When we meet with homeowners for siding and eavestrough quotes, I find that this question comes up a lot:

“Do I really need plywood behind my siding?”

It might not seem obvious because you’re using siding to cover that part of the home’s exterior. But the answer is yes, you need plywood (or OSB) behind the siding. This is because siding needs a solid surface to be attached to, and plywood provides that. Without it, your siding has nothing strong to hold onto. It’s like putting up heavy shelves on a wall without hitting a stud or putting drywall anchors in. It’ll go up, but it won’t last long.

Why Plywood Matters

Many people think of siding purely in an aesthetic sense. But siding isn’t just about making your home look good; it’s there to protect your house from the elements.

Plywood creates a sturdy base that holds nails and fasteners in place so the siding stays secure. Without that backing, siding can shift, rattle, or even fall off in heavy wind or over time. Unsecure siding also leaves room for water to trickle in, and when that happens it’s only a matter of time before real damage starts.

What Happens if Water Gets Under Siding?

Water is one of the biggest threats to a home. If it finds its way under your siding, it can cause problems you may not notice right away:

• Trapped moisture that doesn’t drain or dry out properly.
• Wood rot in the sheathing, studs, or trim.
• Mold and mildew growth inside your walls, which can affect air quality.
• Damaged insulation that no longer keeps your home efficient.
• Structural weakening over time, leading to costly repairs.

This is why siding must be installed over plywood, along with proper underlayments like house wrap, to help keep water out and give it a path to drain away safely.

What The Plywood Does: 4 Real Benefits

1. Strength – Plywood gives the siding a firm, even surface, keeping everything straight and secure.

2. Moisture protection – It adds a barrier that helps stop drafts and water from getting inside your walls.

3. Energy efficiency – With insulation, plywood helps keep indoor temperatures more consistent.

4. Longevity – When siding is installed over plywood, it performs better and lasts longer.

Aside from making your home’s exterior look better (all sorts of different colour options from Canadian manufacturers like Gentek), siding plays an important role in protecting your home from the things outside that want to be inside.

What Happens If You Skip It?

Some people think skipping plywood will save money, but it usually costs more in the long run. Without plywood:

• Fasteners can pull loose
• Moisture can get in and cause rot or mold
• The siding may not line up properly and could look wavy
• In many cases, warranties won’t be honoured if the siding wasn’t installed over a proper base

All of that to save a few hundred bucks on plywood? Not worth it.

Does It Matter What Type of Siding You Choose?

In terms of whether you need plywood backing? No, it doesn’t. No matter the material (vinyl or aluminum), you’ll need a solid backing to anchor the siding into.

Vinyl Siding

Vinyl is flexible and lightweight, which makes it easier to install and more forgiving when it comes to dents and dings. But that same flexibility also means it will show waves, bumps, or uneven lines if it doesn’t have a flat surface behind it. Without plywood, vinyl can look wavy and cheap instead of clean and polished.

Aluminum Siding

Aluminum is more rigid than vinyl, but it dents and bends more easily when struck by hail, sports balls, or even a ladder leaning against the wall. Installing it directly onto studs without plywood backing makes it even more prone to damage and movement. The plywood gives it the strength it needs to hold firm.

Want to learn more about our siding options? Check out our Siding Installation Services in Southern Ontario page to see materials, colours, and styles available.

Do It Right From The Start

At The Eavestrough Company, we always use Canadian-sourced products from trusted suppliers like Gentek, Kaycan, and Royal Building Solutions. That way, your siding has the strength and proper backing it needs to hold up to our Ontario weather.

So, Do You Need Plywood Behind Your Siding?

Yes, you need plywood behind your siding. It’s not an extra step. It’s the foundation that makes sure your siding looks good, holds up properly, and protects your home for years.

Ready to upgrade your siding? Call The Eavestrough Company today for a free estimate and we’ll make sure it’s done right from the very beginning.