Horizontal Siding Seams

A seam is where two siding panels meet.

Horizontal siding seams.

A wraparound lower lip hooks the siding and requires one nail to hold it in place. The joint covers protect the butt joint where two siding planks meet and provide an expansion joint to help prevent siding buckling. The siding expands and contracts with temperature and humidity. While wainscot is traditionally run in a vertical pattern in modern designs we see corrugated metals often run horizontally.

In my opinion caulking between the seams in any lapped siding either horizontal or vertical is not good practice but not just because of any potential vapor barrier effect. Joint covers are primed on the outside for easy painting and coated on the inside with an epoxy backer to inhibit. The seam allows the vinyl to expand and contract along with fluctuations in temperature. It needs to move and breathe.

If you use a pressure washer start by ensuring that the stream is at eye level and pointed straight at the siding not at an angle. If starter strip is used it is necessary to provide at least 3 8 9 5mm clearance for proper engagement of the siding. Drill minimum 3 16 4 8mm diameter weep holes in the bottom of the j channel no more than 24 610mm apart. Use j channel to receive vertical siding.

Since leaks can happen just as easily during the cleaning process as during a rainstorm horizontal siding requires a careful cleaning regimen so that you do not get water behind the siding. This prevents the siding panel from cracking in excessive heat or cold. Think of a wood home as a living thing.