"Is that wet, or is it just cold?" I've asked that out loud, to nobody, maybe forty times since we moved in, usually with my palm flat against a basement wall and Tessa somewhere upstairs pretending not to hear.
In August I finally spent $30 on a General Tools pin moisture meter. It's about the size of a TV remote, with two short metal pins on one end and a small screen. You push the pins into wood, and it shows a moisture percentage. It also has a relative mode for things that aren't wood, like drywall or concrete, which gives you a number that's only good for comparing one spot to another.
The guide that came with it puts dry indoor wood somewhere under 15 percent and says readings above about 20 are where rot and mold have a chance to get going. I'm not a building scientist. That's simply the scale I've been using.
Three things I'd been guessing about
The basement wall by the sump pit. There's a patch of painted block on the north wall, near the corner where the sump pit is, that goes dark after a hard rain. For a year I couldn't tell whether that was water coming through the block or summer humidity condensing on cold concrete. With the meter in relative mode, I took readings the morning after an August thunderstorm: about 40 in the dark patch, 15 to 20 on the same wall a few feet away. Two days later the patch was back down around 20. Condensation would have shown up all along the cold wall, not in one spot after rain. So it's water working through the block near the ground after storms, not a crack pouring water into the basement, and the downspout extensions and regrading we did in May are aimed at exactly that corner. I'll keep checking it after storms.
The window trim upstairs. The two small windows in the upstairs gable ends are the last original wood windows in the house. The sill on the one over the driveway looks rough, with peeling paint and a dark seam at the corner, and I had decided it was rotting. The meter said 12 percent in the middle and 14 at the corner. Dry. It's ugly, not soft. That one moved from the "worry" column to the "paint someday" column in the house sheet.
The garage side door jamb. When I scraped the garage in July, the bottom of the side door jamb felt too soft under the scraper. I primed and painted over it and told myself to figure it out later. The meter read 31 percent in the bottom few inches and 13 percent eighteen inches up. That's rot, or rot on its way. It's going on next summer's list, when the wood has a chance to dry out before I do anything to it.
How I use it now
At work, instead of counting the whole warehouse once a year, we count a handful of locations every week. That's a cycle count. I've started doing the same thing with the house. Once a month I check the same five spots and log the numbers: the basement patch, the garage jamb, the cabinet floor under the kitchen sink around the new shutoff from the PEX job (11 percent, dry), the subfloor under the toilet from the basement side and the wood threshold at the back door.
A pin meter has limits, and I've already hit a few. It only reads the first quarter inch or so. It can't see inside a wall. And the pins leave two tiny holes, so it's not something you jab into a finished floor. Pinless meters scan without holes and read a little deeper, but they cost several times as much. For the questions I actually have, the cheap one has been plenty.
My only regret is the timing. I'd have liked to have it in July, before I put primer and paint over that garage jamb without knowing how wet it was.
It lives on the shelf under the workbench now, next to the Klein tester. Between the two of them, I've mostly stopped asking the house questions out loud. Tessa says I just ask the meter instead, and she's not wrong.
