criminals who make their living by stealing cannabis crops. For that reason many of them adopt Fort Knox-like security. Portcullises on the doors, bars on the windows and even CCTV cameras are not uncommon.

Activity Not all farms are inhabited by the grower so watch out for signs that there is no one actually living there: unkempt front gardens, or if your neighbour never leaves out any bin bags on collection day.

Good neighbourliness If the grower is in residence then it can go the opposite way. Perhaps the most surprising tell for having a grower next door might be their over-the-top neighbourliness as they overcompensate in their efforts not to annoy you or make you suspicious as to what they’re up to. As one grower told me: “I’m the nicest, most law-abiding citizen on my street, because the last thing I ever want is to give someone a reason to want to call the police to complain about me.”

But you may not be the only person trying to spot a cannabis farm on your street. The sinister side to these booming businesses is that they have become lucrative targets for harder and more violent criminals looking to rob them. These people are constantly on the look out for farms within our communities, which in turn exposes the rest of us to potential violence. What’s the solution? The dealers and criminals I spoke with all said that legalisation would put them out of business.

Conor Woodman’s film Exposure: Britain’s Booming Cannabis Business is on ITV on 16 October at 11.05pm

• This article was amended on 17 October 2013. A sentence had been added to the writer’s original copy, which has now been removed.

<p>A new report estimates that 500,000 people grow cannabis in the UK – roughly one person on every street. So how can you tell if your neighbour is raising a crop?</p>

Who, what, why: How can you spot a cannabis farm in your street?

Police say cannabis growers are moving away from commercial and industrial sites towards ordinary houses. But how can you spot a cannabis farm in your street?

Cannabis growing in the suburbs is soaring, with about 21 farms or factories being discovered every day, a new report by the Association of Chief Police Officers says.

The problem has persisted for a while, with insurer Aviva reporting a 30% year-on-year increase in cannabis damage claims last year as criminals turned to rented houses to cultivate plants.

Now the Association of Chief Police Officers (Acpo) says most of the cannabis consumed in Britain is homegrown and is urging the public to keep an eye out for suspicious behaviour in their neighbourhood.

And householders might just want to know for their own sake too.

So how can you spot an illegal drug farm on your doorstep?

Unlike many criminal enterprises, there are telltale signs of cannabis cultivation, according to commander Allan Gibson, Acpo’s lead officer on the subject.

The first thing to look out for is people setting up shop, he says.

“Most of the properties are rented accommodation, and when they move in, they’ll bring a lot of equipment with them.

“It will be ventilation equipment and lighting equipment for irrigation, grow bags, soil – it should stand out as unusual, which is why criminals tend to try and move in when they will be unobserved,” he says.

Gibson says the next thing cannabis growing gangs tend to do is adapt the premises – often by creating venting through floors or re-wiring – but this can easily go unnoticed as plenty of new tenants renovate properties.

Another thing cannabis growers’ neighbours might notice is their absence – or their coming and going at odd hours.

“They won’t be sociable neighbours, they will want to keep a low profile,” says Gibson.

“So if cannabis growers live in permanently, they will barely be seen – and if they are maintaining more than one growth site, they will come and go in the early hours or at night,” he says.

So far, so hard to detect, it seems. But Gibson says there are a couple of obvious indicators that should be easier to pick up on.

Cannabis’s distinctive strong and sickly sweet smell is one of them.

The other is covered-up windows – often constantly pulled curtains or black-out blinds – so nobody can see into the premises and the right temperature is maintained.

Rick Stephens, from West Midlands Police’s cannabis disposal team, agrees windows – usually blackened or “polythened” – are a common giveaway, but he says criminals are getting increasingly sophisticated about covering their tracks.

“In some cases a bay window is created, with a overnight light or TV set up, so the premises looks normal – but actually it is just screened off, with cannabis plants lined up behind,” he says.

Stephens says lighting – which can be spotted by hi-tech thermal imaging cameras which display the heat given off by the strong lights – can also alert suspicious neighbours.

“If we are talking about 500 plants, and work on the presumption that there can be six plants for a set of lights, that’s 80 or 90 lights or transformers that are needed.”

He says initially plants require about 12 hours of artificial light every 24 hours. Growers tend to do this at night, which means it can sometimes be spotted.

“At one house in Wolverhampton, neighbours saw bright lights coming out from a vent under floorboards, under which cannabis was being grown,” he says.

Concerned neighbours can also look out for condensation on windows, or unusual levels of heat coming from a property as a result of lights, according to Bryan Dent, a drugs co-ordinator at West Yorkshire Police.

“It’s going to be considerably warmer than normal room temperature – that will manifest itself in heavy condensation,” he says.

Dent says criminals also often tend to bypass electricity meters, or break into the main meter, to fund the huge wattage used up by the lamps and the fans.

“This might manifest itself in strange electric cables, or digging underground to join into street furniture supplies, such as a lamp post,” he says.

For those who think they are on to cannabis-growing gangs, Gibson says there is one other key tell-tale sign – the criminals do not appear to be environmentally friendly either.

“Growing material like compost and soil is often contained in plastic bags, so we often see them dumped by rubbish bins,” he says.

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Police say cannabis-growing in residential properties is soaring. But how can you spot a cannabis farm on your street?