The annual influx of students into Dublin and other cities, and the impact of the Bacon report on investment in new homes, are creating greater competition for private rented accommodation. The pressure is exacerbated by the number of refugees and asylumseekers looking for somewhere to live.
This situation is being exploited by some unscrupulous landlords who are offering unauthorised, and possibly dangerous, accommodation. And planning officials say the law cannot stop them.
"The legislation is very fragmented," a Dublin Corporation spokeswoman said. "If you are letting accommodation, you are meant to register, and you are inspected by environmental health officers. You are meant to meet minimum standards. You are meant to have a fire safety certificate.
"But if you flout the legislation it takes a long time to process. We must gather evidence, and they say they are getting planning permission or request further information. That can take four or five months, and an appeal can take another four or five months. Meanwhile the rent is coming in."
There are also loopholes, like exemptions for bed-and-breakfast establishments of less than four rooms.
"It was envisaged for places like Connemara where rooms would be rented for a couple of months of the year," said the spokeswoman. "But we've had a case here which claimed to be a B&B and which had four bunk beds in each of four rooms, accommodating 16 people. To us that is a hostel, yet it was exempted from planning legislation.
"With the refugee crisis and the students, we've had complaints about 20 people living in a house in a residential area. People ask us what we're doing about things like this, but there's nothing we can do. The planning legislation can't keep up with it."
Then there are flats built in the roofs of commercial premises with no adequate fire escapes, and unauthorised extensions.
But the penalties for not complying with planning regulations are quite low. In one instance the corporation prepared a case against one landlord, a persistent offender, and went to court with a huge dossier of breaches of the regulations, including the lack of a fire safety certificate. The landlord was fined £50, one tenant's weekly rent, and the building is still rented accommodation. In practice, Dublin Corporation's planning department has two options in this situation. It can seek an enforcement notice in the District Court prohibiting the unauthorised building from being used, or seek an injunction in the Circuit or High Court demanding that it be dismantled.
While the corporation also has the power to go into a building and remove the unauthorised development, it does not do this as lawyers say it could be liable for damage to the main building.
Corporation officials say enforcement orders are very difficult to implement. While the errant landlord can be fined for continuing to use an unauthorised development, the planning inspectors must prove this by five separate visits to the offending property.
If the landlord refuses access the inspector must give three weeks' notice of his intended inspection. If the landlord does not turn up for the appointment the inspector then has to apply to the court seeking to have him fined for not turning up. "The whole process takes from three to nine months. Meanwhile he is still making money on rent," said one inspector.
In one of his cases the landlord has already been fined once for using an unauthorised attic conversion as rented accommodation. The corporation is certain he is still doing so. It now has to prove a "continuing offence", but every time the inspector comes to examine the building the landlord has mislaid the keys, or is called suddenly away on business, or the inspection is made otherwise impossible.
The corporation may go to the High Court for an injunction ordering the person to remove the development. But this requires an enormous amount of preparation, and, again, the landlord can obstruct the collection of evidence.
"We get 1,300 complaints a year," said the spokeswoman. "Most have some substance. To get action it's the High Court or nothing, and it would become unworkable if you tried to get every case into the High Court. Anyway, a lot of them would not merit it.
"There's a need for other sanctions, like some sort of censure attached to the property which would make it difficult to sell on."
However, this might not be a deterrent. Given the existing demand for rented accommodation, why should a landlord sell?
Meanwhile, the Labour Party's spokeswoman on Dublin, Ms Eithne Fitzgerald, has called on the Government to ensure that all tax breaks and State housing payments are dependent on compliance with the law on minimum standards.
The issue is not just one of unauthorised developments which often affect the amenity value of the surrounding area. It could become a matter of life or death if people are crammed into accommodation with no proper fire exits, and fire breaks out.
A separate section of the corporation, the fire prevention unit, has powers to prevent dangerous buildings from being used for certain purposes. But it cannot inspect every suspicious building. And, with the courts handing down fines of £50 for not having a fire safety certificate, the officials might wonder what value society places on their work.