How to Cut and Glue Carpet Seams

Creating Invisible Carpet Seams

Installer Joining Two Carpet Pieces with Iron
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Seaming carpet like a pro requires precise cuts and proper seaming technique with a seaming iron. The trick to a tight-fitting seam is to start with a type of double-cutting technique that matches the two edges perfectly. 

Supplies Needed:

  • Tape measure
  • Pencil
  • Chalk line
  • Board or scrap plywood
  • Straightedge
  • Carpet knife or utility knife
  • Carpet seaming tape
  • Seaming iron
  • Carpet seam roller
  • Books or other heavy objects

Position the Carpet Pieces

Person Laying Out Carpet.
Courtesy of TrendTreasures Inc.

Lay out the two carpet pieces side by side so they overlap by about 3 inches. Make sure that the pile is facing the same direction in both pieces. If you are unsure, check the back of the carpet for arrows indicating the direction of the pile.

Mark and Cut the First Edge

Person cutting carpet lines
Courtesy of TrendTreasures Inc.
  1. Roll back the carpet that is on top. On the backside, measure 1 inch in from its outer edge and mark the backing at 12-inch intervals down the length of the edge.
  2. Snap a chalk line through all of the marks to create a cutting line.
  3. Place a board or scrap of plywood underneath the rolled-back edge to protect the carpet below from the knife blade.
  4. Lay a straightedge along the chalk line, and cut through the carpet with a carpet knife or utility knife, running along the straightedge. Be sure to cut down a single line of threads as you work.

Cut the Second Edge

Pieces of cut carpet
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  1. Lay the newly cut edge of carpet back down over the uncut piece. It should still overlap the bottom piece by about 2 inches.
  2. Place a straightedge along ​the edge of the cut carpet, and use the knife to cut through the bottom piece of carpet, slicing through only a single row of threads, as before.

Position the Seaming Tape

Person Laying Carpet Tape
Courtesy of TrendTreasures Inc.

Center a line of carpet seaming tape underneath the two cut edges of the two pieces of carpet. Lay out the tape along the entire length, with the two pieces of carpet perfectly matched along their edges. Using a single piece of tape for the entire seam helps to keep the seam tight.

Heat the Tape

Person laying with tape heating iron.
Courtesy of TrendTreasures Inc.

Apply a carpet seaming iron to the tape and let it heat the tape as needed. Depending on the type of tape you use, you might need to heat it for several minutes to activate the adhesive. Follow the tape and iron manufacturers' recommendations for heating times. 

Join the Seams

Person laying carpet with tape heating iron.
Courtesy of TrendTreasures Inc.
  1. Move the iron slowly and steadily down the seam and across the tape, allowing it to linger long enough to activate the adhesive at each point. As you move the iron, press the carpet pieces behind it gently down into the tape while pushing the pieces tightly together.
  2. Roll over the joined seam with a seam roller to press the carpet edges into the tape adhesive and ensure they lie flat. 
  3. Place heavy objects such, as large books, tiles, or pieces of wood over the rolled area of the seam to hold the carpet in place while you move down the seam. Leave the weights in place until the adhesive sets.

Complete the Seam

A Carpet Seam
Courtesy of TrendTreasures Inc.

Continue seaming the carpet until you reach the end of the seam. Leave the weights on the seam for another 15 minutes before removing them. The final result should be a carpet surface that appears nearly unbroken, with the threads hiding the seam.