Installation Guide

Page
13
SunFrame Unirac Code-Compliant Installation Manual
R
1411 Broadway Boulevard NE
Albuquerque NM 87102-1545 USA
Total Design Load (downforce) (max of case 1, 2 or 3) P psf Step 1
Module length perpendicular to rails B x ft
Rail Span L x ft Step 4
Downforce Point Load R lbs
Table 9. Downforce Point Load Calculation
Step 6: Determine the Uplift Point Load, R (lbs), at
each connection based on rail span:
You must also consider the Uplift Point Load, R (lbs), to
determine the required lag bolt attachment to the roof
(building) structure.
Total Design Load (uplift) P psf Step 1
Module length perpendicular to rails B x ft
Rail Span L x ft Step 4
Uplift Point Load R lbs
Table 10. Uplift Point Load Calculation
Use Table 11 to select a lag bolt
size and embedment depth to
satisfy your Uplift Point Load
Force, R (lbs), requirements.
It is the installer’s responsibility
to verify that the substructure
and attachment method is strong
enough to support the maximum
point loads calculated according to
Step 5 and Step 6.
Table 11. Lag pull-out (withdrawal) capacities (lbs) in typical roof lumber (ASD)
Lag screw specifications
Specific
5
⁄
16˝ shaft,*
gravity per inch thread depth
Douglas Fir, Larch 0.50 266
Douglas Fir, South 0.46 235
Engelmann Spruce, Lodgepole Pine
(MSR 1650 f & higher) 0.46 235
Hem, Fir, Redwood (close grain) 0.43 212
Hem, Fir (North) 0.46 235
Southern Pine 0.55 307
Spruce, Pine, Fir 0.42 205
Spruce, Pine, Fir
(E of 2 million psi and higher
grades of MSR and MEL) 0.50 266
Sources: American Wood Council, NDS 2005, Table 11.2A, 11.3.2A.
Notes: (1) Thread must be embedded in the side grain of a rafter or other structural member integral with the
building structure.
(2) Lag bolts must be located in the middle third of the structural member.
(3) These values are not valid for wet service.
(4) This table does not include shear capacities. If necessary, contact a local engineer to specifiy lag bolt size
with regard to shear forces.
(5) Install lag bolts with head and washer flush to surface (no gap). Do not over-torque.
(6) Withdrawal design values for lag screw connections shall be multiplied by applicable adjustment factors if
necessary. See Table 10.3.1 in the American Wood Council NDS for Wood Construction.
*Use flat washers with lag screws.
Thread
depth