A cracked exterior wall that allows moisture to pass through makes the installation of decorative plaster inside pointless. This is the type of sequencing failure often observed on renovation sites, which turns a controlled budget into a financial black hole. Before choosing colors or coverings, the priority is to stabilize the building’s envelope, then work inward following a precise technical order.
MaPrimeRénov’ Decree September 2026: What Changes for Your Renovation Project
Since September 1, 2026, decree n°2026-822 has eliminated almost all aids for work done “by gesture.” In practical terms, isolating an attic or replacing a thermodynamic water heater in isolation no longer qualifies for MaPrimeRénov’. The aids are now refocused on large-scale renovations, with a requirement to decarbonize heating and hot water production.
For an interior and exterior renovation project, this evolution requires thinking of the site as a whole. One can no longer rely on aid to finance an isolated item, then another six months later for a second item. The financial setup is done upfront, covering the entirety of the work.
Another point to anticipate: starting January 1, 2027, the company invoicing the work financed by MaPrimeRénov’, eco-PTZ, or CEE must hold the RGE certification itself. No more passing through a non-certified company that outsources to a certified craftsman.
Checking this point before signing a quote will avoid file rejections. You can find feedback and useful resources on work on the Tendances Déco website, particularly for articulating aesthetic choices and regulatory constraints.
Order of Renovation Work: The Technical Sequence to Follow
On the ground, the most costly mistake is starting with interior finishes before addressing the exterior envelope. The principle is simple: work from the outside in, and from the structural work to the finishing work.
Exterior First: Roof, Facade, Joinery
The roof is addressed first. A failing covering exposes the framework, insulation, and interior ceilings. Next comes the facade renovation and, if necessary, external thermal insulation (ITE). Exterior joinery (windows, doors) is installed at this stage, as it conditions the air tightness of the dwelling.
Attacking the facade before the roof is a common mistake. If the covering leaks, water runs behind the new plaster and detaches the insulation within months.
Interior Next: Networks, Insulation, Finishes
Once the envelope is secured, we move on to the networks. Electricity and plumbing are addressed before closing the partitions. Installing drywall and then having to reopen it to run a cable wastes time and budget.
Interior insulation comes after the networks. Then ventilation, whose installation is often underestimated. Without a properly sized VMC, a well-insulated house accumulates moisture and quickly degrades interior materials. Finishes (plasters, paint, floor coverings) come last.
- Roof and framework, then facade and ITE, then exterior joinery
- Electrical and plumbing networks, then partitions and interior insulation
- Installation of the VMC, then screed and floor coverings
- Painting, decorative plasters, and surface fittings last
Renovation Budget: Items Not Detailed in Quotes
The budget for a renovation project rarely goes off track on the main items. It is the lines absent from the initial quote that pose problems.
Construction waste management represents a cost often overlooked. Removing old insulation, disposing of demolition debris, renting a dumpster: these expenses add up. For an average-sized house, the disposal of materials can weigh as much as the installation of a new floor covering.
Discoveries during the project constitute another source of overruns. A floor revealing joists attacked by wood-eating insects, a lead pipe hidden behind a lining, a cracked lintel under a plaster: these surprises only appear once demolition has begun.
To limit unpleasant surprises, it is recommended to allow for a safety margin in the overall budget. Feedback varies on this point, but allocating a portion of the total budget to contingencies remains the most reliable practice to avoid blocking the project midway.
Choosing Renovation Materials: Balancing Durability and Cost
The common reflex is to select the cheapest materials to stay within budget. This may work on a new construction site. In renovation, it’s riskier because existing supports impose compatibility constraints.
A lime plaster on an old stone wall breathes and regulates moisture. Replacing it with a cheap cement plaster blocks hygrometric exchanges and causes rising damp. The cheaper material ultimately costs more in repairs.
For insulation, the choice depends on the support and available space. Mineral wool works well in attics where space is plentiful. In interior renovations with limited spaces, a thin insulating material for equivalent performance preserves the living area, a crucial criterion in urban housing.
- Check the compatibility of the material with the existing support (stone, brick, concrete, wood)
- Compare the cost to installation rather than to gross square meters: some materials require longer implementation
- Prefer certified materials (NF, CE, Acermi for insulation) to secure warranties and eligibility for aids
The choice of materials also determines the lifespan of the project. A porcelain stoneware tile in a high-traffic area will last much longer than an entry-level flexible floor. Investing in the most used areas (entry, kitchen, bathroom) and moderating expenses in less exposed spaces remains the most rational decision when the budget is tight.
Planning a renovation while respecting the technical sequence, anticipating regulatory changes of MaPrimeRénov’, and checking the RGE certification of the contracting company before signing: these three points separate a project that runs smoothly from one that gets bogged down.
