Ask The Experts

Foundation, Drainage, & Water Control

I have heavy mildew growing on the wood ceiling of my porch. I have repainted it several times, but it just reappears within a year or two. What can I do to prevent this?

The growth that you see is a mold (technically mildew is a type of mold), and like all molds it will grow anywhere that organic materials exist and moisture or dampness is sustained for periods of more than a few days.

If the porch is an open type, it will be exposed to exterior moisture and humidity, but the ceiling won’t receive the drying effects of sunlight or wind. This makes the porch ceiling quite vulnerable to mold growth. To make matters worse, moisture will condense on the ceiling during periods of high humidity whenever the ceiling is cooler than the adjacent air. This may be a very common occurrence as exterior temperatures fluctuate throughout the seasons. You should thoroughly wash the ceiling before repainting and add a mildewcide to the paint. A mild chlorine solution is often used for mold cleaning purposes, but the EPA recommends detergent and water. This will reduce, but may not prevent, your mold problem. In our experience, we have found that vinyl or aluminum soffit coverings used as a ceiling are quite resistant to mold growth and may be your best solution.

If the porch is enclosed, moisture from the ground below the porch can rise into the enclosed space and condense on the cold surfaces in fall and winter, causing the mold growth. We find that seasonal homes are very susceptible to mold growth on interior finishes or furnishings from this same source. The best solution in this case is to fully open and air out the space below the porch or cottage, if feasible. It is also helpful to dry the space below using improved drainage around the structure and a good vapor barrier on the ground in the crawlspace. Excess moisture will be prevented from rising from the ground into the enclosed porch or cottage. In addition, it may be wise to provide a modest amount of heat to the living space during the heating season to help effectively dry the air.

We have had a slimy brown substance coming out of the wall of our basement. About 6 years ago they redid the street behind our house, and this is when the problem began. What should we do about it?

While the brown water is undoubtedly objectionable, it is essentially harmless. The slime is almost certainly iron bacteria. Iron occurs naturally in the soil in varying concentrations, and is often found in well water. When the concentration of iron is high enough, iron bacteria live off the ferrous oxide, and produce the slimy brown mess that you see. When the street was redone, they may have changed the direction of water flow, resulting in the seepage into your basement. The best thing that you can do is to seal up the hole. It may be possible to do this from the interior with hydraulic cement. But to be fully effective you may have to excavate on the exterior to the point of entry and seal the outside of the foundation.

I have a fifty year old home with a finished rec. room in the basement, including a wood floor. The wood floor is starting to get soft in some areas. What can I do to prevent this?

As you have probably surmised, the softness in the floor is most likely due to chronic moisture and resultant decay, although termites might also be the culprit. This is not a good situation. In fact, moisture susceptible finishes in a basement are almost always a bad idea to begin with. Even in a well sealed basement with good exterior drainage and proper landscaping around the house, major weather events or accidents are still likely to result in incidences of moisture buildup and damage to basement finishes. Wet interior finishes will result in decay if the moisture is chronic, and at the very least, staining and mold growth if the water entry is only periodic.

At a minimum the wood floor in your basement should be removed. We also recommend that the finishes be removed along the base of the walls, and the walls inspected for decay. Any moldy or decayed components that are discovered in the walls should be removed. In our opinion it would be best to remove all carpeting, gypsum board, and wood finish materials from the basement if repeated moisture damage is occurring.

It isn’t necessary to finish the basement in moisture sensitive materials to have usable living space. Simply painting the concrete floor and foundation walls, if in good condition, may result in a pleasant environment without major risk. For higher quality and more comfortable finishes, vinyl composition tiles or ceramic tiles applied directly to the concrete make a mold resistant and durable floor covering. And, using pressure treated lumber for wall framing, closed cell foam insulation, rather than fiberglass, and cement board or other moisture resistant wall finishes near the floor, will provide walls that are good looking, energy efficient and durable.

Don’t forget to check on your gutters and exterior drainage to try to reduce the amount of water close to the house that might seep into the basement. It may also be necessary to install a basement de-watering system. The most common type consists of crushed stone and drain tile installed below the basement floor adjacent to the foundation walls. The water would be directed to an appropriate exterior discharge point or to a sump pump.

One block foundation wall in my basement has a long horizontal crack about a third of the way down the wall, and is bowing inward about an inch, and I think it’s getting worse. I added some support posts to reduce the load on the wall. Can I just reinforce this wall or do I have to replace it?

You have numerous repair options available to you. We can review the most common, but first we ought to deal with the causes for the movement. Usually block foundation walls push inward due to pressure from the ground on the exterior as it expands due to freezing. The wetter the ground, the more ice will form in the soil and the more pressure there will be against the wall. Improving exterior water control with proper grading and gutter maintenance may significantly reduce or prevent further movement. Also, while it may not seem logical, your foundation wall was more stable with the weight of the house still resting on it. Think about how much easier it is to knock over a stack of children’s blocks with no weight on top than when you’re pushing downward on the stack. If your wall has only bowed inward one inch, you should probably put the load back on the wall.

Cracks and bowing foundation walls are always “red flags” to buyers, but replacement of the affected foundation in this case really shouldn’t be necessary. The easiest form of reinforcement is to install masonry pilasters or steel girders mounted vertically against the wall. They would be firmly anchored to the concrete basement floor and to the wood floor framing above. The appropriate spacing between the pilasters, the size of the pilasters, and the best anchoring methods would depend on the overall condition of the block wall, the height of the wall as well as the exterior grade, and the type and configuration of your floor framing. While common sense can be a good guide, these are determinations best made by a structural engineer. Once the reinforcement has been installed it would be wise to seal the horizontal crack with masonry cement or grout to help in monitoring for any further movement.

I am interested in buying a forty year old ranch type house with a concrete foundation, but it has a couple of visible vertical cracks in the foundation. Is there any way I can know if this is a serious problem or not?

Most concrete foundation walls have one or more cracks. Masonry shrinks as it cures, often resulting in visible cracks. In most circumstances this is considered normal and acceptable. If the cracks are ¼ inch or less in width, and show no evidence of corresponding settlement or other movement, it is likely that the cracks are related to shrinkage and are not a cause for concern. However, if the cracked wall is visibly bowed inward, or is higher on one side of the crack than the other, or if the wall has shifted inward on one side of the crack compared to the other, then actual foundation movement has occurred and, depending on the degree of movement, further evaluation may be appropriate. Slight movement observed at foundation cracks is common as the house foundation and adjacent soils settle into position following the initial construction process. This is not necessarily serious, but monitoring is always wise.

Low quality concrete, poorly designed footers, inadequate soil compaction, and poor drainage are all conditions that could result in serious structural problems. Any evidence of significant foundation movement should be professionally evaluated before purchasing the home. If you are concerned with cracks in a home that you already own, you may wish to measure, record and date the degree of cracking or movement so that you can follow-up with new measurements over the next year or two, and determine if any of the movement is ongoing. In addition, improving the drainage around a home will help ensure that minor movement does not become a major structural concern.

I have had water problems in a crawlspace below an addition on my house. I re-graded the exterior and fixed the gutters, and I have added a plastic vapor barrier on the ground, but I still have excess dampness and there are puddles on top of the plastic. What else can I do?

I would suggest walking around the exterior during a hard rain to look for any weaknesses in your exterior water control system. Be suspicious of any drains that might be damaged and misdirecting water, check around window wells for water buildup, and make sure that any mulch or gravel is not hiding ground that might be sloping toward the house. Assuming that there is nothing more to be done on the exterior, the next steps may involve some additional work in the crawlspace. You may need to install a sump pump with a sealed cover in the crawlspace. You should use a heavy duty plastic sump pit designed for the purpose and a submersible pump with the switch mounted on a vertical float rod. Water from the pump should be piped to the exterior, and the pipe should be properly pitched to prevent freeze problems in winter. In order for the sump pump to work properly you may need to re-level or channel the ground below the plastic sheeting in the crawlspace to direct the water to your sump location. The integrity of your plastic vapor barrier may also need to be assessed. It should be well lapped and well sealed. Depending on the water source, it may be wise to run the plastic up the foundation walls to an attachment point at the top of the walls. If the foundation is made of concrete blocks, look for any open cores on the top of the blocks. These should all be sealed with foam insulation board, spray foam, or plastic sheeting to prevent moisture from exiting from the block cores into the crawlspace air. Make sure any vents to the exterior are fully closed and sealed, and if possible, open the crawlspace to the adjacent full basement to allow some air exchange. Another step that might be helpful would be to install a room dehumidifier in the crawlspace, piped to drain to your sump pit or other appropriate location. These units are expensive to operate however, so you may want to consider blowing a small quantity of air from the living space into the crawlspace instead. This air will be warm and dry for a presumably lower cost and will help reduce the moisture in the crawlspace. If the air from the living space is humid from summer heat, the cool crawlspace will cause moisture to condense out of the air, making things worse, so this idea will only work in summer if you air condition your living space.

I never used to have water in my basement, and now I’ve had water three times when we’ve had heavy rain. What has changed and what can I do to stop it?

No basement is guaranteed to be immune to water entry if the weather is bad enough, and we have certainly experienced some weather extremes in the last couple of years. We have seen some instances locally where underground water patterns have been apparently changed, just as streams and rivers have been changed, by the extreme conditions we have recently experienced. This has resulted in chronic water entry where none occurred before. However, in most cases water entry during extreme weather is the result of readily correctable conditions above ground around the house. Your first line of defense against water entry is the slope of the ground at the foundation walls. The ground should be sloping away from the house on all sides to a distance of at least six feet. Your house should in essence have a shallow dam of dense soil against the foundation walls. We repeatedly see people attempt to control water by installing crushed stone against the foundation to provide drainage. The problem is that this drainage only directs the water toward the foundation, not away. If the surface of the ground is hidden by crushed stone or mulch, the poor pitch toward the house may be hidden. The gravel or mulch will have to be temporarily removed to improve the grade.

The second line of defense is your eaves troughs. Gutters should be properly sized and properly pitched to provide adequate water flow. Larger gutters or more downspouts may improve water control. Make sure the gutter downspouts are well secured and have adequate tailpieces to ensure that water is directed well away from the house. Finally, the most likely cause for increased basement water entry may be loose and sagging gutters, or clogged gutters, resulting in concentrated excess water against the house. Take a walk around your house in the next heavy rain, and see what happens to the water. You’ll probably be able to make the diagnosis yourself.

Last spring I started getting a lot of water on the rear wall in my basement. It pretty much went away by mid summer, but some of my stuff got ruined. It doesn’t seem to leak during the fall or winter. What would be best to stop this seepage?

Based on the information in your question, we suspect that the moisture isn’t due to leakage at all, but rather due to condensation. Under the right conditions, so much condensation will occur that the buildup can result in puddles and slowly flowing water on the floor. Condensation occurs because cold air can’t hold as much humidity as warm air. Consequently the moisture in the air condenses on cold surfaces. In the springtime we can have ideal conditions for this to occur. The ground remains cold in the spring, while the air warms quickly and becomes humid. If warm humid air enters the basement, the moisture will condense on the cold foundation walls. The condensation will be worst on the surfaces that are the coldest, which will typically be the north facing walls. The worst thing to do on a warm humid day is to open the basement windows and allow the humid air to enter the basement. If you’re worried about moisture in the basement, the best thing to do is to keep the windows closed and install an automatic dehumidifier, set up to flow to a sink or floor drain so you won’t have to remember to empty the bucket.

If you are unsure whether the moisture you’re seeing is from leakage or condensation, you can try a simple test. Dry a section of the wall and tape a large piece of aluminum foil tight to the surface. If moisture appears on the face of the foil, you’ll know that condensation is the culprit. If the foil surface is dry, but the wall behind is wet, then it may be that moisture is seeping through the wall. In either case though, you’ll want to control excess water around the exterior of the house and dehumidify the interior.

I have white fuzzy stuff growing in several areas on my foundation walls in the basement. Is this mold, and how do I get rid of it?

While white molds are common, we are unaware of any white molds that grow on masonry. What you are seeing is almost undoubtedly efflorescence, not mold. Efflorescence is actually mineral deposits left behind as moisture that has moved through the foundation walls evaporates from the interior surface of the masonry. Since the minerals can’t evaporate, they remain and can build up to form fuzzy looking collections of small crystals. They are harmless, and can be easily washed off with a sponge or brush, and water. But, expect them to return over time unless the moisture conditions are corrected. The moisture is passing through the walls because the masonry is porous, or small cracks are allowing the seepage to occur. The moisture that is entering the house through the foundation walls can result in mold growth and damage to other materials in the basement, or even the rest of the house. So control is recommended.

The first step is to make sure that your gutters and downspouts are working well, and that the ground is sloping well away from the house. Your foundation should have a water resistant coating on the outside from the surface of the ground to the bottom of the walls. This may have been omitted, or poorly applied. Since a proper application would require complete excavation around the house, we suggest applying a masonry sealer on the interior surfaces as an alternative. The best type of interior sealer is a cementious type of coating, such as Thoroseal, which comes in a powder form to be mixed with water for application with a barn brush. If the foundation walls have already been painted, then a paint based sealer may be your best option. Any loose material should be brushed off the walls before applying any sealer. If you are seeing any significant amount of efflorescence, you should probably also install a dehumidifier in the basement to control moisture in the air. To avoid dumping the bucket every day, a means of automatic drainage is recommended. A trap should be employed if the dehumidifier is set up to drain directly into plumbing waste pipes. While efflorescence is harmless, the moisture that leaves the white fuzzy stuff behind is definitely not harmless, and should be controlled.

My new house was completed in the late spring. The basement has been wet since we moved in, and now I’m getting water on the inside of my windows. The builder says that this will go away. I’m worried about mold. What can we do to stop it?

It is possible that the perimeter drainage system around the house is not adequate, that the gutters are not installed, or installed properly, or that the immediate ground around the house is not sloping away adequately, allowing water to enter the basement. This excess water would then evaporate and move throughout the house. It is also possible that the clothes dryer is not venting properly, a humidifier on the furnace is set too high, or other issues involving your lifestyle are producing too much moisture. However, the far more likely scenario is that the moisture is due to the normal drying process of the materials used to build your house. Massive amounts of water are released from the wood framing, concrete, and plaster as these materials dry during the first year after construction. Moisture in the air condenses on cold surfaces, so it is natural that the concrete walls and windows would become wet. Even the best windows are relatively cold compared to the insulated walls in your home, resulting in condensation when there is too much moisture in the air.

You are right to be concerned about mold growth. Chronic moisture is the key added ingredient necessary for mold growth in the house. The excess moisture may also cause staining or other damage to the finishes in the house. Your best approach will be to temporarily dehumidify the space with a couple of standard residential dehumidifiers. One in the basement and one in the living space should be sufficient to keep the moisture levels in check. The dehumidifiers should reduce the moisture sufficiently if set at a rough middle point between the highest and lowest settings, or “normal”, or if the unit has a relative humidity reading, 40% or less. Dehumidifiers require relatively warm temperatures to work properly, so you may have to keep the basement 65 degrees or higher. If the units run for extended periods of time and either ice-up or don’t fill with water, they are not working properly. In our climate it may be wise to run a dehumidifier in the basement every summer, in any case.