While evaluating an existing home usually requires some detective work, looking at a new house presents a different set of considerations.

The mechanical aspects of a new home -- the heating, plumbing, and electrical systems -- will be required to meet local building codes. Major construction, such as the foundation or the size of joists, will also be covered. But building codes set only minimum standards for safety. Codes are not designed to cover workmanship. A sloppy paint job is not a safety hazard covered by the codes even though buyers might wish otherwise.

Many new home buyers must evaluate their future house on the basis of a model rather than the actual home. Unfortunately, the models sometimes are a combination of showmanship and psychological testing which may not give the buyer a realistic idea of the final product.

Here are some areas to check:

How large are the rooms? If the dimensions of each room are not shown on the floor plan, the house is likely to be small. The model may complicate the issue of size. For example, what is the scale of the furniture used in the model? In some instances, small furniture may be used to give the illusion of greater room size. Rooms may have one label but incompatible furnishings. A dining room may not have a dining room table or there may be a small setting with two chairs.

Are the doors extra? In many models the doors are removed to create an image of increased size. In actuality, most people find foors useful even if it means providing space for them to open and close.

What are you buying? Model homes are often finished with options such as higher grades of carpeting.Ask to see the regular carpets. Also, find out what is under the carpet -- a wooden floor, plywood or a concrete slab.

Other options found in model homes include wallpaper, color schemes other than straight off-white paint throughout the house, finished basements, a fireplace and a deck. Also look for up-graded appliances. The refrigerator in the model may be larger than the standard version or the stove may have extra-cost features.

Lot siting, size and location are extremely important. The model homes may not reflect the physical setting of your home. In addition, model homes often have expensive landscaping that may not come with standard houses.

Be realistic when you check new homes. Look at standard models and past projects by the builder before you make an offer. Also, be certain your offer includes all the features you require to fully enjoy your home.

Peter G. Miller, a broker, teaches the course, "How to Sell Your Home -- With or Without a Broker" through the Consumer Real Estate Center in Washington.