What you’re actually looking at
Hardboard composite siding was made by compressing wood fibers with resin into board. The weakness was always water: once moisture got past the coating or in through the edges, the board soaked it up, swelled, softened, and came apart in layers — worst at the bottom and around penetrations. Minnesota’s freeze-thaw cycle drives that moisture deeper with every winter, which is why the bottom courses go first and why the rot so often reaches the sheathing.
That’s the reason the walk-around works: the failure mode is physical and predictable, so it announces itself in the same five places on every building of the era.
Telling old hardboard apart from modern LP SmartSide
Before you panic, confirm what you actually have. The old failing product and the modern good one share a parent company name, and boards conflate them constantly.
Modern LP SmartSide is a different engineered-wood product, manufactured with the SmartGuard process — a zinc borate treatment that resists moisture, termites, and fungal decay — and backed by a 50-year limited warranty. It is not the product that failed in the 1990s. If your siding was installed in the late 1990s or later, the walk-around above may turn up nothing, and that’s expected. (lpcorp.com)
The siding that fails the press test is the earlier 1980s–90s Inner-Seal / Masonite composite — a genuinely defective product, not today’s SmartSide.
A short note on the class actions
If your boards fail the walk-around, you’re far from the first. LP’s Inner-Seal siding spawned a class action covering roughly 800,000 homeowners, with a settlement fund of up to about $475 million and nearly $1 billion paid out over the life of the program before the claim deadline in January 2003. (Justia — In re Louisiana Pacific Inner-Seal, Lieff Cabraser)
The scale wasn’t national-news abstraction in Minnesota — it was local. A Minnesota case involving Lester Building Systems covered LP siding on roughly 2,600 buildings, with a damages expert estimating $13.2 million to repair the siding across 1991–1996 construction. (Justia — In re Louisiana Pacific Inner-Seal) Whole communities of that vintage are affected, which is why the same failure pattern repeats building to building.
The claim windows are long closed, though. The major settlement wound down around 2002–2003, so for a building owner today this is a replacement decision, not a warranty-recovery one.
You confirmed failure. Now what?
A failed press test means water has been in the wall, often for years, so a patch or a repaint leaves the moisture damage in place. The right scope is a tear-off with a sheathing and rot inspection, a sound water-resistive barrier, and correct flashing at every penetration. For the diagnostic side of this, see signs your building needs new siding.
Most Twin Cities communities replacing old LP/Masonite move to modern engineered wood (LP SmartSide), fiber cement, or steel, picked for budget, fire and code needs, and hail exposure. See fiber cement vs. engineered wood vs. vinyl vs. steel.
FAQ
How do I know if it’s hardboard and not vinyl or fiber cement? Hardboard is a solid composite board that takes paint and feels like dense wood; failing examples swell and soften when pressed. Vinyl is hollow plastic that doesn’t rot. Fiber cement is hard, brittle, and won’t dent under your thumb. If pressing the bottom course leaves a dent, you’re dealing with composite hardboard.
Is all hardboard siding recalled? No. There was no government recall — the failures were resolved through class-action settlements. The original LP Inner-Seal and Masonite hardboard products from the 1980s–90s are the ones that failed at scale.
Can I still file a claim on old LP siding? No. The major LP Inner-Seal settlement wound down around 2002–2003, with the claim deadline in January 2003, so the original claim windows are long past. For a building owner today, the issue is replacement, not warranty recovery.
Is LP SmartSide the same product that failed? No. SmartSide is a later engineered-wood product made with the SmartGuard zinc borate process and a 50-year limited warranty. The failure involved the earlier Inner-Seal / Masonite composite, a different product.
Should we repair or replace failing hardboard? Replace. A failed press test almost always means water has reached the wall, so patching leaves the underlying moisture damage in place. A full re-side with a proper WRB and flashing addresses the actual problem.
Related reading: Fiber cement vs. engineered wood vs. vinyl vs. steel for Minnesota · Best siding for Minnesota cold and hail · Signs your building needs new siding