Installation Guide

Rafters
Rafters are vertical sloping beams that make up the main framework of a roof. These framing members
typically run from the roof peak to the eaves. Rafters support the weight of the roof and the roof load.
• Minimum recommended nominal size for purlins is 2” x 2”
(Two-by-two dimensional lumber).
• Always check with code authorities for specic loading
requirements and stresses, especially with high snow loads.
• Maximum purlin span depends on sheet thickness and rafter
spacing. Always follow local building code guidelines.
• Maximum rafter spacing depends on sheet thickness and
sheet width.
• ‘On center’ is the measurement from the center of one rafter
to the center of the next.
• Always check with local building codes rst to determine span
and on-center spacing for your specic loading conditions.
Note: Blocking may be added between rafters depending on rafter
span. Check with local building codes for lateral load paths for roof systems.
Purlins
Purlins are horizontal framing members that span over rafters, providing additional structural supportfor
the roof. Purlins aid in supporting the weight of the roof deck. They support the roong material and
transfer the load to the structure below. The roof deck is the ‘sheeting’ that covers the surface of the roof.
• The guidelines are organized in xed widths of 24”, 36”, 48”, 72”, and 83”(rafter spacing).
• Ribs are running perpendicular to the width.
• The data is organized according to allowable deection limits.
• Select the maximum design deection and choose the graph with the proper width dimension.
• Then plot, starting from the specied design load (PSF) across the Y axis to the maximum
deection desired.
• The recommended maximum unsupported sheet length is located at the intersection.
Note: A max 1” DMX (deection) is recommended for polycarbonate H-proles.
See loading guideline example on next page.
Loading
Loading on polycarbonate sheets is a combination of several factors that are dependent on building
type and location. Typically, the biggest factors are snow and wind loads. Design load requirements can
be found by standard size charts, local code and code o󰀩cials, or by an engineer. Loading information
provided in this document is generalized and specic requirements must be veried.
• Because of multiwall polycarbonate’s exceptional sti󰀨ness to weight ratio, it is well suited for
load bearing applications such as vertically installed or sloped glazing.
The charts on the following pages provide information to assist in selecting the proper gauge.
[e-mail] | [phone]
9
MULTIWALL POLYCARBONATE
Technical & Install Guide