LP SmartSide: The Siding Half of Minnesota Owns (and Half Washes Wrong)
Drive any subdivision built in the Northland since the 2000s and you're looking at LP SmartSide — the engineered wood strand siding that took over from hardboard and competes with vinyl on every new build. It's tough against hail and our cold, but it has one specific vulnerability that makes washing it a rules-based activity: it's wood strands and resin under a thin engineered overlay, and driven water is its enemy.
Why Pressure Is Off the Table
LP's published care guidance is blunt: clean with a soft brush or cloth and a garden hose, and avoid power washing — pressure can drive water into the substrate, damage the finish, and damage from improper maintenance isn't covered by the warranty. The failure mode is specific to engineered wood: force water past the paint film or into a cut edge, nail head, or panel gap, and the strand substrate absorbs it and swells. Swelling shows up as raised texture, bulging at fasteners and butt joints, and paint failure — and it's irreversible. Replacement is the fix. On a whole wall, that's a five-figure mistake delivered by a $60 rental machine.
Where SmartSide Is Most Vulnerable
| Zone | Why |
|---|---|
| Bottom edges & cut ends | Field-cut edges rely on paint/sealant; driven water wicks straight into exposed strands |
| Butt joints & trim gaps | Designed gaps for expansion — pressure turns them into injection points |
| Nail heads | Every fastener penetration is a path past the overlay |
| Upward spray angle | Lap design sheds falling water; upward spray defeats it entirely |
The Wash That Works (and Keeps the Paper Trail Clean)
Soft washing is effectively the professional version of LP's own instructions: a cleaning solution applied at garden-hose pressures, dwell time doing the work, gentle rinse top-down with the lap direction. It removes the algae film SmartSide grows just as enthusiastically as any siding in our humidity (the north-wall problem doesn't care what the wall is made of) without ever loading the substrate. Two of our standing rules on SmartSide jobs: downward angles only, and moderated chemistry — the factory finish doesn't need strong mixes to release organic film.
If your house is newer construction in Hermantown, the western Duluth developments, Esko, or Superior's newer plats — it's very likely SmartSide. Worth knowing before anyone points a wand at it. (Check any contractor against our 12 questions — the SmartSide answer should be automatic.)
FAQ
Can you pressure wash LP SmartSide siding?
No — LP says so themselves. Driven water swells the substrate irreversibly. Soft wash only.
How do I know if my siding is LP SmartSide?
Newer build, wood-grain texture, rigid and solid when tapped (vinyl sounds hollow and flexes).
What does water damage look like on SmartSide?
Swelling — bulges at nails and joints, thickened edges, cracking paint. Irreversible; panels must be replaced.
Soft wash with downward-angle discipline and a free caulk-and-clearance check. Written quote same day.
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