Is your house too small? Is it poorly detailed and inefficiently planned? Is it difficult to heat or cool? Or is it just plain ugly?

Increasing numbers of homeowners, faced with one or more of these dwelling dissatisfactions, are choosing to remodel and expand their homes rather than moving to new ones. And during times when fewer new construction projects are being contemplated, additions and renovations are keeping many architects and contractors busy.

There are several compelling reasons for improving what you have instead of finding something bigger and probably more expensive, the "move-up" house in real estate marketing parlance.

You may have great affection for your neighborhood and location, especially if you've been there for a while and have cultivated relationships with neighbors, local merchants or friendly bartenders. Your affection may extend to a nearby park or playground, school, restaurant or other familiar spot.

You may be very fond of special elements of your own house and lot: a view, the morning sun in a particular room, a garden or tree you planted.

Your present location in city or suburb may be very accessible. Moving could be less convenient, requiring longer automobile trips on more congested roads to get to work, to visit friends, to attend movies or to shop. You could buy a bigger house but, because of commuting, spend much less time in it.

Economically, it may be less painful to stay put and expand and remodel. If you've owned your residence for a few years and have considerable equity built up because of market appreciation, upgrading may be easier to finance than starting over again with a new purchase and a new mortgage, especially in light of today's lot and development costs.

Additions and renovations can give you a new house without your spending a dime for land, broker's fees or seller's profit. Moreover, the market value added to a property by aesthetic, functional and technical improvements can exceed their cost.

Frequently, owners hire architects only to add a porch or a room, with little modification to the existing structure. But architects sometimes are able to dramatically reshape and refinish an existing house, either preserving and extending its original character or imposing a totally new look by swallowing up or enveloping the old structure.

Occasionally, architectural design can transform an ordinary house into an extraordinary one. Indeed, in design award competitions, residential additions can win out over totally new, custom-designed houses, partly because many talented architects are willing to tackle additions, investing considerable time and thought.

For most homeowners, the biggest payoff is usually not design awards, but enhanced livability -- more space, more rooms, more creature-comforts, better materials, equipment and appliances -- coupled with a higher level of customizing that satisfies the ego as well as the eye.

Of course, there's a downside to doing remodeling and additions to your home -- colossal inconvenience and, if done imprudently, financial overexposure.

Few life experiences match remodeling's attendant mess and disruption if you are obliged, as most people are, to continue living in your house while work progresses.

Inside you must cope with dust, dirt, noise, loss of privacy and compromised security. Parts of the house have to be completely emptied, necessitating the temporary relocation of clothing, personal belongings and furnishings.

Outside, piles of dirt from excavation and debris from demolition accumulate. The contractor's dumping bin may take over a large portion of your street. Trucks continually make their way past your house, contributing to the noise level and occasionally leaving behind lumps of hardened concrete, spots of oil, scraps of wrapping paper, bits of wire and droppings of sand and gravel.

New construction materials have to be stored in driveways and garages or on lawns and terraces, limiting use of parts of your property for weeks or even months. Meanwhile, you go to bed praying that your neighbors won't revolt over the sights and sounds produced by construction work only a few yards away.

And what about your carefully cultivated yard? Prepare yourself. Some of your grass, shrubs, flowers and perhaps one or two trees will be unintentionally damaged or destroyed.

Altering a residence also entails encounters with the unknown and the unforeseen. As the contractor demolishes or digs, he may run into obstacles -- pipes, wires, ducts, asbestos-based materials, rocks -- not shown on drawings.

Even when construction drawings for the original house can be found, the house may not have been built as the drawings indicate. Thus floor or roof joists may be oriented and spaced differently than shown. Partitions assumed to be nonstructural may turn out to be bearing walls. A sewer pipe may exit from the house in a location different than original plans prescribe.

Or previously concealed wood framing, intended to be saved, may be rotting away because of moisture or insect infestation.

Houses not built recently typically violate contemporary building codes and, when modified, may need correcting to pass inspection. For example, entering electrical service and circuit distribution panels commonly need to be beefed up to handle increased loads. New electrical outlets in bathrooms or exposed to weather must be of the ground-fault interrupt type which were not routinely installed 20 years ago.

Guardrails at the edges of elevated platforms, decks and overlooks may need to be higher. Window glass near floor level must be "tempered" to minimize the risk of injury if broken. Many older houses have glass doors or picture windows made with ordinary plate glass.

Unfortunately, changes to accommodate unforeseen or nonconforming conditions almost always add aggravation and cost.

Further aggravation can arise from the psychic stress of living in and with a construction project. On top of the disorder, hundreds of decisions have to be made about design, materials, costs, and financing accompanied by dozens of negotiating sessions between spouses. Building -- or rebuilding -- a house is an acid test for most marital relationships.

However, the greatest risk when remodeling relates to the contractor. No matter how diligent the owner and architect may be, the technical, economic and aesthetic success of a project depends in no small measure on the diligence and competence of the general contractor.

A good contracting firm can make the undertaking almost a pleasure. A bad one can be disastrous.

Competent contractors price projects accurately and fairly, anticipate field conditions, stick to schedules, worry about neatness and neighbors, strictly supervise subcontractors and adhere faithfully to contracts and approved design drawings -- assuming the architect also is competent. Most important, they complete all the work in a professional, craftsmanlike manner.

Marginal contractors are sloppy and slow, manage operations poorly, disregard drawings, and invariably cause delays and financial problems. Accordingly, only builders with credible track records of completed work, satisfied former customers and demonstrated concern for quality should ever be considered.

Unless there is an unexpected and substantial drop in the price of urban land, many homeowners in the 1990s probably will opt for staying put and upgrading what they own. For architects, contractors and materials suppliers geared to residential work, house additions and renovations may be the only way to survive for the next couple of years. Roger K. Lewis is practicing architect and a professor of architecture at the University of Maryland.