You must have heard this before: "Live under my roof and you live by my rules." It is something you would have thought you left behind the minute you fled the family nest. But choose apartment life and you may experience an uncanny sense of deja vu. Except this time, parents are replaced by the management company and the rules are no longer an arbitrary set of principles but a lease.

It's vital to study the terms of the lease before committing yourself because if you rebel against them after signing the lease, you could be facing more than a severe reprimand. In March, one man found this out to his cost when he was ordered by the Circuit Civil Court to pay £7,500 damages to the management company for subdividing his £250,000 apartment in Dun Laoghaire to create an extra bedroom and for replacing carpets with wooden floors. He was ordered to return the apartment to its original condition and pay the management company's legal fees, which amounted to over £25,000.

He had bought the apartment on a 500-year lease containing a number of covenants, including an undertaking not to make any structural alterations or change the layout.

The apartment you want to buy may be a 1970s pit that "oozes potential" but it's important to check out just how far you can go to exploit that potential. This is governed by the lease.

If you yearn to stamp your personality on every sq ft of living space, be warned: frustration could be just around the corner. Some leases are so strict they dictate the type of floor coverings to be used in each room. One 1970s apartment block in Milltown insists that all of its residents have the same office-style canvas slatted blinds.

A standard clause in most lease agreements is that the leasee cannot make alterations or additions to their apartment without the approval of the lessor, which is normally the management company.

In some older apartment blocks, wooden floors are absolutely not allowed. In the more modern developments, they are usually permitted as long as they are properly soundproofed.

As a general rule of thumb, an alteration will not be approved by the management company if it is deemed to have a negative effect on the value or appearance of the property, or if it interferes with other residents' enjoyment of their apartment.

If you want to put in new windows they will have to be identical to the old ones.

In what has become an increasingly litigious society, window boxes are often not allowed in case they fall and injure someone. As far as the balcony is concerned, closing it in, putting up a canopy or hanging out your washing over the rails are all no-nos. According to Ben Gough, of Wyse Estate Agents and Property Managers, these days your balcony might not even be yours. "They are often given to the owners under licence. Under the terms of older leases, you own your balcony and that is it. If it had to be repainted or if it was leaking, the owner had to fix it and if they refused then the management company had great difficulty getting on to it themselves."

In most schemes, TV satellite dishes aren't allowed, which means that dwellers are denied access to a multitude of channels.

And you may well have to find alternative accommodation for old Fido - many blocks have a no-pets rule.

You may be entitled to only one parking space, which could be awkward if you live in a two-car apartment, and there may be limited spaces for visitors.

If you buy a top floor apartment with its own attic, is the attic yours to convert if you wish? Not necessarily - you can use it for storage but if you want to add a roof window then you are into the area of altering the appearance of the property. Usually, the attic space is a common area used to house the water tanks of the apartments in that block.

According to Maria Mason, director of Petra Management Ltd, the best approach to take is a positive one. "If you go about it properly and in a consultative manner, you can do quite a lot." Generally you have to avoid knocking down weight-bearing walls, although you may be allowed to remove partition or plasterboard walls, particularly in newer apartments, but it's best to seek professional advice before going at it with a sledge hammer.

The rules are there for a very good reason, says Mason. "If everyone did their own thing, it would cause havoc and the development would look like a disaster area."

Sometimes a covenant in a lease can be changed, not at the whim of one resident but if a significant number or the majority of residents band together and present their case. But, if nobody complains, can people get away with keeping pets or putting down wooden floors in blocks where they are not allowed?

"You often don't get to enforce the rules until someone complains," says Mason, "but if a wooden floor has been put in, the residents will often know. If it's mostly owner-occupiers in a block, they tend to be fastidious and know what's going on around them. They will know a new floor has been put in, especially if they can hear the people upstairs dragging chairs around."

Prestigious apartment blocks where residents tend to be owner/occupiers - such as St Ann's and Hazeldene in Donnybrook, which have full-time caretakers and where a basic two-bedroom apartment costs £600,000-£700,000 - tend to preserve their exclusivity by having boards of directors that keep a keen eye on the activities of residents. In general, developments with a high proportion of owner-occupied apartments tend to be better maintained than those which have predominantly rented ones. The residents have a vested interest in making sure everyone sticks to the rules - something worth bearing in mind if looking for an apartment.

Do people read the lease in detail? "The majority don't read it" says Mason, "They can be very heavy reading, but it's good to be familiar or get a solicitor to interpret it so you don't end up breaching a convenant."

How often does the management company have to bring a resident to court? Hardly ever. The management company is legally protected by the lease, and in most cases the resident will respond to a stern warning.

According to Sherry FitzGerald's David Lewis, who lives in an apartment, people generally act in the interests of the majority. "I have never seen anything blatant. You might get the odd resident that will smuggle in a little dog, but as long as they are not barking at night or doing their doings in the common area, the other residents may not object."