Hidden Damages
The most expensive part of a deck is the part you cannot see. Here is what came out from behind one we tore off this year.
A 35-year-old cedar deck, and what was behind it
From the yard it looked like an old deck. Weathered, tired, due for replacement, but nothing alarming. The homeowner called us to replace it, not to fix anything.
Then we took it off the house.
The ledger board had failed completely. Not a soft spot. Not one bad board. The band the entire deck was bolted to had rotted, and the damage had spread past it into the wall and all the way over to the patio door.
What was actually wrong
| Flashing | One small piece, at the trimmer joist. That was the only flashing on the entire deck. |
| House ledger board | Rotted through. Complete failure. |
| Trimmer joist | Failed, with spray foam packed into the gap. |
| Sistered joist | Sistered improperly, and rotted. |
| Patio bay door | Damaged. The water had traveled that far. |
| Previous repair | A DIY fix by an earlier owner, fastened with drywall screws, with a lot of nail holes left open. |
Drywall screws are not a structural fastener
They are hardened and brittle. They are made to hold a sheet of gypsum against a stud in a dry room, and they snap under shear load. Finding them holding up a deck is finding a repair that was never going to last, and every one of them was another hole letting water into the wall.
The open nail holes did the same thing. Individually none of them matter. Over years, with nothing shedding water away from the house, they add up.
Why the ledger is the part that matters
The ledger board is the piece bolted to your house that carries one whole side of the deck. Everything else can be replaced from the outside. That one cannot, because it lives inside your wall assembly.
When it is not flashed, water runs down the siding, gets behind the deck, and sits against the band board with nowhere to go and no air to dry it. Nothing shows on the outside while it happens. By the time a homeowner notices anything, the fix is not a deck repair anymore, it is carpentry on the house.
How we flash a ledger board
Two layers, not one.
Double the protection. If the first layer is ever compromised, the second one is still doing its job. It is a small amount of material and a small amount of labor on a new build, and it is the difference between this page and a deck that is still fine in thirty years.
If your deck is twenty years or older
You cannot inspect this from the yard, and we are not going to pretend you can. But there are things worth paying attention to:
- Staining, streaking, or peeling siding on the wall directly under the deck
- Any softness or give where the deck meets the house
- Screws or fasteners at the ledger that do not look like structural hardware
- Caulk or spray foam packed into a joint, which usually means someone was covering something rather than fixing it
- Damage or trim rot around a nearby door or window, which is often where water finally shows itself
The honest version: nobody knows what is behind a ledger until the deck comes off. That is why it is called hidden damage. What we can tell you is that if we open a wall and find something like this, you are going to hear about it before we build anything on top of it.
