Walter Reed Army Medical Center, whose patients are now scattered over 10 buildings in two separate locations, this week will begin bringing them under one mammoth roof with the opening of a new 1,200 bed hospital.

Built next to the original structure at a cost of roughly $134 million, the "new" Walter Reed will be the largest hospital in the metropolitan area and one of the largest medical care institutions in the country.

The old Walter Reed complex was opened in 1909, bounded by Georgia Avenue, 16 M, Fern and Appen Streets NW. Over the years, the country and the Army grew, the demands of two World Wars, along with the Korean and Vietnam Wars forced the growth of Walter Reed, an Army hospital devoted to advanced care of specialized problems.

"This structure just got too old and too inflexible," Maj. Gen., Robert Bernstein, Walter Reed's commanding officer, said in an interview."It was added to, but the problem is that it was added to horizontally."

The result now, not atypically for hospitals, is a Rube Goldberg maze of tunnels, passageways and temporary buildings that have become permanent fixtures over the years.

When the move into the new building is completed next spring, all medical and dental patients will be cared for in one building, an awesome steel and concrete structure that dwarfs the original brick building next to it, with floor space equivalent to 27.5 acres.

The "new" Walter Reed is the equivalent of a 10-story building in height. It has only seven floors open to the public with another eight, six-foot-high interstitial spaces - one between each floor and one on top - for duct work, pipes, electrical wiring and a monorail system to transport records around the hospital. Although these floors between the floors increase the cost of construction, the theory is that they allow maintenance and repair work to go on with a minimum of disruption to the hospital's operation.

The new building also attempts to incorporate esthetic advances in hospital design, using natural woods on walls and doors and bright colors on walls to make the interior more cheerful rather than depressingly institutional.

The building is 480 feet square, but virtually all of the patient rooms have an exterior view because of eight interior courts on the top three floors where patients will stay.

Each floor will have almost 400 beds - more than 85 per cent of the hospitals in this country have totally. The new facility will be able to accommodate 1,600 patients comfortably and even more if more beds are squeezed into rooms as was done during the Vietnam war when the 1,200 bed capacity was increased to 3,000.

As a referral hospital, with military and some civilian patients from all over the world, Walter Reed does more surgery than conventional community hospitals. The new facility will have 16 operation rooms, plus two "surgicenters" fro patients needing minor surgery that does not require hospitalization.

In an effort to use resources more efficiently, Bernstein said, Bethesda Naval Hospital will eliminate its kidney transplant operation when the new Walter Reed is fully operational and will send Navy patients to Walter Reed for their operations.

The present Walter Reed facility lacks a number of diagnostic and therapeutic devices that the new hospital will have. Where patients now have to be sent elsewhere when a computerized tomography scan - a sophisticated form of X-ray - is needed, the new hospital will have a scanner capable of handling the entire body.

The new hospital will also have a 40 by 20 foot therapy pool, ("Don't call it a swimming pool," Bernstein admonished a visitor) to allow nonambulatory patients to exercise. The present pool, located in a separate building and used for both recreational and therapeutic purposes, will be kept for use by the 6,500 persons who work at the medical center.

The new hospital will retain space for the President and the First Lady should they choose to come to Walter Reed for treatment. Although unfinished, the presidential quarters appear to be smaller and somewhat less gracious than the executive suite of the old hospital. The question is somewhat academic. Although the presidential accomodations are used by other important patients - including foreign dignitaries - President Eisenhower was the last Chief Executive to be treated at Walter Reed. His successors - all former Navy men - have chosen to be treated at Bethesda when hospitalization was needed.

The new hospital will have a kind of futuristic, Buck Rogers kitchen and dining hall ("Don't call it a mess hall," said Bernstein) where persons eligible to eat will gain entry by inserting a coded plastic card into a slot that will determine whether they have authorization to eat in the hall and will flash the amount they must pay into a coin slot for the meal before entering.

The kitchen itself is a computerized, automated affair run from a central control panel where such things as heat and cooking time can be regulated. Food can be flash frozen and stored for later consumption by both patients and hospital staff.

Once the transition is completed, the old hospital will be converted to offices to be used by the support staff needed to run the medical center.

Although the primary function of Walter Reed is to care for military personnel and their dependents, the hospital does take a small number of civilian patients. In case of national disaster in the area or elsewhere, the hospital also has contingency plans to take in patients for treatment.