BASEMENT WATER PROBLEMS

Basement leakage is one of the most common problems found in houses. While structural damage caused by leakage is very rare, water in the basement can be a major inconvenience and often causes damage to interior finishes and stored items. In addition, odors caused by mold, mildew, and lack of ventilation are particularly offensive to some people and can even be a source of allergic reaction.

It has been documented that at least 98% of all basements will leak at some point.

Unfortunately, wet basements cannot always be assessed for the severity and frequency of leaks during a one-time visit. There may or may not be clues that indicate a history of basement dampness. Even if visible, the clues do not always give an indication of the severity or frequency of the leaks.

I have found basement water leakage to be one of the most common defects identified during an inspection.  It can also be one of the most preventable. Basement water leakage is very often the result of improper exterior grading, settled/cracked or otherwise improperly sloped exterior paved surfaces, a lack of proper gutters, etc., and sometimes a combination of more than one of these. Very often, the cure can be as simple as correcting one of the above mentioned deficiencies.

Diagnosing Water Problems

The first step in curing a basement water problem is to determine the source.

• • Surface Water - A flow of water from run-off, rain, lot drainage, etc. can be exacerbated by poor soils. This type of water problem is generally restricted to the top four feet of soil.   This is an "external water source."

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  • Ground Water - Water from high water tables, springs, etc. can be exacerbated by poor soils. This type of water problem can extend from the surface down past the level of the basement floor.  This is an "external water source."

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  • Other Water - This category includes all other potential sources, whether they are inside or outside (i.e. condensation due to temperature differences, inside plumbing leakage, outside plumbing leakage, etc.).  This can be both an "external water source," as well as an "internal water source."

Start asking yourself the following: "When does the leakage manifest itself?"  Does it show up immediately after only heavy rains or every time it rains?  Is the leakage usually confined to one specific area? If so, can I associate an external source with this area (such as a window well, a poorly sloped driveway, etc.)?

It is very common to misdiagnose a basement leakage problem as being from an "external water source" (surface water or ground water), while it is actual coming from the "other water" category.  A leaking water line inside a basement wall, sewer backup through a floor drain causing basement flooding, condensation on water pipes & walls during summer months, all can make a localized area very wet.  This can easily be mistaken for basement leakage.

Look for some of the signs that indicate leakage.They can indicate what type of problem you are having and can also help in locate the source of leakage.  Some typical indicators are:

• • Dampness/Staining On Carpets - Indicate past leakage. Identify when and in which locations in the basement this occurs

  • Efflorescence - A whitish mineral deposit that many times is visible on masonry surfaces.  Usually the result of water passing through the wall.

  • Mold/Mildew - Usually located on or near an area that has seen prolonged moisture, giving the mold a chance to grow.  Often associated with an unpleasant odor.

  • Rust Stains - Sometimes seen on concrete floors and carpet, usually due to rusted metal feet on furniture. Rusty nails on baseboards, electrical boxes, etc., all indicate evidence of past moisture.

  • Stained/Darkened Wood - Can indicate past water absorption due to leakage.

  • Dampness/Staining Around Floor Cracks - Can indicate that water is forcing itself up though the cracks due to pressure, water table, etc.

  • Water Bugs - Look for evidence of small insects along the baseboards, behind sofas, in corners, etc.  Some types of insects gravitate towards areas of moisture.

Once you have determined the source of the leakage, you can go about taking steps to repair the problem.

Some Typical Problem Areas & Fixes

Listed below, are some of the more common causes for basement water problems.  Please refer to the "Full Depth Basement" diagram:

• • Poor exterior grading along the perimeter of the foundation walls is likely the number one cause of leaky basements.  Common sense tells us that we want surface water to flow "away" from a building, not to collect and pool adjacent to the foundation walls. A good "rule of thumb" is a 1-to-1 relationship in slope. In other words, at least 6-8 inches of slope away from the foundation walls, extending for the first 6-8 feet.  (items #1 and #2 in diagram)

  • Lack of adequate gutters can force water run-off from the roof directly onto the loose filled area of the "excavation ring".  Ensure that your gutter extensions are long enough, so they extend past the excavation ring. Replace any leaking or rusted gutters. (Item #2 in diagram)

  • Poor grading inside window wells as well as a lack of window well covers can greatly contribute to basement leakage.

  • Plant and shrub overgrowth, especially when very close to the foundation walls, can allow for water to penetrate next to the house by following the root systems.  

  • Landscape edging that is too high and doesn't allow for water to flow over it can act as a dam, restricting water from flowing away from the house.

  • Patch or fill any cracks in foundation walls.  Smaller cracks can be filled with caulk or mortar. Larger cracks, or cracks that extend well below the surface, may require special repairs (epoxy, rubber membrane, etc.), and a specialist should be consulted.

  • Cracked or poorly sloped paved surfaces that are adjacent to the house can greatly contribute to water intrusion.   Any open gaps in driveways, patio slabs, etc., adjacent to foundation walls should be caulked.

  • If the water level inside the sump basket is up onto (or close to) the entry drainpipe (see item #5), it can back up around the building, inside the drainpipe, creating a leakage problem. When water levels are this high, it's time to install a pump.

  • Patch / fill open cracks in basement floors with epoxy to prevent water from being forced up through them.

  • Wrap pipes with insulation. Some water lines are more prone to condensation than others, and consideration should be given to placing insulation wrap on them to minimize the potential for condensation & resulting dripping.

For more difficult basement leakage issues, there are other water control measures that can be undertaken.  Some of these include installation of new foundation waterproofing, new drainpipes, an interior perimeter drain system (often called a "beaver system"), etc.   These measures can be intrusive and very expensive.  They should be considered only if all other options have been exhausted. 

Typical Configuration For A Full Depth Basement Using Hollow-Core Masonry Foundation Walls 

(click image to enlarge)

The following information details what is happening in Figure 1 above:

• 1. Excavated Area – The area that is back-filled after foundation walls are constructed often referred to as the "excavation ring". This is the area of loose soil around the perimeter of any building with a basement. Loose fill is more susceptible to water intrusion than undisturbed soil. It is very important to maintain slope away from the foundations throughout this excavated area. One should also ensure that gutter downspouts are long enough that they don’t discharge into this area.

  2. Soil Settlement – Over time, the loose, back-filled area in the "excavation ring" can settle, causing water to flow towards the foundation walls.

  3. Soil Saturation/Hydrostatic Pressure – Water will have a tendency to flow through & saturate loose fill more readily than undisturbed virgin soil. The soil in the excavation ring can become saturated very quickly, exerting great horizontal changes on the walls, as well as forcing water into the block. Professionally applied foundation waterproofing/damp-proofing will help reduce chances of water entering into the foundation walls above the footing/drainpipe.

  4. Drainpipe System – Most of the water should be captured by the exterior drain system and drained away from the building.

  5. Sump Basket & Pump – Water is collected in a sump basket until it reaches a level that causes the sump pump to activate and pump the water out through a discharge line. 

  6. Sump Basket Discharge – Most municipalities do not allow sump basket water to discharge into the sanitary sewer. Sump basket water should be discharged outside.

  7. Discharge Line – The exterior discharge line should be long enough to extend past the excavation ring, so that the discharged water doesn’t seep back down and get recycled.

 SAMPLE POOL PROJECT STRUCTURAL ISSUES AND WATER LEAKS

Test Recommendations

We recommend that  destructive testing be performed by a certified lab to existing pool floor slabs and walls with minimum of three (3) concrete cores at random location along the pool slabs and walls. Additionally, we recommend that in (2) of the core holes, soil boring test ( SBT) be extracted below the pool to a depth of 25 to 30 feet, or as field conditions permit. The soil test will reveal the type and characteristics of the soil, density, N-values and if weak, unsuitable materials or voids exist below the pool foundations, or between patio structure foundations and pool shell wall. The (3) three optional concrete cores will be tested in the laboratory for compressive strength, thickness and determination of reinforcing bar spacing and size as well as the cover distance. During the concrete core test it also recommended to investigate whether void(s)  exist underneath the pool. ( Reference attached sketch for core locations at said pool).

 Alternative solutions

  Pressure grouting system: if after the core and void investigation underneath the pool result indicated that voids do exist, and then the following method or methods of repair is recommended, subject to engineer of record approval. This method can   be described as follows:

 Pressure grout the void and/or loose organic layer underlying foundation soils below all slabs and walls, of the existing swimming pool, deck tiles, stairs, foundations and walls where cracking occurred;

b.      All pressure grouting grid, depth and method of installation must be submitted to a professional engineer for review and approval prior to installation after securing a building permit. Pressure grout shall be extended beyond the loose materials, and voids and into clear firm granular material found at a depth of 5’ 9’feet below the existing ground surface.

c.       Pressure grouting grid, depth and method of installation, depth and placement geometry grid must be submitted by licensed foundation contractor to our office for review and approval prior permit application and subsequent installation. We recommend pressure grouting grid pattern of three feet by three feet (3’X3’) staggered under all affected pool structure, swim out, planter, spas, steps, and deck areas or as directed by the engineer.

d.      Cracked concrete slab; all failed, loose and damaged concrete deck marble or stone tile surrounding the pool must be removed, concrete and steel installed as per engineers design and repair recommendations. All backfill must be compacted to 100% density per approved drawings and specifications by geotechnical engineer. The following compaction, the removed marble and or stone tiles must be installed level, and to the grade and elevations shown on the drawing and existing specifications, subject to engineer recommendations and approval.

2.      If the concrete core test results found that the thickness of the wall and slab of the pool does not meet the requirement specified in the engineering drawings, minimum 6” walls and thickness, then adequate concrete thickness as depicted in the original drawings is recommended. Potential solution : is to pour new concrete layer with reinforcing steel bars ( to be engineered and  designed by our office or a PE) to meet the minimum requirements set forth in the Building code.

3.      The results of the core and soil tests as well as review of the pool drawings will dictate the final method or combination of methods for proper repairs. All structural repairs must be supervised and witnessed  by our office to insure compliance with repair plans and 2004 Florida Building Code.

4.      In the event that review of engineering calculations for balcony and pool reveal that the maximum soil bearing pressure has been exceeded, then alternative repair design, repair procedures, underpinning or removal and replacement of deep foundations will be warranted. The original design plans, dated 3-29-07 by Mr.Wayne Markham Bennett , PE. Noted that : “soil conditions on this site are sufficient for the design bearing of 2000 PSF. If other conditions arise, contractor must notify this engineer.”

All concrete shall have minimum compressive strength of 2500 PSI at 28 days.