Acoustical Ceilings

Identifying the Starting Point

The height of the ceiling is usually marked inside a special box or circle on the reflected ceiling plan. If not, the ceiling height can be determined by examining the appropriate section view or elevation view in the prints.

When installing an acoustical ceiling, selecting the correct starting point is critical. The starting point may be identified in a number of ways.

The section views and elevation views both provide vertical dimensions that can be used to establish the distance between the floor and the installed ceiling. Of most importance is that the carpenter doing the layout not forget to incorporate the flooring material thickness when calculating the ceiling height.

Example:

Identifying the Starting Point

Detail views may provide vital information that will determine the techniques used for installing acoustical ceilings. Most detail views can be found on the print pages containing the reflected ceiling plan or section views.

The reflected ceiling plan may show the distance from the edge or center of a tile to a column, wall, or landmark shown on the prints.

When examining the reflected ceiling plan there is a distinct difference between a 2'-0" x 4'-0" grid pattern and a 2'-0" x 2'-0" grid pattern. Sometimes the architect may include a note showing "equal" in both directions if the intent is to center the ceiling in the room.

Example:

Ceiling Components

Grid Patterns

Making Miter Cuts

Making Miter Cuts for Outside Corners

To achieve a clean and professional look, wall angle needs a miter cut at the corners. When making the miter cuts, start from the entrance and work around the room so that all the cuts face the back wall. (same principle as vinyl siding)

• Remove 1-1/4" from the wall side of each piece of wall angle (creating a left and right-hand piece)
• Align one piece of wall angle with the reference line extending the tab past the corner
• Secure the wall angle with two screws
• Overlap the tab of the remaining piece of wall angle with the tab of the wall angle installed
• Align the wall angle with the reference line
• Mark the back and front sides of where the wall angles meet, cut, and install with angle piece below

Installing Wall Angle

Installing the wall angle properly ensures that the rest of the grid installation goes smoothly. By carefully following each step in the wall angle process, many costly mistakes can be avoided.

• Establish a level reference line
• Check all four corners of the room to determine the highest point of the room
• Measure the wall angle flange being applied to the wall
• Add this dimension plus floor thickness (if not already installed) to the height of the ceiling
• Measure from the highest point of the floor up the dimension figured in the previous step
• Measure the distance from the level control line to the mark made in the previous step, transfer this measurement to the other three corners of the room

Installing Wall Angle

It is good practice to mark the corners of the room; two surfaces can be marked at the same time. Also when fastening wall angle be sure to hit studs, screws should be spaced no more than 24" o.c.

The flange of the wall angle is being measured and added to the ceiling height to ensure that when the the reference line is snapped, it is not visible on the painted surface of the wall after it is installed. It is also common for carpenters to remove some of the chalk from a chalk line before snapping the lines on a wall, especially if they just filled up their chalk box.

Fastening Hanger Wire

To establish a direct tie, the wire must be wrapped around itself three times within 3" of the wire length, and be spaced no more than 4'-0" apart.

Hanger wires are attached to the overhead structure in a variety of ways, depending upon how the building has been constructed. One commonly used technique is to tie the wire directly, to the ceiling joist.

Most hanger wires are fastened to the grid system at node points, the places where cross tees attach to the main runners. Calculating the border tile dimensions will help determine the first node point, and from there the wires are installed every 4'-0" along the main runner.

Fastening Hanger Wire

Hanger wires must be plumb within a 1 to 6 ratio, which means that every 6" length of wire must not be installed more than 1" out of plumb. When a wire exceeds the 1 to 6 ratio, another wire must be installed in the opposite direction to counteract the pull of the angled wire in a process called counter-splaying.

Hanger wires should extend a minimum of 12" past the main runner to allow for the required three-turn wrap during installation.

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Perimeter wires must be installed within 8" of the ceiling perimeter and attached to the terminal ends of all main runners and cross tees.

Wires hanging down present a danger to the installer and other workers. Recognize these when stepping up on to a bench or ladder or when working around.

Installing Control Lines

The first control line aligns the initial set of main runners. It is spaced along the edge of the main runner furthest from the wall, since this will make it easier to see and will not interfere with cross tee installation.

Control lines help keep a suspended acoustical ceiling grid system aligned and square. They also provide a point to measure from when cutting the main runners to length, and should not be overlooked.

A 1/2" should be added to the equal border calculation to move the control line from the center of the main runner to the outside edge. It is easily fastened to the wall angle by attaching the jet-line to a rivet and inserting the rivet behind the wall angle against the wall.

Marks for mains, tees, and control lines all being made above wall angle.

Installing Control Lines

The purpose of moving the cross tee control line to the center of a tile bay is also to avoid accidentally catching the line when snapping the cross tees into the main runner.

A second control line is used to set the initial run of cross tees and is placed perpendicular to the first control line. This control line is placed 12" away from the rout holes where the cross tees will be installed. This is done so that a rout hole in the main runners can be accurately aligned to the control line and easily seen during installation.

Installing Main Runners and Cross Tees

cut #3

To cut the main runners to the proper length, measure the distance from the cross tee control line to the wall. The cut end of the main runner should be exactly this distance from a rout hole.

cut #2

The web of the main runner should be cut at a slight angle away from the wall and the flange cut square. This prevents the web from contacting the fasteners that hold the wall angle in place.

cut #1

Installing Main Runners and Cross Tees

Insert 4'-0" cross tees into the proper rout holes on both main runners. The first cross tee is placed near the wall and exactly 12" from the cross tee control line. The remaining cross tees will be spaced 2'-0" apart.

Place the cut end of one main runner on the wall angle while aligning it to the control line. Run a hanger wire through a hole in the web toward the uncut end. Make sure the hanger wire remains reasonably plumb and the main runner is aligned with the control line.

After the cross tees have been installed, check the alignment with both control lines and temporarily clamp the ends of the main runners to the wall angle with wedge or spring clamps.

The wire is bent at a 90 degree angle using pliers, Repeat these steps for the second main runner, placing it 4'-0" away from the first main runner.

Securing and Squaring the Grid

Insert the clip of one cross tee into the rout hole that determines the equal-border tile dimension. Insert the other cross tee into a rout hole close to the end of the main runner, confirming the 2'-0" multiple dimension.

To secure the grid to the wall angle that runs parallel to the main runners, start by measuring the distance from the wall to the edge of the main runner and cut two cross tees to this length. Be sure to measure from the end of the flange and not from the end of the clip when cutting these initial cross tees.

Both cut ends will rest on the wall angle. Align both cross tees by measuring to the cross tee control line, and clamp them in place. The full length 4'-0" cross tees are installed between the two main runners. Check the distance from the cross tee control line to their respective locations.

Securing and Squaring the Grid

If the ceiling is not square, unclamp one of the main runners and adjust it until the grid is square. The adjustment will be minor, usually in the range of 1/4". Permanently secure the cut ends of the main runners to the wall using a whitney punch and a pop rivet tool.

If the control lines are not aligned after squaring the grid, adjust the control lines as necessary. This is common for one of two reasons: a measurement mistake was made when establishing the control lines, or the perimeter walls are not square to one another, which is a more common occurence.

The grid must be squared to make sure the ceiling tile fit correctly. The diagonal measurements between the corners of these bays must be equal. The diagonal of a 2'-0" x 4'-0" ceiling tile bay should measure precisely 52-13/16" when using 15/16" exposed grid material.

Completing the Installation

Do not attach the ends of the main runners and cross tees to the wall angle. The 1/4" gap allows the suspended ceiling to move freely during seismic activity and may minimize damage and injury.

The installation progresses as described until the grid reaches the opposing walls. It is important to leave a 1/4" gap between the ends of the main runners and cross tees at the opposing walls.

The final step in the installation process is securing the remaining wires to the grid system, including the perimeter wires.

Acoustical Ceiling Tile

The edges and corners of ceiling tile can easily chip, removing the finish. Carpenters need to be mindful of the finish product when cutting and installing the tiles. Cutting ceiling tile is much easier with a new utility knife blade.

Most ceiling tiles are made of fiberboard and are cut and installed in much the same way as drywall. Always make sure that directional tiles are installed in the proper direction. An arrow will be marked on the back side of the tile. All arrows must point in the same direction or you will see a noticeable difference.

Acoustical Ceiling Tile

• Cut freehand along the scored line until the tile has been completely cut to the required dimension

• Turn the ceiling tile on a slight angle and insert the full tile

• Install the cut tiles in the grid with the finished side facing down

Procedure for less than full ceiling tile installation:

• Measure from the flange edge of the main runner or the cross tee closest to the wall to the surface of the wall

• Place a ceiling tile on a flat surface with the finished side facing up

• Lightly score the face of the ceiling tile in the direction necessary to the dimension measured by (slide-cutting)

Acoustical Ceiling Tile

Setting tiles can be tricky when encountering obstacles above the grid. Plan which corner of the tile to stick through the grid first to avoid these obstacles.

Remember when making the initial cut into the tile that you are lightly scoring the surface and not trying to cut completely through the tile at this point. The score will provide a guide for the knife's blade to follow when completely cutting through the tile in the following step.

Acoustical Ceiling Overview

The following list includes some of the requirements for a high-quality ceiling installation:

The installation of ceiling grids and tiles is a complex process. Considerable care must be taken to make sure the work is safe and of high quality.

• The ceiling grid must be attached to the wall molding at two adjacent walls
• Unattached ends of the grid system must have 1/4" clearance from the wall. They must rest upon and be free to slide on the wall angle
• Hanger wire must be 12-gauge and spaced no more than 4'-0" apart
• Hanger wire connections at the main runners, cross tees, and structures must be secured with a minimum of three full 360 degree turns or 3 wraps in 3"
• Terminal ends of the main runners and cross tees must be supported within 8" of the ceiling perimeter

Procedure:

Laying out and installing an acoustical ceiling

• Calculate equal borders in both directions

• Install the hanger wire on the layout

• Install the control lines

• Install enough grid to square the ceiling

• Secure the grid to the wall angle

• Continue installing the grid until complete

• Cut and install the ceiling tiles

• Review the construction drawings and general notes

• Establish a level reference line

• Establish the elevation height of the ceiling using the reference line

• Install the wall angle, mitering all corners