In Almaden, Los Gatos, Monte Sereno, Saratoga and anywhere near hills in Silicon Valley, there are homes with cupped hardwood floors. Cupping is when the sides of the plants curl upward a little. If you view cupped floors in lighting at an angle, the “lines” between the pieces of wood are more prominent, as shown in the photo to the right. Should you walk across them barefoot, you will feel the elevated sides. When it is severe, there are very distinct ridges.
What causes cupping? It can be caused by installing hardwood that hasn’t cured or sat in the home for a few days first. But often that’s not the issue. Most of the time, it seems to result from water in the crawl space below. As the moisture evaporates, it moves up through the home and through the hardwood flooring.
This doesn’t happen everywhere, but is most common in hillside locations, places that are flat but have hills nearby (as water can travel underground and then pop up, potentially under your house), locations with high water tables (such as Willow Glen, many areas of Almaden such as Almaden Springs, or Los Gatos), or properties where the grading is wrong and water gets pulled toward the home instead of away from it. Although in many parts of the U.S. the soil is sandy and the water drains through, in most of Santa Clara County, we have expansive clay soils. With clay it’s harder for the water to soak through, but also when the soil gets wet it, it expands and pushes on the foundation and anything else in its way.
Are your floors beginning to cup? If so, it’s a red flag to pay attention and find the cause of the cupping before the damage is permanent, or much harder to fix. Check your crawl space for dampness and efflorescence (this requires going all the way into the crawl space). If you aren’t able or don’t want to go into the crawl, make sure to hire someone competent to evaluate the situation. Having a damp crawl space is not good (and if you find it in summer after a 3 year drought you do have an issue!). I would suggest getting an ASHI or CREIA certified home inspector to check it out and advise you on the cause of the cupping and what to do to remediate it. It may be that a hardwood flooring professional would also address this very well – I cannot speak to that but it may also be worth considering.