An interior renovation project often hinges on technical decisions that general guides only skim over. Choice of fastening systems, compatibility between coverings and supports, regulatory constraints related to energy performance: we address here the points that make the difference between a controlled site and a site endured.
Mandatory embedded insulation: the regulatory trap of interior renovation work
Renovating a room is no longer limited to choosing a paint or a floor covering. In a co-ownership, when a renovation project affects walls facing the outside or an unheated room, a thermal insulation requirement may automatically trigger. This mechanism, known as embedded insulation, applies as soon as the work concerns more than a certain wall area.
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In practice, this means that a simple replacement of a partition against a peripheral wall may require the installation of insulation that complies with current regulations. We recommend checking this point even before requesting quotes, as the addition of an insulating layer changes the thickness of the walls, the positioning of electrical outlets, and sometimes the sizing of interior joinery.
For landlord owners, the pressure is even more direct. Since January 1, 2025, a property rated G on the energy performance certificate (DPE) can no longer be rented under new contracts, renewals, or tacit extensions. Properties rated F will follow in 2028, and those rated E in 2034.
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A purely aesthetic refresh without energy improvement now penalizes the property’s value, both for rental and resale, since the sale of a property rated F, G, or E requires an energy audit attached to the deed.
The effective approach is to integrate thermal performance right from the specifications, even for a project focused on layout. We have compiled useful resources on work on Brico Déco Jardin that detail these interactions between aesthetics and technique.
Support-covering compatibility: common mistakes on site
The choice of wall or floor covering cannot be made independently of the analysis of the existing support. A large-format tile laid on a poorly dried anhydrite screed will crack within months. A decorative coating applied to unstabilized plaster will blister by the first winter.
Support diagnosis before intervention
Three checks to systematically conduct before any finishing work:
- The residual moisture content of the support, measured with a carbide bomb for screeds or with a capacitive tester for partitions. A rate that is too high condemns any glued installation.
- The surface cohesion, tested by grid pattern and tape pull-off. A friable support requires a consolidation primer, not just a simple bonding primer.
- The flatness, measured with a 2-meter rule. Tolerances vary depending on the type of covering: a flexible floor requires much stricter flatness than a floating floor.
Skipping this diagnostic phase is the primary cause of incidents on interior renovation sites. The cost of a leveling compound or surface treatment represents a fraction of the cost of redoing a detached covering.
Sequencing of trades in interior renovation
The order of intervention of the trades determines the final quality of the site. In renovation, this sequencing is more critical than in new construction because the margins for maneuver are reduced and corrections are difficult.
Typical sequence for a multi-lot project
The technical logic imposes a precise sequence:
- Demolition and major works first (opening of a shaft, modification of load-bearing partitions with validation from a structural engineering office).
- Dry and wet networks next: electricity, plumbing, ventilation. Ducts and pipes must be in place before closing the partitions.
- Insulation and partitioning, then joint treatment and smoothing coatings.
- Wall coverings before floors, except for bathroom wall tiles which are installed after the waterproofing of the shower tray.
- Interior joinery and equipment last, once the painting is completed.
Reversing two steps, for example, laying a floor before painting the walls, generates splashes, scratches, and corrections that increase the budget. Each lot must deliver a clean support for the next lot.
Management of interfaces between craftsmen
On a renovation site without a project manager, disputes almost always arise at the interfaces. The plasterer blames the electrician for drilling too close to the edge of the rail, the electrician reproaches the plasterer for closing the partition without waiting for the ducts to pass. To avoid these blockages, we recommend formalizing a shared schedule with intermediate reception milestones between each trade.
Renovation budget: items that quotes do not detail
A craftsman’s quote covers supplies and labor, rarely indirect costs. Renting a dumpster for debris removal, parking fees for the construction vehicle in urban areas, removing and reinstalling sanitary furniture to access an embedded network: these items often represent a significant portion of the total cost.
The sale of a property rated F or G now requires an energy audit. For a property owner renovating before resale, the cost of this audit should be included in the overall budget, just like the mandatory asbestos or lead diagnostics in older buildings.
Another underestimated item: electrical compliance. An outdated panel discovered during the project can add several thousand euros to the budget. We recommend having an electrical diagnosis done in advance, even if the law does not require it for all types of work.
Renovating an interior benefits from being thought of as a global project where each technical decision, from embedded insulation to the choice of bonding primer, conditions the final result. A well-sequenced site, with properly prepared supports and a budget that includes peripheral costs, remains the best lever to avoid corrections and meet deadlines.