Mitigating Moisture in Hardwood Floors
Whether we’re speaking of topically applied moisture, or moisture intrusion from the side or beneath the wood floor, moisture intrusion can be tricky to mitigate correctly. In many cases, production schedules often dictate our timeline and how long we have to mitigate moisture-related concerns. With wood flooring being moisture-sensitive, it is very important to understand a few basic principles.
- Understanding properties of wood flooring
- Subfloor drying—plywood/OSB/pine
- Flooring underlayment papers
- Flooring restoration
It’s vitally important to ensure proper mitigation techniques are used to salvage a water-damaged wood floor. In almost all cases, wood flooring manufacturers produce their product between 6-9% moisture content. Therefore, it is necessary to ensure moisture is balanced from above and below the wood floor to keep the wood stable. Elevated subfloor moisture content will cause buckling, cupping, compression and other problems to any wood floor.
Many mitigation professionals use scan-type moisture meters to take their readings during the drying process. These meters can be used to provide a snapshot of moisture conditions throughout the project; however they are not accurate enough for a detailed look at the wood flooring. These types of meters send a signal approximately ¾" to 1" in depth, providing an average moisture content throughout the thickness of the material.
These types of meters work well for the beginning drying process. Once the moisture content is 15% or below, it is recommended to use an insulated pin-type meter. This will provide gradient moisture measurements and provide different moisture levels, whether in the hardwood flooring or the subfloor.
If moisture levels are elevated above the dry standard within the project, cupping of the wood floor is inevitable. It is vitally important to ensure the subfloor and flooring moisture levels is the same as the dry standard within the rest of the property before any remedial floor restoration takes place.
There are a few concerns with drying plywood, as some of the adhesives used to adhere the plies together will provide false negative readings. We must understand the pin meter is a resistance-type meter which measures the resistance between the two pins to obtain a reading. Many plywood adhesives have properties which provide resistance and give us inaccurate test results. In many cases the moisture levels will record higher due to the resistance properties of the adhesive.
This wouldn’t matter if it was a plywood subfloor or the plywood core (back) of the engineered product. It may require cutting a small section of plywood out of the subfloor and placing the pins between the adhesive lines to obtain an accurate moisture reading. This is essential to the success of mitigating the wood floor properly.
Many technicians use drying mats to bring the wood flooring moisture content down. This is fine for the initial drying process of the wood floor; however, once the moisture content gets down around 14% the mat drying must cease. If it is required to continue the drying process it would be recommended to use a tenting system until the dry standard has been obtained. The reason for pulling the mats off around 14% is to prevent fiber structural damage.
In many cases when the mat drying is left on after obtaining 14% (safe zone), excessive shrinking will occur. This scenario could happen in an overnight situation depending on fiber density and porosity of the wood flooring. The mat drying is so effective one could reach the safe zone at 4 p.m. and be in the danger zone by 6 a.m. from cell wall collapse. The tech may not reach the jobsite until after 8 a.m. when structural damage is already done.
Tented drying is simply controlling the air space between the wood surface and the atmosphere. This process is considerably much slower, but does not cause rapid evaporation that could lead to fiber/cell wall damage. The greatest risk we have in tented drying is where the air supply duct enters the tent and provides the driest location, which may cause face checking on engineered and/or solid wood floors. This area should be rotated as the drying process is taking place.
Mitigating moisture in a concrete subfloor was covered last month in this magazine, so I’m not going to get into specifics. I’ll just say whatever requirements are given by the flooring manufacturer/adhesive manufacturer regarding moisture control systems need to be followed under moisture-sensitive flooring like wood. If the test results are not favorable for wood flooring, the adhesive manufacturer will suggest moisture control systems to be used under the wood floor. It’s vitally important to follow flooring manufacturer’s specifications regarding concrete and mitigate appropriately.
Let’s say we have a wood floor mechanically fastened over a wood subfloor that has experienced water damage. The first thing we must identify is what type of flooring underlayment paper was used under the floor. The reason for this is some underlayment papers have a perm rating of .7 to 1, which will make it virtually impossible to dry the subfloor through this underlayment paper (moisture retarder). Even though flooring underlayment paper has been perforated by mechanical fasteners, the water has penetrated through the tears of the paper onto the subfloor.
In many cases the wood floor is still going to have to be refinished; therefore the restoration professional can remove one short plank next to the baseboard to identify the underlayment paper. If the underlayment paper is identified as a low-perm rating product, it would require the drying process to be done from above and below the wood floor. In that case, the drying of the plywood would be from beneath the floor and the wood floor drying would be from the top side.
Timing is important here because of the potential mold growth that could happen in a matter of a few days if moisture levels exceed 15% for an extended period of time. Depending on the starting point of the water damage, i.e. 35%, there may not be enough time to dry the wood floor below the threat of mold. Therefore, in some cases low-perm rating underlayment papers may require removal of the wood floor and underlayment paper to dry the wood subfloor before the restoration process.
Flooring restoration typically means replacement or repair of a few planks up to several hundred square feet. Before this process begins we must understand a few simple rules between mitigation services and flooring professionals. In many cases the mitigation team will say the floor is dry at 12% when the dry standard within the home may be 8% and flooring restoration work cannot begin until the dry standard has been obtained. Sometimes when we’re looking at a 4% difference this may mean one to two months of additional drying on its own prior to any flooring restoration work. If the wood floor restoration is rushed before obtaining the dry standard moisture content, the flooring, which is most likely cupped at the time of remedial work, will experience crowning within months thereafter.
This phenomenon happens when we don’t obtain moisture balance throughout the thickness of the flooring and subfloor to reach the dry standard of the non-concerned area. The delay from the time moisture mitigation began to reaching the dry standard may be outside the timeline of the project. Therefore in cases such as this, it may be required to complete removal of the wood floor and dry the subfloor to the dry standard and replace with new flooring. This process may cost up to 65% more than just waiting the additional time for the floor to properly dry. This is the Catch-22 between the insured and the insurance company and who picks up the tab for the delay or additional costs.
Flooring restoration is not as simple as one may think, as wood flooring can only release moisture at a certain rate and speed. Wood flooring may take several months to reach a dry standard prior to the refinishing process. Often when damaged, cupped wood flooring is given appropriate time to dry; it will most likely be reasonably flat and sometimes undetectable other than a few high edges. Once flooring reaches the baseline, it takes two to three additional weeks to stabilize the wood flooring from previous tension and stress.
When it comes to mitigating wood flooring there is one simple rule: Don’t be in a hurry unless you want to do it over again.