Westman Steel: Snap-Lok Roofing Panel

Description of Panel

The Snap-Lok roofing panel is a concealed fastener roof system that offers a clean, durable finish to any roof. It is available in two sizes, 12” and 16” inches, 26 and 24 gau ge and 16 standard colours. Steel sheets are prepainted Galvalume or bare Galvalume and have the longest life of any roofing sheet available. The high-quality factory baked-on paint system carries a 40 year limited warranty.
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Description of Installation Manual


This Snap-Lok Roofing Panel installation guide is intended for the homeowner, contractor and metal roof installer. Please read and understand the manual content before beginning your roof installation in order to ensure a trouble free installation and maintain applicable warranties. If you have any questions regarding the installation of your metal roof system, please contact Westman Steel.


By using this Guide, you accept the risks and responsibilities for all losses, damages, costs and other consequences resulting directly or indirectly from using this Guide. These installation instructions are intended as guidelines only. Westman Steel assumes no responsibility for the performance or quality of the roof system installation, nor any personal injury or damage that might occur as a result of improper installation.

Westman Steel does not warrant any product or material as meeting the current building codes, laws or regulations of any particular jurisdiction or local municipality.

This manual contains suggestions and guidelines on how to install Westman Steel Snap-Lok roof panels and trim details. The contents of this manual include the guidelines that were in effect at the time this publication was originally printed. In an effort to keep pace with the ever-changing code environment, Westman Steel reserves the right to modify, without notice, any specifications and/or designs at any time without incurring any obligations. To insure you have the latest information available, please inquire or visit our web site. Application and design details are for illustrative purposes only and may not be appropriate for all environmental conditions and/or building designs. Projects should be engineered and installed to conform to applicable building codes, regulations, and accepted industry practices.

All dimensions should be verified by field measurements prior to ordering materials.

Snap-Lok roof panels should be applied on a minimum roof pitch of 3:12 or greater. For roof pitch less than 3:12, please contact Westman Steel.

Oil canning is an aesthetic phenomenon inherent to light gauge cold formed sheet metal and is characterized by a distortion or waviness of flat surfaces of metal roofing and siding products. As oil canning is an aesthetic issue and does not affect product strength or performance, it is not a cause for rejection. There are several factors that influence this behavior, such as sheet metal thickness, dimensions, installation and system design among others . Oil canning can be minimized by considering these factors mentioned above. See Canadian Sheet Steel Building Institute (CSSBI) – Fact Sheet 13.

Safety Considerations

Always wear proper personal safety equipment when working with metal roofing panels and trims. Westman Steel recommends eye protection, ear protection, gloves and fall protection when working with sheet metal roofing products. Check with local safety authorities for requirements regarding guards, fall protection and other safe working procedures.

Avoid working with metal panels on windy days.

Do not walk on the panels until they have been completely fastened to the substrate. Do not step on panel ribs.

Always step on supports.

Metal surfaces can be extremely slippery when wet or covered with frost. Always ensure proper fall protection procedures and equipment are used. Avoid working on wet or snow covered roofs.

Wear soft rubber-soled shoes when walking on a metal roof to avoid damaging the finish.


Steel roofing panels may be cut with metal snips, power or hand shears or nibblers. Circular saws with metal cutting blades are acceptable. Do not use abrasive blades, as they can burn both the paint and zinc coating leading to premature wear at these areas .

When cutting panels, turn the panels painted face down and cut in a location away from other panels to avoid metal particles embedding in the painted face of nearby panels. Always remove metal particles from drilling or cutting immediately to avoid damaging the paint finish. Particles, if left on the panel surface can rust overnight.

Sheet metal edges are very sharp. Always wear eye protection and gloves when handling or cutting metal sheets.

Do not stack cut panels.

Receiving / Handling

Check the delivery of metal roof panels and accessories for quantities and/or damage immediately upon receipt.

Note any damage or shortages at the time of delivery. All errors/omissions must be reported within 30 days.

Handle panel bundles and individual panels with care to avoid damage. Generally, Westman Steel recommends that supports are to be located at no more than 10 feet from each other to provide adequate support from buckling or bending.

Do not drag sheets on the ground or over each other . Obtain the help of others to transport longer individual panels.


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Upon receipt of your roofing panels, store them in a well ventilated, dry location. Rain or condensation can be drawn between the stacked sheets where it can cause premature failure of the protective coating. Do not store panels in contact with the ground. Ensure the panels are adequately supported and elevated off the ground, preferably with a slope to allow water to drain. Cover panels with a waterproof cover spaced off the panels to allow air movement. Store panels inside if possible.

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Tools / Equipment Required

  1. Metal shears, nibblers, power shears or circular saw with metal-cutting cutting blade. Note: Saw cut edges can be jagged, unsightly and tend to rust sooner than sheared edges. Hot metal filings are produced when saw cutting, which may embed in and damage the paint coating. Also, saw cutting burns the paint and galvanizing treatment, leading to the onset of edge rust.
  2. Metal snips
    (left edge, right edge and centerline cutting snips)
  3. Hem bending tool (see image)
  4. Gloves and protective clothing
  5. Safety goggles and ear plugs (Eye and ear protection)
  6. Tape measure and chalk line
  7. Rubber mallet
  8. Screw gun or drill (adjustable clutch recommended)
    – see CSSBI Fact sheet 42 in for more information on recommended types of screw guns
  9. 1/4” and 5/16” sockets – must be lobular and replaced after 10,000 to 15,000 fasteners
  10. Drill bits, screw bits
  11. Pop rivet gun
  12. Caulking gun
  13. Pencils and markers
  14. Utility knife
  15. Locking sheet metal pliers
  16. Hammer staplers

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Flashings and Trims

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To complete the metal roof installation, the following fasteners are used in wood-frame construction:

Westman Steel:22 gauge metal roofing prices #10 x 1” Pancake head wood screws
For attaching concealed fastener coverings and roof panels .
Westman Steel:standing seam metal roof manufacturers #10 Hex head wood screw with self-sealing washer,
various lengths available
Self-sealing screw used for fastening flashings.
Westman Steel:24 gauge standing seam metal roof cost #14 x 7/8” Stitch screw with self-sealing washer
Used to anchor the flashings metal to metal.
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Stainless steel pop rivets
(optional, not supplied by Westman).
Used to connect flashings at corners.

Fasteners must be properly driven to ensure proper seal and strength and provide allowance for expansion and contraction. See the diagram below for proper sheet metal screw fastening.


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The Snap-Lok panel utilizes a concealed fastener system. One edge of the panel contains a punched flange to accept fasteners, while the other side snaps onto the rib of the adjacent panel. Panel fastening requirements differ based on geographic region, local weather characteristics and building codes. Wind forces on roofs are greatest at the corners and edges. Refer to the image below for typical wind pressure zones.

Recommended pancake head fastener spacing for Snap-Lok panels is 15-1/2”.


Once material has been estimated and ordered, the roof panel installation can begin. Roof installation starts from the lowest point and continues upwards in the following general order:

Fascia trim

Eave protection and valley protection

Eave trims

Valley flashing


Roof panels

Gable trims

Ridge caps

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Westman Steel Snap-Lok panels are designed for installation over solid sheathing typically used in the construction of residential roof-decks.

Installation consists of the following steps:

  • Accurately measure the roof, and create a roof plan for estimating and ordering roof panels and accessories
  • Ensure all required roof penetrations are in place before beginning (pluming vents, exhaust, attic venting, )
  • Remove any dirt or debris from the roof surface
  • Make sure there are no nails or other objects protruding from the roof that may puncture the new underlayment or damage the new roof panels
  • Install Ice & Water shield at eaves a minimum distance of 60” upslope of the exterior wall, and valleys with one 36” roll centered with the Check with local building codes for specific requirements. Also, install ice & water shield at any penetrations or skylights
  • Install Westman Steel Underlayment
  • Install fascia and eave trims and valley flashings (refer to attached details)
  • Check for squareness and layout the roof installation
  • Align the first roof panel with the roof edge, and check for squareness and the proper panel overhang at the eave which will depend on the desired trim
  • Fasten the first panel with the appropriate fasteners
  • Install the next two panels loosely, constantly checking alignment with the If the panels are correctly aligned, fasten and engage the locking edge of the panels to the adjacent panels
  • Continue with panel installation, periodically checking alignment and squareness and making adjustments as necessary

Wood Framed Installation

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  • All Sealants shown on the details are a recommendation by Westman. Unless requested prior to ordering, Westman will not supply tape sealant or tube caulking in quotes or cladding packages.
  • Types and location of tape sealant and tube caulking shown on the details are the best recommendation for a proper seal.
  • All screw types shown on the details are the best suited fastener for each location recommended by Westman.
  • Screw length shown on the details are the standard recommended length. Different length fasteners are available and can be supplied if requested prior the ordering.
  • All fasteners shown on the details are supplied by Westman unless notified before booking
  • Panel end lap details can be supplied but may vary based on actual site conditions.
  • Hip and valley details can be supplied but may vary based on actual site conditions. These details are to be used as a guideline only for installation.
  • Ridge venting will not be assumed to be included in quotes or cladding packages. If venting at ridge is required please notify Westman prior to ordering.


A. Do not scale. Details are for guidelines only, and may not be suitable for all building and conditions.

B. Screw length may vary per customer request. #10×1”, #10×1 1/2” and #10×2 are available.

Wood Framed Installation



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