Overview of moisture issues in a building:

The most common problem that homeowners experience is water intrusion (in the form of outside water penetration or plumbing leaks).

Site assessment: very often water intrusion is not as simple as finding a roof leak or a plumbing leak. Though blistering and peeling paint or water stains identify the point of water intrusion into the interior, we must focus on its point of origin.

I often tell building contractors to play the game; "if I were a rain drop, where would I go". If a drop of water hits the peak of your roof, what is the path it takes from there to the closest river? If there is any restriction blocking the flow of this path it may affect the condition of your building.

Roof leaks: obviously the first place we look as homeowners is at the roof. The physical examination of the roofing system may indicate deterioration or damage to the roofing system. From here the water can flow in many directions to its point of infiltration into the house.

Gutters: gutter maintenance is required multiple times throughout the year. If not conducted properly, water will overflow or backflow the gutter system resulting in water intrusion at the roof line by backing up into the soffit or eve areas of the roof into the finished wall system. Overflowing the gutter causes excessive water at the foundation/footing and is a primary cause of water intrusion into the basement or crawl space if the soil plane is not adequately divert water away from the house.

Gutter downspouts: many gutter downspouts discharge water immediately adjacent to the foundation/footing. If the soil on-site elevation is not proper, the water will flow to lower levels (the basement or crawl space). When a house is constructed, the soil is back filled against the foundation and is not sufficiently compacted as this may damage the new foundation. Over time (generally almost 5 years) the soil will settle and become a negative grade towards the foundation. This directs the water into the house.

A second concern which is a primary cause for structural damage of a foundation is expansive soil conditions (particularly in middle Tennessee). Expansive soil is a high clay-based soil which expands and contracts at a significant volume, based upon its moisture content. If we have gutter downspouts at all four corners of the house causing the soil to become wet and expand, and we have flooring system girders supported by piers in the center of the house where the soil is often dryer and subsequently contracted, significant stress is placed upon the building foundation.

Soil drainage: the slope of the soil around the house should drain away from the foundation. The grading of the yard around the building should also incorporate adequate site drainage to divert the water around and away from the building. "Look up the hill"! Is your house acting like a dam in the middle of a drainage path?

Source of leakage: there are basically three types of water leaks;

1. Leakage of the roof for building envelope.

2. Leakage of a plumbing system (supply or drain).

3. Condensation.

We conduct many investigations concerning water intrusion were the building owner indicates that the roofer has been looking for roof leaks for a significant period of time and can't seem to find them. More times than not, the roofer is correct in reporting there is no roof leak. The elevated water vapor concentration of the outdoor air in Tennessee is significant compared to other parts of the United States. When high relative humidity air comes in contact with a building component that is below the dewpoint temperature (often created by the air-conditioning system), water will form.

Methods of identification: one of the most effective means of identifying the location and quantity of water damage is the use of infrared thermal imaging. You can cover a lot of ground and see things that are not visible to the naked eye. Though this process is not cheap (as cameras are quite expensive to own and maintain) it is more cost-effective than blindly searching for the water source.

Moisture meters are of two types; contact and noncontact. Contact moisture meters measure electrical conductivity of a material. More water increases conductivity. Noncontact moisture meters measure the density of a material which changes with the moisture content. Moisture meters are very effective if you know where to place them. They are good for identifying the existing moisture in a water stain for instance. But to search over your entire building (inside and out) is not an efficient means of identification.

It is important not to be tunnel vision and assume we have a leak in the ceiling and it must be from the roof. We must identify the location and the source of the moisture before it can be repaired. Contrary to popular belief, water does not always flow downhill. The effects of capillary action and diffusion can cause water to rise above its source significant distances.

In some cases we have identified very complex moisture paths through the building. Moisture entering into the basement evaporates, increasing the water vapor in the air, which comes in contact with an HVAC or outdoor air leak below the dewpoint temperature causing water to form and flow "as it will" throughout the building until it causes a stain or an obvious point of infiltration in the building envelope. The issue is a water leak in the ceiling, but the problem has to do with site drainage, water intrusion into the basement, excessive indoor humidity, building envelope or HVAC air leakage which creates water leaking through the ceiling. If you do not identify all aspects of this hydrological cycle, you cannot correct the root of the problem.

Solving moisture intrusion problems does not end with identifying moisture. What causes the moisture must be found and corrected.