Utility knife
Use it for: To score and lift old tape without tearing nearby housewrap or trim.
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How to Replace Exterior Flashing Tape
To replace exterior flashing tape, remove the failed tape completely, clean and dry the surface, apply new tape over sound material with firm pressure, and make sure the overlap sheds water instead of trapping it.
This repair is usually worth doing when old flashing tape has lifted, cracked, shrunk, or lost its seal around siding or trim joints. The goal is not just to cover the gap, but to restore a clean water-shedding seal on a dry, solid surface.
Before you start: Match the replacement part to your exact siding flashing before ordering.
Safety first
- Work only in dry weather and on a dry ladder setup.
- Use a stable ladder on firm ground and do not overreach to one side.
- Cut away from your body when scoring or trimming old tape.
- Wear gloves if the old tape edges or flashing are sharp.
- Do not seal over rotten sheathing, loose trim, or hidden water damage and call it fixed.
Tools you may need
Plastic putty knife
Use it for: To scrape off loose tape and adhesive with less risk of gouging the surface.
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Clean rags
Use it for: To wipe away dust, residue, and moisture before the new tape goes on.
Shop cleaning rags
Exterior surface cleaner
Use it for: To help remove dirt and leftover adhesive so the new tape can bond.
Shop exterior surface cleaner
J roller or seam roller
Use it for: To press the tape down evenly and improve contact across the full width.
Shop seam rollers
Extension ladder
Use it for: To reach the repair area safely if the flashing is above ground level.
Shop extension laddersAs an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
Step-by-step fix
Step 1: Confirm flashing tape is the real problem
- Look for tape that is peeling back, split, brittle, wrinkled, or no longer stuck tightly at the edges.
- Check the area around the failed tape for signs that water has been getting past it, such as staining, soft trim, swollen sheathing edges, or siding that keeps pulling loose.
- Press gently on the surrounding surface. The repair makes sense when the surface under the tape is still solid enough to hold a new seal.
- Plan the overlap before you start. New tape should cover the failed area and extend onto clean, sound material so water can keep shedding downward.
If it works: You have a clearly failed section of exterior flashing tape on an otherwise solid surface, and replacing the tape is a reasonable repair.
If it doesn’t: If the tape looks intact, focus on the joint, flashing detail, or siding attachment instead of replacing tape that is still bonded.
Stop if:
- The wall surface under the tape feels soft, crumbles, or shows rot.
- You find widespread water damage behind siding or trim.
- The repair area is too high to reach safely with stable ladder access.
Step 2: Set up the area and remove the old tape
- Pick a dry stretch of weather so the surface can stay dry during the repair.
- Set the ladder on firm ground if needed, and keep both hands free while climbing by carrying tools in a pouch or bucket.
- Use the utility knife to score the edges of the old tape if it is stuck hard or layered under sealant.
- Lift and peel the old tape slowly. Use the plastic putty knife to help separate it without tearing nearby housewrap, trim, or flashing.
- Remove all loose pieces, failed adhesive, and any patch material that would keep the new tape from lying flat.
If it works: The failed tape is off, and the repair area is exposed without loose material left behind.
If it doesn’t: If small bits of adhesive remain, keep scraping and cleaning until the surface is flat enough for the new tape to sit tight.
Stop if:
- Removing the tape tears the water-resistive barrier or exposes hidden damage that needs a larger repair.
- You uncover missing or badly bent metal flashing that the tape alone cannot replace.
Step 3: Clean and dry the bonding surface
- Wipe away dust, chalking, dirt, and loose debris with clean rags.
- Use an exterior-safe cleaner or adhesive remover as needed to break down residue from the old tape.
- Let the area dry fully. New flashing tape bonds poorly to damp, dirty, or oily surfaces.
- Run your hand across the repair area. It should feel clean, dry, and mostly smooth, with no curled edges or grit trapped under where the tape will go.
If it works: The surface is clean, dry, and ready for the new exterior flashing tape.
If it doesn’t: If the surface still feels slick, dusty, or damp, clean it again and give it more drying time before applying tape.
Stop if:
- The substrate is flaking apart or will not hold a clean surface for the new tape to bond to.
Step 4: Cut and place the new exterior flashing tape
- Measure the repair area and cut a piece of tape long enough to cover the failed section and extend onto sound material at both ends.
- Dry-fit the piece before peeling the backing so you know exactly where it will land.
- Start at the lower part of the repair when possible and work so upper layers overlap lower layers in a water-shedding direction.
- Peel back a short section of release backing, stick the tape in place, and keep it straight as you pull the rest of the backing away.
- Avoid stretching the tape. Lay it flat so it can stay bonded as temperatures change.
If it works: The new tape is centered over the joint or seam and fully covers the failed area with proper overlap onto solid material.
If it doesn’t: If the tape lands crooked or wrinkles badly, pull it back right away and replace it with a fresh piece rather than trying to patch over the mistake.
Stop if:
- The joint shape or gap is too irregular for the tape to sit flat and sealed.
Step 5: Roll the tape tight and seal the edges
- Use a J-roller or seam roller to press the tape firmly from the center outward.
- Pay extra attention to corners, edges, and any texture changes where tape can bridge instead of bonding.
- Check that the tape is fully adhered with no fishmouths, bubbles, or lifted ends.
- Trim any excess only if needed to keep the repair neat and to avoid creating a loose flap.
If it works: The tape is firmly bonded across its full width, with tight edges and no visible voids.
If it doesn’t: If an edge keeps lifting, the surface is still contaminated, damp, or unsound. Remove that section, prep again, and apply a new piece.
Stop if:
- Large bubbles, repeated edge lift, or poor adhesion continue after proper cleaning and pressure, which points to a surface or detailing problem beyond simple tape replacement.
Step 6: Verify the repair holds in real conditions
- Inspect the repair once more after a few hours or the next day to make sure no edges have curled back.
- After the next rain or exterior washdown, check the area for fresh moisture, staining, or movement at the siding or trim joint.
- Look at the tape itself. It should still be flat, tight, and directing water past the seam instead of letting it behind the cladding.
- Keep an eye on the area over the next few weather cycles if this spot has leaked before.
If it works: The new exterior flashing tape stays bonded and the area remains dry and stable during normal weather exposure.
If it doesn’t: If water still gets in or the tape starts lifting again, the root problem is likely damaged flashing, a bad overlap detail, or hidden wall damage that needs a broader exterior repair.
Stop if:
- You see continued leaking, recurring movement, or signs that water is entering behind the siding despite the new tape.
Replacement Parts
Find exterior flashing tape on Amazon
Match the replacement part to your exact siding flashing before ordering.
As an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
Verify the repair
- The new tape lies flat with no wrinkles, bubbles, or lifted corners.
- The tape overlaps onto clean, solid material beyond the original failed section.
- The repaired joint stays dry after rain or controlled water exposure.
- Siding or trim near the repair no longer shifts because the water barrier is holding.
FAQ
Can I put new flashing tape over old tape?
Usually no. New tape bonds best to a clean, solid surface. Leaving failed tape underneath often traps dirt, moisture, or loose adhesive and leads to another early failure.
What causes exterior flashing tape to fail?
Common causes are age, sun exposure, dirt on the surface, moisture during installation, poor overlap, or movement in the siding or trim that keeps stressing the bond.
Do I need sealant with exterior flashing tape?
Not always. Many repairs work best with properly installed tape on a clean surface. If the joint depends on a specific flashing detail or sealant joint, address that detail too instead of relying on tape alone.
Can I do this repair in cold or wet weather?
It is better to wait for dry conditions. Tape adhesion drops on damp, dirty, or very cold surfaces, and a repair that looks fine at first may peel back quickly.
How do I know the problem is bigger than the tape?
If you find soft sheathing, rotten trim, missing flashing, repeated leaks, or siding that keeps pulling away, the tape is only part of the problem. Those conditions usually need a larger exterior repair.