But a lot of people find it hard to envisage the potential of a transforming extension on what, to them, looks like an ordinary semi-d.

Just as commonly, with no real experience of doing up a house, they won't know where to start looking for architects, builders and craftspeople and therefore baulk at taking on "a project".

Because of this, estate agents say there is a real premium on older houses in good locations which have been given the latest makeover.

No 8 Trees Road in Mount Merrion, Dublin is, its owners admit, "a tired and ordinary semi-d". But in the past year, Andrew MacHesney and John Rooney of Southlake Properties have been planning a massive makeover of the house which entails doubling it in size and providing the sort of finish that a large contemporary family house in its location should have these days.

They had planned to do the extensive building work themselves, says MacHesney. But the possibility of developerrelated tax liabilities arose had they undertaken the project, so they have decided to sell the property as it is . . . along with the plans they had drawn up and for which there is full planning permission.

Now these plans are no ordinary sketch.

MacHesney has had a full three-dimensional visualisation of award-winning architect Elaine Mahoney's plans made up, all of which are available to view along with the house.

When viewers are shown around the three-bed semi-d by agents Sherry FitzGerald, they also get a presentation of how it would look with its makeover. Andrew MacHesney meets them there and takes them through the pictorial 'storyboard' set up inside, and then gives them a 'virtual tour' using computerprogrammed 3D tools.

These show a very swanky kitchen with a massive centre island, a reconfigured house with an extended living area, a beautiful front sittingroom, and a big attic bedroom.

Floor plans and everything from how you can arrange the furniture to possibilities for windows and floor tiles are all possible to see.

"This was very much a labour of love for me, so I'd like to see the house built as we had envisaged it, " says MacHesney, "although of course a buyer doesn't have to use these plans if they don't want to.

"But the permission is there for them and, with my experience on previous projects, I would be happy to offer my services as project manager, sourcing the materials and making sure that any builder carried out the work correctly."

The house as it stands is a three-bed semi-d of 1,200 sq ft.

The virtual house is extended to the back and the side and becomes a four-bed with sleek kitchen and family space, attic room, en-suitemaster bedroom and a still beautiful private back garden looking out onto Oatlands College.

The asking price for the house is 1.4m . . . a similar house, but with side gardens, nearby sold two weeks ago for 1.51m.

"The house, if it were built to our plans would be 2,500sq ft . . . double its present size, with a high standard of finish.

"I estimate it would cost around 320,000 to 350,000 to extend and build to these designs, with another 100,000 needed for kitchens and bathrooms.

"But it would mean you would own a house worth over 2.2m. The other advantage about buying an older house pre-extension means that you pay less stamp duty than buying a house that has already been extended. " Of course, carrying out the work will take time but, for a buyer prepared to wait about a year, MacHesney believes the finished home will be worth the delay.

"I would like to offer my services to project manage the build, " he says, " because I know exactly how it could look.

But there are also plenty of opportunities for a buyer to put his or her own stamp on the house if they want to make changes, say to the kitchens or bathrooms.

"Our proposals are designed to cater for a family with young children who want the best of modern living . . . and this could be a really stunning property in a great location."

Asking Price: 1.4m Agent: Sherry FitzGerald: 01 2961822