When moisture levels in a building become too high, an army of problems can occur. Unfortunately, signs only become apparent once the moisture has infiltrated the building materials.

These problems may be hidden behind walls, under carpets, in crawl spaces, in roofs, etc., but a moldy smell may be in the air, or people might be complaining about coughing because of lung irritation.

Obvious signs of moisture problems include dry-rot in wood, rust on doorknobs, hinges and other metal parts, mold on wall surfaces, condensation in windows, peeling paint and spalling masonry. The hardwood floor may be crowning or buckling.

One of the serious problems associated with too much moisture is mold growth. These un-welcome organisms sharing indoor spaces with us rely on and thrive only if enough moisture is present. This is true for microorganisms such as fungi, but also for pests like cockroaches and dust mites.

Green plants make their own carbon from air and water. Fungi cannot, they obtain their nutrients from carbohydrates, which they extract out of the materials they live on. Fungi are so adaptable that they learn to degrade almost any carbon containing substance, which includes all organic material such as wood and petroleum-based products. During the process of digestion the fungi release compounds, some of which are toxic and harmful to people.

To thrive and produce spores, fungi need air, water and nutrients. Since air and nutrients (materials containing carbohydrates) are usually readily available inside of buildings, the main factor for us to control growth of fungi is to control the availability of water or moisture. Cold temperatures sometimes slow fungi growth, but for buildings where people want to be comfortable, that is not a solution. The optimal growth temperature for fungi is 65-80ｺF.

Fungi take at least 24 hours to develop. Not every spill can initiate fungi growth. If excess water is removed and the surface dried out within 24 hrs, microbial growth is unlikely.

Wood

For centuries wood has been used in buildings as structural materials, for frames, floors, trim, moldings and furniture. Wood has always been moisture sensitive. It absorbs moisture and looses moisture until equilibrium with the surrounding air has been reached. Fungi grow on wood: In the forest, they help to compost. In buildings, they do the same, causing decay. Fungi growing on wood cause staining, brown rot, white rot and soft rot. Fungi not only deteriorate wood, but produce spore aerosols that can cause asthma and pneumonitis.

Wood not only allows fungi to grow on its surface, but actually changes its dimensions when moisture is absorbed. A janitor reported a drastic example of dimensional changes in wet wood. The floor in the school痴 gymnasium buckled 4 feet high after a leak remained unnoticed during the summer break.

At a relative humidity of 35-50 percent and a temperature of 70ｺ F, wood is stable if its moisture content is between 6-8 percent.

Hardwood floor and furniture manufacturers are very concerned about producing products within this moisture range. If wood is kept within this moisture range its beauty will last for a long time.

 Detection of Moisture Problems.

Handheld Moisture meters are tools to detect excess moisture in materials. Two types of moisture meters exist, resistance meters with pins, and capacitance meters without pins. Meters are usually calibrated to read moisture percentages in wood and sheetrock or gypsum. Other materials are measured with a reference scale 0-100. It is helpful for any application to establish a base value by taking readings in dry material.

Then measure the questionable materials, and compare the values to the base value. Higher numbers indicate more moisture. Mapping a number of readings may indicate where the source for the moisture problem is located. If moisture is suspected behind walls, pin meters with long insulated pins are used to reach the problem areas without having to remove wall sections.

A different measuring method is used to measure the moisture in concrete slabs, concrete walls or brick walls. The in-depth RH method required drilling several holes and setting relative humidity probes to measure the evaporation out of the concrete. When floor coverings fail because of moisture issues, it is very important to determine the source of the problem, otherwise the same defects appear after the floor has been replaced.

Continuous monitoring devices are available to record relative humidity temperature and material moisture and material temperature for days, weeks and years. A great diagnostic tool, graphs show all parameters and their relation to each other.

When checking out moisture problems, inside conditions can be monitored and compared to the outside climate changes. Other applications include monitoring drying of buildings or leak detection. Monitoring devices can be installed throughout a building to warn of critical conditions.

Different recording and downloading options are available. The BL-2 chip from Lignomat, with min/max indicator, records one measurement of relative humidity and temperature or one moisture content reading in material. Readings are saved at preset time intervals. An LED indicator light turns red when critical conditions are reached. The unit can be plugged in a PC to download the data.

The Moisture-Log system uses wireless transmission of relative humidity, temperature and moisture readings to a central collection station. From there the readings can be sent to an on-site computer or over the Internet to a Web browser.

Following is an example of moisture problems in a basement. The only indication of a problem was a musty smell. After mapping moisture readings from the floor to the ceiling on all walls, it was obvious that the problem was along the base of the two walls facing the outside. A Moisture-Log System was installed to record outside and inside conditions, which confirmed that the wall was allowing outside moisture to infiltrate. Inside relative humidity reached 90 percent and did not change much, when the weather changed outside, because too much moisture had been soaked up by the structure over the winter months. It did not help that the building was at the Oregon coast where during the winter it rains a lot.

The remedy is to seal the basement wall from the outside, put a rocky moisture barrier between the concrete wall and the earth and then dry out the sheetrock wall from the inside.