Moisture intrusion can be the cause of building defects, as well as health ailments for the building’s occupants. Red Dog Property Inspections provides clients with an understanding of how moisture may enter a building, and where problem areas commonly occur.
Some common moisture-related problems include:
- structural wood decay;
- high indoor humidity and resulting condensation;
- expansive soil, which may crack the foundation through changes in volume, or softened soil, which may lose its ability to support an overlying structure;
- undermined foundations;
- metal corrosion;
- mould growth. Mould can only grow in the presence of high levels of moisture. People who suffer from the following conditions can be seriously (even fatally) harmed if exposed to elevated levels of airborne mould spores:
- asthma;
- allergies;
- lung disease; and/or
- compromised immune systems.
Note: People who do not suffer from these ailments may still be harmed by elevated levels of airborne mould spores.
How does moisture get into the house?
Moisture or water vapour moves into a house in the following ways:
- air infiltration. Air movement accounts for more than 98% of all water vapour movement in building cavities. Air naturally moves from high-pressure areas to lower ones by the easiest path possible, such as a hole or crack in the building envelope. Moisture transfer by air currents is very fast (in the range of several hundred cubic feet of air per minute). Replacement air will infiltrate through the building envelope unless unintended air paths are carefully and permanently sealed;
- by diffusion through building material. Most building materials slow moisture diffusion, to a large degree, although they never stop it completely;
- leaks from the roof;
- plumbing leaks;
- flooding can be caused by seepage from runoff or rising groundwater; it may be seasonal or catastrophic; and
- human activities, including bathing, cooking, dishwashing and washing clothes. Indoor plants, too, may be a significant source of high levels of humidity.
Climate Zones
In cold climates, moisture vapour problems are driven primarily by high indoor relative humidity levels and low outdoor temperatures during the winter. Mixed climates are exposed to both conditions and can experience both types of problems. Humid climates, in general, will be more of a problem than dry climates. Wind-driven rain is the main cause of leaks through the building envelope.
Red Dog Property Inspections can check for moisture intrusion in the following areas:
Roofs
A roof leak may lead to the growth of visible mould colonies in the attic that can grow unnoticed. Roof penetrations increase the likelihood of water leaks due to failed gaskets, sealants and flashing. The number of roof penetrations may be reduced by a variety of technologies and strategies, including:
- consolidation of vent stacks below the roof;
- exhaust fan caps routed through walls instead of the roof;
- adequate flashing. Oftentimes, inspection discovers missing, incorrectly installed or corroded flashings.
Plumbing
- Distribution pipes and plumbing fixtures can be the source of large amounts of moisture intrusion. If the wall is moist and/or discoloured, then moisture damage is already in progress. Most plumbing is hidden in the walls, so serious problems can begin unnoticed.
- The exhaust fan is one of the most important means of moisture management in the bathroom. A non-functioning exhaust fan overloads the bathroom with damp air. If the exhaust fan doesn’t turn on automatically when the bathroom is in use, consider recommending switching the wiring or switch. The fan should vent into the exterior, not into the roof void.
- The bathroom sink is a common source of moisture intrusion and damage. Although overflow drains can prevent the spillage of water onto the floor, they can become corroded and allow water to enter the cabinet.
- The use of a moisture meter can check for elevated moisture levels in the subfloor around the toilet and tub.
- Bathroom windows need to perform properly in a wide range of humidity and temperature conditions. Check to see if there are any obvious breaks in the weather-stripping and seals. Are there stains or flaking on the painted surfaces?
- Check showers and bathtubs. Is the caulking cracked, stiff or loose in spots? Are there cracked tiles or missing grout that may channel water to vulnerable areas? If some water remains in the bathtub after draining, it may be a warning sign of possible structural weakening and settlement in the floor beneath the tub.
Roof Void
- Inspections look for stains or discolourations at all roof penetrations. Chimneys, plumbing vents and skylight wells are common places where moisture may pass through the roof. Any such locations must be inspected for wetness, a musty smell and/or visible signs of mould.
- Check areas of the insulation that appear unusually thin
- Rust or corrosion around recessed lights are signs of a potential electrical hazard.
Foundations
Building codes typically require damp-proofing of foundation walls. The damp-proofing shall be applied from the top of the footing to the finished grade. Foundation walls should be damp-proofed.
In summary, moisture can enter a building in several different ways. High levels of moisture can cause building defects and health ailments.
