In today's gloomy housing market, trying to sell your existing property and find the right new place can be a bit of a nightmare. Fortunately, there may a simpler solution closer to home, writes Geoffrey Hedge extra living accommodation by converting your loft is a far easier option than moving, and can boost your home's value by more than 20 per cent, according to the Royal Institution of Chartered Surveyors (RICS ) Sadly, not all properties are suitable for conversion. The critical factor is, of course, headroom. If you can stand in the loft and raise your arm straight up unobstructed, there's a good chance your roof is ripe for conversion.

You would normally want at least 2.4 metres clear headroom at the apex, bearing in mind that the new floor structure in a converted loft will typically be a little higher than old ceiling joists. Disappointment is most likely to strike for those who live in 1970s properties, the era of fashionably shallow roofs.

When it comes to designing your new loft accommodation, there are basically two main options - roof only' conversions that employ discreet skylights fitted flush with the roof slopes, or those with large dormers that poke out of the roof to maximise the internal living space.

Of course, there are many other tools in the designer's box, including small traditional cottage dormers' that can help transform the looks of even the dowdiest dwellings.

Hipped roofs can sometimes pose problems because the sloping side roof may coincide with the position of your new loft stairs, often needing to be raised, either by adding a side dormer, or converting the hip to a gable wall.

From a planning perspective, as long as you don't raise the height of the roof, or stick an enormous box dormer on the front, your plans should stand a good chance of sailing through the system - in many cases not even needing permission if they're classed as permitted development'.

But it's best to check with the planners first, because even unobtrusive traditional dormer windows may require consent. Large dormers are generally acceptable tucked away out of sight on rear elevations, but this could depend on whether there happens to be a highway nearby and whether they overlook the neighbours.

With these rules in mind, it is rather puzzling to see so many city streets blighted by formidably ugly, monster pill-box' front dormers. In fact, these were accepted as permitted development' until 1988, but would not normally be acceptable today on new conversions.

The good news is that, generally speaking, the current planning system is loft-friendly. The bad news is, the government is proposing to improve' it.

But, after the botched introduction of HIPS, few people are confident this will make things easier - indeed some experts reckon the proposals will make obtaining consent considerably tougher.

Regardless of the planning situation, there is one other council department you will be getting to know rather well - building control.

This is because converting roofs involves making potentially dangerous structural alterations that need to be carried out in accordance with a structural engineer's calculations.

The works will need to be checked by a building control officer, who will also want to be assured that your new loft rooms don't waste energy by leaking heat, and that in the event of a fire, you could safely escape from the new top floor.

One of the problems that has faced homeowners wanting to convert their lofts is a lack of easily-readable guidance. But now Oxfordshire chartered surveyor Ian Rock has written the new Haynes Loft Conversion Manual which explains in plain English how to design, manage and build a typical loft project.

"Making structural alterations to your roof is the building world's equivalent of dangerous sports, says Ian. "So it is important to know precisely what works need to be done at each stage."

The book features numerous colour photos of properties being converted around the county, including projects in Banbury, Bicester, Cowley and Thame.

"One of the first jobs is normally to beef up the frail old ceiling joists in your loft with some decent new floor joists," explains Ian.

"But these in turn will need to be supported, which may mean inserting a pair of new steel beams across the ceiling joists, about a quarter distance in from front and rear - no easy feat.

"Before you can cut out all the obstructing timber components in your roof to make a useable space, it's essential that the new structural support is in place.

This can sometimes be achieved by building a timber studwork purlin wall' from the new steels below up to the underside of each roof slope.

In some cases you may need an extra steel beam inserted at ridge level to support new flat roof dormer joists."