Basement moisture

Serious problems of dampness and moisture are often accompanied by unpleasant odours. Before deciding to ventilate in the winter or to install a dehumidifier in the summer, try to locate the source of the problem.

What are the indoor sources of humidity?

During the summer, humidity can be the result of condensation that occurs when warm, humid air comes into contact with cold basement walls. If your cold water taps seep with moisture after you use them, it is possible that the lower part of the foundation walls are experiencing the same phenomenon. A poor quality or badly installed vapour barrier will allow the water vapour contained in the warm air to travel through the walls via the electrical boxes or window frames.

If the concrete underneath the wood or carpeting has not been protected by a damp proof membrane, the origin of the odour is usually rotting wood or damp carpeting.

What are the outdoor sources of humidity?

Water infiltrating through cracks can also be the cause of such a problem. Ground that slopes down toward the basement rather than away from it, or rain gutters that empty into a tile drain or a drain that is blocked by leaves might also be the source. Other potential causes are window edges that have become blocked with organic deposits, or a perimeter drain that is clogged with sand or tree roots. Damp ground is more subject to frost, which can cause cracks in the concrete walls.

What temporary measures can I take to disperse the humidity?

Heating your home will help reduce problems of humidity. Once it is warmed up, however, the ambient air may still contain a substantial amount of moisture. As soon as the temperature drops back down, the humidity condenses on cold surfaces and the cycle begins again, adding even more water to porous materials.

While waiting to determine the specific source of the problem and to proceed with corrective measures, clean any mold or black stains with a solution of 1 part bleach and 3 parts water. The solution should stay in contact with the mold or stain for at least 20 minutes. Wear a mask and gloves when performing this task.

If the exterior relative humidity exceeds 70% during the summer, you should use a dehumidifier. Bringing that outdoor air into your home would have the effect of increasing the relative humidity of the basement. During the winter, you can ventilate by opening two windows for 2 to 3 minutes, depending on the outdoor temperature.

What are permanent means of eliminating humidity?

Once preventive measures have been taken and the sources of humidity definitely determined, corrective measures must be taken. Hire a specialist if this involves major renovation work.

A perimeter drain can be unblocked using special equipment. If that approach doesn’t work, the ground around the foundations will have to be dug up and the drainage system replaced. Once the foundation walls have been exposed, insulate them from the outside, especially in the case of concrete block or stone foundations.

The largest cracks in a concrete wall are usually repaired working from the outside, although some specialists guarantee repairs of medium-sized cracks done from the inside.

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