Customer Service: (253) 677-0290
Customer Service: (253) 677-0290
By Daniel, lead builder at Decks Restore. Licensed and insured in Washington, WA LIC #CC DECKSRL797P2.
People on Mercer Island tend to worry about the boards. Will the wood gray, will the composite fade, what stain holds up. Fair questions. But in fifteen years of tearing decks apart on this island, the boards are almost never what failed first. It is the metal underneath.
You live on a chunk of land sitting in the middle of a lake. The air here holds moisture in a way it does not five miles inland, and a deck traps that moisture where you cannot see it: under the boards, around the joist tops, inside the bracket where the post meets the beam. That damp sits on steel for years. Then one day a railing wobbles, or a stair pulls loose, and the homeowner thinks the wood went bad. We pull a board and the real story is a rusted joist hanger that gave up.
Here is what we find when we open up an older Mercer Island deck.
The joist hangers go before anything else. Those are the metal brackets that hold each joist to the rim board, and they take the brunt of the moisture because water runs down the boards and collects right at that seam. On a deck built with cheap galvanized hangers, we have seen the zinc coating eaten through in eight to ten years here. The bracket looks fine from a glance. Push on it and it flakes.
Then the screws and nails. A fastener is small, so it corrodes from the inside out and you get no warning. The head looks normal while the shank has thinned to a wire. That is the loose-board feeling under your foot. The board is fine. The nail holding it stopped being a nail.
Post bases are the third one. Where a support post lands on concrete, water wicks up and pools in the connector. If that base is not the right metal for the job, it rusts at the exact spot carrying the most weight. We replaced a deck two summers ago where three of the four post bases had rusted through and the whole structure was leaning maybe an inch toward the yard. The owner had no idea. From the top, it was a nice deck.
There is a reason the brackets fail and not the wood, and it comes down to chemistry most people never hear about.
Modern pressure-treated lumber is treated with copper-based preservatives. That copper is what keeps the wood from rotting, and it does its job well. The catch is that copper sitting against steel in a wet environment speeds up corrosion. The wood is protected. The metal touching it is under attack. Add the constant humidity off the lake and you have a deck quietly working against its own hardware from the day it is built.
This is not our theory. Fastener makers have published guidance on it for years. Simpson Strong-Tie, who manufacture most of the connectors used on decks across the country, lay out the corrosion risks and which metals survive contact with treated wood, and the short version is that ordinary galvanized hardware is not enough for a wet, copper-heavy environment. We learned that the slow way, by being called back to fix decks other crews built with whatever the lumberyard had in stock.
So here is what goes on a deck we build, and why.
For fasteners that touch the wood, we use stainless steel or heavy hot-dip galvanized, never the bright zinc screws you can buy by the bucket. Stainless costs more per box. On a full deck the difference might be a couple hundred dollars in screws. Against the cost of rebuilding a deck a decade early, that is not a real decision.
For connectors, the joist hangers and post bases, we spec the coatings rated for wet and corrosive conditions rather than the standard finish. Near a pool or a hot tub we go further, because chlorinated splash is its own kind of brutal on steel. The right post base lifts the post slightly off the concrete so water cannot sit in the pocket. Small detail. It is the difference between a base that lasts the life of the deck and one you are replacing in twelve years.
We also flash the ledger, which is the board bolting your deck to the house. A bad ledger connection is the single most dangerous failure on a deck, and moisture getting behind it is how that connection goes bad. Proper flashing keeps water out of the wall and off the bolts. We have seen ledgers on this island where water ran behind an unflashed board for years and turned the framing inside the house to compost. That repair is no longer a deck job. That is a wall.
If you are weighing materials right now, our crew wrote a longer breakdown of how Trex, TimberTech, and Fiberon held up on real Puget Sound decks we built seven or more years ago, which pairs with the hardware question since the board and the fastener have to last the same length of time.
You do not need to crawl under your deck to get a sense of where you stand. A few things you can check standing on it:
Grab a railing post and push, gently. If it moves more than it should, the connection at the base is suspect. Walk the deck and feel for any board that flexes or springs differently than the ones around it; that often means the fastener under it is going. Look at any metal you can see and check for rust streaks bleeding down the wood, which is the hardware telling you it is corroding before it fails outright.
If you want the full version, we keep a 7-point checklist for spotting an unsafe deck that walks through each of these in order. It was written for Tacoma but every point applies here, because moisture does not care about the city line.
The honest part: sometimes the hardware is shot but the boards and the frame are fine, and you do not need a new deck at all. We can pull the failed connectors, replace them with the right metal, and resurface the top, and you get years back for a fraction of a rebuild. Whether that works depends on what we find when we open it up, which is why we look first and quote second. If resurfacing is the route, here is what our deck resurfacing service covers.
A deck on Mercer Island is fighting humidity every day it exists. You cannot change the air off the lake. What you can change is whether the metal holding your deck together was chosen for that air or grabbed off a shelf to save twenty dollars. That single decision, more than the brand of board or the color of the stain, is what decides whether your deck lasts fifteen years or thirty.
If you want someone to come look at what you have, we give free on-site estimates across Mercer Island, Bellevue, and the rest of the Eastside. We will tell you straight whether you are looking at a repair, a resurface, or a rebuild. You can reach our Mercer Island deck team here or call (253) 677-0290.
Daniel has built and repaired decks across the Puget Sound region for over fifteen years. Decks Restore is locally owned, licensed, and insured (WA LIC #CC DECKSRL797P2), with a 5.0 rating across 43 Google reviews.