Metal roofing installation is a sequence of roof-deck preparation, underlayment, flashing, panel alignment, fastening and finish work. This guide was last reviewed on **** and applies mainly to exposed-fastener metal panels installed over a wood roof deck.

In the United States, OSHA generally requires residential construction workers who are 6 feet or more above a lower level to use guardrails, safety nets, personal fall-arrest systems or another permitted fall-protection method. Plan that protection before anyone gets on the roof.

Standing-seam metal roofing uses a different installation method. Its panels use concealed clips and may require specialized seaming. Follow the product manual or hire a qualified metal-roofing contractor instead of applying exposed-fastener instructions to a standing-seam system.

Metal Roofing Installation at a Glance

Installation Stage What You Need to Accomplish
1. Choose the system Confirm the panel type, roof pitch, substrate and local code requirements
2. Prepare the roof Repair damage, remove protrusions and create a flat, dry surface
3. Install underlayment Use the underlayment approved for the selected roofing system
4. Install lower flashings Fit eave trim, valley flashing and other components that go beneath the panels
5. Install panels Start at the correct gable, align the first panel and work across the roof
6. Fasten panels Use compatible, corrosion-resistant screws with sealing washers
7. Finish the details Install gable trim, ridge caps, closures, valley details and penetration flashing
8. Inspect and clean Check the fasteners, seals and alignment, then remove all metal shavings

1. Choose the Correct Metal Roofing System

Metal roofing is not one universal product. Before ordering materials, identify the following:

  • Panel type: exposed-fastener, concealed-fastener or standing seam
  • Substrate: plywood, OSB, dimensional lumber, purlins or metal framing
  • Roof pitch: confirm that the panel is approved for the slope
  • Roof layout: account for valleys, hips, dormers, chimneys, skylights and vents
  • Weather exposure: consider wind, snow, ice, heavy rain and coastal corrosion
  • Local requirements: check permits, structural requirements and fire classifications with the local building department

Exposed-fastener panels are usually simpler and less expensive to install, but their fasteners remain visible. Standing-seam panels conceal the clips and fasteners, but they require a different process.

Do not use exposed-fastener panels on a low-slope roof without confirming that the manufacturer approves the application. The panel system, substrate, slope and flashing details must work together.

2. Set Up Fall Protection Before Going Onto the Roof

Roof installation presents a serious fall risk. Before work begins, provide:

  • A properly secured ladder or scaffold
  • Roof-edge protection where required
  • A correctly installed personal fall-arrest or restraint system
  • A safe way to lift and stage the panels
  • Gloves, eye protection and suitable footwear

Metal panels become slippery when they are wet, dusty, frosty or oily. Avoid installation during rain, frost or strong winds. Never use unsecured or partially fastened panels as a work platform.

3. Gather the Materials and Tools

Materials

  • Metal roof panels
  • Manufacturer-approved underlayment
  • Eave, gable, valley and ridge flashing
  • Inside and outside closure strips
  • Compatible corrosion-resistant screws
  • Screws with sealing washers for exposed-fastener panels
  • Butyl tape, mastic or approved sealant
  • Pipe boots and penetration flashings
  • Ridge vent, if required by the system
  • Touch-up paint approved by the panel manufacturer

Tools

  • Tape measure and chalk line
  • Drill or screw gun with an adjustable clutch
  • Correct driver bits
  • Metal snips, nibblers or a manufacturer-approved cutting tool
  • Folding tool or hand seamer
  • Aviation snips
  • Level and framing square
  • Soft-bristled brush
  • Clean, soft-soled footwear
  • Gloves and safety glasses

Use fasteners approved for the substrate. A screw suitable for plywood may not be suitable for solid lumber, metal framing or spaced supports. ASC Building Products, for example, lists different fasteners for plywood, dimensional lumber, steel framing and trim connections.

4. Inspect and Prepare the Roof Deck

A metal roof needs a structurally sound, relatively flat base.

  1. Remove loose roofing, damaged sheathing and protruding nails.
  2. Replace rotten or structurally damaged decking.
  3. Remove moss, dirt and debris.
  4. Check for fasteners or sharp objects that could puncture the underlayment or panels.
  5. Install roof penetrations, curbs and structural blocking before placing the panels.
  6. Confirm that the roof plane is flat and that the eaves and gables are straight.

Some jurisdictions allow metal roofing over existing shingles. That decision depends on local requirements and the manufacturer's instructions. Do not install over rough wood shingles, trapped moisture or structural damage. Removing the old roof to expose the decking gives you the best opportunity to inspect and repair the substrate.

5. Install the Underlayment

Install the approved underlayment across the entire roof deck before placing the metal panels.

Follow the product instructions because underlayment requirements vary by system and climate. For example, the ASC Building Products light-gauge installation guide specifies minimum 30-pound asphalt-saturated felt or a synthetic underlayment certified for that roofing system. Its example installation starts at the eave, runs parallel to the eave, uses 3-inch side laps and 6-inch end laps, and calls for high-temperature underlayment in valleys where snow, ice or heavy rain are expected.

Do not cover torn or poorly sealed underlayment with finished panels. Repair or replace damaged areas first.

6. Install the Eave, Valley and Other Underlying Flashings

Install the components that belong beneath the roof panels before laying the panels. Depending on the roof design, these may include:

  • Eave flashing
  • Valley flashing
  • Pre-hung gutters
  • Sidewall or endwall flashing
  • Starter strips
  • Valley closure material

The installation sequence matters. A bead of caulk cannot replace a properly designed valley or wall flashing. Use the panel manufacturer's illustrated details for valleys, walls and other complicated areas.

7. Mark the Layout and Install the First Panel

The first panel controls the alignment of the rest of the roof.

  1. Measure the roof from gable to gable.
  2. Mark a straight layout line square with the eave.
  3. Confirm the required eave overhang and ridge setback.
  4. Position the first panel at the manufacturer-specified starting gable.
  5. Install the required inside closure at the eave.
  6. Check that the ribs are straight and that the panel is square to the eave.
  7. Fasten the panel according to the manufacturer's screw pattern.

Do not use a crooked roof edge as your guide. Use a chalk line or another measured reference so the panels stay square. If the first panel is out of alignment, the eave can become progressively misaligned across the roof.

8. Fasten the Metal Roofing Panels Correctly

Fastener placement affects both the weather seal and the connection between the panels and the roof structure.

Follow the Specified Fastener Pattern

There is no universal screw spacing for every metal roofing panel. Spacing depends on the panel profile, wind zone, substrate, roof geometry and tested system design.

Use the manufacturer's installation guide instead of estimating the number of screws. ASC's light-gauge guide, for example, lists maximum recommended fastener-row spacing and panel-lap spacing for its own profiles. Those measurements should not be transferred automatically to another manufacturer's product.

Drive Screws Straight and to the Correct Depth

Exposed-fastener screws should be:

  • Perpendicular to the roof plane
  • Tight enough to seat the sealing washer
  • Loose enough to avoid crushing or splitting the washer
  • Long enough to reach the required depth in the substrate

A screw that is overdriven can damage the washer. An underdriven screw may leave a path for water around the fastener. Use a screw gun with an adjustable clutch or depth-control nosepiece when possible.

Use Compatible Metals and Fasteners

Use corrosion-resistant fasteners approved for the panel material and the installation environment. Isolate dissimilar metals because contact between incompatible metals can cause galvanic corrosion. Exposed fasteners should normally include sealing washers and match the panel or trim finish.

9. Lap and Install the Remaining Panels

Continue across the roof one panel at a time.

  • Keep each panel aligned with the layout line.
  • Lap panels in the direction recommended for prevailing weather.
  • Apply butyl tape, neoprene mastic or another approved seal where the manufacturer requires it.
  • Install panel-lap screws at the specified locations.
  • Check the eave line regularly to catch cumulative misalignment.
  • Maintain the required ridge gap or setback.
  • Do not walk on panels until all required fasteners have been installed.

Remove metal filings and shavings as you work. Shavings can stain the roof and damage the painted coating if they remain on the panel surface.

10. Install Gable Trim, Ridge Caps and Closures

Complete the roof edges and high points after the field panels are installed.

Gable Trim

Install the gable or rake flashing according to the panel detail. The trim should cover the exposed panel edge and direct water away from the roof assembly.

Ridge Cap

A typical ridge installation includes:

  1. Sealing or fastening the required upper closure
  2. Installing the ridge vent, if the system is vented
  3. Positioning the ridge cap over both roof slopes
  4. Lapping and sealing successive ridge-cap pieces
  5. Fastening the ridge cap with the specified stitch screws or other approved fasteners

Some systems require the gable flashing to be installed before the ridge cap. ASC's installation details specify that sequence for its light-gauge panels.

Valleys and Penetrations

Valleys, chimneys, skylights, plumbing vents and roof-to-wall transitions need purpose-built flashing details. Do not use surface-applied caulk as the primary waterproofing method.

If the roof has several penetrations or complicated transitions, professional installation is the safer choice.

Common Metal Roofing Installation Mistakes

Avoid these mistakes:

  • Installing a panel system below its approved roof pitch
  • Fastening into damaged or rotten decking
  • Using ordinary screws instead of manufacturer-approved roofing screws
  • Overdriving or underdriving sealing washers
  • Installing the first panel out of square
  • Omitting closures at the eave or ridge
  • Combining incompatible metals
  • Leaving protective film on the panels in sunlight or extreme temperatures
  • Walking on ribs, seams or unsecured panels
  • Leaving metal shavings on the finished roof
  • Installing over trapped moisture or structural damage
  • Using generic flashing details around chimneys, valleys and skylights

ASC advises removing strippable film before installation and warns against leaving it exposed to direct sunlight or ultraviolet light. The same guide advises walking only on flat areas of installed panels, not on seams or ribs.

Should You Install Metal Roofing Yourself?

You can consider a DIY installation for a simple gable roof with exposed-fastener panels, a sound roof deck, few or no penetrations, no major valleys or dormers, a moderate pitch and proper fall-protection equipment.

Hire a qualified roofing contractor for:

  • Standing-seam systems
  • Steep roofs
  • Complex roof geometry
  • Structural repairs
  • Multiple valleys
  • Chimneys or skylights
  • Any project where safe fall protection is unavailable

The contractor should be able to identify the exact panel system, explain the flashing sequence and install the roof according to the manufacturer's tested details.

Final Installation Checklist

Before calling the metal roof complete, verify that:

  • Every panel is aligned and fully fastened.
  • Screws are straight and the sealing washers are compressed correctly.
  • Panel laps contain the specified tape, sealant or mastic.
  • Eave, gable, valley and ridge flashings were installed in the required sequence.
  • Closures are continuous where required.
  • All penetrations have the correct flashing boots or assemblies.
  • No damaged panels, exposed underlayment or open seams remain.
  • All metal shavings and debris have been removed.
  • The roof has been checked against the manufacturer's installation manual and local code requirements.

The manufacturer's installation guide controls panel spacing, fastener patterns, minimum slope, flashing details and warranty requirements.