Painting LP SmartSide Siding: Prep, Cut Edges and a Finish That Lasts
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Painting LP SmartSide comes down to the edges. The face of the board is well protected, but cut ends, bottom edges and nail holes let water in. Clean the siding, replace swollen boards, caulk the joints, seal every exposed cut and nail head, then build a thick, flexible finish over sound wood.
We see a lot of SmartSide in newer subdivisions around O'Fallon and Wentzville, plus garages, sheds and pole barns all over the outer suburbs. It's tough siding when it's finished right. When it isn't, the trouble shows up low on the wall first, and by mid-October you can often spot it in the shadows along the bottom courses.
What is LP SmartSide, exactly?
LP SmartSide is engineered wood siding. It's made from wood strands bonded together with resin, treated to resist decay, and pressed with a textured surface that looks like wood grain.
That matters for painting. SmartSide isn't solid lumber and it isn't fiber cement. It's a wood product, and wood products swell when water gets inside. The face of each board handles weather well. The weak spots are wherever the board was cut, nailed, notched or bumped during install, because those spots expose the strands underneath.
You'll find it as lap siding, vertical panels (including a T1-11 style groove), trim and soffit. It's on plenty of houses. It's even more common on outbuildings, since it's sturdy and goes up fast.
Is my SmartSide primed or prefinished?
Primed SmartSide arrives with primer only and has to be finish-painted after it's installed. Prefinished SmartSide arrives with color already applied. Both need care, just on different timelines.
| Primed boards | Prefinished boards | |
|---|---|---|
| Arrives with | Primer only | Color finish already on |
| Needs paint at install? | Yes. Primer by itself isn't a finish. | No, but field cuts and touch-ups still need attention |
| Where it usually fails | Primer left bare too long, edges skipped | Unsealed field cuts, nail damage, fading on sunny walls |
| When to recoat | On the paint's normal cycle | Once the color fades, chalks or wears thin |
Not sure which you have? The builder's paperwork usually says. On an older house a contractor can often tell by looking at the finish and the edges, but paperwork beats guessing.
Where does LP SmartSide fail first?
It fails where water sits or soaks in: cut ends, bottom edges, nail holes and anything too close to the ground or a roof. Swollen, fuzzy or flared edges are the giveaway.
Walk the house and look at these spots:
- The bottom edge of the lowest course, especially where mulch or soil sits close
- Board ends that butt into trim, corners and window casings
- Notches cut around vents, hose bibs and electrical boxes
- Nail heads that were overdriven and broke the surface
- Boards that meet a roofline, like a dormer wall or the side of a garage
- Any wall a lawn sprinkler hits every morning
- Boards behind a downspout splash
Clearance is a big one. Siding that's tight to grade or tight to shingles never really dries out after a rain. Sprinkler spray is sneakier. It soaks the same lower boards day after day all summer, and you won't notice until the edges puff up.
Minor swelling can sometimes be sanded back, sealed and finished. Boards that have gone soft or swelled badly need to be replaced first. A coating won't shrink a swollen edge back down, and it can't stop water getting in from behind.
How should SmartSide be prepped before painting?
Clean it, fix it, caulk it, then seal every exposed edge before any finish goes on. Prep is where these jobs are won or lost.
Cleaning comes first. Engineered wood needs a gentler wash than brick, so pressure has to be matched to the surface. Blasting it with a narrow tip can raise the fibers and force water into joints. After washing, the siding needs time to dry.
Next comes repair. Swollen or soft boards get replaced, and any new boards get their cut ends sealed before they go up. Then caulking. Gaps at trim, corners and butt joints get filled with a quality exterior sealant so water can't run behind the boards.
The last prep step is the one most often skipped. Every exposed cut edge and every broken nail head gets sealed. A nail that punched through the surface is a tiny open door into the strands, and on a full house there can be hundreds of them. Our application process lays out the full sequence: cleaning and washing, repairs, caulking and sealing, primer, then multiple coats of ceramic topcoat.
For a deeper look at installing and finishing engineered wood, Fine Homebuilding has good detail on edges, flashing and clearances.
Why does film thickness matter on engineered wood?
A thicker film covers edges and texture better and lasts longer on sunny walls. Thin paint wears through first at the edges, which is exactly where SmartSide can least afford it.
Standard exterior paint goes on around 1 to 2 mils, and most homeowners end up redoing it every 5 to 7 years. Rhino Shield of Missouri installs a ceramic elastomeric coating that builds to 8 to 10 mils. It expands and contracts as the siding moves through humid summers and freeze-thaw winters, and it bridges hairline cracks instead of splitting along them. See how we handle this siding on our LP SmartSide coating page.
Is mid-October too late to paint?
No. Mid-October still works for most of the metro, as long as you get on the schedule before real cold sets in. Coatings need dry siding and mild days to cure properly.
Fall is actually a good time to look. The humidity's down, and the summer's sprinkler and storm damage is easy to see on the lower courses. Get the siding inspected now and even if the calendar runs out, you'll know exactly what needs doing in spring.
It's also a good time to think long term. Our coating is backed by Rhino Shield's own 25-year transferable warranty, so the goal is to stop repainting every 5 to 7 years, not to schedule the next round.
Done right, the result can make a house look new again. Here's how one homeowner put it:
"After talking with Rhino Shield I went with them. It took them about a week or so to complete and the house looks brand new! Definitely worth the price and looks incredible!!!"
— Todd T.
Every house runs on its own timeline, and jobs that need board replacement take longer. But "looks brand new" is the right target for siding that's still structurally sound.
Related reading: Painting Hardie Board Siding: Prep, Primer and a Finish That Lasts
Frequently Asked Questions
Can you paint LP SmartSide siding?
Yes. Primed SmartSide has to be finish-painted after installation, and prefinished SmartSide can be recoated once its color wears. The key is sealing cut edges and nail heads and replacing any swollen boards before the finish goes on.
What kind of paint is best for LP SmartSide?
A high-quality exterior finish applied at a good film thickness over clean, sealed, sound boards lasts longest. Thin films wear through first at edges. A thicker, flexible coating covers the texture and edges better and handles Missouri's temperature swings.
Do you need to seal the cut edges of LP SmartSide?
Yes. Cut edges expose the wood strands inside the board, and unsealed edges soak up water and swell. Seal every field cut, notch and broken nail head before painting, and seal the ends of any replacement boards before they're installed.
Why is my LP SmartSide swelling at the bottom?
Swelling at the bottom edge usually means water got into an unsealed or damaged edge. Ground splash, too little clearance, sprinkler spray, downspout runoff or worn paint can all cause it. Lightly affected boards can sometimes be sealed and finished, but badly swollen ones should be replaced before coating.
Want a second opinion on your SmartSide?
Our St. Louis exterior painters will check the edges, the clearances and every wall before recommending anything. Request your free estimate or call 314-239-7947.
