Moisture Mapping
A handful of random meter readings is fine for just following up hunches about a moisture problem, but to see the big picture, do what the pros do and create a moisture map. A series of meter readings taken in a grid, a moisture map allows you to visually identify the location and extent of moisture in an area—most importantly, the perimeter where the high-moisture zone ends and the “dry” zone begins. By plotting varying moisture levels relative to the “dry” area, moisture maps sketch a picture of moisture migration into the area, often suggesting its source. Moreover, making multiple mappings (say, a week apart) can track moisture increases—or, with luck, decreases that indicate the problem has been corrected successfully.
Moisture mapping is not difficult and can be done several ways. You can map the readings on a piece of paper or a computer screen, or chalk them onto the wall or floor itself. The critical first step is to read a known “dry” area to establish the baseline value, then calibrate the meter. When using a pin-type meter (generally preferred where pins are permitted), always insert the pins to the same depth to ensure accuracy. Many pros use their most sophisticated tools just to document the perimeter. Floors, walls, and even entire houses are often mapped to chart relative moisture levels and movements. Outdoors, moisture maps help explain what’s going on water-wise in gardens, landscapes, and agricultural fields.