There is some confusion on proper stretching patterns when installing wall-to-wall carpet. In my opinion, there is no single right way to do it. Stretching requirements will be dictated by the individual carpet type and job layout. The one constant is that the majority of the stretch in carpet is in the length (with the exception of a couple of odd knitted pieces and some Wiltons). Keeping this in mind, when you are stretching a piece of carpet, the majority of the stretch should angle stretches (at approximately 15 degrees) the length of the material, followed by straight or slightly angled stretches across the width. Now, this puts me at odds with the stretching diagrams in the back of the CRI manuals, but I disagree with those stretching patterns anyway, so that's OK. The following drawings are the stretching techniques that work for me.
As I said before carpet stretches mostly in the length. Some carpets, KaraLoc and Axminster, for example, stretch only in the length and not at all in the width. CRI 104 and 105 recommend stretching synthetic-backed carpets (ActionBac) 1 to 11/2 percent in both the length and width. Well, that might be a little extreme for a 12-foot width when you consider 1 percent is 1.44 inches and 11/2 percent is 2.16 inches, but don't spare the horses; stretch the carpet tight.
Next, leaving the tail in place, make an angle stretch toward the corner of Walls B and C. Move the stretcher head to the other side of the first (straight) stretch, making an angle stretch. Bump and secure Wall B. Place the stretcher tail on Wall B approximately 2 feet from the corner of Walls A and B. Stretch straight from Wall B to Wall D, then execute one angle stretch to Wall A. Bump and secure Wall A. Move the stretcher tail to the corner of Walls A and B, making angle stretches of approximately 15 degrees down the length of Wall D to Wall C. Next, execute straight stretches from Wall A running the length of Wall C to Wall D.
When stretching a patterned carpet (Figure 2), a slight variation is needed to help keep the pattern straight. After setting and stretching Walls A and B, taking care to assure the pattern is straight, make a sharp angle stretch from the corner of Walls A and B toward the corner of Walls C and D, pulling the pattern to the same point in corner CD as it is in corners BC and AD. This will leave the un-stretched carpet on Walls C and D with a bow in the pattern, which straightens out perfectly when the carpet at those walls is stretched.. My favorite stretching method is what we call a butterfly, or as some people call it, a fan stretch (Figure 3). This is a great way of stretching a room for an installation team working together.
The start is similar to the first stretching pattern we discussed. Start by securing 3 to 4 feet of Wall A. Stretch straight across to Wall C. Bump up and secure Wall B. Next, place your power stretcher in the center of Wall B and make a straight stretch from the center of Wall B to the center of Wall D.
Next, make angle stretches of approximately 15 degrees from Wall B to the corner of Walls A and D, then return to the center of Wall D, making angle stretches from Wall B to the corner of Walls C and D. The beauty of this stretching pattern is that while you are completing the angle stretches to the corner of Walls C and D, and breaking down the stretcher for the width, your partner has bumped up and secured the remainder of Wall A. Then, while you stretch Wall C (straight or slight angle stretches), your partner trims in and finishes the stretched walls. A smooth piece of teamwork, quick with no wasted effort.
These three basic stretching patterns, or a variation of them, will get you through most of stretching situations you will come up against. Yes, I know I can hear some of you saying, "Well that's fine if the room is square, but I got closets, alcoves, and hallways in the real world." That's true, so let me impart the lesson I teach my son: break down these areas to a collection of squares or rectangles, and make those the focus of your installation.