The Masonite and LP hardboard class actions
Two nationwide settlements covered defective hardboard siding from this era. Masonite hardboard was the subject of a class action covering an estimated 4 million homeowners whose siding swelled, rotted, and failed; the settlement covered siding installed from January 1, 1980 to January 15, 1998, and more than $1 billion was paid across related composite-siding litigation (Lieff Cabraser; In re Masonite Corp., MDL 1098). LP Inner-Seal (an OSB-based product) had its own nationwide settlement covering siding installed 1985 to January 1996, with most payments in the $6,000–$8,000 range (Lieff Cabraser).
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 KC’s freeze-thaw cycling and wet springs only accelerate. This was never cosmetic; it was the cladding failing at its actual job of keeping water off the wall.
| Product | Era covered | Scale | Outcome |
|---|---|---|---|
| Masonite hardboard | Installed 1980–1998 | ~4M homeowners | >$1B paid (related litigation) |
| LP Inner-Seal (OSB) | Installed 1985–Jan 1996 | Nationwide class | Payments ~$6,000–$8,000 |
Why this matters for Kansas City multifamily
KC’s apartment, condo, and townhome stock is disproportionately from the defective-hardboard window. With a metro median build year around 1980–1982 (Census Reporter), a large share of multifamily buildings were clad during the 1980–1998 Masonite and 1985–1996 LP Inner-Seal periods. That doesn’t prove any specific building has it — but it makes “what hardboard do we have?” a question worth answering before planning a replacement.
For a board, identifying the product changes the plan in two ways. It confirms that swelling board is a known material failure, not a maintenance lapse. And it signals that water has likely reached the sheathing, so a rot-repair allowance belongs in the budget from the start.
How to tell if your building has failing hardboard
You can usually spot failing hardboard by the pattern. The bottom edges, cut ends, and areas below windows fail first, because that’s where water collects — and on a multifamily building, the same pattern repeats across units on the most exposed elevations.
- Horizontal swelling or “mushrooming” along board bottom edges
- Layers visibly separating (delamination)
- Soft, “punky” spots that dent under thumb pressure
- Dark streaking, fungus, or moss near grade and below windows
- Paint that fails repeatedly no matter how often it’s redone
If several of these show across the building, this is a replacement conversation, not a repaint one. See signs your building needs new siding.
Is modern LP SmartSide the same thing?
No — 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 waxes, resins, and zinc borate for resistance to moisture, fungal decay, and termites. It’s warranted against hail up to 1.75 inches (LP Building Solutions), flexes through freeze-thaw rather than cracking, and ships in longer, lighter boards that speed large reclads.
The distinction is a money decision. A board that crosses off “LP” because of the 1990s litigation may be discarding one of the strongest hail-and-cold value materials for KC multifamily for the wrong reason. The fair caution with SmartSide is that it’s a wood-based product, so its lifespan tracks coating and flashing integrity. For the full material picture, see best siding for Kansas City hail.
What to replace failing hardboard with
Most KC boards replace failing hardboard with steel, modern engineered wood (SmartSide), or fiber cement — picked by the building’s biggest risk, with hail leading the decision in Kansas City. But the material is the easy part. 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.
Who reviews this
Reviewed against the install side by our Kansas City install partner. (Class-action details are summarized from Lieff Cabraser and the In re Masonite MDL. This page is general information, not legal advice.)