HILE a permit is not necessary to build a roof deck, approval is if you rent or live in a co-op. David Stark and Avi Adler, who own their building in Brooklyn, needed no one's permission.

Because the roof was water damaged when they bought it, they had it retarred. Given the roof's slope, they had to build an intricate deck frame to create a three-tier surface.

The pressure-treated, rot-resistant wood deck, at $6.78 for each 12-foot length of 1-by-6-inch board, was built in sections for ease of maintenance. "That way you can remove sections if you have to reroof or repair an area, or if you need to clean the drains out," said Jim Bartholomew, their architect. The deck frame was lifted and set on neoprene strips to ensure proper drainage.

A skylight was replaced by a more up-to-date-looking one of aluminum and glass ($3,700 for the skylight), matching the patio doors. Cedar louvers were added to the sides of the pergola structure as privacy screens.

Aside from shielding Mr. Adler and Mr. Stark from their neighbors, the louvers create compelling shadows at various times of day. The pergola roof is covered with translucent acrylic panels ($2,400 for the panels), making the porchlike area usable rain or shine.