Is Your Deck Dry Enough to Stain? Drop Test and Moisture Meters

Stain needs to soak into the wood. If the pores are full of water, it sits on top, dries unevenly and peels. Checking that the boards are dry is quick, and it is the step most often skipped.

The water drop test

Sprinkle a few drops of water on several boards, including one in the shade:

• Drops soak in within a minute or so: the wood is dry and open enough to take stain.
• Drops bead up or sit on the surface: the wood is still wet, or an old sealer or mill glaze is blocking it. Wait, or clean and strip the surface first.

Test a few spots, because boards near the house, under planters or in shade dry more slowly.

Using a moisture meter

A pin-type moisture meter gives a number. Many stain makers ask for wood moisture below about 15 percent; check your stain’s label, as some water-based products accept a little more. Push the pins in across the grain and take readings on several boards. Readings are for the species setting on the meter, so choose the closest wood type.

What reading to aim for (the advice disagrees)

Search for a target number and you will find many: 12 percent, 15 percent, “under 17,” even “19 or less.” Part of the reason is that the numbers come from different places. Indoor woodworking aims much lower than an outdoor deck can reach, while some stain makers allow a wetter board for water-based products. A deck that sits outside all year rarely settles as low as furniture wood does, because sun, shade, nearby ground and every rain move it up and down.

A practical way to use the number:

• Your stain’s label or data sheet comes first. If it names a moisture limit, that is the one to meet.
• If the label gives none, about 15 percent or lower is a common figure from stain makers, and the water drop test should agree with it.
• Compare boards with each other. If the sunny boards read 12 and the shaded corner reads 20, the corner is not ready, whatever the average says.

Getting a meter reading you can trust

A cheap meter used carefully tells you more than a good one used once. A few habits help:

• Pin or pinless. Pin meters measure between two pins pushed into the wood. Pinless meters read a shallow zone under the pad without marking the board. Both read mostly near the surface, and pinless readings can be affected by wood density and any old finish still on the boards.
• Set the species. Pressure-treated southern yellow pine, cedar, redwood and dense hardwoods like ipe all read differently. If your meter has no matching setting, use its chart or the closest wood.
• Read the middle of the board, not the ends. Board ends and edges dry first, so a reading near a cut end can look drier than the rest of the board.
• Take several readings. Check sunny boards, shaded boards, boards near the house and any spot where water pools. Note the highest readings, not just the lowest.
• Mind the temperature. Pin meter readings change with wood temperature, and some manuals give a correction for very cold or hot boards. Check the manual if you test on a cold morning.

Surface readings are not the whole story. Moisture varies through the thickness of a board, and deck builders note that the only exact check is a reading at the center of a cut piece. Nobody does that on a finished deck, which is why many pros pair a meter with the drop test and the stain maker’s wait time instead of trusting a single number.

Dew can fool the test

On a clear, still night the deck surface often cools to the dew point and collects moisture, even when no rain falls. In the early morning a dry deck can fail the drop test simply because the top is damp. Test after the dew has burned off, and stop staining early enough in the afternoon that the finish can set before evening dew returns. Our guide to dew point for painting and staining explains how to spot a high-dew night in the forecast.

How long to wait

Shade, humidity and cool nights all add time. The drop test or meter reading is more reliable than a count of days.

What makes some decks slow to dry

• Shade and trees: boards that never see direct sun, or that sit under leaves and pollen, can stay damp for days after the sunny parts are ready.
• Low decks: a deck close to the ground has little air moving underneath, so the boards dry mainly from the top.
• Tight board gaps and debris: dirt packed between boards holds water against the edges. Clear the gaps with a putty knife before you clean.
• Cool, humid weather: in spring and fall, a day of drying may do what a few hours do in summer.

Why new pressure-treated wood needs to wait

Pressure-treated lumber is soaked with a water-based preservative, and it often arrives at the store still wet from treatment. It has to dry before it will take stain. Test it with drops of water every week or two; when the drops soak in, it is ready. Kiln-dried after treatment (KDAT) lumber has already been dried and can often be stained much sooner. Many new boards also have a smooth, shiny “mill glaze” from planing, and some stain makers suggest a deck cleaner or light sanding to open it up.

What happens if you stain wet wood

Stain on wet boards can’t soak in. It sits on the surface, dries blotchy, and is the most common cause of stain that peels or flakes within a season. Water-based stains are somewhat more tolerant of damp wood than oil-based ones, but none work well on wet boards. If you stained too soon and the finish is peeling, the fix is usually to strip or clean the loose stain, let the wood dry properly and start again.

Planning the week around drying time

Drying is the step that decides your schedule, so plan it backward from the day you want to stain:

1. Pick a dry stretch. Look for three or four days in a row with no meaningful rain. A dry day before staining, the staining day and a dry day after is the minimum.
2. Clean first. Wash or treat the deck on the first dry day, so the boards have at least a day or two to dry before you stain.
3. Test on the morning you plan to stain. Do the drop test after the dew is gone. Morning dew can make dry boards seem wet for an hour or two after sunrise.
4. Have a backup day. If the shaded boards fail the test, stain the sunny sections first and leave the rest for later.

In humid places and in fall, a long enough dry stretch can be hard to find. Our state guides show how many wet days each month brings where you live.

After the wood is dry

• Stain when the air and the deck surface are within the label’s range, often around 50 to 90 °F.
• Avoid direct midday sun on dark boards, which can flash-dry the stain and leave lap marks. Work in the shade as it moves across the deck.
• Leave enough dry time before rain or dew. Many stains need roughly 12 to 48 hours; the label gives the figure.

Our deck staining forecast looks for dry days before and after the job, and our pressure washing forecast helps you plan the cleaning day ahead of it.

Frequently asked questions

What moisture content should wood be before staining?

Many stain makers ask for about 15 percent or lower, and advice online ranges from about 12 to 19 percent. Your stain’s label or data sheet gives the figure that applies, so check it before you rely on a general number.

Can I stain a deck in the morning after dew?

Wait until the dew has dried and the boards pass the water drop test, which is often mid-morning on a sunny day. Dew on the surface keeps stain from soaking in, even if the wood underneath is dry.

Are cheap pinless moisture meters accurate on a deck?

They are useful for comparing boards, such as sunny ones against shaded ones, but they read only near the surface and can be thrown off by wood density and leftover finish. A pin meter set to the right species gives a more useful number.