Nine hardie siding installation mistakes we keep seeing on Chicago jobs
Most of these are invisible from the curb. They show up two or three winters in, when the homeowner notices a stain, or a soft spot at the base of a wall, or a board that's started to cup. Here's what to inspect — on a new install, or on the estimate before you sign.
Hardie is a forgiving product when it's installed correctly, and an unforgiving product when it isn't. The forgiveness is what makes it the most-recommended siding in our area; the cost of getting it wrong is what makes vetting the installer more important than picking the brand. These are the nine mistakes we see most often, ranked roughly by how much damage they cause when they go undetected.
1. Overdriven nails
This is the most common and one of the most damaging. Hardie wants the fastener head to sit flush with the surface — not countersunk, not standing proud. When a nail gun is set too aggressively, the head punches through the surface fibers and the board is no longer mechanically supported the way it was designed to be. Multiply that by every nail on a wall and you have a wall that's slightly less stiff, slightly more prone to cracking at fasteners, and noticeably uglier on close inspection.
How to check: stand close to the wall on a sunny afternoon. Overdriven nails show up as small dark dots where the shadow falls into the divot. They should be flush.
2. Wrong fasteners
James Hardie specifies hot-dip galvanized or stainless steel nails of specific dimensions, or approved siding screws for specific applications. We've seen jobs done with electroplated nails (the shiny ones) that start rusting through the finish within two or three Chicago winters, leaving streaks down the wall. We've seen pneumatic finish nails used to save money — they don't have the holding power and they corrode. We've seen the wrong length nails that don't catch enough of the stud behind the sheathing.
How to check: ask your contractor specifically what nails they're using, and look for the box on site. "Hot-dip galvanized, 6d or 8d siding nail" is the right answer. Anything else, push back.
3. Insufficient ground clearance
The manufacturer spec is 6 inches above grade, 2 inches above hard surfaces (decks, patios, pavement, sidewalks). On a Chicago lot where the grading is tight against the house, we see installers fudge this — taking siding down to 3 or 4 inches above the soil to "make it look right." Two springs later, the homeowner has a flowerbed against the wall, soil splashing on the bottom course every storm, and accelerated edge wear that wasn't necessary.
Worse: we've seen siding installed right at grade behind a future patio or deck. As soon as that patio or deck goes in, the clearance is gone and the wall is locked into permanent moisture contact.
4. Missing or sloppy flashing
Flashing is the part of the install that you can't see once it's done, which means it's the part that gets shortcut. Specifically:
- Kickout flashing where a roof intersects a wall. Without it, water runs off the roof, hits the siding, and pours behind it.
- Window head flashing. A small piece of metal or rubberized membrane that directs water out over the trim instead of behind it.
- Step flashing at sidewall-to-roof transitions, properly interleaved with the siding course.
- Z-flashing at horizontal joints in panel siding or where a band board meets a different siding material.
Most water damage we see on hardie installs is at flashing details, not at the field of the siding. The boards themselves are doing their job. The flashing isn't.
5. Caulk where there should be a gap, gap where there should be caulk
Hardie's official guidance has evolved here, and there's room for legitimate professional disagreement, but the broad rules: butt joints between siding boards should not be caulked tight (they need a small gap and a flashing tab behind them, sometimes called "joint flashing" or "butt flashing"). Joints between siding and trim, however, should be sealed.
We see this reversed all the time. Crews caulk every butt joint to make the wall "look clean," which traps moisture and stresses the joint as the boards move seasonally. Then they leave the trim-to-siding seam unsealed because the gap looks acceptable. Reversed.
6. Poor butt joint placement
Butt joints — where two boards meet end-to-end on a long wall — should land over a stud, not in the field between studs. They should be staggered course-to-course so you don't have a vertical line of butt joints stacking up the wall. And they should be tight but not forced; a hairline gap that gets covered by the next course's flashing tab is correct, a forced-tight joint that's bowing the board is not.
How to check: on a long wall, look for vertical lines of butt joints. They shouldn't exist. If you see them, the crew was lazy about layout.
7. Reveal inconsistency
The "reveal" is how much of each board is exposed to the weather — typically 5 inches on a 6.25-inch wide hardie board, or 7 inches on an 8.25-inch board. A good crew snaps lines and uses a gauge to keep the reveal consistent course-to-course. A rushed crew eyeballs it. By the time they've climbed twenty courses up a gable, the reveal has drifted a quarter inch or more, and the eye picks it up immediately — the wall looks "off" even if you can't say why.
This is a workmanship issue, not a structural one, but it's the most visible signal of a careless install. If the reveal isn't consistent, what else got rushed?
The boards themselves are doing their job. It's almost always the flashing, the fasteners, or the joinery — the parts you can't see once the wall looks done — that fail.
8. No drainage plane
Hardie should be installed over a continuous water-resistive barrier — house wrap (Tyvek, Typar, etc.) or a fluid-applied equivalent. On retrofit jobs where the old siding came off and the sheathing looks "fine," some crews skip the wrap entirely, or install it in patches just behind the visibly damaged areas. That's not how it works. The wrap is the backup drainage plane for the wall. If any water gets behind the siding — and over twenty years, some always will — the wrap is what gets it out.
On higher-end Chicago jobs, we're also seeing more use of a rainscreen — furring strips or a drainage mat between the wrap and the siding that creates an air gap for drying. It's not required, but on a north wall behind a row of mature trees in Edgebrook or Ravenswood, it's not a bad idea.
9. Painting hardie that wasn't supposed to be painted
This is more about the punch-list than the install proper, but it comes up enough to mention. ColorPlus hardie comes from the factory with a finish that's bonded, baked, and warranted. If a touch-up crew comes through and brush-paints over chips with the wrong product (or even with house paint instead of the ColorPlus touch-up bottle), you've put an incompatible film over a factory finish and the warranty on those spots is compromised. We've seen ColorPlus installs that look like ColorPlus from a distance and a mess up close because somebody touched up scuffs with Behr.
If you have ColorPlus, insist that any touch-ups use the manufacturer's matched touch-up paint, applied with the small applicator brush, and that the painter not "feather it out" beyond the actual chip.
What to do with this list
Two things. If your install is recent — say, in the last year — walk around the house and check the items above that are visible from the ground. Reveal consistency, ground clearance, fastener appearance, ColorPlus touch-up quality. If something looks off, your contractor's workmanship warranty is the time to address it.
If you're hiring for an install that hasn't happened yet, bring this list to the contractor walkthrough. Ask specifically about flashing details, fastener spec, ground clearance plans, and butt joint layout. The contractor who answers thoughtfully and shows you photos of their previous flashing work is the contractor you want. The contractor who waves a hand and says "we do this every day, don't worry about it" is the one who's installed the homes we hear about later.
The takeaway
None of these mistakes is rare. None is mysterious. Each one is something a careful crew avoids and a careless crew creates. The boards themselves — the actual hardie product — are not the variable here. The variable is who's holding the nail gun and whether they care.