If you have a heating and ventilation system, ask a contractor to come and check it. Inspect your sump pumps and perimeter systems, including the doorway drainage system. You can replace them. Where necessary, place filters in the ductwork. Use a dehumidifier to reduce condensation on walls. This will work once you seal air and duct leaks. Efflorescence often occurs on the exterior near ground level as well as on the inside.
The only way to stop efflorescence is to eliminate the water. The time to anticipate and stop capillarity was when workers laid the foundation — from the outside. A proper foundation wall has a damp-proofing coat asphalt, plastic, or another impervious layer on the exterior to keep moisture out or the walls, and good drainage alongside the walls leading to a drain pipe at the bottom the footing.
A damp-proof layer between the footing and wall, or a coarse gravel bed beneath, stops capillarity from below. And a polyethylene plastic membrane or bed of coarse gravel underneath protects the concrete floor. Coarse gravel stops capillarity because the gaps between stones are too large to draw water. Consult your local building inspector and several contractors who specialize in basement moisture problems before taking this step. Efflorescence will definitely limit your success if you try to block capillarity from the inside.
Even worse, the mineral salts temporarily blocked from emerging on the surface of the wall, will crystallize below the surface, inside the concrete pores, and crack off the surface of the concrete.
The best solution is to keep as much water away from your foundation as you can. Moisture from high humidity condenses on and within cool walls. This moisture can also carry minerals to the wall surface. We recognize water vapor best as the humidity in the air. In fact, water vaporizes inside concrete from the pool of water that capillarity draws up. This water vapor spreads through the concrete, heading to wherever the air is drier.
Eventually, it filters into your basement, raising the humidity and increasing the feeling of dampness. Fortunately, you can successfully paint concrete above the tide line and block water vapor movement into your basement. Of the three types of paints readily available, alkyds enamels retard vapor better than latex acrylics and concrete-based coatings, though all block most vapor.
Runoff percolates through porous topsoil and then stops at the compact soil near the base of the foundation.
Hydrostatic pressure forces the water through gaps or cracks in walls and footings. Water also moves through porous walls by capillary action. A damp crawl space or wet basement walls and floors just after a storm or as snow melts are telltale signs the problem is runoff.
Look for ways runoff can enter your basement or crawl space. Check that the ground outside slopes away from your house at least 1 inch vertically for every 1 foot of horizontal travel. Then make sure downspout runoff isn't pooling or percolating into soil near the foundation during a storm, and that downspout seams aren't leaking; installing downspouts seams-out makes this check easy.
Next, check that driveway curbs are channeling runoff to the street. Look for unsealed cracks on the driveway surface, which can allow water to collect below grade. Some houses on hilly sites have a swale: a shallow trench with gently sloping sides and a gravel bed covered by topsoil and grass.
The swale catches runoff, channeling it past the house or off to other drain systems. Unfortunately, a swale can eventually clog with silt and so can the original underground footing drains buried at the base of your foundation. If you're dealing with a full basement, start by patching cracks in the foundation and sealing basement walls. For both basements and crawl spaces, you need to address outside entry points next by patching cracks in the driveway using cold-mix asphalt patching compound.
For a concrete sidewalk or driveway, use ordinary cement. Also, clean gutters so they won't overflow. If your home is not equipped with gutters, install them. And make sure the soil around the foundation slopes away from the house 1 inch per foot for a distance of 4 feet.
And add downspout extensions if needed so gutters drain 4 feet away from the house onto splash blocks. Many homes have an existing underground drainage system. Unfortunately, the system often breaks apart or fills with silt after several decades. You can call in a drain-and-sewer-cleaning contractor who will use a long power snake to try to clear the lines.
But often they just have to be capped off at the surface and abandoned. This comes from a time when basements were not used as habitable space. The sump pit usually contains a pump designed to lift the water to the ground surface outside the foundation wall. This pump can fail.
PROBLEM: If heating ducts are installed beneath a basement floor slab, the drainage system may be inappropriately left at a level higher than the duct. In effect, the duct becomes the drainage system. With standing water within the heating duct, there are potentially serious health consequences from mold contamination.
A drain tile and coarse aggregate can be placed under the ductwork. They can be severe if floor joists are not properly connected to the foundation wall, thus permitting the wall to move. Also, soil settling causes cracking. Places where walls meet rigid structures like the fireplace often crack as well. Usually, drainage removes the water from cracks, but repair may be necessary. The best way to approach any building problem is to first do the things that are easy and low cost.
Then proceed in a logical order doing the next least costly technique with the most positive likely result. With moisture problems, the best approach is almost always to remove or control the source of the moisture, not to try to stop it at the last line of defense.
First, the simplest and least costly techniques are to remove excessive internal moisture sources in the basement humidifiers, cooking and ventilate other sources clothes dryer, bathroom.
Second, if condensation in the summer is the problem, do not ventilate the basement directly with warm, humid air. Ventilation through an air conditioning system or with a dessicant-type heat exchanger is recommended. Dehumidification can be used as a means of reducing the symptoms of humidity and odor in a basement, but it is not a permanent or complete solution. In fact, if a dehumidifier is used in a basement with moisture problems, it may cause greater damage.
By drying out the basement air, moisture is drawn into the basement more rapidly causing efflorescence and spalling of concrete and further damage to interior finishes. It is appealing to solve a basement moisture problem with a membrane or coating on the inside.
It's less expensive than a drainage system and seems to work for a time in some cases. The water is still there, however, and eventually these systems deteriorate or simply move the water to another pathway into the basement.
Evaluate gutters, downspouts and surface grading: The recommended approach after removing interior moisture sources is to evaluate the gutters, downspouts and surface grading around the house.
These should be corrected first and may solve the problem. Interior or exterior drainage system: Then, if a moisture problem persists, proceed with an interior or exterior drainage system. All of these techniques are described below. If your goal is to finish a basement that has water problems, it is recommended to first deal with the water problem. Sub-slab depressurization system: An active sub-slab depressurization system including a washed-rock layer below the slab is recommended.
This draws moist air from beneath the slab and may help to reduce the amount of moisture vapor that enters the home through openings in the slab. It also assists in controlling radon and other soil gases. Sumps and other open connections to the soil outside the foundation and below the slab should be blocked and sealed.
A great number of basement water problems can be solved by handling rainwater and surface drainage properly using gutters and downspouts with extenders or splashblocks to carry the water away from the foundation.
Sloping the grade away from the house, which may require hauling fill to the site, is very important. This should be done before any below-grade drainage system is installed, since the above-grade corrections may solve the problem.
Even if a drainage system is required, removing water at the source as much as possible is necessary. Installing an exterior drainage system at an existing building is the most costly, but also the most effective water control approach. This requires digging up the area around the foundation and rebuilding it similar to a new house installation.
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