Panel siding needs clearance below it to grade, roofs, decks, and other horizontal surfaces so the bottom edge does not sit in water, and it needs gaps at panel joints and around openings so the material can expand without buckling. Those clearances and gaps protect against moisture wicking, rot, and expansion damage. The exact dimensions are set by your panel manufacturer. This guide explains what each clearance is for so you know what you are confirming.
Clearance to grade
The bottom edge of siding is kept up off the soil, walks, and paving by a set minimum. Set it too low chasing a grip while you hang it and the panel wicks ground moisture, and engineered wood that stays wet will swell and rot. This is exactly the failure a proper support line prevents, because you are not resting the sheet in the dirt to hold it.
Clearance to roofs, decks, and horizontal surfaces
Where siding meets a roof, a deck, or a horizontal trim, a gap and the right flashing let water drain and dry instead of sitting against the panel edge. Your manufacturer sets the dimension.
Gapping at joints and openings
Panels expand and contract with moisture and temperature. Butt joints between sheets, and the edges around windows and doors, are gapped and then flashed or sealed per the manufacturer so the movement does not buckle the wall or open a leak.
Flashing does the sealing, not caulk alone
Clearances and gaps only work with the right flashing and a continuous water-resistive barrier behind the panel. The gap gives water somewhere to go. The flashing sends it out.
Where to get your numbers
- Your panel manufacturer's installation instructions for the exact clearance and gap dimensions. These govern.
- APA panel-siding guidance for the general principles.
- Local code, which can set a stricter minimum clearance to grade.
The rule that applies to all of it
Clearances and gaps are set by your panel manufacturer, and this guide does not replace them. Panel siding is also a minimum two-person job. A support tool holds the panel steady so you can set it to the right clearance instead of resting it in the dirt to hold it. It does not replace a second worker or the manufacturer's requirements.