If you’re a homeowner looking to install a metal roof, you may be asking:
Can You Install Metal Roofing Over Shingles?
Quick Answer:
Yes, metal roofing can sometimes be installed over existing shingles.
However, the shingles should not be covered if the roof has active leaks, rotten decking, trapped moisture, structural damage, or too many existing roofing layers. The roof should be inspected before panels, purlins, trim, or fasteners are ordered.
Cumberland’s over-shingle methods also differ by panel. The ABM Panel and ABSeam Panel should each be installed according to their own current guide.
Replacing a shingle roof does not always require a complete tear-off. In some cases, you can install metal roofing over shingles, but only after the existing roof and the proposed metal roof system have been reviewed.
The condition of the shingles, roof deck, rafters or trusses, ventilation, flashing, and roof edges all matter. Local building codes and the installation instructions for the chosen panel must also allow the assembly.
When Is a Metal Roof Over Shingles Possible?
The 2024 International Residential Code (IRC) permits some roof re-cover projects when they follow approved manufacturer instructions. It does not permit a roof re-cover when the existing roof is water-soaked or too deteriorated to support the new roofing. Model building codes often restrict roof recover when two or more roof-covering applications are already present. The locally adopted code and any amendments control the project.
Why the Roof Inspection Comes First
Installing a new roof over old shingles can make it harder to see the condition of the deck below. A professional inspection helps determine whether the shingles are simply worn or whether leaks have already damaged the sheathing, framing, insulation, or attic.
The inspection should review:
- Active and past leaks
- Soft or rotten roof decking
- Sagging areas
- Shingle condition and number of layers
- Rafters, trusses, and other structural parts
- Roof slope and geometry
- Valleys, dormers, chimneys, and penetrations
- Attic moisture and ventilation
- Eave, rake, fascia, and gutter conditions
Test openings or partial removal may be needed when the deck cannot be properly evaluated from above or below. The Metal Construction Association also notes that leaving an old roof in place can limit access to the deck and make hidden leaks or damage harder to identify.
A metal roof should never be used to cover rot, active leaks, or structural problems. Those issues should be repaired before the new roof system is installed.
Do Shingles Need to Be Removed Before Metal Roofing?
Not always.
Tear-off may not be needed when the existing roof is dry, structurally sound, allowed by code, and compatible with the chosen metal roof system. Avoiding tear-off may also reduce labor and roofing waste.
Removal is usually the better choice when:
- The roof deck needs significant repair.
- Water has entered the roof assembly.
- The shingles are badly curled, uneven, or loose.
- The roof already has too many layers.
- The added roof height creates difficult flashing or edge details.
- The manufacturer does not approve the proposed assembly.
- Local code requires removal.
Tear-off also gives the contractor full access to the roof deck, which can make repairs and waterproofing details easier to complete.
Do You Need Purlins Over Shingles?
It depends on the panel system.
Purlins are horizontal wood or metal members installed over the existing roof. They can provide a level fastening surface, connect the new roof to solid framing, and create separation between the shingles and metal panels.
However, purlins also raise the height of the roof. This can change:
- Eave and rake details
- Gutter position
- Flashing heights
- Chimney and wall transitions
- Pipe boots and other penetrations
- Snow-retention placement
- Ridge and attic ventilation
Purlin size, spacing, fasteners, and attachment points must come from the installation guide and the project’s structural requirements. There is no universal purlin spacing that is correct for every roof.
The Metal Construction Association recognizes both direct-to-deck and over-purlin retrofit methods, but the correct method depends on the roof covering, structure, panel, and manufacturer’s tested assembly.
Installing ABM Panel Over Shingles
Cumberland’s ABM installation guide describes placing purlins over the shingles and securing those purlins through the existing roof into the rafters, rather than fastening them only to the roof sheathing. It also calls for specific eave and rake trim changes and says local code should be checked for multilayer-roofing weight limits.
The purlins help keep the painted underside of the ABM Panel from resting against the rough shingle surface. This separation helps prevent the shingles from rubbing against the metal as the panels expand and contract with temperature changes.
The exact purlin layout, fastener length, screw pattern, trim, and moisture-control details should be confirmed for the project. For exposed-fastener installation details, see Should Metal Roofing Screws Go on the Rib or the Flat?.
Installing ABSeam Over Shingles
ABSeam is a standing seam system with concealed clips, so it should not be treated as if it has the same installation requirements as ABM Panel.
The standard ABSeam installation instructions describe installation over a properly aligned solid substrate with approved felt or equivalent material. They also allow purlins in certain applications and require the buyer to verify structural loads, local codes, and the suitability of the roof design.
The ABSeam Panel Book also shows an over-asphalt-shingles method using purlins and a recommended vapor-control layer between the shingles and metal roof system. The booklet recommends following the full installation guide for more detail.
Because these are panel-specific assemblies, customers should confirm the current method with Cumberland before ordering. Learn more about the differences in ABM Panel vs. ABSeam Panel.
Underlayment, Vapor Control, and Ventilation Are Different
These terms are related, but they do not mean the same thing.
Underlayment is installed beneath the metal roofing as part of the water-shedding and separation system. Its type and location depend on the panel and roof assembly.
A vapor-control layer helps slow the movement of water vapor through the roof system. The correct material and placement depend on the building use, insulation, climate, and interior moisture level.
Ventilation moves air through the attic or roof cavity. A balanced system commonly brings air in near the eaves and allows warmer, moisture-laden air to leave near the ridge.
A product may perform more than one function, but the three terms should not be used interchangeably. Cumberland’s ABSeam guide treats vapor control and ventilation as separate parts of condensation management and recommends consulting building officials or an engineer about proper ventilation for the area.
Flashing and Roof Edges Must Be Reworked
A metal roof retrofit is more than laying panels over the old roof.
Adding purlins and metal panels changes the height of the roof surface. Existing flashing may no longer reach high enough or fit the new panel profile. Eave trim, rake trim, sidewall flashing, endwall flashing, valleys, pipe boots, gutters, and ridge details may all need to be replaced or redesigned.
Model building codes require reroofing flashings to be rebuilt according to approved manufacturer instructions. Damaged or deteriorated vents, edging, and similar roof components should also be replaced.
The correct metal roofing accessories should be selected as part of the complete roof system, not added as an afterthought.
Metal Roof Over Shingles Pre-Order Checklist
Before ordering panels, confirm:
- Are there existing or past leaks?
- Is any decking soft, rotten, or damaged?
- How many layers of shingles are on the roof?
- Is the roof slope suitable for the chosen panel?
- Are the rafters or trusses in good condition?
- Does local code allow the roof recover?
- Does the manufacturer approve the assembly?
- Will the existing ventilation continue to work?
- What underlayment or vapor-control layer is required?
- How will flashing and penetrations be rebuilt?
- How will the eaves, rakes, fascia, and gutters change?
- What purlins, fasteners, trim, and accessories are required?
Panel information and current installation documents are available on Cumberland’s downloads and installation guides page.
The Bottom Line
Can you install metal roofing over shingles? Sometimes, but the decision should be based on the complete roof system.
A sound roof with an allowable number of shingle layers may be a good candidate for a metal roof retrofit. A roof with leaks, rot, trapped moisture, weak decking, or structural problems should be repaired before it is covered.
ABM Panel and ABSeam also have different over-shingle methods. Follow the guide for the exact panel being purchased, confirm local code requirements, and review the full assembly before ordering.
For a broader comparison of the two materials, read Metal Roof vs. Shingles. You can also learn more about long-term performance in How Long Does a Metal Roof Last?.
FAQs
Can metal roofing be installed directly over shingles?
Some metal roof systems allow direct-to-deck installation over an existing roof. However, Cumberland’s over-shingle guidance for ABM Panel and ABSeam uses panel-specific purlin assemblies. Do not assume the metal panels can simply be placed against the shingles.
Do old shingles need to be removed first?
Not in every case. They may remain when the roof is dry, structurally sound, allowed by local code, and approved by the panel manufacturer. Removal is needed when the roof has serious damage, too many layers, or an unsuitable assembly.
Do you need purlins over shingles?
Purlins are part of Cumberland’s described over-shingle methods for ABM Panel and ABSeam. Their size, spacing, fasteners, and attachment must follow the panel guide and project requirements.
Can ABM Panel go over shingles?
Yes, Cumberland’s ABM guide describes an over-shingle method using purlins fastened into the rafters. The existing roof still needs to be inspected, and the complete assembly must meet local code.
Can ABSeam Panel go over shingles?
Cumberland’s ABSeam materials show an over-asphalt-shingles method using purlins and a recommended vapor-control layer. ABSeam has different installation requirements from ABM Panel, so its current guide should be followed.
Does installing metal over shingles cause condensation?
Not automatically. Condensation is more likely when warm, moist air reaches a cold surface and the roof lacks proper vapor control, insulation, or ventilation. These details should be designed for the building and climate.
How many layers of shingles can be covered?
That depends on local code. The 2024 IRC generally does not allow a roof recover when two or more roof-covering applications are already present, but the locally adopted code and amendments control the project.
Will a metal roof hide a damaged roof deck?
It may cover the deck, but it will not repair it. Rotten sheathing, active leaks, and structural damage can continue to worsen beneath the new roof.
Does local code allow metal roofing over shingles?
Some jurisdictions allow it when the existing roof and new assembly meet their requirements. Others may require tear-off based on roof condition, number of layers, structural loads, fire classification, or local amendments. Approval should be confirmed before materials are ordered.
Have Questions About Your Roof?
Thinking about installing metal roofing over an existing shingle roof? Contact Cumberland Supply before ordering. We can help you review panel options, purlins, underlayment, trim, fasteners, ventilation, and the installation guide for your roof system.
