Floor Refinishing in Cupertino

Cupertino Conditions That Affect Floor Refinishing

Derived statistic, not a published normal: averaging NOAA Local Climatological Data hourly observations at San Jose International Airport across the ten Julys 2015-2024 (Local Standard Time) gives 82.1% relative humidity at 04:00 (n=392) and 49.3% at 16:00 (n=317). San Francisco International averages 61.3% at 16:00 by the same method. The figure describes the station, not the city. NOAA's published table gives Sacramento a July afternoon mean of 29%.

NOAA's San Jose airport station records 1991-2020 January normals of 59.8°F average high and 41.8°F average low, with an annual precipitation normal of 13.5 inches. Cold, damp conditions do the reverse and stretch cure times, which mostly costs patience — a floor that is walkable is not yet a floor that is ready for furniture or rugs.

NOAA's San Jose airport station normals at a July high of 80.8°F against 66.3°F at San Francisco Downtown. Cool, damp days in Cupertino lengthen finish cure times compared with a hot, dry one — a scheduling factor rather than a quality one.

Seasonal Gaps in Cupertino Floors, by the Numbers

Seasonal gaps between boards are a common reason people ask about refinishing, and Cupertino's measured climate shows how much of that gapping is simply the wood moving with the seasons. Measured at Moffett Federal Airfield, then brought to 70°F, the air averages 40.1% relative humidity over the heating season and 61.2% over summer, which settles wood at roughly 7.7% and 11.2% moisture content. For a traditional 2¼-inch oak strip floor that is about 0.030 inch of seasonal shrinkage per board (about 1/34 inch); for 5-inch plank, about 0.066 inch. Gaps in that range that open in winter and close by summer should not be filled — filler packed into a winter gap gets crushed out, or pushes the boards toward cupping, once the wood takes its moisture back.

Source: Hourly ASOS dewpoint observations 2015–2025, Iowa Environmental Mesonet (Iowa State University); equilibrium moisture content from USDA Wood Handbook FPL-GTR-190 Eq. 4-5; movement from FPL-GTR-282 Eq. 13-3 and Table 13-5

What's Under the Finish

The Eichler Design Handbook — Fairgrove (January 16, 2001) states that 'the Fairgrove neighborhood consists of a group of 220 Eichler homes built in the early 1960's,' bounded by Phil Lane, Tantau Avenue, Bollinger Road and Miller Avenue. The handbook describes Eichler homes as characterized by 'single stories with mostly low pitched or flat roofs, multiple indoor/outdoor patios or atriums, slab foundations, and extensive glass,' with 'technological innovation such as radiant-heat floors.' Fairgrove was rezoned 'R1e - Single Family Eichler' following a citywide architectural survey, so the boundary is a zoning line and can be checked against a parcel. It is a single tract, not a citywide condition. Citywide, 63.8% of housing predates 1980. No source publishes a citywide slab-versus-raised share.

Raised floors are where the best refinishing candidates live: solid wood over a crawlspace, often with decades of wear and plenty of thickness left. It is also where cupping comes from. Sanding a cupped floor flat before the crawlspace moisture is fixed produces a floor that goes concave the other way once it dries — so the moisture reading comes first and the sanding comes second.

Source: NAHB analysis of the Census Bureau Survey of Construction, foundation type by region (2024)

Cupertino Homes We Work In

ACS 2020-2024 five-year estimates count 22,158 housing units; 26.9% (5,959 units) were built in the 1960s, the largest decade. Another 20.1% date to the 1970s and 14.2% to the 1950s. Only 1.3% predate 1940. Cupertino's 1960s, 1970s, and 1950s stock is where refinishing pays off most: homes of that period often have original wood under carpet, and when the wear layer is intact, refinishing keeps a floor that cannot be bought new. We check thickness at a vent or a doorway before recommending it.