The complete siding system behind every Modex install
Siding is only as good as what's behind it. On every LP SmartSide and James Hardie job we do, we build a full weather-resistant system — drainable housewrap, properly flashed windows and doors, a rot-proof base detail, and color-matched trim. Not just panels nailed to a wall. It's the part you never see, and it's the part that decides whether your wall is dry in 20 years.
Reviewed by Joe Dvorak, Owner, Modern Exterior Systems
What's in the system
Seven layers we build on every siding job
Every one of these is standard on a Modex re-side — not an upsell, not an optional package. Here's the sequence, from the sheathing out.
Full tear-off to the sheathing
We pull the old siding all the way down to the bare wall — not a layover. That's the only way to see what's actually happening behind it before we cover it up for another 30 years.
Sheathing repair, line-itemed
If we find rotted OSB or plywood, we replace it and show you the photo. It's a line item on your quote, not a day-of surprise. On older Minneapolis homes with failed window flashing, this is common — and the reason a tear-off matters.
Drainable housewrap on every wall
We wrap the whole home in Kingspan GreenGuard RainDrop — a drainable, breathable air/water barrier with 3D drainage channels. It's the same wrap DiamondKote private-labels as its "5D" system. We use it on every LP SmartSide and James Hardie job.
Flashing and drip caps at every opening
Window heads, door heads, horizontal band boards, roof-to-wall transitions, and kickout/diverter flashing that sends roof water into the gutter — not behind your siding. This is where most rot starts, and where most contractors cut corners.
Rot-proof starter and base detail
A proper starter course and base detail give the first row of siding a clean, ventilated transition off the foundation — keeping ground moisture and bugs out of the bottom of your wall.
Siding installed to manufacturer spec
LP SmartSide, James Hardie, or EDCO steel — fastened to the manufacturer's spec for our wind and freeze-thaw, with the gaps and clearances the warranty actually requires. Install error is the fastest way to void a great product's warranty.
Color-matched trim and finish
Corners, J-channel, fascia, and sealant in colors matched to your siding and finish — DiamondKote, ExpertFinish, or Hardie ColorPlus. The weatherproofing details disappear into a clean exterior instead of standing out.
The layer you never see
Drainable housewrap: Kingspan GreenGuard RainDrop
A flat housewrap stapled to the wall holds water against your sheathing. A drainable wrap gives it somewhere to go. We install Kingspan GreenGuard RainDrop — a 3D drainable air/water barrier — on every LP SmartSide and James Hardie home we side. It's the exact wrap DiamondKote private-labels and sells as its "5D" system. Here's what it actually does behind your siding.
Drainage. 3D drainage channels let any water that gets behind the siding fall straight back out — instead of soaking into your sheathing.
Drying. The contoured air gap keeps your wall's envelope breathing, so it dries instead of staying damp against the OSB.
Deflection. An air and water barrier that stops wind-driven rain and air infiltration before it ever reaches the wall.
Diffusion. Vapor-permeable, so moisture from inside the house escapes at the right perm rate rather than getting trapped in the wall.
Durability. Jobsite-tough — it holds up through framing exposure and decades of Minnesota freeze-thaw without breaking down.
Why the system matters
Almost every rot job we open up started with bad flashing
When we tear off old siding, the rot we find is rarely random. It's under a window with no head flashing, below a roofline with no kickout sending water into the gutter, or at a band board where water ran behind the trim for years. The siding looked fine from the street the whole time.
That's the whole argument for the system. A beautiful James Hardie or LP SmartSide wall installed over flat wrap and missing flashing is a slow leak with good curb appeal. Done right — drainable wrap, flashed openings, proper clearances — the wall sheds water for decades and the warranty actually holds. We'll show you the photos of what's behind your siding before we cover it back up.
Questions homeowners ask about the system
What is a complete siding system, and why does it matter?
A complete siding system is everything behind and around the siding panels — drainable housewrap, flashing at every window, door, and roofline, a rot-proof base detail, and color-matched trim. It matters because siding panels don't keep water out on their own; the system behind them does. We build all of it into every LP SmartSide and James Hardie job in the Twin Cities, not as an upsell.
What housewrap does Modex use?
We use Kingspan GreenGuard RainDrop — a drainable, breathable air/water barrier with 3D drainage channels — on every LP SmartSide and James Hardie job. It's the same wrap DiamondKote private-labels and markets as its "5D" building wrap. The drainage channels give any water that gets behind the siding a path to fall back out instead of soaking the sheathing.
Does every siding job include new flashing?
Yes. We flash every window head, door head, horizontal band board, and roof-to-wall transition, and we add kickout/diverter flashing to send roof water into the gutter instead of behind the siding. Missing or improper flashing is the single most common cause of the hidden rot we find when we tear off old siding.
Will you replace rotted sheathing if you find it?
Yes, and you'll see the photo. When we tear off to the bare wall and find rotted OSB or plywood — common under poorly flashed windows on older Minneapolis homes — we replace it and show you exactly what we found. It's a line item on your quote, not a day-of surprise.
Is the housewrap and flashing system an extra cost?
No — it's standard on every Modex re-side. The drainable housewrap, flashing, starter detail, and color-matched trim are built into our quote, not sold as a separate "weatherproofing package." The only true add is sheathing repair, which we only charge for if we find rot, and only after we show you the photo.
See what's going on behind your siding
We'll walk every elevation, check your flashing and trim, and write a line-item quote that spells out the whole system — drainable housewrap, flashing, sheathing repair if you need it, siding, and finish. No door-knockers, no pressure, no lump-sum mystery number.
Further reading
Deeper writeups on the topics this page covers — written for homeowners by a Twin Cities installer.
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