Checking Moisture content in Subfloors
1 Checking Moisture content in Subfloors
Determining moisture content is essential for quality control within the engineered timber
flooring installation process. Laminate timber flooring installers must know the moisture content
of the wood flooring and the subfloor.
We are at a time when humidity levels are very high. In homes minus climate control (new or
existing houses), these high humidity levels will elevate the wood subfloors' moisture level,
which can impact newly installed wood floor boards.
Irrelevant to what type of engineered timber flooring he is installing, every installer should have
a meter for inspecting wood subfloors. Moisture meters have culminated into the most crucial
tool for flooring installer, but it is probably the most neglected tool in the industry. Continuing to
work without a moisture meter increases your chance of failure. The wood floor boards installers
and moisture Meters can also be employed by all flooring trades. Moisture Meters can be
utilized to check subfloors for water crevasses, moisture content of wood subfloors before
establishing any flooring, and if the hardwood is at the right tier for the subfloor.
1.1 There are two kinds of Moisture Meters for wood subfloors:
1.1.1 Pin or Invasive: This is the older of the two. The pins measure electrical
resistance across opposite sides of the pins inserted into the wooden product.
Generally, pin meters will measure from 6% to 30%. This testing method was
developed to measure timber's moisture content but is arguably problematic for
large areas of walls and polished timber floors where pinholes may be unsightly,
especially in materials such as drywall and on solid surfaces where the pins
1.1.2 Pinless or Non-Invasive: This meter can effortlessly be moved across the floor
to identify wet areas or a wet subfloor and is not influenced by temperature and
rough surfaces. Pinless or Non-Invasive meters will also calculate from 6 – 30%.
Bearing a reading from the surface of such materials can be tricky, as the surface may be dry
owing to low humidity. Nevertheless, below the surface, the material or substrate may be wet.
Non-invasive moisture meters that operate on the principle of impedance measurement
employing direct contact electrodes have been adapted to the requirements of various
industries over the years. Direct contact electrodes present more accurate results, versatility,
Page 4 of 2
the profundity of signal penetration, and reproducibility of readings than other Non-invasive
When the wood subfloor takes on extra moisture, it expands. The flooring will shift, buckle, or
cause joint show-through with this expansion. Loose-Lay flooring established in new
construction during the hot, humid summer months typically has some failure during the first
heating season. The flooring is established when the subfloor has picked up the extreme
moisture and swelled. The flooring supplies some expansion space and looks good for a few
months. The heat is turned on in October/early November, and the drying procedure of the
subfloor starts. The subfloor dries out, shrinking, and the once good evolution zone gets tighter.
The subfloor resumes to dry, and the engineered timber flooring begins to buckle because the
fullness created by the subfloor shrinkage now has nowhere to proceed.
Engineered timber flooring over crawl rooms has been a problem since the beginning. Every
wood subfloor beyond a crawl space should be tried for moisture. The crawl space should also
be reviewed for a minimum of 6 mil black poly blanketed in stone overlapped and running up the
walls. The minimum height for a crawl space is 18″ elevated and should have vents or a
dehumidification system. If the room is not vented, the excess moisture is entrapped, and the
dry subfloor will pick up this moisture and cause flooring problems. If the humidity is not
controlled in the crawl space, this will compel the subfloor to go through a lot of up and down
transitions leading to a engineered timber flooring failure.