Sometimes owners add up the cost of a renovation and expect to reap the amount spent in the sale price. While some may be rewarded come auction time, a windfall is rarely the case.

''You need to see the big picture when you're renovating a home,'' says Andrew Nimmo, co-director Lahz Nimmo Architects.

''It's not just about making a quick profit. It's seeing how the house will feel in time, when the children are older and want their independence.''

Nimmo and his life and business partner, Annabel Lahz, renovated their double-fronted Federation-style home in Haberfield. The main changes to the house, which is in a conservation area, were to the back. A new open-plan area, described as a large ''cube of space'', was added at a cost of $100,000, together with a substantial outdoor deck protected by a polycarbonate roof and lined with timber battens.

''This outdoor deck functions as a second living area,'' Nimmo says.

''It's made a huge difference to the house, strengthening the link to the garden.''

When Nimmo and Lahz bought the house, it had been subdivided into two flats. As well as narrow passages, the interior featured a warren of rooms, with the bathrooms positioned to the north and the living areas to the south, away from sunlight.

''The only connection to the garden was through a single back door,'' says Nimmo, who designed large sliding glass doors to the new deck. While a new kitchen and bathrooms were included in the renovation, Lahz Nimmo Architects also made use of existing structures, such as the back garden's garage, described by Nimmo as an eyesore.

''We could have knocked it down, but it was solid and functional and just required some 'dressing up','' Nimmo says.

One side of the garage was clad in timber and there was sufficient room to include a laundry and wine cellar. According to Nimmo, one of the most important features that can maximise value in renovating a home is providing good natural light and ensuring vistas of the garden can be enjoyed from as many vantage points as possible.

And rather than spend the budget throughout the house, the couple focused on areas that would be used. The outdoor deck/pavilion, which covers about 50 square metres, cost an estimated $50,000. However, there were several items that didn't appear on the renovation agenda, such as a pool or airconditioning.

''Pools don't generally increase the sale price,'' Nimmo says. ''They require continual maintenance and they take up a large chunk of a backyard.

''If there's good cross-ventilation, why put in airconditioning?''

Architect Joe Toscano, co-director of DP Toscano Architects, was also mindful of not overcapitalising on two adjoining houses in Hawthorn, Melbourne.

One house is a 1920s Californian bungalow; the other, grander home is Edwardian, built about the start of the 20th century. DP Toscano Architects removed the dividing fence and created a large communal back garden. A shared outdoor pavilion-like room (about five metres wide by 15 metres in length) extends across the two properties.

As well as the addition of the pavilion, both houses were recently renovated, with new kitchens, living areas and bathrooms.

As the properties varied in scale, the bungalow being more modest, the architects selected appropriate materials. The kitchen in the Edwardian house features Corian benches and polished concrete floors, while the bungalow has laminate joinery and timber floors.

For the Edwardian house, the architect's budget was about $40,000, while the kitchen for the bungalow was less than $20,000.

''You can spend twice the amount on a kitchen if you want top-shelf appliances,'' Toscano says.

''But when you're selling a home, buyers don't often appreciate the names that are associated with that price point.''

Light fittings can be another drain on the budget. With this in mind, Toscano used task lighting as well as standard lamps where necessary. As important in reining in budgets is the inclusion, or more importantly, the exclusion, of customised joinery.

''You can buy freestanding, off-the-shelf joinery,'' Toscano says. ''And because it's freestanding, this doesn't form part of the chattels when selling.''

Architect Marcus O'Reilly is also conscious of not simply fulfilling an endless wish-list when renovating. For his own home, an Edwardian house in St Kilda, Melbourne, he added a two-storey wing. A new kitchen, dining and living area was included at ground level, with a main bedroom and en suite on the first floor. The kitchen cost about $25,000.

''There's no need to spend $50,000 on a new kitchen with triple ovens,'' O'Reilly says.

''I recently designed quite a modest kitchen for a restaurateur. We used simple and inexpensive appliances. It was more important to get the layout right.''

Like Lahz Nimmo, O'Reilly sees the inclusion of swimming pools as a questionable feature in a back garden. ''Having one doesn't mean the sale price heads north,'' he says.

''You are better off spending this money on increasing the amount of natural light, whether that takes the form of skylights or simply larger windows.''