I've talked about this in videos, at job sites, and in too many conversations to count — because I keep seeing homeowners get burned by contractors who looked fine on paper and delivered a result that failed within two seasons. The problem is rarely dishonesty. It's usually a lack of knowledge about what actually makes a deck staining job last. These questions separate contractors who know from contractors who don't — and the answers will tell you more than any review ever could.
What product are you using — and what category does it fall into?
This is the most important question on the list. The product category — not the brand, not the color, not the sheen level — determines whether your deck stain will last or fail. There are two fundamental categories: film-forming products (solid stains, deck paints, water-based synthetics) that sit on top of the wood and eventually peel, and non-film-forming penetrating stains that go into the wood and don't peel because there's no surface film to fail.
If a contractor proposes a solid stain, a latex deck paint, or a "deck restore" type product, that is a red flag regardless of brand or price. These products will always fail in a Wisconsin climate. The only product category that belongs on an exterior wood deck in the Midwest is a non-film-forming, penetrating stain — ideally oil-based.
"We use a penetrating oil-based stain — non-film-forming, so it goes into the wood rather than sitting on top. Specifically we use [product name]."
Any mention of solid stain, deck paint, "deck restore," or an inability to explain what category the product falls into.
What chemicals are you using to wash the deck — and why?
Pressure washing alone does not clean a deck properly. Water removes loose dirt and surface debris, but it doesn't kill mold and mildew at the root, neutralize the wood's pH after chemical treatment, or address the mill glaze or tannin bleed that affects how well new stain adheres. A contractor who answers "just water" to this question is skipping steps that matter.
A proper wash process involves at least two chemical stages: a cleaner or brightener to open the wood grain and treat biological growth, and often a brightener or wood prep solution to neutralize the pH and ensure the wood is chemically ready to accept stain. The specific products vary by wood type and condition — a contractor who can explain their process fluently is one who understands why they're doing each step.
"We use a wood cleaner to treat mold, mildew, and oxidation, followed by a wood brightener to balance the pH and prep the surface for stain penetration. We test moisture content before anything goes on."
"We just pressure wash it." No mention of chemical prep, or a vague answer that doesn't describe a specific process.
Will you sand the deck — and what grit?
Sanding is not always required on every deck, but it should always be considered and the contractor should have a clear answer about when they sand and why. For decks with rough or splintered boards, weathered grain that's gone fuzzy, or any surface that chemical prep alone won't smooth out, sanding opens the wood grain and significantly improves how well the stain penetrates and how long it lasts.
When sanding is done, grit matters. The right grit for deck boards is 80 — coarse enough to open the grain and remove the gray oxidized surface layer, but not so aggressive that it scratches or gouges the wood. A contractor who sands with 40 grit is too aggressive and will leave scratch marks that show through the stain. A contractor who sands with 120 grit is closing the grain rather than opening it, which actually reduces penetration. 80 grit is the answer, and a contractor who knows their craft knows that number without hesitating.
"We assess each deck individually. Where sanding is needed — splintered boards, heavy oxidation, rough grain — we use 80 grit. It opens the grain without damaging the wood surface."
A contractor who never sands regardless of deck condition, or one who can't answer what grit they use.
How long will the project take from start to finish?
This question isn't just about scheduling — it's a diagnostic. A contractor who quotes a same-day turnaround for a deck that needs to be chemically washed, dried, sanded, and stained is either skipping steps or applying product to wood that isn't dry. Stain applied to wood with elevated moisture content will not bond correctly, will not penetrate properly, and will fail earlier than it should.
A properly done job on an average deck typically spans at least two days: prep and wash on day one, a drying window, and stain application when the moisture content confirms the wood is ready. Sometimes this can be compressed to a long single day depending on conditions, wood type, and weather — but if a contractor is promising a quick single-visit wash-and-stain without any mention of drying time, ask them directly how they're confirming the wood is dry before they apply product.
"Prep and wash on day one, we verify moisture content, and apply stain once the wood is confirmed dry — typically the following day or after a sufficient drying window depending on conditions."
Same-day wash and stain with no mention of drying confirmation, or a timeline that doesn't allow for proper prep.
What does maintenance look like going forward?
The answer to this question reveals more about the product and process than almost anything else. If a contractor has done the job correctly — right product category, right prep, right application — ongoing maintenance should be simple. Clean the deck periodically, recoat every 3-4 years with the same penetrating product, done. No stripping, no sanding down to bare wood, no starting over.
If a contractor struggles to describe a simple maintenance path, or if the maintenance they describe involves stripping, heavy sanding, or product removal every few years, that's a signal that the product they're using forms a film that will eventually fail and need to be removed. Penetrating stains maintain simply. Film-forming products do not.
"Maintenance is simple — clean it as needed and recoat every 3-4 years with the same penetrating stain. No stripping, no peeling to deal with, no starting from scratch."
Any answer that includes stripping, heavy sanding, or the caveat that "all deck stains peel eventually." They don't — penetrating stains fade and wear, but they don't peel.
What the Answers Tell You
A contractor who can answer all five of these questions fluently and correctly is one who has done this work seriously and understands the craft. A contractor who stumbles on product category, can't name their chemicals, doesn't know their grit, doesn't account for drying time, or describes a complicated maintenance future is showing you the result before the job even starts. Ask the questions. Trust the answers.
For what it's worth — we're happy to be asked all of these before you commit to anything. Our answers are on this website, in our process, and in every estimate we give. If you want to talk through your specific deck before making any decisions, the estimate is free and there's no obligation attached to it.