Installing carpet on concrete or steel stairs can be difficult. Of course, it can be glued direct; the problems arise when the customer wants pad under the carpet. This presents the installer with the choice of a double-glue or a tackless installation.
Generally, there are two ways of attaching tack strip to steel or concrete stairs: gluing or nailing. If forced to glue, I prefer to use contact cement.
Apply the cement according to the manufacturer’s guidelines. Coat the back of the tack strip and the surface it is to be adhered to, and allow them to dry completely. Once dry (usually 20 to 40 minutes), place the strip in position and tap it with a hammer to make good contact and ensure the best bond. Construction adhesive can also be used, although it generally takes at least 24 hours to dry properly.
I prefer to do the risers first, followed by the treads. This saves wear and tear on the knuckles that can be caused by contact with the pins of the tack strip on the treads.
Steel stairs require a variation on the drill-and-drive theme. Gluing is always an option, but I prefer another way. On a recent jobsite with installation professional Dick Schmidt, I had to opportunity to record the technique.
The installer will need 1/8-inch pop rivets with a ½-inch range, a pop rivet gun, pop rivet washers (Note: compare size and buy bulk washers. The #6 zinc are much cheaper), 9/64-inch steel drill bits, and a hot glue gun. I have used sheet metal screws in the past, but found a couple of problems doing so:
Cutting to fit
When cutting the strip to fit the stair, I always try to do the risers in one piece, saving the balance for use on the treads or in a room. First, place two, 2-inch pieces of strip facing pin to pin, and tap them together with a hammer. This provides a block on which to rest the riser segment of strip while drilling, as well as providing the proper spacing from the tread (Figure 1).
It is my experience that it is better to adjust the tread piece of strip to account for carpet thickness. Using a hot glue gun, apply a few dabs of glue to the back of the strip (Figure 2). This will hold the strip in place during drilling.
Next, drill a hole every 6 inches through the strip and the steel risers (Figure 3). I use a 9/64-inch drill bit instead of a 1/8-inch bit because the extra 1/64-inch makes inserting the pop rivet easier, without affecting the holding power.
Place a washer on the pop rivet (Figure 4). This will prevent the rivet from pulling through the tack strip. Next, secure the strip to the riser (Figure 5). Space the rivets as though they were nails (Figure 6).
For steel treads, install them with the same procedure as the risers, using pop rivets. If the treads are constructed of a pan filled with concrete, use the aluminum drive nails. The space between the tackless should be equal to the thickness of a piece of the carpet folded twice. As difficult as it is nailing tack strip on wood stairs, it is twice as difficult on concrete. For that reason, I prefer the drill-and-drive method using 1/8-inch masonry bits and aluminum drive nails.
Drilling in concrete
When drilling into concrete, it is important to have the proper equipment. I would recommend a hammer drill with at least 2,000 rpm and 40,000 to 60,000 bpm (blows per minute). Using a hammer drill with a 1/8-inch bit, drill through the strip into the concrete (Figure 7). The aluminum drive nails are slightly larger than the hole, and compress tightly into it, securing the strip without chipping the concrete.