Design spans between supporting purlins, Sunlite® technical guide – Palram SUNLIT User Manual
Page 13
SUNLITE® Technical Guide
11
11
8. Screw buttons: Improved performance can be obtained by replacing the
washers with special plastic screw buttons, fitted with a suitable rubber gasket,
with or without a closing cap. They fit the thickness of each type of sheet (6, 8,
10, 16 mm, and possibly 25 mm), differing by sleeve length. Their advantage:
the sleeve prevents excessive tightening and local squashing around the
screw, and is softer on the sheet, reducing risk of tear or shear around the
screw’s stem. They also offer a seal between the fastener hole and the open
channels of the sheet, preventing possible infiltration of water and dirt into
the internal space of the sheet. Screw buttons can suit the 6.35mm (1/4 in.)
screws mentioned above, although it is recommended to use slightly longer
screws to accommodate the button thickness.
Palram recommends perforating SUNLITE for fastening as little as possible, and
prefers the use of clamped edge installation. Palram recommends that the
use of fastening screws in a glazing system, even with plastic buttons, should
be limited to economical, price conscious projects only. Two or four-sided
clamped glazing is a preferred choice.
Design spans between Supporting Purlins
According to Designated Loads for the Roofing and Cladding Method
Max. Recommended Spans between Support Purlins - Flat / Slightly Curved Roofing/Glazing
Structure
Thickness
Distance (center-to-center) between supporting purlins - according to wind/Snow loads below
50 Kg/m²
10 psf
80 Kg/m²
16 psf
100 Kg/m²
20 psf
120 Kg/m²
25 psf
mm
mm
Inch
mm
Inch
mm
Inch
mm
Inch
Twin Wall
6
900
36
800
32
650
26
500
20
8
1150
46
1000
40
850
34
650
26
10
1250
50
1150
46
1050
42
900
36
Triple Wall
8
1120
44
970
38
820
32
620
25
10
1220
48
1125
45
1020
41
870
35
16
1600
64
1450
58
1250
50
1130
45
X-Lite
16
1650
65
1500
59
1300
51
1180
46
25
1850
74
1700
68
1550
62
1425
56
32
2050
82
1900
76
1750
69
1600
63
35
2075
82
1925
76
1775
70
1625
64
Notes:
1. Span calculation is based on general professional know-how, previous experience & specialized expertise with this type of products.
2. Spans depicted are drawn from loading tests and extrapolations based on L/20 deflection (5%) at the specific span and load using continuous multi-span
supports. The values refer to mid-spans. Edge-spans (lower & upper ends) should be approx. 20% smaller.
3. SUNLITE panels can withstand higher loads and/or wider spans without failure. However the involved deflections will exceed L/10 (10%) of the span, which is
unacceptable in most cases.
Curving SUNLITE sheets gives them higher strength and rigidity, as in the case of two-sides clamping described in the next page.
>2 mm more than
diameter of button stem
Rubber gasket
Plastic button
Fastening screw
Optional cover
>30 mm
Figure 14