Why Is My Masonite Siding Crumbling — and What’s Behind It?

Thomas Williams, All American Renovations – Elite member of James Hardie™ ALLIANCE · Metro Atlanta and Middle Georgia

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If your house went up in the 1980s or 90s and the siding is swelling, flaking and coming apart at the edges, it’s almost certainly hardboard — a pressed wood-fiber product that soaks up water and gives up. Of everything I tear off a Georgia house, that stuff comes off in the worst shape. And the part you can see is not the problem.

Here’s why I’m writing this one.

You’ve been looking at it for a couple of years now, telling yourself it’s cosmetic. Somebody suggested paint. And the thing you actually can’t shake is the suspicion that whatever’s happening out there has been happening on the inside too, and you have no way to look.

That suspicion is correct, and this post is about how to think about it.

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What Is That Stuff, And Why Is It Falling Apart?

It’s a pressed wood-fiber board. Sawdust and resin, compressed into a plank, primed, and nailed to your house.

When it gets wet and stays wet, it acts exactly like what it’s made of. It swells. It delaminates. The layers separate.

When I pull it off, it looks like cardboard or OSB that’s been saturated — it just crumbles to pieces in your hands. Not cracked. Not broken. Crumbling.

I’ve got one right now — double Dutch lap, eleven-inch boards — that’s in horrific shape, and it’s a house somebody has been living in and looking at every day.

And I’ll be honest that it’s not a material I have any love lost for. The composites they were putting on houses in the eighties and nineties are, hands down, the worst-looking siding I take off a home.

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An Important Line I’m Going To Draw

Everything I just said is about the boards that went on houses in the 1980s and 1990s.

LP still exists as a company and they sell a modern engineered wood siding today. That is not the same product, and I’m not going to tell you it is. I’ve never installed it. I don’t have tear-offs to look at, because it hasn’t been on a house long enough for me to be pulling it off. And if you aren’t certain which of them is on your wall, there’s a two-minute test at a broken edge that settles it.

So if somebody quotes you modern engineered wood, do not let this post talk you out of it — go ask somebody who actually installs it. What I can speak to is what comes off a thirty-year-old Georgia house, and that’s the whole of what I’m speaking to.

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The One Thing To Understand Before You Get A Single Quote

Whatever you can see from your driveway is the best-looking version of what’s on that wall.

That’s it. That’s the whole idea, and it changes how you should think about the next six months.

If you can see that kind of damage on the outside, what do you think is already behind it? The outside of that board had sun on it, and air moving across it, and it still lost. The back of it has been sitting in the dark against your sheathing with nowhere for moisture to go.

And if you’ve got woodpeckers (here’s a video from JamesHardie on their youtube page) working your wall, start there. There is usually a reason a bird keeps coming back to the same spot, and a lot of the time that reason is something living inside the wall that it’s trying to get at. Not always — sometimes a bird is just drumming. But a woodpecker that keeps returning is worth taking seriously, and patching the hole doesn’t answer the question. I’ve got a wall in front of me right now where somebody screwed metal patches over two holes and the birds moved a few inches and kept going.

And start with your chimney chase, if you have one. That’s the tallest, most exposed run of siding on most houses, it takes weather from three sides, and it’s where I find trouble first. Look for courses that have separated horizontally, and look for caulk somebody has smeared into a seam — that second one is the tell, because caulk in a seam means someone already noticed and chose the cheap answer.

Go look at the worst spot you can find — usually low on a wall, or at an outside corner, or on a chimney chase, or where the siding runs into a roof line. Whatever that spot looks like, that’s your best case, not your worst.

That is not me trying to scare you into a job. It’s the single most useful assumption you can carry into a conversation with any contractor, including the one who tells you it’ll buff out.

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What’s Behind The Siding On A House That Age? Usually Nothing.

I mean that literally. Not “a thin layer.” Nothing.

On most houses built here in the 1980s and 90s, there is no weather-resistant barrier behind the siding. No housewrap, no felt — the siding is nailed to the sheathing and that’s the assembly.

Here’s why, and it isn’t a story about bad contractors.

I’m not going to tell you what the code required in a Georgia subdivision in 1988, because I’d be guessing and you’d have no way to check me. What I can tell you is two things I’m sure of.

The first is what Georgia’s residential code is now. The state’s mandatory code today is the 2024 International Residential Code with Georgia Amendments, and it requires a water-resistive barrier behind the siding. That’s the standard a wall I build today has to meet, and it’s the standard your wall is going to get compared to.

The second is what I actually find when the siding comes off a house from that era, which is nothing. No housewrap, no felt, siding straight to sheathing, over and over again. Whatever the rules were then, that’s the assembly that got built, and it’s the one you own.

It means something specific for your house, and it’s the reason this post exists.

On a modern house, the siding is the first layer and the wrap behind it is what actually keeps water out. On your house, the siding is the only layer. When a board swells, splits, or opens at a joint, whatever gets past it lands directly on your sheathing.

That’s why hardboard failure and sheathing rot show up together so often. It isn’t two problems. It’s one problem with nothing in between.

One exception worth checking. If your siding has been replaced in the last twenty years or so, this may not apply to you — a re-side would likely have brought a barrier with it. Worth finding out which situation you’re in before you plan anything.

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So What Do You Actually Find Back There?

Sometimes nothing much. I want to say that first, because it’s true and because it’s the part a contractor selling you a job leaves out. Plenty of tear-offs come off ugly and the sheathing underneath is fine.

But on the bad ones, three things show up.

Rot in the sheathing. The panel behind the siding goes soft. You find it with a screwdriver.

Rot in the framing itself. That’s a different conversation, because now it’s structure and not skin. I’ve pulled a corner off a house and found the stud behind it eaten away for most of its height.

And sometimes something is living in there. On a job I’m working right now, we opened a wall and found the framing destroyed and insects in it. I am not a pest control guy, and I’m not going to stand here and tell you what they are — I have my suspicion, and my suspicion isn’t worth anything. What we did is bring in somebody licensed to identify it, and that’s what should happen every time.

If a siding contractor tells you with confidence what insect is in your wall, ask him what license he’s saying that under. It matters, because that answer can end up on an insurance claim or a disclosure form with your name on it.

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What Does This Do To My Price?

This is the real fear behind the question, so let’s take it head-on.

If you want the range before we get anywhere near the repair question, I’ve written out what siding replacement costs in Middle Georgia and what moves one house from the bottom of that range to the top. Read those first. This section is only about the part nobody can see yet.

Nobody can tell you what’s behind your siding until the siding is off. Not me, not anybody, not from a photograph and not from your driveway. Anybody who quotes you a hard number for repairs they haven’t seen is either padding it or about to surprise you. That’s the whole of whether a quote holds once demolition starts, and on a house this age it’s the first question I’d put to every bidder.

Here’s how we handle that, and you should ask every contractor how they handle it. We put the worst-case repair work on the proposal as line items you can check or uncheck, priced up front — and then we bill you for what actually got used. If we planned for sixteen sheets of sheathing and used four, you pay for four.

That means the number you sign isn’t a guess, and it isn’t a trapdoor either. What you’re looking at is a ceiling, and most of the time you come in under it.

If a quote for a thirty-year-old hardboard house has no repair allowance on it at all, that’s not a cheaper contractor. That’s a change order that hasn’t happened yet. It’s the same mechanism behind why we’re usually not the lowest bid — a low number is low because something got left off it.

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Why I Put Fiber Cement Back On These Houses

Short version, because this post isn’t a pitch.

The failure mode above is a water problem — a board that absorbs and holds moisture. Fiber cement doesn’t have that particular weakness, which is the whole reason it took over this market. If you want the longer comparison against vinyl, engineered wood and the rest, that’s the best-siding-for-a-Georgia-house question, and I’ve also written an honest account of whether James Hardie is worth the money from a contractor who can’t sell you a different fiber cement.

And there’s a detail almost nobody knows: James Hardie doesn’t sell one board everywhere. There’s a product engineered for our climate and a different one engineered for the north. The board that comes to Georgia was designed for Georgia — our humidity, our heat, our storms. That’s a big part of why I struggle to name a situation down here where fiber cement is the wrong call.

One honest caveat, on the maintenance side. If you buy it primed and painted, you’re on a five to seven year paint cycle — ten if you’re lucky. If you buy the factory finish, ColorPlus carries a 15-year limited warranty that covers paint and labor, and I’ve got installs out there that still look the way they did the day we put them on. That difference is real money and you should decide it on purpose, not by default.

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The Uncomfortable Part

Waiting costs you more on this one than it does on most things, and I don’t like saying that because I’ve spent a lot of words in other posts telling people not to rush.

The difference is the mechanism. A cracked board doesn’t get worse on its own. A saturated one does, because the water is already inside it and it doesn’t come back out. Every season that goes by, more of what’s behind it goes from “fine” to “a line item.”

That’s not a reason to sign something this week. It’s a reason to get the wall looked at this season rather than next spring, and then take your time picking who does the work.

And one more thing that cuts against me: I can’t diagnose your house from photographs. I can tell you what I’m probably looking at, which is genuinely useful before you spend a Saturday meeting contractors. I can’t tell you what’s behind the wall, and neither can anybody else.

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What I’d Tell You If You Called Me

1. Find the worst spot you can see, and treat it as the best case. Not the average. The best.
2. Don’t paint it. Paint on a saturated board buys you a season and costs you a season’s worth of further damage underneath.
3. Ask every bidder how they price what’s behind the siding. Allowance? Change order? Billed as used? The answers will differ more than the totals do — and keep in mind that an estimate and a proposal are not the same document.
4. If anybody finds insects, get somebody licensed to say what they are. Before it goes on any piece of paper.
5. Decide the finish question on purpose — factory finish versus primed and painted is a maintenance decision, not a color decision.
6. And get two or three opinions. If they all tell you the same thing, you know where you stand — and here’s what I’d actually be comparing when you line them up.

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