Here is the second part concerning wet basements (humidity in the basement) where the waterproofing of the foundations, the drainage system and the presence of mold on the foundation walls will be discussed.
In general, we find that the walls of poured concrete foundations, prior to 1958, are not waterproof. Indeed, the concrete of that time was not of good quality, because the technology for the manufacture of concrete was not advanced enough.
Foundation concrete is generally brittle and porous in older buildings. In addition, the waterproofing membrane - installed outside on foundation walls - if it exists of course, is old and non-functional in most cases.
It should also be noted that the drainage system, at the base of the foundations, became compulsory around 1955. It is very likely that there is no French drain, around a building before this time, to intercept groundwater that may accumulate in the soil.
The lack of adequate drainage at the perimeter of the foundation walls and the absence of an effective waterproofing system outside - on foundation walls with porous and lower quality concrete - means that foundation walls are always soaked in water or very humid. This situation causes the formation of mold on foundation walls, indoors, and often causes water to enter the interior of the building.
Mold and efflorescence
The majority of basements in residential buildings, lacking a French drain, have odors of humidity. It is through renovations in the basement, and after removing the finish on the walls that people discover a black layer of mold and fungal growths on the walls and building materials. It is then observed that the concrete is very wet that there is a lot of bloom on the foundation walls. It is also possible that the concrete is brittle and very weak.
In reality, the solution may vary depending on the condition of the foundation walls or, more precisely, the strength of the concrete. If the latter is very weak and crumbles, in this case, consideration should be given to the total replacement of the foundation walls carried out by a company specialized in the field.
If the foundation walls can be repaired, repair work must therefore be carried out depending on the condition of the concrete. After repairing the concrete and cracks, it will be necessary to waterproof the foundation walls and install a French drain outside. Exterior landscaping works play a considerable role in keeping water away from the building and in not straining the drainage system at the base of the foundations. Adding an adequate fill to the perimeter of the house when installing a French drain, correcting the slope of the land, installing copings for basement windows, etc. are important works that keep the basement dry.
In case of mold contamination, it is advisable to carry out renovation work, inside the basement, after decontamination carried out by a specialized company. Then, the structure affected by humidity or by water infiltration must be replaced.
It is therefore essential, before purchasing an older property, to pay particular attention to the condition of the concrete of the foundation walls, the waterproofing of these walls and the drainage of the foundations (French drain), because Corrective work could prove to be very expensive.