Most of the clients who use my services, as a building engineer, in the area of ​​hidden vice (expertise in hidden vice), ask me if the discovered deficiencies are or are not hidden defects. From the outset, I tell them that I am neither a lawyer nor a judge, but that my role is to collect the clues and perform the tests to prove that the defects were not apparent at the time of purchase and that these vices are harmful. normal building function and / or occupant safety.

Sometimes there is an error and omission on the part of the pre-purchase inspector. Indeed, in some cases, apparent symptoms clearly indicate (for a building professional) that there is a possibility of the presence of a defect. Despite these obvious symptoms, the inspector did not recommend to the potential buyer to perform a hidden defect with a specialist. For example, if there is significant condensation on windows during the winter, it may be the result of a problem of air infiltration, ventilation or a deficiency of the windows themselves. In the event that the pre-purchase inspector finds a serious problem of condensation, he must then recommend an in-depth expertise to determine the cause.

What is a vice?

A defect is defined as a defect or problem which renders the building unfit for its use or which diminishes its usefulness. In general, the defect is a faulty workmanship or a construction that does not respect the rules of the art. The defect must be so serious that if the buyer had known it, he would not have bought the building or at least he would not have paid the asking price (Me Jeffrey Edwards).


Furthermore, the hidden defect is defined as being a serious defect that the buyer was not able to detect and that the seller did not bring to his attention before the sale. The defect must be hidden, that is, a prudent and diligent buyer could not have noticed it at the time of the sale.

Pre-purchase inspection with a building expert is not required by law. However, a serious, careful and careful examination of the building is required. For this reason, it is recommended to use a recognized specialist to prevent the judge from coming to the conclusion that the buyer was negligent during the examination of the building and that the defect was apparent.

Expertise in vice Cache (opinion of the building expert):

The expert who is called upon to give his professional opinion, as part of an expertise in hidden vice, must take into account several factors to establish his diagnosis, including the age of the building and the useful life of components of the building. The specialist will have to make the distinction between hidden defect and normal wear of the components. We offer you some real examples of litigious cases:

  • By removing a gypsum board in the basement, the buyers discovered that the wall of foundations was blackened and that there was condensation on it. By cleaning up the basement, they realized that the problem was all over the basement. The air quality test later confirmed the presence of mold in the house. Was it a hidden vice?
Mold and condensation on the foundation wall

© Mold and condensation on the foundation wall

  • In another file, the buyer noted, at the time of the transaction, several cracks in the foundation walls. After the purchase, she found that these cracks flowed abundantly in the basement and that there was mold and building materials deteriorated. Thus, the cracks were visible on the outside, but water infiltration and damage to the interior of the basement were not apparent. Can we then speak of a hidden vice?
Water infiltration through the crack in the foundation wall

© Water infiltration through the crack in the foundation wall

  • A new buyer bought our client's house from the 80 years. A test was done to check the French drain with a drain camera. He revealed the existence of fine particles and roots in the drain. Despite this, there had never been any infiltration of water in the basement. Was it a hidden defect or not?
Expertise in hidden defects, fine particles in the French drain

© Fine particles in the French drain

  • A buyer used our services (hidden defect expertise) after discovering that the floor joists of the ground floor were in a state of advanced deterioration because of a recurring water infiltration problem. the junction between the exterior cladding and the foundation walls, at the perimeter of the house. Again, was it a hidden vice?
Expertise in hidden defects, advanced deterioration of floor joists

© Advanced deterioration of floor joists

  • A couple found a nest of carpenter ants, in the wood of the floor structure, under the French window of the ground floor. The damage was great, even the insulation was punctured and damaged by the ants. The customers believed to be in the presence of a hidden defect. Was it really the case?

Expertise in hidden defect, wooden structure damaged by carpenter ants

© Wooden structure damaged by carpenter ants

Finally, the opinion of the building expert and the lawyer specializing in this type of litigation is very important in order to guide the new buyer in his efforts. The building specialist and the lawyer work together to build a good record so that the buyer can defend his rights with the seller.