Page 104 - Westform Product Catalogue July 2025 Public

ROOF PREPARATION

JULY 2025

Westform’s Prolok 12 & 16 profile can be used in both new and old construction. We recommend
Prolok be installed over a solid substrate, installation over strapping is possible. The following steps should

be taken to prepare the roof for installation of any roof panel.

1. Make sure there are no nails or other objects that
might puncture the underlayment of the roof panels.

2. Check/plan all details for possible roof penetrations which
must be added to the roof prior to roof panel installation.
(vented ridge/vented end wall - plumbing stacks)

3. Cover the roof deck with underlayment, overlaying 6”, check manufacturers installation manual for underlayment. When

installing over strapping, run the underlayment parallel with the metal panels, making sure that the underlayment is tight.

4. Snap a chalk line along the gable end where the first panel will be installed. This line should be the width of the panel
+ 1/2” away from the edge of the roof and square with the eave. Use the 3-4-5 method to square the roof. Use the largest
3-4-5 increments that will fit on the roof plane.

3-4-5 Right Angle Squaring Method
5-10-15
3-6-9
90 0
4-8-12

EXISTING ROOF

In some cases metal roofing can go over existing roofing. For those roofs use 1 x 4 strapping on 16” O.C. screwed through to

the rafters. The minimum pitch for Prolok 12 & 16 is a 2/12 pitch.

1. Remove moss and debris, inspect the roof for damage, make any necessary repairs, secure any warped or loose sheeting.

2. Remove current venting and prepare for continuous profile ridge venting.

3. Screw down 1 x 4 on 16” O.C.

4. Install underlay parallel with the panels, making sure the underlayment is tight.