Wet basement problems
15 février 2011
Unexpected water in your basement can damage walls and floors, destroy carpeting, ruin furniture and quickly lead to mould. And perhaps the most upsetting of all: as basements are so often used for storage, water downstairs can ruin irreplaceable items like photo albums, antiques and family heirlooms.
When you experience a flooded basement for the first time, it’s imperative to determine if the water problems are going to reoccur or if it was a one-time event. Can you safely leave your property downstairs once you’ve got the mess cleaned up? Or does everything need to come upstairs immediately? What’s certain is that if water in your basement is a consistent problem, it’s time to start making decisions.
Determining where the water is coming from is essential to solving this problem.
Beyond observable flooding around your home and in your neighbourhood, there are four common sources of water entering basements:
- Surface water running down 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
- Sanitary sewer water from a clog in your home’s sewer line, the municipal sewer line or the 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
Each source has its own particularities and requires its own course of action. Find out more about your home’s drainage system by consulting a contractor or plumber.
If this is the first instance of water problems in your basement, the first thing to check for is surface water draining down next to the foundations. Water coming in at one location or only at the exterior foundation wall indicates surface water problems.
Here are some things to look for once you get outside.
Overflowing gutters: 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 also available to prevent leaves from getting into the gutters in the first place.
Overflowing gutters: downspouts
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 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 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; the second downspout can act as a backup 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.
Downspouts should extend three metres from your home. While many homeowners do not like downspouts extending out this far, three metres is the minimum distance needed to discharge water coming off your roof far enough away from 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.
Sealant around pavement that abuts the house sometimes cracks over time due to age or incorrect installation. If the sealant is cracked, it must be removed and replaced with new sealant.
Does your yard or the land around your home slope away from your home? It should. 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 20 cm is kept between the top of the earth and any wood or stucco on the house.
If there are large hills nearby sloping toward your home, and you think they may be causing the problem, a civil engineer may be required to analyze the situation and determine the appropriate solutions.
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 rain gauge so the system does not turn on when there has already been plenty of rain for the plants and lawn.
Did you find it?
You may have gotten a little wet as you investigated possible surface sources of water, but if you found a problem, the good news is that flooding in the future is preventable. Fix the culprit and your basement should stay dry.
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 rise 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.
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.
Storm water backing up into your home
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 too small when 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.
Usually, the installation of an interior perimeter basement drain system connected to a sump pump will take care of the problem. If it doesn’t, the (more expensive) alternative is 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. 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 backing up into your home
If the water is coming up through floor drains or sink drains in the basement, then the problem is often water backing up from the municipal sanitary sewer system. 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.
There are other possible explanations too. Sewer backups can be caused by individual service lines being plugged by grease, waste, tree roots, breaks in pipes or saturated ground. Sewer mains can also be plugged by vandalism or large items dropped down manholes.
This kind of flooding is an enormous problem for homeowners, as it’s largely out of your control and probably means fecal waste backing up into basements. Not only is it disgusting, but it can also be a serious health hazard.
In order to keep your individual lines clear, you can install backflow preventers that help stop sewer water from flowing backward into the house. Proper maintenance of your individual lines (for example, pouring tree root killer down your toilets once a year) can also go a long way in preventing sewage backups. Still, the problem is often out of your control.
Sewage in your basement means a major cleanup and a lot of uncertainty about future problems. If it’s something you’ve seen in your home, you’ll have to get your city government involved. At the very least, be aware of the problem and don’t leave anything valuable near your downstairs drains.
Ces conseils sont fournis à titre informatif et préventif seulement. Ils sont d’ordre général et n’engagent pas la responsabilité de Desjardins Assurances. La vigilance est de mise et il est recommandé de consulter un expert en la matière pour obtenir des conseils complets et pertinents pour chaque situation.
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