Rafter Spacing, Blocking Placement for Load Support of 25mm Polycarbonate---

 

Blocking is framing member that fits between rafters or studs.

Purlins sit on top of rafters, run perpendicular & require Base & Cap.

 

Rafter spacing & blocking placement for poly. See Structural Load, Info on snow & wind..

See Polycarbonate Position & Attach for mid-sheet attachment of roof & wall sheets.

Thickness	Rafter Spacing	80 lb. load	100 lb. load
25mm 6-wall	48 3/4" to 49"	every 3 ft.	every 2.5 ft.
25mm 6-wall	24 3/8" to 24 1/2"	not needed	not needed
25mm X-wall	48 3/4" to 49"	every 4 ft.	every 3.3 ft.
25mm X-wall	24 3/8" to 24 1/2"	not needed	not needed

Mfg. specs for selecting sheet thickness, rafter spacing & blocking placement to support load on roof or wall. Load in lbs./sq. ft. Roof slope over 7/12 snow slides off. Spacing may be relaxed. No specs available.

 

Bldg. dept. has snow & wind load for your area. Supporting load is factor of frame strength and poly. sheet rigidity. Follow chart and poly. will support load. For frame member size see Spans for Rafters. Get bldg. dept. approval.

 

To allow for movement of condensation past blocking, set blocking 3/8" back from outer surface of frame, see Blocking. When using 48-3/4" to 49"on-center rafter spacing, a neoprene spacer is placed at center of blocking. This eliminates bowing of sheet.

 

Note: The sheet must be supported on all 4 edges with a minimum of 1/2" of sheet bearing on the frame. When using sheets that have been cut along the width, and no longer have a rib at the edge, position so first rib is supported by a minimum of 1/2" of frame.

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