Attics can be turned into splendid spaces for children or teen-agers thirsting for a room of their own.

In a turn-of-the-century home I designed, the teen-age daughter wanted her own space, far removed from her three boisterous brothers on the floor below.

With her approval, I selected a simple wallpaper, in a large, open grid pattern background, to cover all the vertical surfaces. All the diagonal and horizontal areas, designed into the typical attic construction, are painted in the beige background color of the paper.

To create a bit of diversity, I used a glorious reproduction brass bed -- our one big expense -- as the centerpiece of the room. Beige sheets with white accents reinforce the wallpaper and paint. Incidentally, these less flamboyant patterns are finally coming into their own, in department store linen shops.

The other expenses were minimal. Inexpensive, brown, polyester carpet covers the restorable floors of this garret, and helps to visually expand the small space. Unpainted modular drawer units, finished in glossy white paint, in the three-drawer combination, form a storage unit and night table under the small window beside the bed.

Similar two-drawer units, placed side by side at the lowest point of the room, create a seating area that's low enough to provide headroom at the cramped end of the room, and wide enough to accommodate an extra bed for an overnight guest. Wall-mounted, adjustable lamps make both bed and seating a cozy spot for good reading.

Geraniums, lots of inexpensive pillows, and a real antique -- a comfortable Morris chair covered in beige velour -- all help to convert yesterday's leftover space into usable, handsome, contemporary space.