Carpet Seam Peaking in stretch-in carpet installations
Seam peaking is normal when joining carpet and then stretching carpet into place. Adequate carpet tension is necessary to ensure that in normal use conditions, the carpet does not ruck (waves in the carpet surface) and cause loss of performance life.
Peak occurs when a carpet is stretched at right angles to a seam because the combined carpet backing absorbs the forces of stretching until it reaches the point where the carpet has been joined together with seaming tape adhered only to the carpets secondary backing.
As the stretch forces are applied to the seamed area, the seaming tape is pulled upward to align itself with the approximate centre of the combined carpet backing. This creates an elevation or lump in the carpet along the seam which consequently causes the pile to gap open in a v-configuration.
When the main source of light falls at an angle across the peaked seam, the pile on the side closer to the light source reflects more light, resulting in a shade similar to the effect of a shadow falling on the carpet.
The effect of Seam peaking should dissipate over the course of a few months after carpet installation
For further information, view the Carpet Institute of Australia factsheet.