Metal Roof Panel Types Explained: Which Profile Fits Which Roof
Exposed fastener, snap-lock, mechanically seamed and steel shingles, with the gauges, finishes and minimum slopes that decide between them.
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The short answer
Residential metal roofing comes in four families. Exposed-fastener ribbed panels are screwed through the face and suit shops and simple roofs. Concealed-fastener snap-lock panels, such as ProLock, click together over a nail strip and need about 3/12 slope. Mechanically seamed standing seam is crimped closed and handles low slopes. Steel shingles imitate shakes or slate. Gauge, finish and slope requirements vary by product.
A metal roof is not one product. Between a ribbed barn panel and a snap-lock residential panel there are differences in fastening, slope limits, expansion behaviour, price and how the roof ages. Picking the wrong family for the roof is the most common expensive mistake: an exposed-fastener panel on a house where the owner wanted a clean look, or a 3/12 panel specified for a 2/12 porch roof.
Nearly every residential and light commercial job fits one of four families: exposed fastener, concealed-fastener snap-lock, mechanically seamed standing seam and steel shingle or tile profiles. The four families are covered below. Within each, the gauge of the steel, the paint system and the substrate the manufacturer requires change how it performs. This guide walks through each, and points to the installation guides for the ones you are likely to build.
Always treat the manufacturer's installation manual as the final word. The values below are common ones from the industry, not a substitute for the literature on the product you buy.
Tools
- Tape measure
- Roof pitch gauge or smartphone inclinometer
- Roof report or roof plan
- Manufacturer installation manuals for the profiles you are comparing
Materials
- Manufacturer product data sheets
- Colour chips or finish samples
- Notes on deck type and roof slope
Safety first
- Do not walk a roof just to identify its slope. Measure pitch from the attic rafters, from a gable end or from a roof report instead.
- Metal roofs are slippery, especially with morning frost or moss. Panel type does not change that, so plan fall protection for any work on one.
- Panel edges and cut ends are sharp. Gloves are needed even when only handling samples.
Step by Step
Step 1: Measure the roof slope and note every low-slope section
Slope is expressed as rise over 12 inches of run, for example 4/12. Read it from a roof report, a framing drawing or a pitch gauge on a rafter in the attic. Check every plane, not just the main one. Porch roofs, dormer tops and shed roofs are often 2/12 or flatter and are where the wrong panel gets specified.
As a rough guide, most snap-lock and nail-strip panels want 3/12 or more. Exposed-fastener ribbed panels commonly need 3/12 as well, though some manufacturers allow 1/12 to 2/12 with added sealant at laps and factory lengths. Mechanically seamed standing seam is the family designed for low slopes, often down to a half inch of rise per 12 inches with seam sealant. Confirm each number with the manufacturer, and see how to measure and order for taking measurements off a roof report.
Tip: Slopes under 3/12 on an otherwise steep roof should be listed separately. They may need a different panel, or a low-slope membrane roof instead.
Step 2: Understand exposed-fastener ribbed panels
Common names are R-panel, PBR, 7/8 corrugated and ribbed panels. Panels are typically 36 inches of coverage, usually 26 or 29 gauge steel, and fasten to purlins or strapping or directly to a solid deck. Laps are made with the edge rib of one panel over the next, with sealant tape in the lap.
Their strength is speed and cost. Their weakness is the face screws: each one is a rubber washer that can crack in UV or back out as the metal moves, and many roofs need the screws checked or replaced after roughly 15 to 25 years, depending on sun exposure. See how to install exposed-fastener metal panels and metal roof screws for the pattern and torque.
Step 3: Understand concealed-fastener snap-lock panels, including ProLock
In BC, ProLock (sold by the manufacturer, Domtek Building Products, as Pro-Lock) is the snap-lock product most residential roofers mean. The manufacturer lists 12 inch and 16 inch panel widths, 26 and 24 gauge steel, a 3/12 minimum slope, and installation over solid plywood decking with a synthetic underlayment, without clips. The panel is held by screws through a flange and the next panel snaps over it. Rib profiles include striations, an XD profile and minor ribs. Confirm current details in the ProLock installation manual.
Snap-lock is the usual step up from exposed fastener on a house: clean lines, no face screws and a simpler install than mechanical seaming. Because the flange is fastened solidly, long panels cannot slide the way they do on clips, so panel length and expansion need attention. The install sequence is in how to install ProLock snap-lock panels.
Watch out: Do not assume snap-lock panels from different manufacturers are interchangeable, even at the same width. Flange dimensions, lock shape and fastener slots differ.
Step 4: Understand mechanically seamed and clipped standing seam
Standing seam uses tall seams, often 1 to 2 inches, joined over clips that are screwed to the deck. Panels are 12 to 18 inches wide in 24 or 22 gauge steel, or aluminum or copper. A seamer folds the seam once or twice, which makes it the most weather-tight panel, rated for very low slopes, in some cases about a half inch of rise per 12 inches, with sealant in the seam.
It is the most expensive option in both material and labour, and it is where careful installation pays off the most. Clip layout, fixed and floating zones and seaming are covered in how to install standing seam, and movement is explained in thermal movement in metal roofs.
Step 5: Consider steel shingle and tile profiles
These are stamped steel or aluminum panels, often with a stone-coated finish, in roughly 12 to 15 inch by 50 inch sections that interlock and are nailed or screwed high on the panel. They suit steeper roofs and owners who want the look of a traditional material without the weight.
Their detailing behaves more like shingles than like long panels: short laps, nailing and lots of trim. They are less common than panels in BC, and finish and installation details vary enough between brands that the manufacturer manual is essential.
Step 6: Choose gauge and finish
Lower gauge numbers mean thicker steel. 29 gauge is thin and used on agricultural buildings. 26 gauge is the residential workhorse. 24 gauge is heavier, flatter looking and more expensive, and it is the choice for wide flat panels where oil canning is a worry. Aluminum and copper are options for coastal and high-end work.
Finish matters as much as gauge. Silicone-modified polyester is the usual economy coating, while PVDF (fluoropolymer, sold under brand names such as Kynar 500) is the premium paint system with better fade and chalk resistance. Galvalume substrate resists rust at cut edges better than plain galvanized in most settings. Ask for the paint and substrate specification, not just the colour.
Step 7: Match the deck, underlayment and substrate to the panel
Snap-lock and standing seam panels generally require a solid deck, commonly at least 1/2 inch plywood and sometimes 5/8 inch, with a synthetic or high-temperature underlayment. Exposed-fastener panels can go over solid deck or over strapping on open framing. Reroofing over shingles may need strapping to create a flat, ventilated plane.
See underlayment for metal roofs and how to strap a roof for metal for the rules on each.
Quick Comparison
These are typical values, not guarantees. Each product carries its own slope limit, fastening rules and warranty terms.
- Exposed fastener: 36 inch coverage, 26 or 29 gauge, screws through the face, commonly 3/12 minimum, lowest cost, best for shops, barns and simple roofs.
- Snap-lock (ProLock type): 12 to 16 inch coverage, 24 or 26 gauge, hidden screws through a nail strip or flange, about 3/12 minimum, residential look without seaming.
- Mechanically seamed standing seam: 12 to 18 inch coverage, 24 or 22 gauge, hidden clips, seams crimped closed, suitable for low slopes and long runs, highest cost.
- Steel shingle or tile: short interlocking sections, steeper slopes, suited to a traditional look.
Fraser Valley Notes
Long wet winters mean moss and needle debris collect in the low ribs and behind trims, so choose profiles that shed debris and leave gaps open at eaves. In Hope and up the Fraser Canyon, heavy wet snow can release suddenly from slick panels, so plan snow guards above doors, walkways and lower roofs. Summer heat in the 30s C in Chilliwack and Abbotsford makes dark colours get very hot, which matters for thermal movement and for the underlayment rating.
Common Mistakes
- Choosing by looks alone and ignoring slope. A 3/12 minimum panel on a 2/12 porch roof leaks at the laps.
- Assuming exposed fastener and concealed fastener cost and last the same. Face screws need checking and replacement as washers age.
- Using 29 gauge on a house and then being surprised by oil canning and denting.
- Ordering snap-lock panels without checking the decking requirement. Most need a solid deck, not open strapping.
- Mixing brands of panel and trim. Profiles, closures and flashings are designed as a set.
- Ignoring the paint specification. Cheaper coatings chalk and fade sooner on south slopes.
When to Call a Professional
Choosing a panel is a consumer decision, but installing one usually is not. Roofs with multiple slopes, valleys, skylights, chimneys or any low-slope section need a detailed layout, and mistakes at trims and valleys are where metal roofs leak.
If your roof is under 3/12 anywhere, has a complex shape, or sits where snow and wind are severe, ask a roofer to review the slope and deck before you order anything.
Fraser Roofing does free roof inspections across the Fraser Valley, from Hope to Abbotsford. See our Metal Roofing service or the towns we cover.
Metal Roof Panel Types Explained: Questions
What is the best type of metal roof for a house?
For most houses with a pitch of 3/12 or steeper, a concealed-fastener panel such as snap-lock or standing seam is the usual choice because no screws show and the roof looks clean. Exposed-fastener panels cost less and suit shops, garages and sheds. The right answer depends on slope, budget and how the roof will be detailed at walls, valleys and penetrations.
Is 24 gauge or 26 gauge metal roofing better?
Twenty-four gauge is thicker, stiffer and resists oil canning and denting better, but costs more per square. Twenty-six gauge is the common residential standard and performs well on most roofs. Wide flat panels and dark colours benefit most from 24 gauge. Check the manufacturer's warranty terms and the panel width before deciding.
What slope does a metal roof need?
Most snap-lock panels and many ribbed panels want at least 3/12, meaning 3 inches of rise per 12 inches of run. Mechanically seamed standing seam with sealant can go much lower, about a half inch of rise per 12 inches on some products. The manufacturer's installation manual sets the real limit, so confirm it for the exact profile.
What is ProLock metal roofing?
ProLock, sold by Domtek Building Products as Pro-Lock, is a concealed-fastener snap-lock panel in 12 inch and 16 inch widths, made in 24 and 26 gauge steel. It needs a minimum 3/12 slope and solid plywood decking with synthetic underlayment, and it installs without clips. Confirm the current specifications in the installation manual.
Do metal roofs need special underlayment?
Yes. Metal roofs get hot, so the underlayment should be rated for high temperature, commonly a self-adhered membrane or a synthetic rated to around 220 to 250 degrees Fahrenheit. Ice and water shield goes at eaves and valleys, and a slip sheet may sit under the panels. The panel manufacturer's manual lists approved underlayments.
Related Guides
All Metal Roofing guides|The full How-To Library
This guide is general education. Always follow the product manufacturer's installation instructions, the BC Building Code and WorkSafeBC requirements, which take priority over anything written here.
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