Read the spec sheet.
Then read the warranty.

LP's SmartSide warranty is a five-page document called a Prorated 50-Year Limited Warranty, and it is a fair example of how every siding warranty is built. The headline is 50 years. The table under it splits those years in two. Years 1 through 5: if a board has a manufacturing defect (LP names three kinds: buckling, the overlay cracking or peeling or separating, or the zinc borate failing to stop termites or decay), LP pays the labor and the material to repair or replace it, priced by an independent construction estimator. Years 6 through 50: LP pays material only, no labor, and the payment drops 2.22 percent a year. Year 6 pays 97.78 percent of the material. Year 28 pays about half. Year 50 pays almost nothing. The whole thing is capped at twice the original price of the affected product.

The hail clause is its own row and it is worth reading twice. LP covers a crack or dent bigger than 3/8 inch from hail up to 1.75 inches across, for the full 50 years. You file with your homeowner's insurance first, then LP pays material only, at current retail, minus what insurance paid and minus your deductible, then reduced by the same proration schedule. The document says plainly that if that math comes out negative, LP owes nothing. That is not a trick. It is how every hail clause in this category works, including the vinyl makers', and it is the honest reason to carry a good insurance policy rather than count on the siding warranty for a storm.

The finish is a separate warranty with its own clock. On ExpertFinish, LP covers peeling, blistering, cracking, chalking, and fade past 5 delta E for 15 years. Years 1 through 5 it pays labor and paint to put one coat of solid color back on; years 6 through 15 it pays a share that drops 10 percent a year. The substrate warranty is 50; the finish warranty is 15; the catalog prints it as 5/15/50, and now you know what each number is.

Three lines decide whether any of it pays. Installation: the warranty excludes product "not installed by a licensed contractor and/or in strict compliance with all applicable building codes and Instructions," siding in contact with the ground, cut ends not primed, paint not applied within the window, and any problem that started in the framing, flashing, or wrap behind the board. It also excludes any aesthetic issue from face-nailing. Notice: you tell LP within 30 days of finding the problem and before anyone repairs it, with the production date and mill number off the board. Transfer: the original purchaser, the original owner of the house, and the next owner are covered. After that, no one.

None of that is a criticism. It is a strong warranty and it is longer than most in the category. The fiber cement makers read differently in one important way: James Hardie is 30 years and non-prorated, meaning year 29 pays the same as year 1, with no labor and a cap of twice the retail cost, transferable once. Nichiha is 30 years prorated: full price for three years, minus 2 percent a year through year 20, and no reimbursement after year 21, no labor, one transfer on single-family houses, and Tennessee is on its list of covered states. The vinyl warranties are "lifetime" for the original owner who lives in the house, and CertainTeed converts to a 50-year prorated schedule when the house sells while Royal transfers once at full coverage. Every one of them excludes labor after the first few years, every one excludes the installer's mistakes, and every one puts hail on your insurance first. The wrapper says 50 years or lifetime. The table says which years pay in full, who pays the labor, and how many owners. Both are the same document, and the table is the one that pays.