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The Deck Looked Fine—Until I Looked Underneath
From the backyard, nothing about this deck looked particularly concerning. But the real story was hiding where nobody normally looks.
🗂️ Inspection File: The Dangerous Deck
At first glance, this deck didn't give me much reason to worry.
The decking looked decent.
The railings were standing.
Nothing from above screamed dangerous deck.
But when I walked across it, something didn't feel right.
I could feel the deck moving slightly under my weight.
The deck boards looked okay—not great, but certainly not like they were about to fall apart.
So I started looking closer.
I worked my way around the deck and checked underneath.
Posts.
Connections.
Joists.
Then I got to the main support beam.
It was partially hidden behind an overgrown hedge, so I had to push the branches aside to get a proper look.
And that's where the whole story changed.
The beam carrying a large portion of the deck was rotted.
Badly enough that what had looked like a perfectly usable deck from above was now a serious safety concern.
And you'd never know it just by looking at the deck boards.
That's the thing about houses:
Sometimes the most important clue isn't what you can easily see. It's what you can't.
🔩The Root Cause
Wood decks live outside.
Rain, snow, melting ice and years of moisture exposure can eventually take a toll on the structure underneath them.
And the visible deck boards don't always tell you what's happening below.
A deck can have reasonably good-looking boards while beams, joists, posts or connections underneath are deteriorating.
Once rot becomes significant in a structural member, this isn't just a maintenance issue.
It's a question of whether that part of the deck can still safely carry the load it was designed to support.
In this case, the answer was a big NO.
🛡️Next Steps
If you find rot in a beam, post, joist, deck board or another major structural component, don't judge the deck by how solid it feels when you walk across it.
Have the structure properly evaluated before continuing to use it.
The visible damage may only be part of the problem, and determining how safe the deck is to use isn't something you can reliably do from the top of the deck.
In this case, the main support beam needed to be replaced.
And once a major structural component like that has deteriorated, the repair can quickly become much more involved. Depending on the condition of the rest of the structure, replacing one rotten beam can sometimes lead to rebuilding a large portion—or even all—of the deck.
📈Prevention Tips
A few times each year, take a look underneath your deck—not just at the surface.
Look for dark, deteriorated or crumbling wood.
Pay particular attention to beams, joists and posts.
Check places where pieces of wood meet and where water may sit.
If you're unsure about a suspicious area, gently poke it with a screwdriver. Soft, spongy or easily penetrated wood can be a sign of decay.
Look for loose, rusting or deteriorated fasteners and connectors.
Watch for areas that stay wet long after the rest of the deck has dried.
Don't paint or stain over rot. It may hide the damage, but it doesn't restore the strength of the wood.
If something looks questionable, have it checked before loading the deck with people, furniture or a barbecue.
And don't assume a fresh coat of stain or good-looking deck boards means the structure underneath is okay.
The important stuff is often underneath.
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👀Worth a Look
Want to learn more about Decks?
This Old House — How to Inspect Your Deck and Make Sure It’s Safe
Family Handyman — Easy Deck Inspection and Repair Tips
Bob Vila — Should I Repair or Replace My Deck?
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⏭️ Next Time
Something on the outside of the house wasn’t supposed to move.
I’ve been finding the same problem on multiple inspections this year—and our extreme weather may have something to do with it.
Until next time,
Ron Henderson, CMI
Certified Master Inspector
Was this useful? Drop me a line at: [email protected]
Disclaimer: The Inspection Insider is an educational media publication. Content is based on general home inspection experience and real-world findings, and is intended to help homeowners understand what to watch for — not to assess, diagnose, or provide an opinion on any specific home or condition. Nothing published here constitutes a professional home inspection or should be treated as one. If you have concerns about your home, hire a qualified home inspector or licensed tradesperson to evaluate it in person.
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