Painting guide
Nashville Wood Siding Repaints: What Cracks, Knots, and Bare Spots Reveal
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Painted wood siding fails in patches, not evenly across a wall. Four or five different conditions can sit on a single elevation, and the repaint gets planned and scheduled as though there were only ever one.
Walking the wall properly takes twenty minutes, and what you find in those twenty minutes changes the shape of the project rather than just its size.
Cracking along the grain
You are looking for fine cracks that run the length of a board, following the grain rather than crossing it, and they are easiest to see in low light raking across the surface.
Wood takes up and gives off moisture, and it swells and shrinks as it does. A coating over it has to move with that. A film that is still flexible does; a film that has lost flexibility with age cracks along the direction the movement takes it, which is along the grain.
What it means for the repaint: the cracking itself is the old film reaching the end of its useful flexibility. Painting over it does not restore anything, and the new film will follow the cracks in the old one. Where cracking is extensive, the film underneath is at the end of its service and the preparation is more than washing.
What it is not: a sign that the wood is failing. Grain cracking in the coating with sound wood beneath is a coating condition.
One reading belongs with this one, because it changes what the cracking means. At any place where the coating has broken away cleanly, count the layers in the edge. A wall painted five or six times carries a stack of films, thicker and more rigid than any single coat, and rigidity is the opposite of what a coating over moving wood needs. That stack tends to crack in interconnecting lines rather than along the grain, and where it does, the preparation has become a removal question rather than a scraping-and-spot-priming one. On an older house that also changes the lead-safe answer, because removal at that scale is substantial paint disturbance rather than incidental scraping.
Bare wood showing through
Here the coating has gone entirely and the wood underneath is open to the weather, whether it got that way by flaking, by scraping, or by a board being replaced and never coated.
Bare wood that has been exposed for a while is a different surface from bare wood that was cut yesterday. Ultraviolet degrades the surface fibers of exposed wood, leaving a thin layer that is soft, gray and poorly attached to the sound wood below. Paint applied over that layer bonds to something already loose.
This is why the amount of bare wood changes the sequence rather than just the effort. Exposed areas need the degraded surface removed, then sealing before the finish, and how much of the wall that applies to is the difference between spot work and a wall-wide job. Once bare patches appear across most of an elevation rather than in a few places, priming the whole surface stops being an upgrade and starts being the sensible option, because the alternative is a wall carrying two different foundations under one finish.
Measure it honestly. The bare area after the loose paint comes off is larger than the bare area you could see before, and usually by more than the look of it suggested.
Bare wood is at least visible. The next condition is one where the wood is intact, the coating is intact, and something is coming through anyway.
Knots and dark spots bleeding through
These show up as round or oval discolorations, usually amber or brown, coming through the paint film at what are often regular intervals along a board.
Knots contain extractives, the resins and compounds that concentrated where a branch met the trunk. They migrate. Warmth draws them out, and they move up through a coating and appear on the surface, which is why a knot that was invisible when the wall was painted can surface long afterwards.
The important point: this is a staining mechanism, not an adhesion mechanism. The paint has not let go. Something has come up through it. That means the answer is a blocking product rather than better adhesion or another coat, and adding more finish coats over a bleeding knot produces a thicker film with the same stain coming through it.
Blocking products are not interchangeable, and the distinction worth knowing is that some are formulated to hold back this kind of extractive bleed and some are not, which is why a primer that solved a different problem elsewhere on the house may do nothing here. The label will say what a product is intended to block. Two other things decide whether it works: it has to go directly onto the cleaned knot rather than over the stain that has already surfaced, and the whole knot has to be covered rather than the visible mark, because the mark is smaller than the source.
Cracking, bare wood and knots are all conditions of the board itself. The next group is not about the boards at all, but about the points where they end, meet, or are held down.
Nail heads, joints and butt ends
These three get overlooked because they are small, and they matter because they are where a wall is least able to defend itself.
Fastener heads that show rust staining are corroding. The stain will migrate through a new coating in the same way a knot does, and the fastener itself may be losing hold.
Butt joints, where two boards meet end to end, are where end grain is exposed. Federal wood-siding guidance singles these out, directing protective treatment to “all lap and butt joints, edges and ends of boards” and noting that paint normally fails in those areas first. Open or failing joints let water straight into the board ends.
The bottom edges of boards shed water and hold it at the same time. Every drop that runs down the wall pauses there.
None of these are painting problems on their own. They are the places where a painting problem becomes a water problem, and the joints among them carry a decision of their own: sealant that has hardened, split or pulled away from one side has stopped working and gets cut out rather than painted over, because a coating will not restore a joint that has already failed.
Trim gets counted separately from siding for the same reasons in a more concentrated form. It carries far more exposed end grain per foot, at every miter and every cut end; its profile gives water horizontal faces to sit on that siding does not have; and it holds most of the joints on a house, which means most of the sealant. A house can have sound siding and finished trim at the same time, and a survey that averages the two gets neither right.
Surface condition versus material condition
Every condition so far has been a surface reading on wood that is still sound: what the coating is doing, and what the exposed face of the board looks like.
There is a different question, and it needs answering before the preparation is planned. Is the wood still wood?
Press the boards at the bottom edges, at butt joints, and anywhere that has been consistently wet. Sound wood resists. If a board gives under thumb pressure, you have crossed from a surface condition into a material condition, and the project is a different shape. Going further than a thumb means putting a tool into a painted surface, which carries a condition of its own on an older house, so the method and that condition both sit in Peeling Paint or Wood Rot? What Nashville Homeowners Should Check rather than here. Deteriorated wood gets replaced or repaired as carpentry, and no amount of preparation or priming substitutes for that, which is why this check happens first.
One thing has to be settled before any of that preparation begins, and it depends on the age of the house rather than on anything the survey found.
Before anyone starts scraping
If the house was built before 1978, settle the lead-safe question before the first scraper touches the wall. Every removal step described above takes material off a painted surface: scraping back grain cracking, taking the degraded layer off bare wood, cutting out failed joints, and stripping a thick multi-layer coating most of all. On a house of that age, removal on that scale is not something the federal lead-safe rule leaves alone, so settle it with Painting a Pre-1978 Nashville Home: When EPA Lead-Safe Rules May Apply first.
Sources. Three documents, all opened 10 September 2026.
USDA Forest Products Laboratory, Wood Siding: Installing, Finishing, Maintaining, by Feist and Oviatt, revised December 1983: https://research.fs.usda.gov/download/treesearch/20959.pdf. Source for the treatment of lap and butt joints, edges and board ends, and for the statement that paint normally fails in those areas first. Its product advice is not reproduced here; what is used is its account of where water reaches wood.
Two Sherwin-Williams problem-solver articles. On knots and dark spots: tannin staining, https://www.sherwin-williams.com/homeowners/how-to/problem-solver/dirt-stain-discoloration/tannin-staining: brownish or tan discoloration caused by tannins migrating from the substrate through the paint film, typically on staining woods such as redwood, cedar and mahogany, or over knots in other species, and it records that where the film is intact and the discoloration appears later, water within the surface is carrying the staining substances out. On the cracking pattern of a thick multi-layer coating: alligatoring, https://www.sherwin-williams.com/painting-contractors/products/resources/SW-ARTICLE-PRO-ALLIGATORING: patterned cracking attributed to the natural aging of oil-based films under temperature fluctuation, and to hard rigid coatings applied over softer more flexible ones.