Sheffield Metals 1.5” Snap-Lock 550 Profile: Specifications, Uses, & More

1.5″ snap-lock profiles are a standard in architectural metal roofing projects, so you might be asking: Does Sheffield Metals International offer a 1.5” snap-lock profile option?

Are you a contractor, manufacturer, fabricator, architect, or another industry professional looking for a 1.5” snap-lock standing seam metal roof profile? Or, are you a building owner doing research on the different panel and seam types for use for your home or property’s new metal roof?

1.5″ snap-lock profiles are a standard in the architectural metals industry, so you might be asking: Does Sheffield Metals International offer a 1.5” snap-lock profile option? 

The answer is yes; in fact, we have a couple of 1.5″ snap-lock profile options. For now, we’re going to cover the Sheffield Metals 1.5” Snap-Lock 550 and its specs, engineering, uses, and more. 

Sheffield Metals is proud to offer a complete line of engineered and non-engineered standing seam profiles for metal roof and wall systems. Whether your project is commercial or residential, low or steep slope, solid or open-framed decking – we have a profile that is right for you.

Let’s talk in detail about the Sheffield Metals 1.5” Snap-Lock 550 profile.

Sheffield Metals 1.5” Snap-Lock 550 Specifications

The Sheffield Metals 1.5” Snap-Lock 550 profile is a newer profile in the industry, but it still has a couple of shortened nicknames, including:

  • SMI 1.5” Snap-Lock 550
  • SMI 1.5” SL 550
  • SL 550
  • 1.5” SL 550

Other manufacturers offer profiles that are similar to the SMI 1.5” Snap-Lock 550. However, we’re ONLY discussing the Sheffield Metals 1.5” Snap-Lock 550 profile and not any other manufacturer’s products for this article.

Panel & Seam Type

The Sheffield Metals 1.5” Snap-Lock 550 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). Snap-lock profiles don’t require hand or mechanical seaming during installation.

Metal Materials 

For the 1.5” Snap-Lock 550 profile and its engineering, you can use 22 to 24-gauge steel (Galvalume) or .032 to .040 aluminum to form the panels. For reference, you can use the same metal materials in a heavier (thicker) gauge or a narrower width panel and still have valid engineering.

Keep in mind that copper is not a suitable material to use for any snap-lock profile systems.

Panel Width

With the 1.5” Snap-Lock 550 profile, the panel width for our engineering is 15” for aluminum and 19” for steel (Galvalume). This specific panel requires approximately 5-1/8” of the metal sheet/coil to make the seams and edges, which means you’ll need to order 24” coil(s) for steel panels and 20” coil(s) for aluminum panels.

For reference, if you take the square footage of the roof and multiply that number by 1.27, it will equal the amount of coil needed to manufacture the panels in the SMI 1.5” SL 550 profile (this calculation doesn’t factor in waste).


Click here to download the Standing Seam Coil Estimation Calculator!

Seam Height

The seam height is approximately 1.5 inches.

Slope Minimum & Requirements

The SMI 1.5” Snap-Lock 550 profile can be installed on roof slopes down to a 2/12 pitch in certain circumstances, which is lower than most other snap-lock profile options. We discuss more slope requirements for this profile in the “When to Use the Sheffield Metals 1.5” Snap-Lock 550 Profile” section of this article.

Roof Deck Substrates

We have tested the 1.5” Snap-Lock 550 Galvalume assembly over plywood for our engineering on this profile. The same profile was also tested as an aluminum assembly over plywood, b-deck (metal decking), and b-deck with ISO (polyisocyanurate insulation). 

This profile is not for use over 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 1.5” SL 550 panel profile qualifies for these weathertight warranties (based on the project design).

Paint & Substrate Warranties

Both steel and aluminum SMI 1.5” SL 550 roof systems carry a 40-year transferable PVDF paint/finish warranty (available from Sherwin-Williams). Additionally, substrate warranties are available; the warranty lengths, inclusions, and exclusions will vary depending on the material type. 

Installation Details

This profile has installation details for steel systems over plywood and aluminum systems over plywood, b-deck, and b-deck with ISO. Metal roof installation details are in-depth product guides detailing the location of components/accessories and explain the basic practical installation methods at various roof points. Please visit the profile product page to download the installation details for the 1.5” SL 550 profile.

Miscellaneous Specifications & Requirements

There are a few other specifications recommended for the SMI 1.5” Snap-Lock 550 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 or S-5-U 

Engineering, Testing, & Approvals on the SMI 1.5” Snap-Lock 550 Profile

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

Substrate material: Steel 

Deck type(s): Plywood

Result: Pass (completed Class 90 and went on into UL 1897. During UL 1897, the system maintains a positive pressure and increases negative pressure until the system fails).

Substrate material: Aluminum

Deck type(s): Plywood, b-deck, and b-deck with ISO

Result: Pass (completed Class 90 and went on into UL 1897)

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

Substrate material: Steel 

Deck type(s): Plywood

Result: Pass

Substrate material: Aluminum

Deck type(s): 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: Steel 

Deck type(s): Plywood

Result: Pass

Substrate material: Aluminum

Deck type(s): Plywood, b-deck, and b-deck with ISO

Result: Pass

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

Substrate material: Steel 

Deck type(s): Plywood

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

Substrate material: Aluminum

Deck type(s): 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: Steel 

Deck type(s): Plywood

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

Substrate material: Aluminum

Deck type(s): Plywood, b-deck, and b-deck with ISO

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

Florida Building Code (FBC) – Non-HVHZ

Substrate material: Steel ONLY

Deck type: Plywood ONLY

Result: Approved

Texas Department of Insurance (TDI)

Substrate material: Steel ONLY

Deck type: Plywood ONLY

Result: Approved

UL 90 Construction Numbers

SMI 1.5″ SL 550 UL 90 Test – Construction No. 373

  • 12” wide 24-gauge panel over purlins spaced at 4 feet

SMI 1.5″ SL 550 UL 90 Test – Construction No. 467

  • 18” wide (UL 90) / 19.5” wide (UL 60) 24-gauge panel over purlins spaced at 3 feet

When to Use the Sheffield Metals 1.5” Snap-Lock 550 Profile

The roof slope is at or above a 2/12 – Snap-lock profiles are typically intended for steep-slope applications because they are hydrokinetic systems, which means they must shed water quickly to remain water-tight. Most snap-lock profiles have a minimum slope requirement of 3/12, but the SMI 1.5” SL 550 is different. Due to the ASTM E 1646 water penetration testing, Sheffield Metals allows it to be installed at slopes as low as a 2/12; however, keep in mind that this ability is based on certain conditions like geographic location and building design. This profile does so well in testing because it has a continuous locking mechanism on the male leg down the entire length of the panel instead of other snap-lock systems that only lock on to the clips.

You want or need to install an engineered metal roofing system – One reason the SMI 1.5” Snap-Lock 550 is so popular is that it’s engineered, tested, and proven to perform with numerous material types and roof deck substrates. Choosing an engineered panel profile ensures that you’re installing a system backed by actual data gathered by a third-party testing company and is rated following industry-wide standards

You want a commercial weathertight warranty – Another reason you might want to specify and install the SMI 1.5” SL 550 is that it qualifies for our commercial weathertight warranties, including limited 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.

Your project is residential or commercial – The SMI 1.5” SL 550 system is frequently installed on both residential and commercial projects, which further adds to the versatility of this profile.

You’re doing a DIY project – While we always recommend using skilled metal roofing installers, some DIYers will be able to install this metal roof type because it requires less labor-intensive installation techniques. For example, we’ve had DIYers purchase panels in this profile from a distributor and successfully install them on their tiny homes, sheds, and accent pieces.

You want a tested 1.5” snap-lock profile – This profile is often used as an alternative to the SMI 1.5” SL 450 option because the 1.5” SL 550 has more available engineering. Additionally, some property owners choose the 1.5” SL 550 because the seam height is shorter than the SMI 1.75” SL profile and therefore a little more low-profile.

When NOT to Use the Sheffield Metals 1.5” Snap-Lock 550 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 1.5” Snap-Lock 550 is no exception. Flatter pitches don’t allow water to drain adequately, leading to premature degradation, color splotches/changes, and the overall failure of the roofing system.

Over open framing – We do not recommend installing the 1.5” SL 550 profile over an open-framed roofing structure (without a solid roof deck). However, we offer standing seam profile options for use over open framing, including the Sheffield Metals 2.0” Mechanical Seam

You don’t like the look of a boxy, wider seam – The shape of the SMI 1.5” SL profile is sometimes considered too industrial or bulky because it has a wider, more box-shaped seam, which tends to be less of an appeal for residential applications.

Completed Projects Using the SMI 1.5″ SL 550

Final Thoughts on the SMI 1.5” Snap-Lock 550 Standing Seam Profile

The Sheffield Metals 1.5″ Snap-Lock 550 profile is a good fit for a variety of roof applications, which is why it’s commonly installed in architectural metal roofing projects.

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 1.5″ SL 550 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?
  • Is this roof being installed by a professional? DIYer?
  • Do I want/need a quick, 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 1.5″ Snap-Lock 550, that are designed to meet your project requirements.

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


Contact Sheffield Metals today!