Yes, you can often install a metal roof over existing shingles, and it’s a common practice that offers several advantages. However, there are important considerations and limitations.
When it’s typically allowed:
- Most building codes permit one layer of shingles to remain when installing metal roofing
- The existing shingles must be in reasonably good condition (not severely damaged, curled, or rotting)
- The roof deck underneath must be structurally sound
Advantages of installing over shingles:
- Saves on tear-off and disposal costs (can save $2-4 per square foot)
- Faster installation process
- Provides extra insulation layer
- Less mess and disruption during installation
- The shingles can act as a sound dampener
Requirements and considerations:
- You’ll need to install furring strips or a ventilated underlayment system to create proper ventilation
- Some areas may require removal of ridge shingles for proper ventilation
- The roof structure must handle the additional weight (though metal roofing is lightweight)
- Any damaged or loose shingles should be secured or replaced first
- Flashing areas typically need complete replacement
When removal is necessary:
- If there are already multiple layers of roofing
- Severe damage to existing shingles or roof deck
- Local building codes prohibit it
- Insurance requirements (some insurers prefer complete removal)