FSM Service Tech

Why is my Basement Wet in the Summer?

Summer is here, but despite the hot weather, rainstorms are very common.


On hot summer days, a damp or wet basement is still very common. Ever wonder why your basement is wet during the summer? Here are some reasons why:

  • Humidity – One of the reasons why the basement is wet during summertime is humidity. Humidity is the concentration of the water vapor present in the air. The heat and humidity cause the ground to expand and contract, and it is easier for water to evaporate into dryer air than into more saturated air. Air humidity is greater in the summertime simply because warm air can hold more moisture than cold air. This humid indoor air increases the risk of basement water damage because a lot of finished basements use drywall. Drywall is a gypsum plaster pressed between two sheets of paper, and condensation can easily soak through and saturate the walls.
  • Ventilation with Humid Outside Air – As the walls warm the air, moisture is created just like condensation on a cold drink on a hot summer day. Humid climates are over ventilated due to duct leakage and induced air change from internal air pressure effects due to unbalanced airflow and door closure.
  • Capillary Suction – This occurs in fine voids (capillaries) with wetting surfaces and is caused by surface tension. Water can be drawn upward through small pores in concrete footing and slab and laterally through walls. Capillary suction moves moisture through porous materials.
  • Air Leakage Through Walls and Floor – Also called sweating, condensation shows up as water droplets, wet spots, or puddles on basement floors. In most houses, a stack effect is created because warm water air rises.
  • Water Vapor Diffusion Through Foundation Walls – Even without leaks, small amounts of moisture in the form of water vapor can pass directly through a building’s envelope, through a process called diffusion. It’s dependent on the permeability of the material and the driving force of the vapor pressure differential. Vapor retarders such as foundation waterproofing and polyethylene slow down this process.
  • Rain or Groundwater – Water often makes its way into basements due to poor grading. The ground around your foundation should slope away from the house, not towards it. If draining in the wrong direction, water will accumulate against your foundation and eventually make its way inside.

These are just the common reasons why basements are wet during summertime. The question is, is it going to be a problem? Not only does a wet basement feel and smell nasty, but it also poses a great risk to your home’s value. Left unchecked, basement moisture can ruin floors and walls, encourage mold, even damage roofing. Some wet basements are easy to cure simply by clearing gutters and by diverting gutter water away from the foundation. Other ways to stop your basement from being wet during summertime are to add Insulation. This can reduce condensation by making cold surfaces warmer. Air-sealing prevents cold air from getting in and keeps the basement interior warmer. Insulating basement foundation walls creates a thermal barrier between the cold wall and relatively warm interior air.

Protect yourself from a wet basement this summer by contacting us at FSM today! We offer free moisture control quotes to homeowners in our Michigan service area. Each quote includes an on-site inspection and written quote. We proudly serve Metro Detroit, Ann Arbor, Saginaw, Traverse City, Grand Rapids, Lansing, Kalamazoo, Battle Creek, Muskegon, Jackson, Troy, Bloomfield Hills, Sterling Heights, Charlevoix, Flint, Clio, Gaylord, Madison Heights, Midland, Lexington, Mt. Pleasant, Adrian, and the surrounding areas in Michigan.

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