Save More Walls

September 17, 2007
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One of the most disruptive things for a customer is the hassle of having water-damaged drywall replaced. Days of tear-out, replacement, taping, mudding, skim coats, priming and painting can ruin a customer’s attitude.

One of the most disruptive things for a customer is the hassle of having water-damaged drywall replaced. Days of tear-out, replacement, taping, mudding, skim coats, priming and painting can ruin a customer’s attitude. By the end of the process, they are more than happy to see the restorer back out of their driveway for the last time.

Because they can be surfaced and covered in a variety of ways, walls present a significant challenge to restorers when they become wet. A successful restorer can be profitable and build a more loyal customer base by learning to save more walls.

For basic walls with a single layer of wallboard and flat paint, the only drying tool needed is an air mover to blow warm, dry air along the wall. In some structures, the surface of the wall is covered with a non-permeable covering, or there are multiple layers of wallboard. In these cases, it may be necessary to remove base molding, drill holes and introduce air movement. Airflow inside the wall cavity increases the rate of evaporation and allows the wall to dry from both inside and out.

When drying inside a wall cavity, follow some basic steps to ensure success:
  1. Determine the type of wall. This can be done by opening receptacle and switch covers, by making inspection holes or by other intrusive means.
  2. Check for wicking with a non-invasive meter.
  3. Check insulation with an invasive, deep-wall probe if the water came from above or if standing water was above the bottom plate.
  4. Use the dot system to evaluate wall-drying progress.
  5. Document progress daily and document when affected areas have reached a dry standard.

Image 2

The Dot System

The dot system (Image 1) employs the use of removable, colored dot stickers to indicate the relative amount of moisture present in a material. Typically, either two or three colors are used in the dot system. Each color represents either the level of moisture or the intended restoration procedure.

During the initial inspection, use green, yellow and red dots to indicate moisture levels in affected materials that will be dried. By general definition, the dot colors represent the following amounts of moisture:
  1. Green – Within acceptable tolerance of the dry standard.
  2. Yellow – Abnormally wet but not saturated, at risk for secondary damage.
  3. Red – Near saturation, high risk for secondary damage.
When using the dot system, moisture is tracked by the size of the area that is wet, as opposed to the actual moisture level. For example, when monitoring gypsum wallboard, document the inches of migration up the wallboard with a measuring tape. Measure from the floor surface to the colored dot placed on the wall, and document this height. For further, more detailed documentation:
  1. Photograph the walls with the dots in place.
  2. Take moisture readings from bottom plates behind the baseboard.
  3. Take moisture readings from the baseboards and wall near the baseboard.
The dot system should be recorded on the moisture map to show the extent of migration. Dating the colored dots being used will help, or number them in relation to the days of drying (e.g., “Day 1,” Day 2”, etc.)  Proper labeling will assist in the evaluation process, as many dots may be used over the course of drying.

Demonstrating Progress

Another way to differentiate data from day to day and to show drying progress is to overlap the colored dots (Image 2). For example, a section of gypsum wallboard may initially be wet up to 6 inches in height. Taking for granted that the moisture levels were near saturation, place a red dot on the wall 6 inches from the floor. When updating the dots on the second day, moisture levels will likely have changed. Place new dots slightly over the previous dots, with the initial dot still visible. This indicates that two days of monitoring have passed, while showing the change (by color) in the amount of moisture. If the material has returned to an acceptable moisture level, place a green dot partially over the red dot. The result will be two dots – green overlapping red – showing the wet material has returned to an acceptable moisture level within two days.

It is possible for a wall to return to a dry standard near the highest edge of migration, but to remain abnormally wet near its base. If this is the case, place a new red or yellow dot (whichever is appropriate) at the new height.

Image 3

Monitoring Tips for Plaster

Equilibrium Relative Humidity (ERH) testing is used to measure moisture in plaster construction (Image 3). To use this method, follow a two-step process:
  • Install the relative humidity probe at the surface of the plaster or within wall cavities behind it.
  • Contain the air space using a vapor retardant material such as polyethylene sheeting; this will help determine the degree of moisture present within the material.
When using this method on plaster, it is necessary to either allow greater acclimation time within the ERH testing containment when surfaces have lower permeability, or increase permeability of the surface through perforation.

Non-invasive or invasive moisture meters may also be used to measure moisture in plaster. When using non-invasive moisture meters, readings are relative (qualitative) and are only effective when compared to a dry standard. Beware of metal lath, which can elevate non-invasive readings.

When using invasive meters, short 1/2-inch tapered pins are most practical, as they will leave only very small pin holes behind. Because the pins are not insulated, it is not necessary to insert them completely if surface readings are high. When surface moisture is present, it will influence any attempted reading within the depth of the material. This is because penetration will have to occur through the moisture, and surface moisture will therefore continue to influence readings as pins are forced into the material.

Monitoring Tips for Gypsum Wallboard

Non-invasive moisture meters are primarily used when evaluating gypsum wallboard. Because many non-invasive meters are only calibrated for wood, it is imperative to measure against a dry standard when using one.

Invasive moisture meters may be used to supplement non-invasive readings; this will ensure that moisture is not trapped beyond the reach of the non-invasive moisture meter. Many installations, such as firewalls, sheer walls and apartment common walls, have more than one layer of wall material. When this is true, non-invasive moisture meters will not accurately measure the entire depth of the wallboard. Verification through invasive moisture metering is necessary to ensure that the entire wall installation is inspected.

Image 4

Drying Progress Is Key

If a wet wall is not making drying progress, options for modifying the drying system should be evaluated by considering the basic rule of evaporation: Evaporation will increase as materials are made warmer, as air is made drier and as air is moved more rapidly across the wet surface. Under this principle, there are several options for action, beginning with the least disruptive:
  1. Add more direct airflow on the outside of the wall.
  2. Move the dehumidifier output so that it is closer to the wet surface.
  3. Warm wall surfaces.
  4. Carefully remove the baseboard and continue airflow along the outside of the wall.
  5. Drill holes below baseboard level to allow the wall to breathe, and continue airflow along the outside of the wall.
  6. Blow direct airflow into the wall using air movers or inter-air dryers.
  7. Feed air movers that are blowing into the wall with a dehumidifier.
  8. Completely remove all wet wallboard and any wet insulation.
Clearly, every wall can present a different drying challenge. The most successful restorers will be ready to employ any and all of these options to reach drying goals efficiently.

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