What is butyl tape used for on a metal roof?
Short answer. Butyl tape is a sticky, non-hardening rubber sealant tape used on metal roofs to seal panel side laps and end laps, the joints between trim and panels, and closure strips at eaves and ridges. Unlike caulk, it stays flexible for years and is compressed between metal layers by the fasteners, so it seals without being exposed to the sun.
Where it goes
- Side laps of exposed-fastener panels, especially on lower slopes, where the code allows a reduced slope only with applied lap sealant.
- End laps where two panels overlap along the slope.
- Closure strips: tape on both sides of foam closures at the eave and ridge seals them to panel and trim.
- Trim joints: where eave, rake, ridge, valley and wall trims meet panels and each other.
- Penetrations: under flashing flanges and pipe boot bases.
Butyl tape vs caulk
Tube sealants are often exposed to sun and weather and can harden or pull away. Butyl tape sits between two layers of metal, out of the sun, squeezed tight by fasteners. It stays tacky and flexible, moving with the panels as they expand and contract. Many systems use both: tape inside the joint and a compatible sealant on exposed edges.
Installation tips
- Apply to clean, dry metal; dust, pollen and oil prevent adhesion.
- Keep the release paper on until the moment of placement.
- Place tape where the fasteners will pass through it or just upslope of them, per the manufacturer's detail.
- Do not stretch it thin; a continuous bead without gaps seals best.
- Use the width and thickness the panel maker specifies.
How long it lasts
Protected inside a joint, quality butyl tape can last many years, often as long as the panels. Exposed butyl degrades faster in Georgia sun.
What it will not fix
Tape cannot rescue a joint lapped the wrong way or a panel installed below its minimum slope. See metal roofing in Georgia and common causes of roof leaks.