The industry standard is to overlap panels. Butt seaming can be done on glass or Level 5 super smooth walls, but when the film shrinks, a gap will appear.
The difference between the two seam types is how graphics are paneled next to each other. For wall graphics, generally, an overlap seam is recommended to compensate for any potential shrinkage that may occur over the service life.
Butt seam and overlaps are the two most common types of seams when it comes to multi-panel graphics. Each have their own advantages and reasons for use.
Overlaps
As the name implies, an overlap seam involves overlapping the paneled graphics at the edges. This type of seam has the advantage of giving extra coverage at the seams of graphics to accommodate for any potential shrinkage.
The industry standard for overlaps is 1/2" to 1" (12-25mm). Calendered films shrink more than cast films so a minimum of 1" overlap for calendered films is highly recommended.
Butt Seam
This technique is commonly used on floor and window graphics. Butt seaming can be done on glass or Level 5 super smooth walls, but when the film shrinks, a gap will appear.
To make a butt seam, the panels still need to be printed with bleed and initially overlapped. Then, carefully cut the overlapping graphics without cutting the application surface. Remove the excess films on the top and bottom panels and reapply without heat.