5 common mistakes in new-build construction

Building a new home is an exciting project… but one that is sometimes fraught with pitfalls. Even in recent construction, defects can appear, often due to avoidable mistakes. Here are the five most common errors we encounter in the field during our assessments, and how to prevent them.

1. Poor management of damp

Too often underestimated, damp can cause serious damage: mould, peeling of finishes, corrosion of reinforcement. Poor basement waterproofing, the absence of a damp-proof membrane or insufficient ventilation are frequently the cause.

Our advice: check that waterproofing materials and systems comply with standards, and favour balanced (double-flow) ventilation in well-insulated homes.

2. Thermal and acoustic insulation defects

Untreated thermal bridges, careless installation of insulation, or poor airtightness lead to energy loss and everyday discomfort. On the acoustic side, the absence of decoupling between partitions can cause noise nuisance.

Our advice: request an airtightness check (blower-door test) and verify that the insulation meets passive-house or low-energy standards.

3. Non-compliant installation of joinery

Poorly installed windows can lead to water infiltration, heat loss or opening/closing problems. This is often the result of poor sealing or misalignment.

Our advice: have the installation checked by an independent professional, especially at the time of the site handover.

4. Non-compliance with the DTU or installation standards

Each trade must follow precise rules (DTU, or unified technical documents) to guarantee the durability of the works. All too often, deadlines or costs push certain contractors to take shortcuts.

Our advice: use a rigorous project manager or request an independent technical assessment during the works to ensure the rules are being followed.

5. No inspection before handover

Handover (réception) is a crucial stage. Once signed, you accept the works as they stand, unless you record reservations (formal objections). Yet many defects go unnoticed by a non-expert.

Our advice: be accompanied by a building expert at the time of the property handover. They will be able to detect defective work and help you formulate relevant reservations.

In conclusion

A new building is not synonymous with perfection. As experts, we regularly observe that avoidable mistakes can have a lasting impact on the quality and value of a property.

AC Expertises supports you at every stage, from the construction phase through to handover, to guarantee the compliance, safety and performance of your home.