Hardboard and Masonite Siding on Westbank Homes: How to Spot It and What Replaces It

Written by Turnkey Siding

How Do You Know if Your Westbank Home Has Hardboard Siding?

Quick Answer: Hardboard siding can look like painted wood lap siding, but it’s made of compressed wood fibers. The giveaway is usually the bottom edge of each board. Where water has gotten in, hardboard swells, softens, and flakes at the drip edge, and part of that swelling can stay after the board dries. If that’s what you see across several walls of your Westbank home, from Marrero to Terrytown, plan on replacement instead of piecemeal repair.

Hardboard can look fine from the street and tell a different story up close. Walk around the house on a dry afternoon and look low on the walls, especially near sprinklers and downspouts.

What Is Hardboard Siding?

Hardboard is a panel product made by pressing wood fibers under heat and pressure. The problem is how it reacts to water over the long term.

Anton TenWolde and Charles Carll, researchers at the USDA Forest Products Laboratory, studied hardboard siding durability after many failures were reported in the United States in the 1980s and 1990s. They noted that failures often come from improper installation or detailing. They also explained the core weakness: solid wood swells when wet and returns to almost its original thickness when it dries, while hardboard can keep part of that swelling permanently. When the swelling is extreme, they wrote, paint can crack and nail heads can pull through the paint, which opens new paths for water into the board.

Their testing also found that hardboard performance varied a lot from one mill to another, and even within boards from the same mill. So two houses on the same street can age very differently.

The study put 13 different hardboards on outdoor test fences for 38 months and sprayed them with water for an hour a day through the summer. The researchers concluded that the industry’s lab test for residual edge swell was imperfect but useful, since boards that swelled more in the lab were more likely to show edge welting and paint cracking at the drip edge outdoors.

Signs of Failing Hardboard on a Westbank House

• Swollen or soft bottom edges. Press the drip edge with a thumb. Sound wood feels firm. Failing hardboard feels spongy or looks puffed out.
• Cracked or peeling paint along the drip edge. The Forest Products Laboratory study tied permanent swelling to paint cracking in exactly that spot.
• Nail heads sunk into or pushed through the paint. That’s a path for water straight into the board.
• Mildew streaks and rough, fuzzy surfaces. These often show up on shaded walls that stay damp after rain.

If you’re finding soft spots, check inside for staining or musty smells on the same walls. Our guide to signs of water damage behind siding covers what that can look like.

Why Hardboard Struggles in Marrero and Harvey

The Westbank gets the same Gulf Coast humidity and heavy summer rain as the rest of the metro, and water that lingers near a foundation after a storm keeps the lowest boards wet. Hardboard’s weak point is the bottom edge, so anything that keeps that edge wet speeds up the damage. Sprinkler heads aimed at the wall and mulch piled against the siding both count.

Ground clearance helps on two fronts. LSU AgCenter recommends leaving 8 inches between cladding and finished grade so termite tunnels stay visible, and that same gap keeps the lowest boards out of splash and standing water. Termites are part of the picture too, and our post on Formosan termites and siding explains what to watch for during tear-off.

Repair or Replace?

If the damage is limited to a few boards on one wall, replacing those boards and fixing the water source can buy time. Bring a sample of the existing board when you shop for patches, because profiles and textures vary and a mismatch shows once it’s painted. Paint won’t undo swelling that has already set in, so it’s a cosmetic fix at best.

When soft edges and cracked paint show up on most walls, replacement is worth pricing. Our guide to siding repair vs replacement and our checklist on when to replace siding can help you decide.

Check the Paint Rules on an Older House

If your house was built before 1978, EPA’s Renovation, Repair and Painting Rule applies to paid work that disturbs painted surfaces. Exterior jobs that disturb more than 20 square feet of paint have to be done by an EPA-certified firm using lead-safe practices. Ask to see the certification before tear-off.

Masonite Siding Replacement on the Westbank: What Are Your Options?

Replacement options include:

• Fiber cement. Manufacturers describe it as dimensionally stable, and LSU AgCenter lists fiber cement among termite-resistant materials. See our fiber cement siding services in Marrero.
• Vinyl. It has to be installed loose enough to move with heat. See our vinyl siding services in Marrero.
• Engineered wood. Modern engineered wood is its own product category, and our fiber cement vs engineered wood comparison explains the trade-offs.
• A mix. Some homeowners use fiber cement on the lower walls and gables and a different product elsewhere, with the transition at a natural break.

Whatever you choose, tear-off is the moment to see what years of wet hardboard did to the sheathing and framing. We check for soft sheathing and rot before new siding goes on. A full replacement may need a permit in Jefferson Parish, and our permit guide for New Orleans and Jefferson Parish explains how to check. If your house is in a mapped flood zone, read our flood zone siding guide before choosing materials for the lower wall.

Frequently Asked Questions

Is Masonite siding the same as hardboard?

Many homeowners use “Masonite” as a catch-all name for hardboard siding. What matters for your house is the material itself: pressed wood fiber boards that can swell when wet.

Can I just paint my hardboard siding?

Fresh paint protects boards that are still sound. It won’t fix edges that have already swollen, because part of that swelling can stay after the board dries.

Is hardboard the same as today’s engineered wood siding?

They’re both wood-based, but engineered wood is sold as a separate product category today. Compare current product specifications instead of assuming they behave the same way.

Do I have to replace all of the siding at once?

No, but if most walls show swelling, doing it in one project can cost less than chasing failures wall by wall.

Get an Honest Read on Your Siding

We’ll walk your house and tell you whether you’re looking at a repair or a replacement. Turnkey Siding serves Marrero and Gretna along with the rest of the Westbank. Call 504-882-9704 or request a free estimate.