The 2×4 Challenge: The Truth about Drying Wood Materials

What is "Dry" for Wood Anyways? Can Anyone Agree? In My Experience, No. Not Really.

After 25+ years in the industry, I am still tackling this topic. Since everyone has their definition of “dry,” it’s no surprise that no one can agree on something so fundamental. If the experts can’t agree, how can we assure our clients we’re doing the right thing for them? So let’s start by defining the boundaries of this discussion.

From the IICRC/ ANSI S500 2021 Definitions:

“Drying: the process of removing moisture from materials.”
“Drying Plan: A subsection of a work plan, the drying plan is a restorer-developed and implemented plan that establishes target ranges, means, and methods for controlling humidity, temperature, and airflow to achieve the drying goals, and in accordance with project Limitations, Complexities, Complications, and Conflicts.”
“Dry Standard: a reasonable approximation of the moisture content or level of a material prior to a water intrusion.”
“Drying Chamber: see drying environment.”
“Drying Environment: a controlled environment, which may be defined by existing or temporary barriers, in which evaporation from damp or wet materials is encouraged, leading to an accelerated reduction in their moisture level or moisture content. A project may have multiple, separate drying environments, which may have varying determinations for Category and assignment of Class.”
“Drying Goal: the target moisture content or moisture level in a material established by the restorer to be achieved at the end of the drying process.”

Notice how these definitions don’t tell you what exactly “dry” is down to the number because this varies based on atmospheric conditions and geographic location. However, if we take ASHRAE’s comfort standard into consideration we can conclude the following:

The Indoor Pre-Loss Environmental Condition of Most Homes: If you cannot locate a room in your home that is unaffected, most homes are maintained between 70–80-degree F, between 40-55% RH. This creates an EMC (Equilibrium Moisture Content) in wood of 7.7-9.9%. Typically, Dry Standard is found in an unaffected area of the home. In a hurricane event, the entire home is either wetted by water OR is exposed to high interior humidity. The humidity and water will elevate the EMC in building material so finding a pre-loss EMC will not be possible. If this happens, YOUR EMC can be found by going to the following website and putting in you average interior temperature and Relative Humidity.

You will typically get a value of 7.7 to 9.9% EMC in the Florida region.

The WME Danger Zone

From my Property & Casualty 360 Structural Drying for Insureds:

“Often, when you are told that 16% or 20% is an acceptable dry standard, it’s a misrepresentation of the standard.

The standard says that no matter what EMC you get from the materials in the house, you cannot leave a material at an EMC that would support microbial growth — and 16% is documented to support growth. It also says that an acceptable dry standard is within 10% of what the other similar materials in the house were pre-loss.

So think of that 9.2% material we discussed earlier. An acceptable goal is 9.2% + .92% or up to 10.12%. This goal also varies based on location.

How to DIY the 2x4 Challenge

IMPORTANT NOTE: This demonstration is normally performed with the use of remote monitoring. Although we utilize Omnisense equipment throughout the process, you can take daily readings and create your own drying log.

Step 1: Gather Your Materials

6

2″x4″x120″(10′) for sides of drying chamber & wetting chamber – Please ensure they run true with no warping, racking or twisting.

2

2″x4″x30″(2.5′) for ends of wetting chamber.

4

2”x4”x96″ (8′) for the ends of the drying chamber – Please ensure they run true with no warping, racking or twisting.

3

Kiln Dried 2”x4”96 (8′) – for the wetting chamber.

Please take your moisture meter with you to your supply store and ensure that they are 8 to 10% EMC using the Relative setting at 3” from each end and in the middle. If you can get relatively dry 2×4′, please install the screw at 3” from either end and in the center of the member to confirm. Failing to do this has resulted in weird demos several times. Most lumber is not dried to 8-10% EMC. We need wood that is dry for this demo.

Important Note: Dry standard at this time of the year should be 8 to 11% at the highest. Don’t find the wood required until the last moment because (insert your home supply store name here) hardly ever has a truly dry piece of wood, regardless of whether it’s marked “Kiln Dried”. I have found 30+% in the middle multiple times when 3” from either end is 8.5%. Sometimes you can find something that’s been around the shop for quite a while that will work.

1 LB Box
(Or in Large Quantities)

3 or 3.5” stainless steel exterior uncoated screws + extra drill bits that match the above screw drive. They typically require star or slotted bits depending on the brand. You can get these at Lowes & Home Depot. Power Pro & SPAX are good brands.

(1) 40 PK

NOTICE: Nothing is touching the water.

12″ to 16″ alligator clips/test leads. Note: These will free up your hands and create flexibility with your meter or sensors when taking readings during pictures.

10

Omnisense S-11 Sensors (If Using Remote Monitoring)

1

Omnisense Gateway (If Using Remote Monitoring)

3

Plastic Door Shims

1

LRG Dehumidifier (We use a 3500i Dri-Ez, which allows for remote monitoring of dehumidifier performance and interior T / Rh / GPP.)

1 BOX

20-ft x 100-ft Clear 6-mil poly (FR)

2 PK

3-Inch Duct Tape

2 PK

ZipWall Dust Barrier Zipper Kit

2

Sawhorses

Step 2: Assemble Your Drying Chamber

Frame Enclosure - 4'x4'x10'

In the pictures below, you’ll notice we use PVC to build our wetting chamber. You are more than welcome to do this. Follow the same measurements.
Build the frame and line with poly. Fasten the poly with yellow duct tape.
Install Zipper (2 Zippers opening from center for access to interior.
OPTIONAL: Include a PORT to the right of the zipper for an AC or Airscrubber output.

Setup In the Drying Chamber

Add 2 Sawhorses inside the containment to hold the 8’ 2×4’s

Run power to the chamber and add the dehumidifier.

Step 3: Create Wetting Trough

Use (2) – 2”x4”x120”(10′) for the sides and (2) – 2”x4”X30”(2.5′) for the ends.
Line the chambers with 6 Mil Poly, ensuring you do not cut the poly as it needs to hold water.

You don’t want another water loss!

Step 4: Preparing the Wood Members

Find several 2”x4”x96” Kiln dried members and place (2) 3” uncoated Stainless Steel screw in the 2”x4”.
Place the screws midline in the 1.5” side of the 2”x4”’s parallel to the ground and approximately the distance apart of whichever penetrating meter you are using has its penetrating probes spaced for easy survey later on.
Place the screws according to the supplied diagram as follows:

- i) 3” from both ends
- ii) 1’ from either end
- iii) 2’ from either end
- iv) 3’ from either end and
- v) In the center at 4’ from either end

Positioning the Members in the Wetting Chamber

Place the 2’x4” members in the wetting chamber and shim all members so they’re level.

When the water is added, we will need all of the members at the same level so the same amount of the wood on EACH member is wetted. As we will have screws centered on the 1.5” face of the 2×4, we can add not more than 3/8” to ½” of water to the Wetting Chamber so the water does not touch the screw or screw head. As there are screw heads approximately ½” from the ground, getting these members level is VERY important!