Sheffield Metals 1.75” Snap-Lock Profile: Uses, Engineering, & More

Are you a contractor, regional fabricator or manufacturer, architect, or another industry professional looking for information about a 1.75” snaplock standing seam metal roof profile? Or, are you a building owner doing your research on the different panel and seam types to use for a new metal roof on your home or property?

If you’re familiar with the architectural standing seam market, you’ll know that 1.75” snaplock systems are some of the most specified metal roof profiles out there.

So, you may be asking yourself: Does Sheffield Metals International offer a 1.75” snaplock profile option? The answer is yes, the Sheffield Metals 1.75” Snap-Lock

How much do you know about this profile, the available testing/engineering, when to use it, and when not to use it?

Sheffield Metals offers a complete line of engineered and non-engineered standing seam profiles for metal roof and wall systems. So whether your project is residential or commercial, solid substrate or open framing, big or small – we have a profile that is right for you.

Let’s talk in detail about the Sheffield Metals 1.75” Snap-Lock profile.

Sheffield Metals 1.75” Snap-Lock Specifications

The Sheffield Metals 1.75” Snap-Lock has a variety of names and phrases that you might have heard, including:

  • SMI 1.75” Snap-Lock
  • The “inch and three quarters” Snap-Lock
  • SMI 1.75” SL

Like we mentioned, many variations of the 1.75” snaplock profile are popular in the architectural metals world. However, in this article, we are ONLY discussing the Sheffield Metals 1.75” Snap-Lock profile and not any other manufacturer’s products.

Panel & Seam Type

The Sheffield Metals 1.75” Snap-Lock profile is a standing seam panel type and has a standard snap-lock seam. Snap-lock panel profiles are concealed fastener systems that feature rollformed male and female legs, where the female leg snaps on over the male leg (the male leg is attached to the roof deck by hidden clips and fasteners). Snaplock profiles don’t require hand or mechanical seaming during installation.

Metal Materials 

For the 1.75” Snap-Lock, you can use 22 or 24-gauge steel (Galvalume) or .040 aluminum to form the panels. Or, you can use the same metal materials in a heavier (thicker) gauge or a narrower width panel and still have valid engineering.

Panel Width

With the 1.75” Snap-Lock profile, the panel width for our engineering is 16” for aluminum panels and 18” for steel panels. This specific panel requires approximately 6-1/8” of the metal sheet/coil to make the seams and edges.

For reference, if you take the square footage of the roof and multiply that number by 1.34, it will equal the total amount of coil needed to manufacture the panels in the SMI 1.75” SL profile.

Seam Height

As the name suggests, the seam height is approximately 1.75 inches.

Slope Minimum & Requirements

The SMI 1.75” Snaplock profile can be installed on roof slopes down to a 2/12 pitch, which is the absolute minimum and is dependent on the application. We discuss more about slope requirements for this profile in the “When to Use the Sheffield Metals 1.75” Snap-Lock Profile” section of this article.

Roof Deck Substrates

For our engineering on this profile, we have tested the 1.75” Snap-Lock assembly on plywood, b-deck (metal decking), and b-deck with ISO (polyisocyanurate insulation). This profile is not recommended for use over most open framing applications. 

Weathertight Warranties

Sheffield Metals offers optional 5 to 35-year weathertight warranties on commercial structures that use select SMI engineered profiles. The SMI 1.75” Snap-Lock profile can qualify for these weathertight warranties based on the project design.

Paint & Substrate Warranties

Both aluminum and steel 1.75” Snap-Lock roof systems qualify for Sheffield Metals’ 40-year transferable paint/finish warranty. Additionally, there are substrate warranties available; warranty length, inclusions, and exclusions will vary depending on the material type. 

Installation Details

This profile has installation details for steel and aluminum systems over plywood, b-deck, and b-deck with ISO. Metal roof installation details are an in-depth product guide detailing the location of components/accessories and also explain the basic practical installation methods for these products at various points on the roof. Please visit the profile product page to download any of the installation details for the 1.75” SL profile.

Miscellaneous Specifications & Requirements

There are a few other key elements that are specific to the SMI 1.75” Snap-Lock profile, including:

  • Panel surface options: Smooth or embossed (optional)
  • Panel clip requirement(s): Required per engineering
  • Compatible S-5! attachment clamp(s): S-5-S, S-5-S Mini, S-5-U, S-5-U Mini

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Engineering, Testing, & Approvals on the SMI 1.75” Snap-Lock Profile

Uplift Testing: UL 580 & 1897 (Standard for Tests for Uplift Resistance of Roof Assemblies)

Substrate material(s): Steel and aluminum

Deck types: Plywood, b-deck, and b-deck with ISO

Result: Pass (exceeded Class 90 / went on into UL 1897. In this phase of the test, the system maintains a positive pressure and increases negative pressure until the system fails).

Air Infiltration Testing: ASTM E1680 (Standard Test Method for Rate of Air Leakage Through Exterior Metal Roof Panel Systems)

Substrate material(s): Steel and aluminum

Deck types: Plywood, b-deck, and b-deck with ISO

Result: Pass 

Water Penetration Testing: ASTM E1646 (Standard Test Method for Water Penetration of Exterior Metal Roof Panel Systems by Uniform Static Air Pressure Difference)

Substrate material(s): Steel and aluminum

Deck types: Plywood, b-deck, and b-deck with ISO

Result: Pass 

Impact Resistance Testing: UL 2218 (Impact Resistance of Prepared Roof Covering Materials)

Substrate material(s): Steel and aluminum

Deck types: Plywood, b-deck, and b-deck with ISO

Result: Class 4 (best rating / most likely to resist surface penetrations based on testing criteria)

Fire Rating: UL 790 (Standard for Standard Test Methods for Fire Tests of Roof Coverings)

Substrate material(s): Steel and aluminum

Deck types: Plywood, b-deck, and b-deck with ISO

Result: Class A (best rating / least likely to combust or catch fire)

Florida Building Code (FBC)

Substrate material(s): Steel ONLY

Deck types: Plywood, b-deck, and b-deck with ISO

Result: Approved

Texas Department of Insurance (TDI)

Substrate material(s): Steel ONLY

Deck types: Plywood, b-deck, and b-deck with ISO

Result: Approved

UL 90 Construction Numbers 

SMI 1.75″ SL UL 90 Test – Construction No. 261

  • 10.5″ wide panel .032 – 22-gauge – 24-gauge over 3′- 4′- 5′ purlins

SMI 1.75″ SL UL 90 Test – Construction No. 508

  • 16″ wide .032 aluminum panel over plywood ISO optional up to 10 inches

SMI 1.75″ SL UL 90 Test – Construction No. 508A

  • 10″, 12″, 16″ or 18″ wide 24-gauge panel -OR 10″, 12″ or 16″ wide .032 aluminum over nailable ISO

SMI 1.75″ SL UL 90 Test – Construction No. 414

  • 18″ wide 24-gauge panel over plywood with up to 10″ ISO

SMI 1.75″ SL UL 90 Test – Construction No. 303

  • 10″-18″ wide 24-gauge panel OR 16” wide .032 aluminum over b-deck with 1″-4.5″ ISO

SMI 1.75″ SL UL 90 Test – Construction No. 343

  • 10″-18″ wide 24-gauge panel over plywood OR OSB optional ISO up to 1.5″

SMI 1.75″ SL UL 90 Test – Construction No. 255

  • 10″-18″ wide 24-gauge panel over purlins 4′ (UL 90) 5′ (UL 60) – ISO optional

SMI 1.75″ SL UL 90 Test – Construction No. 254

  • 12″ wide panel over purlins at 5′ for 22-gauge panels / 4′ for 24-gauge panels – ISO optional

When to Use the Sheffield Metals 1.75” Snap-Lock Profile

The roof slope is at or above a 2/12 – The SMI 1.75” SL profile is a great option for steep-sloped roofs, as snap-lock systems are more suited for hydrokinetic roof conditions. Many snap-lock profiles have a minimum slope requirement of 3/12, but the SMI 1.75” SL can be installed on some slopes as low as 2/12 (due to the ASTM E 1646 water penetration testing). However, keep in mind that installing this profile down to the 2/12 slope while still maintaining the engineering is based on certain conditions, including geographic location and building design. It’s best to check with Sheffield Metals before the installation begins.

You want or need to install an engineered metal roofing system – One reason the SMI 1.75” Snap-Lock is so popular is that it’s engineered, tested, and proven to perform on numerous roof deck assemblies (plywood, b-deck, and b-deck w/ISO) with different materials (steel and aluminum).

You want a commercial weathertight warranty – Another reason you might want to specify and install the SMI 1.75” SL is that it qualifies for our commercial weathertight warranties, including limited weathertight warranties and no dollar limit weathertight warranties. If you have a commercial project and the property owner is already significantly investing in a metal roof, we strongly recommend looking into protecting their investment with a weathertight warranty.

You don’t want to use extra time or labor to seam panels – With snap-lock profiles, panels have male and female legs that snap together after being rollformed, so no labor-intensive mechanical seaming is needed. Another by-product of no mechanical seaming is that it takes less time to install a snap-lock profile than a mechanically seamed profile.

When NOT to Use the Sheffield Metals 1.75” Snap-Lock Profile

When the roof slope is below a 2/12 – In general, snap-lock profiles should not be used for roof pitches of 2/12 or below, and the SMI 1.75” Snap-Lock is no exception. Flatter pitches don’t allow water to drain adequately, leading to premature degradation, color changes, and the overall failure of the roofing system.

You don’t like the look of a wider seam – The shape of the SMI 1.75” SL profile is sometimes considered industrial or bulky because it has a wider, box-shaped seam, which tends to be less of an appeal for residential applications.

You don’t want a taller seam – If you want a standing seam metal roof with a shorter or more low-profile seam, the 1.75” SL profile is likely not the best choice for you. You might want to consider a 1.0” or a 1.5” profile instead.

Completed Project(s) Using the SMI 1.75″ SL

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Final Thoughts on the SMI 1.75” Snap-Lock Standing Seam Profile

While the Sheffield Metals 1.75″ Snap-Lock profile isn’t the only snaplock option that we offer, it remains a profile that is frequently specified by architects and installed/fabricated by contractors and manufacturers.

In this article, we discussed the specifications, engineering/testing, and use cases for this profile. However, if you’re still trying to decide between the 1.75″ SL or another profile, you can better understand which one is best for you by asking yourself these questions:

  • What is the pitch of my roofing structure?
  • Is my project commercial or residential?
  • Do I want/need an engineered metal roofing system?
  • Do I want/need a weathertight warranty?
  • How much do I want to spend?
  • Is my budget flexible? Am I able to cover added labor or material costs?
  • Do I want/need a quick or less labor-intensive installation?
  • How long and wide do I want/need the panels to be?

Here at Sheffield Metals, we’ve dedicated ourselves to providing our customers with the materials, instructions, details, and support on all metal roofing and wall system projects. That’s why we offer a variety of tested and proven panel profiles, including the SMI 1.75″ Snap-Lock, that are designed to meet your project requirements.

To inquire about our panel profile options, please contact one of our experienced technical representatives today!


Download the "Standing Seam vs. Exposed Fastener: A Comparison Guide" here!