Foam Closure Strips 101: Inside vs. Outside, Ribbed vs. 5V Profiles
Foam closure strips are a small but essential part of any metal roofing job. They seal the wavy gap left where a corrugated or ribbed panel meets a flat trim piece, like a ridge cap, eave, or rake edge. Getting the right metal roofing closure strips means matching two things correctly: whether you need an inside or outside closure strip, and which panel profile it needs to match. Here's how to make both calls, so your roof stays sealed against wind-driven rain, dust, and pests.
Quick Comparison
| Product | Material | Typical Use | Notes |
|---|---|---|---|
| Foam Closure Strips (Non-Adhesive) | Foam, profile-matched | Eave, ridge, and rake closures | Fitted and mechanically fastened under trim |
| Foam Closure Strips (With Adhesive) | Foam with adhesive backing | Same as above, faster installation | Sticks in place before fastening |
| BG1 Expanding Universal Closure Roll | Polyurethane foam, made in Europe | Universal gap sealing, expands to fit | Flexible roll format fits varied gaps |
| Direct*Seal Long Life Universal Closure Roll | UV-protected foam | Long-term exposed closure applications | Built for extended UV/weather exposure |
| FillerStrip Die Cut Closures | Die-cut foam, profile-specific | 5V, 3/4in rib, and PBR/MR-12 panels | Sold inside and outside, 100 pcs per pack |
What Closure Strips Actually Do
Metal roof panels have a wavy, ribbed, or corrugated profile, but the trim pieces they meet, ridge caps, eave trim, rake trim, are flat. That mismatch leaves small gaps that follow the shape of the panel ribs. Closure strips are cut or molded to match that wave pattern, filling the gap so wind-driven rain, dust, insects, and small animals can't get up underneath the roofing system. Skip the closure strips and a metal roof looks finished but leaves an open path for moisture and debris at every ridge, eave, and rake transition.
Inside vs. Outside Closure Strips
"Inside" and "outside" describe which side of the panel profile the closure strip is built to seal. An outside closure sits on top of the panel, matching the profile from above, and is typically used where trim caps down over the top of the panel ribs, like at a ridge cap. An inside closure fits underneath the panel, following the profile from below, and shows up at eaves and other spots where the closure needs to block the gap from beneath rather than above. Mix the two up and you'll leave gaps that defeat the whole point, so double-check which side of the installation you're sealing before you order.
Matching Closure Strips to Panel Profile
Panel profile is the other half of the equation. A 5V panel has a distinctive five-rib wave pattern, 3/4 inch ribbed panels have a tighter, more frequent corrugation, and PBR/MR-12 panels have their own wider rib spacing common in agricultural and commercial buildings. FillerStrip die cut closures are manufactured to match these specific profiles, which is why they're sold as separate SKUs: 5V inside, 5V outside, 3/4in rib inside, 3/4in rib outside, and PBR/MR12 inside/outside. Put a 5V-profile closure on a 3/4in ribbed panel and it simply won't seal, because the wave pattern won't line up with the panel ribs.
Universal and Long-Life Roll Options
Not every closure situation calls for a profile-specific die-cut strip. The BG1 Expanding Universal Closure Roll is a polyurethane foam roll that expands to conform to a variety of gap shapes, which makes it a good option when an exact profile match isn't available or practical. The Direct*Seal Long Life Universal Closure Roll adds UV protection, so it's a better fit for closures that stay exposed to sunlight over the life of the roof rather than being fully covered by trim.
Real-World Usage Examples
- Ridge cap installation: Outside closure strips fitted under the ridge cap to seal the top of 5V or ribbed panels.
- Eave and rake trim: Inside closure strips sealing the underside gap where panels meet eave or rake trim.
- Agricultural buildings with PBR panels: PBR/MR-12 profile-matched closures used at ridge and eave transitions.
- Odd or irregular gap conditions: BG1 Expanding Universal Closure Roll used where a die-cut profile strip doesn't fit cleanly.
- Exposed closure applications: Direct*Seal Long Life closure roll chosen for areas with prolonged sun exposure.
Frequently Asked Questions
What is the difference between inside and outside closure strips?
An outside closure strip seals the panel profile from above, commonly used under ridge caps. An inside closure strip seals from below, commonly used at eaves.
Do I need adhesive or non-adhesive foam closure strips?
Adhesive-backed strips are convenient for holding the closure in place during installation. Non-adhesive strips rely entirely on mechanical fastening under the trim. Either works structurally, but adhesive can speed up the install.
How do I know which panel profile closure I need?
Match the closure strip to your panel's rib pattern, such as 5V, 3/4in rib, or PBR/MR-12, since each profile has its own specific closure strip shape.
Can a universal closure roll replace profile-specific closures?
An expanding universal closure roll like the BG1 can work as a flexible substitute in many situations, but a profile-matched die-cut closure typically gives a cleaner, more precise seal.
Why do closure strips matter for a metal roof?
Closure strips block the gaps left where a wavy metal panel meets flat trim, keeping out wind-driven rain, dust, and pests that could otherwise get underneath the roofing system.
Find the right closure strip for your panel profile in Duco Plus's Closure Strips collection at https://ducoplus.com/collections/closure-strips.