Diagnose Before You Repaint
Common Paint Problems on Portland Houses
Exterior, interior, cabinet and deck painting across the Portland metro and Vancouver, WA. Estimates are free, on site, and carry no obligation. Painting for pay in Oregon takes an active CCB license, or a Washington L&I registration across the river: verify one before you sign.
Peeling or Flaking Paint
What it usually means
Peeling means the paint has lost its grip on the surface, and the USDA Forest Products Laboratory’s Wood Handbook names water as the main cause. Rain gets in behind the film through worn caulk, overflowing gutters, roof leaks or siding that sits in splash-back near the ground, and repeated wetting and drying pries the paint loose. It is usually worst at the ends of boards, where end grain soaks up water fastest. Two other causes look the same from the sidewalk. Bare wood left in the sun before it was primed loses its paint-holding surface, and the Handbook says as little as a week of exposure measurably shortens the life of the paint. New paint coming off old paint, which the Handbook says usually happens within a year of a repaint, means the old surface was not cleaned well enough first.
What you can check yourself
After a rain, look directly above the worst peeling for the water source: a dripping gutter seam, cracked caulk at a trim joint, or a downspout splashing the bottom course. Sherwin-Williams says wood siding should sit at least 6 inches above the ground.
What fixes it
Exterior painting fixes it, but only after the water source is dealt with: caulk, gutters, flashing, or a bottom board sitting in splash-back. The painter scrapes loose paint back to a sound edge, sands the transitions smooth, primes bare wood promptly, and applies two topcoats, the system the Wood Handbook recommends. On a house built before 1978, scraping disturbs paint covered by the federal RRP rule, so in Oregon the painter needs a CCB Lead-Based Paint Renovation license on top of a CCB contractor license.
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Blisters or Bubbles
What it usually means
Blisters are bubbles where the paint has lifted off the layer underneath, and the cause decides the fix. The USDA Forest Products Laboratory’s Wood Handbook describes water blisters, which form between the wood and the primer and usually contain water when they first appear. The water gets in through badly flashed doors, windows and vents, unsealed end grain, or overflowing gutters, or it moves out through the wall from showers, plumbing leaks and humidifiers inside. The Handbook notes that oil-based paint blisters far more readily than latex, and dark colors more than light ones because they run hotter in the sun. Sherwin-Williams describes a second type, heat blisters, from painting a surface in direct sun while it is too warm. Indoors, it adds damp basements and fresh latex hit by steam or humidity before it has fully dried.
What you can check yourself
Note where the blisters are. A cluster outside a bathroom, kitchen or laundry room points to moisture moving out from inside, which the Wood Handbook lists as a cause, and that needs a vent or fan as well as paint.
What fixes it
A painter cuts a blister open to see how deep it goes. If it reaches bare wood or drywall, it is a moisture problem: fix the leak, flashing or ventilation first (Sherwin-Williams suggests vents or exhaust fans for moisture from inside), let the surface dry, then scrape, sand and repaint. If it stops at an older coat, scraping, dulling any gloss and recoating is usually enough. Exterior painting covers siding and trim; interior painting covers bathrooms and other damp rooms.
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Mildew, Algae or Moss
What it usually means
Mildew is a fungus that lives on the surface of paint and wood, feeding on dirt and on oils in the finish. The USDA Forest Products Laboratory’s Wood Handbook calls it probably the most common finish complaint after peeling. It shows up as gray or black speckling, often with green algae alongside, wherever moisture lingers: shaded walls, siding behind tall shrubs, and eaves, soffits and porch ceilings where dew forms overnight. Mildew does not rot wood, but the Handbook says it can punch tiny holes in a coating and keeps new paint from bonding if it is painted over. On paint that is otherwise sound, it is a cleaning job, not a sign the house needs repainting.
What you can check yourself
Put a drop or two of household bleach on a dark spot. The Wood Handbook says mildew usually bleaches out within a few seconds; a spot that stays dark is probably dirt, tannin stain or iron stain.
What fixes it
Washing comes first: a commercial mildew cleaner or a dilute bleach solution with a little powdered detergent, scrubbed gently and rinsed with the spray pointed down, never mixed with ammonia. If the paint underneath is sound, that may be all it needs. If the house is due for paint anyway, exterior painting starts with that wash and finishes with a paint containing a mildewcide, as the Wood Handbook recommends. Mildew on a deck or fence is cleaned off the same way as the first step of deck and fence staining.
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Chalky or Faded Paint
What it usually means
Chalk is the fine white powder that comes off on a cloth or your hand. Sherwin-Williams describes it as the paint film breaking down at the surface as it weathers, which can also make the color look washed out. A light powder is normal on exterior paint, and it is usually heaviest on the walls that get the most sun. It comes on sooner and heavier with oil-based paint, low-grade paint, interior paint used outdoors, paint thinned too much or spread too thin, and porous surfaces that were never sealed. Fading is a separate issue: the USDA Forest Products Laboratory’s Wood Handbook notes that many dark colors fade to an unacceptable look long before the paint fails, and that white is always a safe choice. On older houses, the Handbook adds that exterior lead paint weathers into flakes and powder that collect in the soil.
What you can check yourself
Wipe a dark cloth across a sunny wall rather than using your bare hand, especially on an older house. A light dusting is normal; heavy powder, or primer showing through, means the wall is due for washing and new paint.
What fixes it
Exterior painting, starting with a thorough wash. Sherwin-Williams tells painters to wash or power wash chalk off with a suitable cleaner, rewashing and scrubbing until it is gone, because new paint sticks to loose powder instead of the wall. On fiber cement, James Hardie warns that a pressure washer can damage its siding and suggests a garden hose and soft brush. For the new coats, Sherwin-Williams recommends higher-quality acrylic paint for the best chalk resistance. If the topcoat has worn through to the primer, the Wood Handbook says it is time for one or two new topcoats.
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Cracking or Alligatoring
What it usually means
Cracks mean the paint film can no longer move with the surface under it, and the pattern tells you which problem you have. Fine cracks running along the grain, common on smooth flat-grain boards, come from a film that is too thin or not flexible enough, according to the USDA Forest Products Laboratory’s Wood Handbook. Cracks running across the grain usually point to thick layers of old oil-based paint. Sherwin-Williams describes alligatoring, a scaly pattern like reptile skin, as oil paint that has lost its elasticity through years of temperature swings, or a hard coating laid over a softer one, or a topcoat put on before the coat under it was dry. Indoors, deep irregular cracks that look like dried mud usually mean the paint went on too thick or pooled in corners.
What you can check yourself
Look at which way the cracks run on a few boards: along the grain, across it, or in a scale pattern. Telling the painter that one detail helps sort a recoat from a strip-and-repaint before anyone quotes.
What fixes it
Light cracking along the grain can often be sanded and given one or two more topcoats, which the Wood Handbook recommends when it is not severe. Cross-grain cracking and alligatoring do not recoat well: the old paint has to come off, to bare wood outside, before priming and repainting. That is exterior painting, or interior painting for mud-cracked walls and trim. Thick old oil paint on a pre-1978 house may contain lead, and the federal RRP rule bans open-flame burning and limits heat guns to below 1,100 degrees Fahrenheit.
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Soft or Rotting Trim
What it usually means
Trim that gives under pressure is decayed wood, and the USDA Forest Products Laboratory’s Wood Handbook is blunt about it: decayed wood does not hold paint. Decay needs liquid water. The Handbook puts the start of decay above 20 percent moisture content and notes that humid air alone rarely gets wood that wet, so soft spots almost always trace to a specific leak: an overflowing gutter above fascia, rain running into the end grain of a sill or casing, or a board sitting in splash-back. The Handbook says end grain can take on water 10 to 100 times faster than the face of a board, which is why rot starts at board ends and bottom edges. Decay often begins in the middle of a board while the surface still looks fine.
What you can check yourself
Push a small screwdriver into window sills, the bottom ends of trim boards and the lowest course of siding, the probe test the Wood Handbook describes. If it sinks in easily, that wood needs replacing, not paint.
What fixes it
The decayed wood has to be replaced before anything is painted, and the water path that rotted it fixed. Exterior painting quotes often include small carpentry repairs, such as a sill, a length of fascia or a few trim boards; ask how much the quote covers. New wood should be primed and its cut ends sealed, which the Wood Handbook ranks among the most valuable steps for keeping water out, before two topcoats. Rot spread across several walls is a siding job before it is a paint job.
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Stains Bleeding Through
What it usually means
Brown or tan marks coming through fresh paint mean something in or behind the surface is dissolving and moving into the paint. Outside, it is usually tannins, the water-soluble extractives in wood. The USDA Forest Products Laboratory’s Wood Handbook names western redcedar and redwood as the classic sources and says the stain shows up two ways: spread through the paint, from water soaking a thin coating, or in streaks running down from joints, from water getting behind the siding through gutters, roof leaks or condensation. Knots bleed too. Indoors, Sherwin-Williams lists water from a leak above, tobacco and fire smoke, grease and rust as the common stains, and the Handbook adds knots and finger-jointed trim in humid rooms like bathrooms and kitchens.
What you can check yourself
On cedar siding, check the stained spot after the next rain for water running behind the boards. The Wood Handbook says that once the cause is fixed, the discoloration usually weathers away in a few months.
What fixes it
Stop the water first: a roof leak, a gutter, a bathroom with no fan, or a plumbing drip above a ceiling stain. Then the stained area is cleaned, sealed with a stain-blocking primer, given time to cure, and topcoated. The Wood Handbook is specific that more coats of the same paint will not stop a stain that bled through one coat; it takes the right primer. Exterior painting covers cedar siding and trim, and interior painting covers ceilings, walls and woodwork.
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Chipping Paint on a Pre-1978 Home
What it usually means
On a house built before 1978, chipping or peeling paint may contain lead, and that changes who can work on it and how. The federal Renovation, Repair and Painting rule (40 CFR Part 745) covers paid work that disturbs paint in housing built before 1978, unless a certified inspector or risk assessor, or a certified renovator using an EPA-recognized test kit, has found the affected surfaces free of lead-based paint. The USDA Forest Products Laboratory’s Wood Handbook advises assuming that one or more old coats contain lead. It also notes that exterior lead paint weathers into flakes and powder that build up in the soil near the house, and that sanding without proper equipment can carry lead dust inside.
What you can check yourself
Look up the year built on your county assessor’s record, and keep children and pets away from paint chips along the foundation. Leave the scraping and sanding to a lead-safe painter.
What fixes it
Lead-safe painting comes first: the same repaint, done under containment with cleanup checked at the end. In Oregon the painter needs a CCB contractor license plus a CCB Lead-Based Paint Renovation license, and the CCB says only LBPR-licensed contractors can bid or work on pre-1978 homes. In Vancouver and the rest of Washington, the firm needs RRP certification from the Department of Commerce. The federal rule bans open-flame burning, power sanding without a shroud and HEPA vacuum, and heat guns at 1,100 degrees Fahrenheit or more.
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Chipped or Worn Cabinet Finish
What it usually means
Cabinets get handled more than any other painted surface in a house, so a weak finish shows there first: chips along door edges, worn patches around pulls, or paint that peels off in sheets. Peeling in sheets is an adhesion failure. Sherwin-Williams’ guidance is that any coating applied over a hard, slick, glossy surface is likely to peel, and kitchen cabinets add a film of cooking grease on top. Benjamin Moore’s data sheet for Advance, a cabinet enamel, calls for surfaces free of grease and oil and for cabinetry to be sanded with 220-grit paper or coarser before priming. Chipping soon after a job can also mean the doors went back into hard use before the finish had hardened, which the same data sheet says develops over time.
What you can check yourself
Check the cabinet floor under the sink and the edges of a few doors for swelling, soft spots or a vinyl film lifting at the corners. Water-damaged boxes and thermofoil doors change the answer from paint to new doors or new cabinets.
What fixes it
Cabinet painting, with the steps the paint makers describe: degrease, sand glossy surfaces dull, prime, and finish with a hard cabinet enamel rather than wall paint. Doors and drawer fronts are usually removed and finished separately. Plan for a gentle start: Benjamin Moore’s Advance data sheet says to keep heavy abrasion off and shelves out of service for at least 5 to 7 days, and that optimum hardness can take up to 30 days. In a pre-1978 kitchen, sanding painted built-in cabinets falls under the federal RRP rule.
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Gray, Slippery or Worn Deck
What it usually means
Gray, silvery boards mean sunlight has broken down the wood surface. The USDA Forest Products Laboratory’s Wood Handbook explains that UV light starts degrading lignin, the natural glue between wood cells, within a few hours, and that wood which looks silver or gray is severely weathered and needs much more sanding before a film-forming finish will stick. Decks and fences take more weather than siding because rain sits on horizontal boards and posts stand in wet ground, and the Handbook notes that algae and mildew grow on damp wood. Peeling stain is common too: the Handbook says film-forming finishes, including solid-color stains, are prone to peeling on decks, and that decks are usually replaced because of checking and splitting rather than rot.
What you can check yourself
Sprinkle some water on a few boards. The Wood Handbook’s goal is water that beads up rather than soaking in right away; if it soaks in, the deck is due. Keep any pressure washer on a low setting, since the Handbook warns that aggressive power washing roughens the wood.
What fixes it
Deck and fence staining, starting with cleaning, stripping any peeling film, and letting the wood dry all the way through. Badly weathered boards need sanding, and split or soft boards are replaced before any stain goes on. The Wood Handbook recommends penetrating finishes for decks: they need reapplying more often than paint, but they seldom crack or peel, so the next refresh is a light job instead of a strip. Ask for railings and stairs priced separately from the deck surface.
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Paint problem FAQs
Why is my exterior paint peeling?
Usually water. The USDA Forest Products Laboratory’s Wood Handbook names water as the main cause of peeling: rain getting behind the paint through worn caulk, gutters or leaks, often worst at the ends of boards. The other common causes are bare wood that weathered in the sun before it was primed, and new paint put over old paint that was not cleaned, which the Handbook says usually peels within a year of the repaint.
Can you paint over peeling paint?
Not until the loose paint is gone, because new paint comes off with whatever it sits on. The peeling paint has to be scraped to a sound edge, sanded smooth, and the bare wood primed, and the water source has to be fixed. Sherwin-Williams tells painters to test adhesion in a 6 to 12 inch radius around peeled areas first. On a house built before 1978, that scraping falls under the federal RRP rule and has to be done lead-safe.
Is chalky paint a problem?
A light powder is normal weathering. Sherwin-Williams describes chalking as the paint film breaking down at the surface, and it gets heavier with low-grade paint or paint spread too thin. It matters when you repaint: chalk has to be washed off completely, or the new paint bonds to the powder instead of the wall. Heavy chalk with primer showing through means the house is due for new topcoats.
How do I know if old paint has lead?
If the house was built before 1978, assume some layer contains lead unless testing shows otherwise. The federal RRP rule applies to paid work on those homes unless a certified inspector or risk assessor, or a certified renovator using an EPA-recognized test kit, finds the affected surfaces lead-free. In Oregon, the Oregon Health Authority certifies lead inspectors and risk assessors and publishes a list of certified firms.
What causes paint to bubble or blister?
Most blisters are moisture pushing paint off from behind: rain past flashing, unsealed end grain, gutter overflow, or humidity moving out through the wall from inside, according to the USDA Forest Products Laboratory’s Wood Handbook. Sherwin-Williams adds heat blisters, from painting a surface in direct sun while it is too warm. Moisture blisters come back unless the water source is fixed and the wood dries before repainting.
Is the black stuff on my siding mildew or dirt?
Put a drop or two of household bleach on it. The Wood Handbook says mildew usually bleaches out within a few seconds, while dirt, tannin stain and iron stain do not. Mildew on sound paint needs washing with a mildew cleaner or a dilute bleach and detergent solution, not a repaint. Never mix bleach with ammonia or with cleaners that contain it.
Sources
- Wood Handbook: Wood as an Engineering Material, Chapter 16 "Finishing Wood" (USDA Forest Service, Forest Products Laboratory, FPL-GTR-282 (2021))
Why paint peels, blisters and cracks on wood siding; washing off mildew, dirt and chalk before a recoat (the chapter does not explain what causes chalking); moisture content of covered outdoor wood in the Pacific Northwest; extractive (tannin) bleed, with western redcedar and redwood as the classic sources; mildew on painted wood; decayed wood and how to probe for it; why bare wood left in the sun before priming loses adhesion; and penetrating versus film-forming finishes on decks.
Checked 2026-10-07.
- Peeling: Due to Moisture (Outside) (Sherwin-Williams). Explanatory, not the governing text.
The usual moisture sources behind exterior peeling (worn caulk, clogged gutters, interior moisture, roof leaks, siding too close to the ground, painting a damp surface); that wood siding should sit at least 6 inches above the ground; and testing adhesion in a 6 to 12 inch radius around peeled areas.
Note: A paint manufacturer’s professional guidance, not a standard.
Checked 2026-10-08.
- 40 CFR Part 745, Subpart E: Residential Property Renovation (the RRP rule) (U.S. Environmental Protection Agency (via eCFR))
The federal lead-safe work rule for paid renovation, repair and painting that disturbs paint in housing built before 1978, including the work practices it prohibits, such as open-flame burning and power sanding without HEPA exhaust control.
Checked 2026-10-07.
- Specialty Licenses and Certifications: Lead-Based Paint Renovation (LBPR) Contractor License (Oregon Construction Contractors Board)
That Oregon administers the lead-safe renovation rule itself, so a painter disturbing paint on a pre-1978 Oregon home needs a CCB Lead-Based Paint Renovation license in addition to a CCB contractor license.
Checked 2026-10-07.
- Blistering (Sherwin-Williams). Explanatory, not the governing text.
Heat blistering from painting a too-warm surface in direct sun; moisture blistering from water moving out through walls, damp basements, and latex exposed to dew or humidity soon after drying; and the different repair when a blister reaches the substrate versus only a previous coat.
Note: A paint manufacturer’s professional guidance, not a standard.
Checked 2026-10-08.
- Chalking (Powdering): causes and repair (Sherwin-Williams). Explanatory, not the governing text.
What chalking is (the paint binder breaking down at the surface under weather) and that a chalky surface has to be cleaned until sound before it is repainted.
Note: A paint manufacturer’s professional guidance, not a standard.
Checked 2026-10-07.
- James Hardie FAQ (James Hardie)
The manufacturer’s guidance on cleaning and repainting fiber cement siding.
Checked 2026-10-07.
- Alligatoring (Sherwin-Williams). Explanatory, not the governing text.
What alligatoring is (patterned cracking like reptile scales) and its causes: aging of oil-based paint through temperature swings, a hard coating over a softer one, topcoating before the coat below is dry, and painting over gloss. Repair is removing the old paint.
Note: A paint manufacturer’s professional guidance, not a standard. Its removal methods include a heat gun, which the federal RRP rule restricts on pre-1978 homes.
Checked 2026-10-08.
- Mudcracking (Sherwin-Williams). Explanatory, not the governing text.
Deep, irregular cracks like dried mud, caused by paint applied too thick, paint built up in corners, or contaminants left on the surface; repaired by scraping or sanding smooth, priming if needed, and repainting.
Note: A paint manufacturer’s professional guidance, not a standard.
Checked 2026-10-08.
- Tannin Staining (Sherwin-Williams). Explanatory, not the governing text.
Brown or tan discoloration from tannins migrating through paint, typical of redwood, cedar and knots; that later staining through an intact film points to water in the surface; and sealing with a stain-blocking primer after the moisture source is fixed.
Note: A paint manufacturer’s professional guidance, not a standard.
Checked 2026-10-08.
- Staining: Water, Smoke, Etc. (Sherwin-Williams). Explanatory, not the governing text.
Household stains that bleed through paint (water, tobacco and fire smoke, grease, rust); that the water source must be found and repaired; and that stains must be cleaned and sealed with a stain-resistant primer before topcoating.
Note: A paint manufacturer’s professional guidance, not a standard.
Checked 2026-10-08.
- Lead-Based Paint Program: Renovation, Repair and Painting (RRP) (Washington State Department of Commerce)
That Washington runs its own RRP certification, which is what applies to pre-1978 homes in Vancouver and Clark County.
Checked 2026-10-07.
- Lead-Based Paint: Inspection and Abatement Professionals (Oregon Health Authority)
That the Oregon Health Authority certifies lead inspectors and risk assessors (among five disciplines) and publishes a list of certified abatement and testing firms that homeowners can use to hire one.
Checked 2026-10-08.
- Peeling: Over Hard, Slick Surfaces (Sherwin-Williams). Explanatory, not the governing text.
That any coating applied over a hard, slick, glossy surface is likely to peel, and that such surfaces should be cleaned, sanded dull and, if still slick, given a bonding primer.
Note: A paint manufacturer’s professional guidance, not a standard.
Checked 2026-10-08.
- ADVANCE Waterborne Interior Alkyd Satin 792, Technical Data Sheet (Benjamin Moore, 792 US 041023)
Cabinet prep from the maker of a common cabinet enamel: surfaces free of grease and oil, glossy areas dulled, cabinetry sanded with 220-grit or coarser before priming; no heavy abrasion or return of shelves to service for at least 5 to 7 days; up to 30 days to reach optimum hardness.
Note: One product’s data sheet. Other cabinet enamels publish their own cure and recoat times.
Checked 2026-10-08.
Next steps
- ServiceAll painting servicesExterior, interior, cabinets, decks, lead-safe and commercial.
- CostPainting cost guidePortland-metro ranges for each kind of work.
- GuideHow long exterior paint lastsWhy Portland weather wears paint out, and when to repaint.
- Service areaService areasPortland-metro city guides, including Vancouver, WA.
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