Rafter Layout Base and Cap for Polycarbonate

Rafter Layout:               Next: Determine blocking placement to support the load on your frame.

Poly on vertically rafters. Use spacers if high humidity greenhouse.     Then See Install DetailsRafter Layout

When using nominal 4 ft. on-center spacing.
Outside of structure to center of first or last framing member & Base is 48-1/2″ – if using Corner Trim *
Dimension between Intermediate framing members & Base is 49″ On-Center.
Note: Spacer shown above is 3/8″x1″x1″. One Spacer in middle of 4 ft. sheet, two spaced on 6 ft. sheet.

When using nominal 2 ft. on-center spacing.
Outside of structure to center of first or last Base is 48-1/2″, if using Corner Trim *
Dimension between Intermediate framing members is 24-1/2″ On-Cenrter.
No spacers needed on blocking, but hold back 1/4″ as shown above.

* If sheet to overhang rafter, as it comes down the slope, 1st and last rafter spacing is less, plan for overhang 2-3″
• See Position & Attach for mid-sheet attachment of roof & wall sheets.

Polycarbonate Greenhouse and Sunroom Building Supplies