How Does Water Get In My Basement?

In order to prevent wet basements, it is important to understand where the water is coming from.

  • Surface water running down foundation walls
  • Groundwater in water-saturated soils being pushed into the basement by hydrostatic and/or lateral pressure

When homeowners experience wet basements for the first time, it is imperative to determine if the water problems are going to reoccur or if it was a one-time event. Essential to solving this question is determining where the water is coming from.

Controlling surface water

  1. If this is the first time for basement water problems, the first thing to check for is surface water draining down next to the foundations. Water coming in at one location and only at the exterior foundation wall are typical indications of surface water problems. Here are some things to look for:
  2. Keeping gutters clean of debris should be a part of every homeowner’s routine maintenance program. Depending on the surrounding trees, gutter cleaning may be required a few times a year. Products are available to prevent leaves from getting into the gutters.
  3. Are gutters overflowing because there are not enough downspouts on the house? If you don’t mind getting wet, you can do a self-check (your gutters must be cleaned out first). After at least 15 minutes of heavy rain, check your gutters. If you see any water overflowing, you have a problem. Any water over flowing out of the gutters is running down next to the house foundations. Even if the water is not getting into the basement, it could be causing unseen problems like eroding soil from under the house footings, which can lead to cracking of walls and ceilings. The easiest solutions to overflowing gutters are to either add another downspout on that run of gutter or to increase the size of the downspout. The best solution between these two is probably adding another downspout because the second downspout can act as a back-up if the other gets blocked. However, if you choose to replace the existing downspout with a larger one, make sure the contractor increases the size of the corresponding hole in the gutter. It doesn’t do much good to install a larger downspout if the gutter hole is left small.
  4. Do the downspouts extend at least 10 feet from the home? While many homeowners do not like downspouts extending out this far, 10 feet is the minimum distance needed to discharge water coming off your roof far enough away from the house. Be careful not to discharge downspouts too close to your neighbor’s property. Most towns and cities have ordinances that prevent downspouts from discharging too close to the property line and causing water problems for neighbors. Your local building safety or inspections department can provide you with the minimum distance.
  5. Do the downspouts drain into the footing tile system? It was common practice in the first half of the 20th century to have the downspouts draining into the footing tile system around the house. Vertical tiles were installed up from the footing tile system at each downspout location and the downspout was inserted into the open end of the tile. Sometimes the gaps around the down spout were mortared shut. Having the water from the roof drain down next to the footings can add to hydrostatic pressure problems, especially if the footing tile is leaking or blocked. This can occur over time due to soil movement or damage from tree roots. If the downspouts are draining into the footing tile system, the downspouts should be modified so they drain onto the ground and discharge at least 10 feet from the house. The vertical tile should be capped with a preformed cap or concrete.
  6. Are there any paved areas next to the house that slope toward the house? Sometimes paving settles over time and water flow can change direction towards the house. If this is the case, the paving should be removed and replaced so it slopes away from the home.
  7. At paved areas that abut the house, is there sealant in the joint at the pavement-house wall intersection, and if so, is it cracked? Sealant sometimes cracks over time due to age or incorrect installation. If the sealant is cracked, the cracked sealant must be removed and replaced with new.
  8. Is the ground around the home sloping away from the home at least 10 feet? Look for any depressions in the ground next to the home foundation walls. If any are found, fill in with dirt so the water drains away from the house. Use a clay-type soil that sheds water instead of sandy soil that allows water to soak into the ground. Make sure that at least eight inches is kept between the top of the earth and any wood or stucco on the house. If this cannot be done, the house may have been built too low and to correct it may be too expensive to be feasible.
  9. Are there any hills sloping down toward the house that may be the source of the water? If this is the case, a civil engineer may be required to analyze the situation and determine the appropriate solutions.
  10. Is there a lawn/shrub irrigation system discharging too much water next to the house? Avoid placing lawn irrigation next to the house. If this cannot be avoided, instruct the installer to limit the amount of water dispersed next to the house. Make sure the irrigation system includes a working rainstat so the system does not turn on when there has already been plenty of rain for the plants and lawn.

Controlling subsurface groundwater

If no surface water sources are found, then the source of the water is likely subsurface groundwater under hydrostatic pressure. Unfortunately, subsurface groundwater problems are more difficult and more expensive to fix than surface groundwater problems. When the groundwater levels outside the basement rises above the level of the floor, the basement acts like a boat in a pond. If a boat is sitting in water, water will leak in through any open cracks or holes. It works the same way with a basement. Hydrostatic pressure can push water through hairline cracks. Symptoms of this are water coming up through cracks in the basement concrete floor or water coming in at multiple locations. If you have an older house within town and the house has a basement with no sump pump, it is likely the perimeter foundation drain system connects directly into the city storm sewer system. If the level of the basement is below the street level, there is the potential of storm water backing up in the city storm sewer system and being pushed into the perimeter foundation drain system. This can saturate the soils around the house at the basement level with storm water under hydrostatic pressure, causing water to leak in. Another source of subsurface groundwater is an underground spring. No matter where it is coming from, the best way to control subsurface groundwater is to install some type of perimeter drain system to relieve hydrostatic pressure. The groundwater is pushed into the drain system and not into areas where it can damage carpets, walls or belongings. The water drains by gravity into a sump pit where a sump pump discharges it out of the house. There are two basic types of drain systems for wet basements. One is a perimeter above-slab gutter system installed at the base of the exterior foundation walls on top of the floor slab. It doubles as a base material for the wall. The other type of drainage system is a below slab perimeter drainage system. The below slab system requires the partial removal of the concrete floor slab and installation of drainage pipe making it more expensive than the base gutter system. It is believed that an under-floor drainage system is better because the under-floor drains are believed to relieve the hydrostatic pressure before the water reaches the bottom of the floor slab.

 

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