Causes and Remedies of Moisture in Basement

10/16/2019

Though moisture related problems are common in basements, these issues are often not understood or treated with importance. Moisture in basement is a serious concern for basements that are connected to the building’s living space via ductwork or other openings. Presence of too much moisture is not only uncomfortable and annoying, but it may also be responsible for health related concerns for the occupants. Damp subfloor areas provide the perfect conditions for the growth of moulds and mildew. If left unattended, subfloor moisture also has a negative impact of the structural integrity of the building. Therefore, before finishing a basement, it is important to deal with the moisture related problems.

Understanding the Problem:

Correction of basement moisture problem starts with understanding the source of water and the mechanism that is allowing the moisture to enter the basement. Sometimes, basement moisture problems are also linked to poor construction with settling foundations, cracking, etc. One of the most common structural issues leading to this problem is the lack or a good downspout and gutter system. Also, it is important for the ground surface to slope away from the building foundation. Often times, basement moisture is also caused by a non-functioning or missing subsurface drainage system.

If your basement has a moisture problem, it can be identified by symptoms such as

• Standing water on floor.
• Odour, mold and mildew.
• Deterioration of wood or carpet
• Damp, humid air.
• Water trickling out of walls.
• Staining and blistering of wall covering.
• Rot and decay of joists, wood headers, columns, and sill plates.
• Spalling of concrete or masonry.

Moisture Sources:

• Rain and Groundwater: As a result of a 1-inch rain, a 2,000-square-foot house experiences approximately 1,250 gallons of water falling directly on its roof. Some part of this water will certainly make its way to the basement, if the downspouts, gutters, and grading systems are not proper. Seasonal rain or flooding may also raise the below-grade water table.
• Interior Sources: Different living habits and activities of the occupants are also responsible for the creation of moisture inside basements. Some common sources include cooking, showering, and using unvented clothes dryers and humidifiers.
• Humid External Air: The basement windows are often kept open during the summer to allow fresh air to come in. However, this humid and warm air tends to condense on the cool walls and floors of the basement.

Mechanisms of Moisture Movement:

• Capillary Suction: This mechanism involves moving moisture through materials that are porous in nature. Through small pores in concrete slabs and footings, capillary action can draw water upward. In many basement walls, a ring of dampness is created by this effect.
• Air Leakage: Warm air always tends to rise, and sometimes creates a stalk effect. As a result, a negative pressure is induced on the basement, drawing moist air through all openings and cracks into the foundation.
• Vapour Diffusion: This refers to the vapour state movement of moisture through a material. In a basement, through concrete walls and floors, vapour tends to diffuse from the wetter ground towards the relatively drier basement interior.

Causes of Basement Moisture Problems:

• Inadequate Grading
• Missing or defective downspouts or gutters.
• Window wells with improper design
• Faulty drain tiles and sump pits
• Improperly designed underslab ducts causing improper drainage
• Structural cracks

Solutions to Basement Moisture:

If you are facing moisture problem at home, the first thing you should do is to control or remove the moisture source rather than making a last minute effort to stop the damage. The easiest and the most inexpensive way to do this is the elimination of all sources of excess moisture from the basement.

Though dehumidification can help reduce basement humidity and odour, it is not a comprehensive solution. In fact, as it dries out the basement, it also rapidly draws moisture into the basement. Interior coatings of membranes can be used, but this is a temporary solution because these systems tend to deteriorate over a period of time.

Recommended Approach:

• After removing the sources of interior moisture, evaluate the downspouts, gutters, and surface grading. Your moisture problem may get solved by these corrections.
• If the problem still persists, proceed with an exterior or interior drainage system. If the basement has water problems, deal with them first.
• It is also advisable to use a sub-slab depressurization system with a washed-rock layer underneath the slab. These systems are capable of drawing out moist air trapped under the slab and helps control soil gases.

Finally, the most common and effective way to control basement moisture is the installation of a subfloor ventilation system. Talking about sub-floor ventilation, ExtractAir is one of the most trusted names in the industry with a thorough understanding of all aspects of subfloor moisture and its remedies. Please contact our experts today to discuss your subfloor moisture problems.