Which side of my house is hardest on wood finishes, south or west?

Why west is worse than south

It seems like south should be the toughest exposure, since it gets the most sun over a year. But wood finishes do not fail from total hours of light alone. They fail from heat, from ultraviolet light and from moisture cycling, and the west wall gets the worst combination of all three.

In the afternoon the air is at its warmest, the morning marine layer has long since burned off, and the sun hits a west wall almost square on. Surface temperatures on a dark west-facing door or fence can run far above the air temperature. The finish softens, the wood underneath dries and shrinks, and the two move at different rates. Then the evening fog arrives and the surface cools and dampens quickly. That daily shock is what cracks varnish, chalks paint and bleaches stain. The front door in the photo above is a west-facing example: gray, sun-bleached and failing while the rest of the house was fine.

What each exposure does to wood

Every side of a house has its own failure pattern, and reading those patterns tells you what the wood needs.

• West: fade, chalking, cracked film finishes, checked and cupped boards. Finishes last roughly half as long here as on the shaded sides.
• South: steady fade and drying, especially from late fall to early spring when the low sun reaches under eaves and hits walls it misses in summer. Decks and rail caps on the south side gray quickly.
• North: little fade, but the wood stays damp longest after fog or rain. Mildew, green algae, black spotting and slow rot at sills and post bases are the north-side problems.
• East: morning sun dries the dew gently and the wall is in shade by the hot part of the day. Finishes last longest here and the maintenance interval can stretch.

Overhangs and reflections change the math

Exposure is not only compass direction. A west-facing door under a deep porch roof can be an easy door, because the overhang blocks the high afternoon sun for most of the year. The same door with no overhang at all is the hardest surface on the property. We look at where the shadow line falls in summer and winter before we recommend a finish.

Reflected light matters too. A light-colored stucco wall, a pool, or a pale concrete patio bounces sunlight back up onto wood that is nominally in shade. The underside of a pergola over a pool deck often fades faster than the top of the rafters for exactly that reason.

Finishing by exposure instead of one rule for the whole house

On the west and unprotected south sides we lean toward finishes with more pigment, since pigment is the actual sunscreen, and toward penetrating finishes that wear rather than peel. Clear varnish alone on a west door is a short-term look. A lighter color on a west wall also runs cooler and holds up longer than a dark one.

On the north side the priority flips to moisture: a mildew-resistant finish, good drainage at the bottom of posts and trim, trimming back plants that keep the wall wet, and a yearly wash to remove the spores before they stain.

Recoat intervals follow the same logic. A west-facing deck or door near the coast typically wants attention every year, the south side close to that, and the east and north sides every two to three years or longer. Maintaining each side on its own clock costs less than refinishing everything whenever the worst side gives out.

A quick exposure walk you can do yourself

On a sunny afternoon around three or four, walk the house and put your hand on the wood. The surfaces that are hot to the touch are your west and unprotected south exposures and they will need the most protection. Then go out early on a foggy morning and note what is still wet at ten. Those are your north and shaded surfaces, where mildew and rot are the risk. Two walks tell you more than any product label.

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