Knoxville basements and their water
Knoxville sits in the Tennessee Valley, and many of its older homes have full basements or deep crawlspaces. Those spaces are cool because the ground around them is cool. That's useful in August and a problem when humid air gets in. Add heavy rain and a winter with plenty of freezing and thawing, and most basement complaints here come from three directions: condensation, storm water and cracks.
Knox County's license rule
Basement waterproofing on an existing house is residential repair work, and Tennessee has a county rule that reaches Knox County:
- For residential remodeling or repair work on an existing home costing more than $3,000 and less than $25,000, Tennessee requires a Home Improvement Contractor's license in Knox County.
- In Tennessee, a state contractor's license is required for a construction project totaling $25,000 or more, including materials, labor and profit, and the license must be in place before a price is bid or offered.
Ask which license the company holds and look it up on the state's Commerce and Insurance lookup before you sign.
Cool ground, humid air
NOAA's engineering weather data for Knoxville puts the groundwater temperature at about 61°F at 50 feet. Basement walls and floors in contact with that ground stay cool through the summer. Knoxville's summer air isn't as muggy as the Gulf Coast's, but NOAA still counts about 702 hours a year with a wet-bulb temperature at 73°F or higher, and the summer design point is 90°F with a 75°F wet-bulb. Warm, damp air meeting a 60-something-degree wall leaves water on the wall.
That's condensation, not a leak. Signs: dampness that appears in summer and disappears in winter, sweating cold-water pipes, and moisture spread evenly rather than below one crack. The fixes are humidity control:
- run a dehumidifier sized for the space, set to drain on its own;
- keep basement windows shut in muggy weather;
- insulate cold-water pipes and ducts;
- don't vent a dryer into the basement.
Storm water
NOAA lists a 100-year rainfall rate of 3.3 inches per hour for Knoxville. Water that leaks in during or right after a storm usually starts outside: an overflowing gutter, a downspout dumping at the wall, a flower bed that slopes the wrong way. Check those before buying an interior system, and ask any contractor whether it looked.
Winter: freezing, thawing and snow
NOAA lists about 50 freeze-thaw cycles in an average year in Knoxville and a 50-year ground snow load of 9 pounds per square foot. Snow piled against a foundation melts into the soil beside the wall, and repeated freezing of wet soil can open small cracks over time. Shovel snow away from the foundation, and ask a contractor to tell you whether a crack is shrinkage, which can be sealed, or movement, which needs a structural opinion first.
What a good assessment looks like
Before you get a price, you should get a diagnosis. Ask the company:
- where the water is coming from, and how it knows;
- whether it checked gutters, downspouts and grading;
- whether any of the dampness is condensation;
- whether any cracks show movement;
- what it would do first if your budget were small.
Comparing quotes
List the scope of each quote item by item: outside drainage fixes, interior drain length, the sump, the pump, a backup, wall membranes, crack repairs and a dehumidifier. Add the license held, the total, and the warranty terms, including whether the warranty transfers when you sell.