Preventing Mold in your Home – Part 5 Drywall/Sheetrock (gypsum board) Walls

One of the least expected but most affected materials in your home after being exposed to standing water from a sudden and unexpected water escape are the walls. Often people think that the flooring like carpet laminate and hardwood are the only affected materials, On the contrary this is simply not the case.

Most walls are constructed using 2×4 lumber and/or steel framing studs, these walls are then covered with drywall/sheetrock (gypsum board) and finished by taping and mudding seams and painted to finish. The drywall/sheetrock is extremely absorbent when exposed to standing water, in fact it is usually the material in a building that will take the longest to dry. It is important to perform any moisture survey as discussed in the previous blog post (“What’s Wet? And how to find it – Mold Prevention”) so that one can determine which materials are affected and to what degree these materials are wet. Typically, drywall that is exposed to standing water will wick water (Capillary action) up to 18 inches in 24 hours meaning water will absorb into that drywall from the bottom and climb up the wall. When left unchecked these wet materials especially the paper on the backing of the drywall will be a perfect breeding ground for mold to grow. By touching walls with your hand, you will not be able to determine if the wall is dry or wet simply because the human touch is not sensitive enough.
When wet walls are attended to in a timely fashion drying without tearing out walls is usually an option. The exception in some cases is when walls are insulated with Batt insulation in combination with vapor barrier. These insulation components greatly limit air flow in the wall cavity making drying more difficult. Walls when finished are an expensive component in homes and buildings therefore proper mitigation and drying procedures are important and cost effective.
The most cost-effective way to dry wet interior walls is to remove the baseboard/base-trim to access the drywall/sheetrock beneath. Once this portion of the drywall is exposed you can easily drill holes below the baseboard line and above the framing plate to promote air flow into the wall cavities.
Important safety note: Do not remove, drill, or engage any drywall/sheetrock surfaces that were constructed and installed prior to 1990. Asbestos fibers may be present in the drywall joint mudding compound and was very commonly used in drywall muds between 1960 through to 1980. Disturbing these asbestos fibers is extremely hazardous to human health and can cause long term disease leading to death. The use of asbestos fibers in construction materials was outlawed in Canada and the United States by 1980; Despite this fact, manufacturers were still permitted to use up these materials until they were depleted from there raw stocks.
Once vent holes are drilled, fog a registered anti-fungal, anti-bacterial disinfectant using a thermal fogger into the wall cavity; this will demote mold growth.
The use of proper drying fans and or injection drying equipment will ensure walls are dried effectively therefore limiting the loss of finished materials. It is important to note that drying exterior walls with insulation components is usually not as effective.
Important note: Baseboard/base-trim is usually installed using finishing nails and a bead of caulking on top to cover imperfections. It is important to first cut this bead of caulking at the top of the baseboard where it meets the walls using an exacto knife/box cutter knife. Doing so will ensure that the caulking bead will not tear the finish painted layer off the drywall above the baseboard line.
Important safety note: When drilling holes into wall cavities it is extremely important to be aware of the placement of framing, plumbing water supply, sanitary sewer lines as well as electrical wiring. Accidentally drilling into these components can cause damage from water escapes and electrical shock which can lead to bodily harm and even death. According to modern building code Electrical wiring is to be installed in the middle of the framing to prevent accidental piercing from fastening components. It is good safety practice to identify the location of the framing materials so that you may avoid drilling vent holes through framing which may contain electrical wiring.
After creating vent hole sites below the baseboard lines and incorporating the use of dryer fans or injection drying equipment the wall cavities should dry down too acceptable levels within 3 to 8 days.
Once the wall cavities are dried, re-installing the baseboards should cover vent holes providing they were drilled and placed properly below the baseboard line. Some older type of baseboards which measure less than 2” in height may not cover vent holes. In these cases, install new taller baseboards to cover vent holes. Vent holes that have been placed on walls intended to be fire-rated or a fire-block will need to be filled and fire taped to maintain the walls fire resistant properties.
The use of the above-described techniques can save drywall/sheetrock walls and therefore limit the cost of repairs to water damaged building structure. Disaster restoration technical procedures like this are extremely valuable to limit the cost associated to the loss of building components after an unexpected water escape.

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