A suspended ceiling is created by installing a series of tiles into a metal grid that's suspended from a room's ceiling joists. Having to create the gridwork that makes up the core of a suspended ceiling takes far more effort than putting up a traditional plasterboard ceiling, but if careful attention is given to the details you'll end up with a ceiling that's versatile, with an easily accessible cavity between the ceiling and the ceiling joists, and you'll have replaceable ceiling tiles that can quickly be changed to alter the look of the ceiling whenever you wish.
Determine the height of the ceiling. You should check your local building codes to see if a minimal height is required. Mark a level line on the walls at the desired height using chalk and a carpenter's level. Leave at least 4 inches between the joists and the grid to allow space for angling in the ceiling tiles, 6 inches if installing tiles containing light fixtures.
Nail the L-shaped perimeter moulding into place, using 6d nails in the wall studs. You can locate the studs by using a stud finder. The top of the moulding should be aligned with the chalked lines of your ceiling height, and the moulding can be cut to fit using tin snips, with ends butted together for long stretches of wall.
Use chalk to mark the runner placements. The runners make up the long portions of your grid and will be directly suspended from the ceiling joists. Measure the length of the room parallel to the joists and divide it by the panel size to obtain the number of panels you'll be using. Runners should be placed in 4-foot increments.
Install the 16-gauge hanger wire that supports the runners to the joists with the use of hanger wire screws. Hang wire from the joists along the runner paths, with the wires long enough to extend past the level of the runners by 6 inches.
Make a reference grid to guide the cutting and placement of runners and cross tee sections by extending string from the wall mouldings along runner paths. Generally, cross tees are 48 inches long and placed perpendicular to the runners every 4 feet. The reference shows both the placement of the runners and the level to be installed.
Cut the runners to size. The runners come with cross tee placement points which will hold the metal cross tee pieces that complete the grid when connected to the runners. Cut the runners so that when hung their cross tees will intersect forming perfect squares.
Assemble the gridwork. Install the runners perpendicular to the ceiling joists, using the reference grid. Bend the metal wires at the grid level and attach them to the runners by running them through the holes in the gridwork. Mount the cross tees in the runners to make squares, completing the gridwork.
Cut and remove the reference grid string.
If the partial panel size is large, nearly the size of a full panel, plan for a single row of partial panels. If the space is a small one, it may be more visually appealing to create a row of partial panels on each end of the rows of full panels.
The ceiling joists may be uneven; if so, measure ceiling cavity size using the lowest joist to ensure proper clearance for tiles.