Sometimes the answer to this question is simple: when there is water infiltration. At other times, the link between the question and the answer is less direct.

This article does not deal with the technical aspects but rather provides a more comprehensive view of the reasons for replacing a French drain.  So let’s go, here are the three reasons for replacing a French drain:

1) There is a problem in the basement.

2) The basement will be renovated.

3) The landscaping will be refreshed.

There is a problem in the basement

The first is obvious and is the subject of almost all the blogs of companies that work in the field. The problems resulting from an inefficient French drain will therefore simply be listed without being explained:

  • Water infiltration in the basement
  • Humidity in the basement
  • Efflorescence at foundation walls
  • Cracks in the foundation walls
  • Mold and odor in the basement

The basement will be renovated or the landscaping will be refreshed.

Here there is no problem. No water infiltration, no cracks or mold: everything is fine.  However the building is no longer new and like all the other materials in the building, those of the French drain degrade over time.

Here are a few examples from a CMHC study on the useful life of building materials. The study was conducted in 2000 and was conducted in Ontario:

Materials Useful life
Water supply, copper 25 to 41 years
Waste water drainage sewer, cast-iron 28 to 42 years
Windows, aluminium 28 to 30 years
Foundation, waterproofing ans drainage 24 to 30 years
Garage door, steel 11 to 18 years
Exterior door, steel 14 to 24 years
Roof, asphalte, multi-layer 16 to 24 years


The entire study is available via the following link:

A basement that dates from the construction of a building before the 1970s, even if it is coated with finishing materials, is not airtight between the foundation wall and the basement wall finishings.  And in this case, it is good that way: The construction techniques of the time did not provide the foundation with excellent waterproofing against the underground humidity from the outside. On the other hand, coatings of interior finishing materials were not airtight and allowed humidity to dissipate (at least to some extent).

That said, when a basement is renovated with contemporary high-performance (airtight) techniques, the foundation humidity can no longer be dissipated. It remains trapped in the finishing materials and promotes the development of mold.  In addition, the moment that a basement is old and due for a refreshment coincides with the useful life of the French drain.

When refurbishing landscaping, it is advisable to compare the useful life of a French drain with the age of the building. The implementation of landscaping is costly, whereas the replacement of a French drain damages or destroys all the elements of paving, asphalt and landscaping at the perimeter of the building. It is better to replace the French drain and then do the landscaping:  to proceed in the opposite order is absurd and costly …

So there you go.

Thank you for reading and, for any question, do not hesitate to contact me

M. Collin


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