A moisture meter, like this one from Tramex, takes the guesswork out of estimating when wood paneling or flooring is dry enough to install.
Moisture meters $15–$460+
Moisture is a stealthy force in buildings, typically as invisible as it is universal, and the fundamental tool to detect it has long been the moisture meter. Lumber, furniture, and flooring companies rely on
moisture meters to guarantee their products are below a promised moisture content (typically 7% to 8% for flooring) and will not shrink or deform once in the hands of the end-user. Contractors use moisture meters to determine if rooms or concrete subfloors are dry enough to install flooring, or to assess flood damage. In building inspection, taking multiple moisture readings in a careful pattern can detect areas that exceed normal moisture levels. This may explain why paint is peeling, wood is deteriorating, or brick is spalling—and even point to causes, such as a leaky roof.
Like their kindred inspection tools, moisture meters come in three common types. Pin-type meters, the original versions, work by penetrating the material surface with two pins, then measuring the electrical conductivity between the them: more moisture, more electrical flow. Conductivity is displayed as a number (once by analog meter, now usually digital). Meters are typically calibrated for wood to directly read percentage of moisture content, but they’re also applicable to other materials, such as gypsum (drywall), acoustic tile, or masonry when interpreted on a relative scale of 0 to 100. Some meters now use colored displays, such as red for high moisture content, green for dry. Since the pins must be inserted into the surface, readings can depend on the depth of penetration and, in some situations, do not qualify as a non-destructive test. However, pins make this the only meter type that can detect the exact location of moisture.
A good read:
How To Survive a Home Inspection
Pinless meters (aka EMF and capacitance meters) avoid pin issues by identifying moisture via the principle of electrical capacitance. Here, the tool emits an electromagnetic field through sensors pressed against the material, then measures the material’s ability to store energy. Pinless meters are the tools of choice where any impact to the surface is out of the question—say, taking readings over decorative wallpaper. However, since they can read to ” to 1” below a surface, they also have the ability to evaluate moisture beneath finishes such as bathroom tile or sheet flooring that cannot be penetrated or do not show any evidence of moisture.
All-in-one meters (aka pin/pinless) combine both meter types in one tool, and are popular with professionals who want to compare readings—one to find a high moisture area, another to pinpoint its location.
Through indirect evidence, a moisture meter can find more than moisture—problems like insects or mold.
No surprise, today there are apps that will plot digital moisture maps from meter readings
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.
Drone flyovers make the danger of clambering up a steep roof to inspect shingles or the condition of a chimney a thing of the past.
Courtesy Chimney Champions
With over 7 million of the little buzzers in the air as of 2020, no overview of inspection tools can get by without at least a snapshot on drones. Camera-carrying drones are now common for closeup visuals of building exteriors (and even interiors) in places that were formerly accessible only by aerial lifts, scaffolds, or ropes—think roofs, or almost any place over three storeys aloft. Drone photography gets complicated and expensive, though.
As with spacecraft, the final image is actually a mosaic of overlapping digital shots composited together by a service, then corrected for vibration and other shortcomings. The results, however, can be revealing: from a comprehensive view of the entire roof, to a measured depiction of the skeletal framework of the whole building.
As recently as a couple of years ago, only photo-type cameras appeared on drones, but today IR cameras for thermal inspections are one of their most popular applications, particularly for commercial buildings. In fact, along with thermograms and photogrammetry (making measurements with photos), there’s now a burgeoning inspection/survey drone industry for hire, using sensors ranging from LiDAR (light-scanning radar for measuring) to those detecting methane.
Thermal Imaging Infared Camera ($1000+)
Another branch of military research to bear ever more peacetime fruit is the thermal imaging camera.
These tools detect thermal energy—specifically infrared radiation (IR), a range of wavelengths often experienced as heat. Along with visible light, IR is part of the electromagnetic spectrum, but like X-rays, microwaves, and radio waves, it cannot be seen with the naked eye. Thermal imaging cameras employ sensors that change electrical resistance, voltage, or current when heated by IR, then display this information as an image called a thermogram that can be viewed and analyzed.
A technician uses infrared imaging to look for leaks in a complex series of pipes.
Thermal imaging came into practical use during the Korean War for identifying targets and foes through battlefield smoke or darkness, and later to fight fires on ships. Expensive and security-sensitive, it remained in the military until after the 1991 Gulf War, when reduced equipment sizes and costs opened it up to the public. Law enforcement put thermal imaging to work in surveillance and security, and municipal firefighters adopted it for search and rescue and to identify fire hot spots. Since the 2000s, even more compact and economical cameras have become standard inspection tools. Utilities use thermal imaging cameras to look for overheating in high-voltage power lines, and the building industry relies on them to find heat leaks and improve HVAC-system efficiency.
Today’s thermal imaging cameras come in many forms and complexities, from helmet mounts for firefighters to handhelds for building inspectors. Basic cameras just read the temperature under crosshairs on the image, then display the temperature as a number, or multiple numbers for comparison. More sophisticated cameras display relative temperatures as colors, typically aseither a black/white/grey range or, in the most sensitive cameras, a palette of multiple colors—say, white for hottest, reds and yellows for intermediate, blue or black for cold. Specialized cameras can offer a color alarm feature that only displays an image where the temperature is above or below a user-selected range, for example displaying only the hot spots around a window or on mechanical equipment.
Like conventional photography, the quality of a thermogram depends on the design, cost, and operation of the camera. At the top of the list is detector—that is, the number of pixels and thereby temperature data points. The higher the resolution, the clearer the image.
A thermal imaging camera can cost from $1,000 to $10,000, with resolution commonly the biggest difference between an expensive camera and a cheaper one. Also important is thermal sensitivity, or to what degree the camera can distinguish a difference in temperature between two surfaces.
Better cameras also allow the user to adjust for emissivity (how well a material radiates infrared energy, compared to a perfect radiator); reflective temperature (compensating for temperature reflected from surroundings); and thermal tuning (adjusting the temperature range the camera detects).
Infrared imaging reveals the temperature of a structure through color, identifying areas of energy loss in bright orange. It clearly identifies a trouble spot where one would not be expected: the “hot” area just right of the left window bay.
Courtesy FLIR Systems
Thermal imaging cameras can’t see through walls, but they can tell a great deal about the condition of a building by “taking the temperature” of its surfaces in multiple ways:
Energy Audit Also called a thermographic inspection, this survey of the building’s exterior or preferably its interior (where temperature differences are less affected by air movement and more accurate) can determine the effectiveness of insulation—whether a building needs it and where. Thermographic inspections are also valuable before a house purchase to evaluate its condition, and after adding insulation to assure it was done correctly. Inspections even can reveal the condition of existing insulation, such as settling or saturation from a roof leak.
Building Leakage Thermographic inspection also will zero in on air leaks that allow heat to escape or infiltrate the building. When combined with a blower door (a fan attached to a door that tests airtightness by exaggerating air leaks), an inspection can locate air leaks around windows and doors or through building defects (such as wall penetrations or faulty siding) when they show up in the thermogram as black streaks.
Mechanical Systems As with utilities, thermal scans of electrical systems can detect overly warm connections or circuit breakers, indicating potential problems. Similarly, scans of HVAC equipment and the like can point to areas of friction or wear.
Moisture Detection The non-invasive nature of thermal imaging cameras coupled with their ever-growing sophistication and affordability has made them increasingly popular for moisture detection. Rather than measuring electrical resistance or capacitance like a traditional moisture meter, thermal imaging cameras can identify areas of moisture when they show up as anomalies in a thermogram, due to the effects of evaporative cooling.
Material Defects In high-level inspections, such as structural investigations, thermal imaging is also a tool for finding defects in materials. For example, moisture trapped in a porous material such as wood increases its thermal conductivity, and shows up in a thermogram as a cooler area.
Thermal imaging cameras may be obtained through a service (some utilities do work for a nominal charge or for free), rented, or purchased outright.