This is actually an article that I wrote about 10 years ago, but still applies today. Water in a basement is still a major headache, although there are many things that you can do to help prevent or at least minimize it. Let me know if you have any questions or comments.
Nothing is more frustrating than dealing with a wet basement. It can damage walls and flooring and ruin personal property items such as irreplaceable photo albums and family heirlooms. Insurance coverage for wet basements varies from state to state and company to company. But typically, the damage from water seeping in from the outside or backing up from the sewer is not covered by standard homeowner policies. In some cases, special coverage can be purchased to cover these risks, but it is usually limited in the types of personal property it covers and amounts of coverage that may be purchased.
It is up to each homeowner to know how to prevent water damage before it starts. This can be done through proper home maintenance and installation of systems intended to remove water before it gets into the basement.
This article will explain:
- What are the causes of wet basements
- Routine maintenance that can help avoid wet basements
- Repair options for wet basements
In order to prevent wet basements, it is important to understand where the water is coming from. There are four common sources of water that seeps into basements :
- Surface water running down next to the foundation walls
- Groundwater in water-saturated soils being pushed into the basement by hydrostatic pressure
- Storm sewer water from the municipal storm sewer system backing up into the home’s existing perimeter foundation drain and leaking into the basement (this can only occur if perimeter foundation drain system is connected to the municipal sewer system)
- Sanitary sewer water from a combined municipal storm/sanitary sewer system backing up into the home’s drain system causing sewer water to come up through sink drains and floor drains on lower levels.
Basement water problems are often unpredictable. A home may have had a dry basement for years, but start to have water seepage problems during a wet spring, even though the wet weather is not the worst that the house has seen in the past. Area development may cause groundwater levels to rise, may increase storm water runoff and overload storm sewer systems, or affect underground springs. The waterproofing on the exterior side of the basement walls may have developed cracks due to house settlement. Tree roots may have damaged and blocked the underground drain tile. Or, it could be as simple as forgetting to clean out the gutters.
When homeowners experience wet basements for the first time, it is imperative to determine if the water problems are going to reoccur or was it a one-time event. Essential to solving this question is determining where the water is coming from.
Controlling Surface Water
If this is the first time for basement water problems, the first thing to check for is the possibility that large quantities of surface water are 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:
- Are the gutters overflowing because they are blocked with leaves? 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. There are gutter-to-downspout connectors in the shape of a “Y” that widen the downspout hole. There are no standard tests to determine how well they perform, so the homeowner must rely on the word of the product manufacturer in regarding their effectiveness.
- Are gutters overflowing because there are an inadequate number of downspouts on the house? There are construction industry standards that are used to calculate how many downspouts are needed. Unfortunately, these calculations are rarely done on homes.The adequacy of the downspouts can be checked during a heavy rainstorm. The first step is to clean out the gutters as described in Item 1. Next, if you don’t mind getting wet, and it is not lightning, go out and look at the gutters during a heavy rainstorm after it has been raining heavily for at least 15 minutes.If you see any water overflowing the gutters, you have a problem. Any water overflowing 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 downspout if the other one gets blocked.
Most downspouts are 2 in. x 3 in. in size. The next standard size is 3 in.x 4 in. While this doesn’t seem like much, increasing 2 in. x 3 in. downspouts to 3 in. x 4 in. doubles the capacity of the downspout. 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.
- 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 accepted as the minimum distance needed to discharge the water coming off the roof far enough away from the house.When designing the gutter system on a new house or for gutter replacement, a little pre-planning helps keep the horizontal run of the downspouts out of the way and less noticeable. Many times the downspouts can be located so the 10-foot horizontal run can go along a fence or be hidden in a flower bed or by bushes.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.
- 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 downspout were mortared shut.Having the water from the roof drain down next to the footings can add to the 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 with concrete.Footing tile systems sometimes drain into city storm sewer systems. Many cities and towns do not allow rainwater from the roof to drain into city sewer systems because the rainwater would overload the city sewer system. This could cause the sewer system to back up into homes and create enough water pressure to lift manhole covers off the ground.
- 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 toward the house. If this is the case, the paving should be removed and replaced so it slopes away from the home.
- 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.Before putting in new sealant, install a closed-cell backer rod into the crack at the proper depth. Then install an appropriate sealant on top of the backer rod. The building material retail center should be able to help you select the correct sealant type and correct size backer rod. You will need to know the type of pavement (concrete or asphalt), the house material (concrete, concrete block, or brick), and the width of the joint. The backer rod will help prevent the sealant from cracking in the future.
- 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.When adding soil next to the house, make sure that at least 8 in. 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.
- 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.
- 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 in the zones 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.
If any of these problems are found, they should be corrected.
Controlling Subsurface Groundwater Under Hydrostatic Pressure
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. A basement is not built as watertight as a boat. Hydrostatic pressure can push water through hairline cracks.
Symptoms that point to subsurface groundwater under hydrostatic pressure 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, there are two primary methods of controlling subsurface groundwater.
- Install waterproofing on the exterior face of foundation walls.
- Install a perimeter drain system to relieve the hydrostatic pressure and discharge the groundwater away from the house by using a sump pump.
Installing waterproofing on exterior walls is probably not going to take care of the problem. Hydrostatic pressure can force water up from below the floor slab where it is impossible to install waterproofing after the slab is in place. Installing waterproofing on the exterior side of the foundation walls is expensive too. The earth must be dug away from the wall, then the waterproofing applied, and the earth filled back in. Any future movement in the foundations may open cracks in the wall that the waterproofing cannot bridge, allowing water to enter.
What is more typical is to install some type of perimeter drain system. The intent of the perimeter drain system is to relieve the 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:
Unfortunately, there are no published studies on the effectiveness of these systems. Nor are there studies on which type of system works best. Because effectiveness has not been historically measured, decisions must be based on what is believed to make the most sense.
It is believed that an underfloor drainage system is better than an above slab gutter system. This is because the underfloor drains are believed to relieve the hydrostatic pressure before the water reaches the bottom of the floor slab. If the drain pipe can be placed as low as possible without being placed below the bottom of the footing, it is assumed this is the best location:
The perimeter drain pipe can be placed around the entire building or a portion of the structure. Runs of drain pipe also can be placed below the middle of the basement floor slab to relieve hydrostatic pressure under the middle of the floor. The decision on how much drain pipe to install and where to install it is usually based on the past experience of the installer based on the magnitude of the basement water problem.
An important component of a perimeter drain system is the sump pump. If the sump pump fails to work during a heavy downpour, water could leak into the basement.
Storm Water from the City Storm Water System Backing Up Into House
In many older houses with basements (mostly pre-1980), there is a perimeter foundation drain outside the exterior wall, at the level of the basement floor, next to the footings at the time the house was built. A pipe was usually installed from the perimeter foundation drain to the street where it was connected to the city storm sewer system.
This can become a problem as the city storm sewer system becomes inadequately sized as more development causes more rain runoff. When this happens, the rainwater in the sewer system can get so high that water flows backwards toward the house. The perimeter foundation drain fills with water and releases large quantities of water into the soil next to the footing and basement floor.
The soil becomes water-logged and the water which is under hydrostatic pressure leaks into the basement. This is a common problem and many cities have outlawed the practice of connecting perimeter foundation drains to the city storm sewer system.
What should you do if you have this situation? Usually the installation of an interior perimeter basement drain system connected to a sump pump will take care of the problem. The interior perimeter basement drain system can usually pump the water out and onto the ground as fast as the water is backing up from the city storm sewer system.
If that doesn’t take care of it, the other, more expensive alternative would be to dig up and cap the pipe that is running from the house to the street from the perimeter foundation drain. However, this is not always possible because many times, this pipe is also draining sanitary waste from toilets and sinks in the house.
If you believe you have this problem, contact an experienced contractor for advice.
Sanitary Sewer Water from Municipal Sewer System Backing Up Into House
If the water is coming up through floor drains or sink drains in the basement, then the problem is likely water backing up from the municipal sanitary sewer system. This usually occurs in older sections of some cities that have combined sanitary and storm sewer systems. During heavy rains, combined sewer systems can become overwhelmed with water. This can cause sewer water to back up in the system and sometimes into homes.
This creates a mess for most homeowners because it usually means they are getting other people’s fecal waste backing up into their basement. To correct this, cities should update their sewer systems so the sanitary sewer and storm sewer are running in separate pipes. Until this work is complete, the homeowner can install backflow preventers that help stop sewer water from flowing backward into the house.
Unfortunately, because the city sanitary system works in conjunction with every house sanitary piping, the backflow preventer usually cannot be located on the house’s main sewer line. It usually requires several backflow preventers at all basement drain locations, such at every floor drain, every sink, and every toilet.
These backflow preventers require routine maintenance to make sure they are kept free of debris.
Water in the basement is one of the most frustrating problems a homeowner can face. Most homeowner insurance policies do not cover water damage from groundwater seepage or sewer back-up. Some insurance companies offer special coverage for this type of damage, but the type of items that are covered is usually very limited.
Because much of the cost to replace damaged items and clean up the mess is not typically covered by insurance or limited in coverage, much of the financial burden falls on the homeowner. Being prepared can help prevent these types of water problems.
- Inspect your house and make sure surface water and water from the roof are flowing away from the house.
- If you have finished areas in the basement and do not have a sump pump, consider installing a perimeter drain system with a sump pump.
- Practice semi-annual maintenance by cleaning out gutters at least twice a year and testing your sump pump before the start of the wet season.
If your house has had any basement water problems in the past, don’t risk further problems by not doing something about it. Assess your situation and take the proper steps to keep it from happening again.