Knocking two flats into one is catching on. Designers report more clients are casting a covetous eye on their neighbours' flat. But it's not for the faint-hearted. You would have to move out for the duration, and be prepared to invest in the total restoration of both apartments, including the unseen structural, wiring and plumbing works. It can often be cheaper to move and start again. However, if there's a special reason to stay, such as a prime location or view, the design possibilities are exhilarating. Not every adjoining flat can necessarily be co-joined, so your first step would be to determine precisely what can be done. One designer says that newer flats can be more suitable, because they're often easier to convert. Another prefers older buildings because they're less likely to have internal structural walls. So, buyer beware. Discretion could save you money, experts say. Vendors might negotiate harder if they're aware of your motivation. The next step is to be open-minded about the new design. Simply doubling the number of existing, pokey rooms would be a wasted exercise, says designer Carol Ip Hoi-yan, who runs Ip Interiors with her sister Tammy Ip Kar-yan. 'Normally, when one buys a flat in Hong Kong, it doesn't have a proper-sized bathroom or kitchen, and the bedrooms are together on one side,' says Carol Ip. 'If you start with two flats, you can separate the parents and the children to gain more privacy, and create much more user-friendly living space.' Typically, in such a design scenario, the two flats' floor plans will be a mirror image. Logically, the first and second bedrooms on one side are then merged to form a new master suite with walk-in closet and larger bathroom. Often there's still room to add a private study space. In the new design, the original kitchen, maid's room and utility room of one flat are combined to create a modern, more functional kitchen with breakfast nook, while the service areas are moved to the wet areas of the (former) second flat. Knocking out the dividing wall between the two living rooms is often all it takes to double your entertaining space and allow room for a larger dining table. The demolition will be the shortest component of the job, usually being done within one day. Ensure that your contractor has appropriate insurance cover before he starts, Ip says. If you can't completely remove walls for structural reasons, an alternative is to add a wider than average opening, or build in an overhead bulkhead. Larger windows can also be installed, to give a sense of proportion to the larger space. Ip says she's handled a side-by-side project in Tsuen Wan and an upstairs-downstairs combination in Mid-Levels. The up/down scenario is more expensive because it involves an internal staircase and extra structural work, but in this case it was worth it because the top floor enjoys 360-degree sea views. 'I don't know where you could get that anywhere else in the Mid-Levels,' says Ip. Renovation prices vary on the finish, but Ip quotes a starting price of about HK$1,000 per square foot for building works and basic-level fixed finishes. Architect Barrie Ho Chow-lai, of Barrie Ho Architecture Interiors, advises renovators to make sure all the planned works and ceiling heights are authorised to avoid trouble down the track, especially with the neighbours. He says Hong Kong lawyers 'make a very good 'living' from disputes about illegal building works. Ho says it's best to start with a quality building such as Laguna Verde in Hung Hom, where he recently completed a project. The two flats, when combined, provided the owners with 5,500sqft of floor space. Even so, Ho devised a flexible layout. 'The owners like to exercise, but a [dedicated] gym would be extravagant,' says Ho, who solved the issue by making space for a treadmill. Guest accommodation was needed, so he designed a multi-functional opium bed in the former kitchen. The new living room is twice the original size, but still serves a dual purposes. 'One side is fully occupied by a sofa - to imply relaxation - while the other side is a more formal living space that makes good use of my own furniture brand, Ming Collection,' Ho says. The home is fitted with a Poggenpohl kitchen. The budget for such a renovation would be about HK$2.5 million, Ho says. Buying off-the-plan is a smart move if you're considering amalgamating two flats in a new building. Ask the developer to leave out the lower quality fittings that usually come as standard. And the money you save can go towards more expensive European brands.