Two products share the LP name, and a board that confuses them makes an expensive mistake in either direction. The LP Inner-Seal hardboard made between 1985 and 1995 was genuinely defective — it absorbed water, swelled, delaminated, and rotted, generating one of the largest class actions in siding history. Modern LP SmartSide is a different engineered-wood product built on different technology, and the old failure says nothing about how today’s SmartSide performs. So if your 1980s–90s townhome or condo community has swelling composite board, you’re not imagining it — and the first job is figuring out which LP you actually have, because that determines the whole replacement plan.
This page keeps the two straight: the legacy product that failed, and the modern product that boards too often reject by association.
What was the LP Inner-Seal class action?
It started as a 1996 class-action lawsuit over LP’s hardboard composite siding manufactured from 1985 to 1995 — siding that failed by drinking in moisture and breaking down. The numbers are what make it stick: LP paid roughly 130,000 warranty claims before the litigation closed in 2002 (court records, Justia). At the time it was described as the largest case in the history of the siding industry.
The defect was baked into the early product. The composite board wicked water at its edges and cut ends, then swelled and delaminated — a process a climate like Minnesota’s, with its freeze-thaw cycling and saturated springs, only accelerated. This was never a paint-deep cosmetic issue; it was the cladding failing at its actual job of keeping water off the wall.
What happened in Minnesota specifically?
Minnesota had its own significant LP case, which matters because it involved multifamily-scale buildings, not just single homes. In the In re Louisiana-Pacific Inner-Seal litigation, a Minnesota case tied to Lester Building Systems involved LP siding on roughly 2,600 buildings, with a damages expert estimating $13.2 million to repair the siding across construction from 1991–1996 (Justia).
That scale is exactly why so many Twin Cities townhome and condo communities built in the late 1980s and 1990s are still carrying — or have recently torn off — failing LP/hardboard. If your community sits in that vintage, you’re dealing with a documented local problem, not a one-off, and that documentation strengthens both an insurance conversation and a board’s case for funding the replacement.
How do I tell if my building has failing LP/hardboard?
You can usually spot failing hardboard composite by swelling, delamination, soft or punky edges, fungus or dark staining near the bottom courses, and board faces that have a “fingernail” softness when pressed. The bottom edges, cut ends, and areas below windows fail first because that’s where water collects. On a multifamily building, the pattern often repeats across units on the most weather-exposed elevations.
Quick diagnostic checklist:
- Horizontal swelling or “mushrooming” along board bottom edges
- Layers visibly separating (delamination)
- Soft spots that dent under thumb pressure
- Dark streaking, fungus, or moss near grade and below windows
- Paint failing repeatedly no matter how often it’s repainted
If several of these show across the building, this is a replacement conversation, not a repaint one. See signs your building needs new siding.
Reviewed against public source material from Ben Juncker and Craftsmans Choice, without presenting their contractor credentials as this sites own.
Is modern LP SmartSide the same thing?
No — modern LP SmartSide is not the defective Inner-Seal product, and conflating the two is the single most common board mistake on this topic. SmartSide is engineered-wood siding made through LP’s SmartGuard process, which treats each wood strand with a blend of waxes, resins, and zinc borate for resistance to moisture, fungal decay, and termites. It carries the 5/50 limited warranty — five years of full labor-and-material replacement, then prorated material coverage out to fifty years — and that warranty covers hail damage up to 1.75 inches when properly installed. It flexes through freeze-thaw rather than cracking, ships in longer boards with fewer seams, and runs roughly 15–25% under full fiber cement, which is why it’s one of the strongest cold/hail value picks for Twin Cities multifamily.
The distinction is a money decision: a board that crosses off “LP” because of the 1990s litigation may be discarding an excellent modern option for the wrong reason. The fair caution with SmartSide is that it’s a wood product, so its lifespan tracks coating and flashing integrity — true of how any cladding relates to the wall behind it. See engineered wood siding services and the full material comparison.
What should you replace failing LP/hardboard with?
Most Twin Cities boards replace failing LP/hardboard with fiber cement, modern engineered wood (SmartSide), or steel — picked by the building’s biggest risk, the same way the choosing siding material pillar lays it out: fiber cement for fire rating and premium resale, engineered wood for cold/hail value, steel for the best hail and lifecycle performance. But the material is the easy part of this decision. Because the original failure was a moisture failure, the replacement only succeeds if it corrects what let water in.
That makes the supporting line items non-negotiable: a continuous water-resistive barrier, flashing at every opening, kick-out flashing where roofs meet walls, and a generous rot-repair allowance — because hardboard failures usually mean water has already reached the sheathing. A bid that quotes only “remove and replace siding” is quietly leaving out the work that caused the damage in the first place. See what a real siding bid must include.
Frequently asked questions
Q: Was LP siding recalled? There was no government safety recall; it was resolved through a class-action settlement. LP Inner-Seal hardboard (1985–1995) was defective and LP paid roughly 130,000 warranty claims before the suit closed in 2002. People often call it a “recall” loosely, but it was litigation and warranty payouts.
Q: Is LP SmartSide bad too? No. SmartSide is a different, modern engineered-wood product made through the SmartGuard process (zinc-borate-treated strands) and backed by the 5/50 limited warranty, which even covers hail to 1.75 inches. It’s one of the better-performing materials for Minnesota cold and hail. Don’t reject it just because it shares a manufacturer with the 1990s Inner-Seal product.
Q: Can I file a warranty claim on old LP Inner-Seal siding now? The Inner-Seal class action closed in 2002, so the original claims window is long past. Today the practical path for failing legacy hardboard is replacement, sometimes with an insurance discussion if a storm event is involved. Consult a professional for your specific situation.
Q: Does failing LP siding mean there’s damage behind it? Often yes. Because the failure mode is moisture absorption and swelling, water frequently reaches the sheathing and framing. Any replacement plan should budget a rot-repair allowance and address the WRB and flashing, not just the visible siding.
Editorial note: warranty terms are summarized from LP’s published pages (linked above) and were current at publication; confirm the live warranty document for any project.
Last updated: 2026-06-27. Part of choosing siding material. Not sure which LP you have? Ask for a building walk-through.