Rotting wood or just tired paint? How to tell the difference on your house

Paint failure versus wood failure: the quick answer

Press a screwdriver or an awl into the wood under the peeling paint. If the tip skates off or barely dents the surface, the wood is sound and you most likely need preparation and paint. If the tip sinks in with little pressure, or the wood comes up in short, crumbly pieces, you are looking at rot, and paint alone will not fix it. Peeling paint is a sign that moisture is reaching the wood, so it is worth checking either way.

I'm Ben Henderson, owner of Preservan Dallas. We at Preservan repair rotted windows, door jambs, trim and posts in place, and a surprising number of the homes we inspect turn out to need less than the owner feared, while others are hiding much more under paint that looks almost fine. This guide shows you how to tell which one you have before you call anyone.

Why the paint goes first

Paint and rot are linked by water. Moisture weakens the bond between paint and wood, so paint tends to blister, crack and flake wherever water gets in and stays. The National Park Service's brief on repairing historic wooden windows makes the same point: areas of paint failure usually identify where water is getting in and where deterioration may follow. It also adds an important caution that I repeat to homeowners all the time. Failed paint does not by itself mean the wood is in poor condition, and wood is often sound beneath unsightly paint.

So treat peeling paint as a map. It shows you where to look, not what you will find. The next step is to check the wood itself at exactly those spots.

The reason this matters is timing. Decay fungi need wood that stays wet. A U.S. Forest Service review of decay in buildings by Carll and Highley describes optimum conditions for most decay fungi at moisture contents above fiber saturation, typically about 25 to 30 percent. Paint that has failed lets water in and then, around the edges that still hold, slows the drying. That combination is how a cosmetic problem turns into a structural one.

The screwdriver test, done properly

You need a flat screwdriver, an awl or an ice pick, a roll of painter's tape and about half an hour. The Park Service brief describes two traditional probe methods, and both work well on a house.

• Pry test: push the tip into the wood at a shallow angle and lift a small sliver. Sound wood comes up in long, fibrous splinters. Decayed wood lifts in short, irregular pieces because the fibers have lost their strength.
• Push test: press the tip straight in, perpendicular to the surface. Rot that started on the hidden side can leave a thin, firm skin on top, and steady pressure will break through it into soft wood underneath.
• Check the edges: probe the corners, the end grain and the joints, because decay usually starts where water collects and spreads from there.
• Mark what you find: put a strip of tape on every soft spot so you can see the pattern and show it to whoever comes to look.

Reading the pattern on your tape

Once you have marked every soft spot, step back and look at where the tape landed. The pattern often tells you more than any single spot. A cluster at the lower corners of several windows on one wall usually points to a shared cause, such as a sprinkler zone, splash from a patio or a wall that takes the worst of the weather. Soft spots that follow a line under the roof edge point to the gutters. A single soft spot at the base of one door jamb often means water is running down the face of the door and collecting at the threshold.

Write down what you see next to each piece of tape, and take a photo of each one with something for scale. If you call a repair company, those notes and photos make the inspection faster and help you check that nothing gets missed in the quote.

Signs that point to rot

Beyond the probe, these are the signs we see most often on houses where the wood itself has failed. One alone may mean little; several together in the same spot usually mean decay.

Pay particular attention to a spot that has been repainted recently and is already failing again. Fresh paint over wet or decaying wood rarely lasts a season, so a short-lived paint job is often the clearest clue that the problem sits in the wood rather than on it.

• Wood that feels soft or spongy, or gives slightly when you press with a thumb
• Paint that bubbles or flakes in one area again and again, even after repainting
• Cracks, open gaps at joints, or dark discoloration in the wood
• A musty or damp smell near a window or door
• Crumbly or hollow-sounding areas near the bottom of a sill, jamb or post
• A door that has started to drag, or a window sash that no longer sits right

Signs that point to paint only

If the probe meets firm wood everywhere, the problem is likely the coating. Paint can chalk, crack or peel from age, sun, poor preparation or a mismatch between old and new coatings, all without the wood underneath being harmed. Wide areas of peeling on a south or west wall, with firm wood beneath, are typical of a paint problem rather than a rot problem.

In that case a good painter is the right call, not us. A painter explains the different kinds of paint failure in what peeling and chalking paint means for a house. The one thing I would ask is that whoever paints probes the sills and joints first, so a soft spot does not get sealed in under fresh paint.

Could it be insects instead of rot?

Sometimes the wood is soft or hollow for a different reason. Small round holes, fine powdery debris, or mud tubes running up a foundation wall are signs of insects rather than fungal decay. Termite-damaged wood can look sound on the surface and be hollow just underneath, which the probe will reveal quickly.

If you see those signs, call a licensed pest professional before anything else. We repair wood weakened by termites and other insects, and in many cases we can stabilize and rebuild it without major reconstruction, but we do not provide treatment or pest control, and no repair should go in while the insects are still active. If you have children or pets at home, this guide on pest control when you cannot just spray covers the options.

Where to probe on a typical house

Rot shows up in predictable places because water does. Start low and work up, and pay the most attention to horizontal surfaces and the bottoms of vertical pieces. On houses around Dallas, I would add anything a lawn sprinkler reaches, because those spots get wet far more often than rain alone would make them.

Then go inside. Look at the interior window stool and the wall below each window for staining, bubbling paint or a soft spot. Look at the floor and baseboard beside exterior doors. Water that shows up indoors means it is getting past the window or door rather than only sitting on the outside, and that raises the urgency.

• Window sills, especially the corners and the joint where the sill meets the jamb
• The bottom few inches of door jambs and brick mold, and the threshold
• Garage door frames where they meet the driveway
• Fascia and trim below gutters that overflow
• The base of porch posts and columns, and deck posts near the ground
• Trim and siding within reach of sprinklers or splash from paving

What to do with what you found

If everything is firm, plan for preparation and paint, and look at why the paint failed so the new coat lasts longer. If you found one or two small soft spots with firm wood around them, you have time to get proper quotes, but prime any bare wood in the meantime so it stops soaking up water. If the probe sinks in deep, the softness runs along a whole sill or into a post, or water is showing up indoors, do not wait for the next dry spell.

It is tempting to dig out the soft spot and fill it yourself. For a very small, shallow area that can work, but there are real limits, which I lay out in what filler can and cannot do on rotted wood. And whatever you do, find the water. A repair under an overflowing gutter will be soft again in a few seasons. I cover that side in how to keep rot from coming back.

When you want a second pair of eyes

If you are unsure what you are looking at, an inspection settles it. Ours is free: a technician probes every suspect area, including ones you may have missed, photographs the damage and sends an itemized digital quote with recommendations. If it turns out to be paint and not rot, we will tell you, because we do not upsell work that is not needed.

Where there is rot, we remove the decayed fibers, stabilize the sound wood, rebuild the missing section with structural epoxy, shape it to the original profile and finish it to match. Most repairs take about a day, and every epoxy repair carries a ten-year warranty. For the full picture of how decay works and how we repair it, see what rot is doing inside a soft window sill. We serve Dallas and the northern suburbs from Addison and Carrollton to Frisco, Allen and Wylie.

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