Spring is the season for possible flooding due to temperature rise and melting snow. While all of our homes are built with sump pumps, exterior foundation coating, and drain tile, the source of most basement moisture sources is rainwater & groundwater. See below information from the City of Madison Engineering Dept for some valuable information heading into spring:
Rainwater and Groundwater
In a one-inch rain, 1,250 gallons of water fall on the roof of a 2,000-square-foot house. Without proper grading, gutters, and downspouts, some of this water flows into the basement. The below-grade water table can also rise due to flooding or seasonal site conditions. This is why drain tile systems are recommended around basement walls even in sandy or gravel soils.
Under normal conditions basements are designed to be dry (if somewhat damp/humid) spaces. In large part humidity is unavoidable because the concrete used to construct basements is a porous material and will allow water/ moisture to pass through it at a very slow rate. New construction is designed to avoid serious, free flowing water problems in many ways, including: provision of sump pumps, exterior basement coatings and extensive tile/pipe drainage systems surrounding the foundation. Generally even these new homes need to have a dehumidifier operating in these spaces to keep humidity levels within the recommend range. Generally the recommended humidity level for basements is between 40% and 50%. If basement moisture is allowed to reach 60%, the basement will likely have a musty smell.
And please remember to keep your sump pump plugged in at all times!