Renovating a property involves several trades, administrative procedures, and a budget that is often underestimated. Between the initial diagnosis and the completion of the work, each poorly calibrated step can lead to additional costs or delays of several weeks. This article measures the discrepancies in cost, duration, and complexity between the main areas of property renovation to help you make informed decisions.
Cost and Duration Discrepancies Between Major Renovation Areas
Not all work areas weigh equally on the budget or the project timeline. The table below summarizes the typical magnitudes observed for a medium-sized old house.
| Type of Work | Relative Share of the Overall Budget | Indicative Duration | Administrative Complexity |
|---|---|---|---|
| Thermal insulation (walls, attics, floors) | High | Several weeks | Medium (subsidies conditioned on energy performance diagnosis) |
| Heating system replacement | Medium to high | Several days to two weeks | Medium (RGE certification required for subsidies) |
| Electrical compliance | Medium | One to three weeks | Low (Consuel certificate) |
| Plumbing renovation | Medium | One to two weeks | Low |
| Exterior carpentry (windows, doors) | Medium | Several days | Variable (preliminary declaration if facade modified) |
| Facade renovation | Variable | Two to six weeks | High (urban planning permission, sometimes ABF) |
Insulation and heating account for the majority of the budget for an energy renovation. Other areas, taken individually, cost less, but their cumulative effect can double the planned budget if the initial assessment was poorly done.
To delve deeper into each area and compare concrete feedback, the work on Bulle Immobilière details the achievements by category and type of housing.
Multi-Year Work Plan in Co-Ownership: A Game-Changing Constraint
Since January 1, 2025, the multi-year work plan (PPT) is mandatory for all co-ownerships over fifteen years old, regardless of their size. This document outlines the necessary work on a ten-year roadmap.
For an owner-occupier or landlord, this changes the logic of renovation. Undertaking private work without checking the co-ownership’s PPT risks having to redo insulation at one’s own expense that the syndicate plans to address collectively two years later.
Checks to Conduct Before Starting Private Work
- Request the PPT adopted in the general assembly from the property manager and check the scheduled items (facade renovation, external insulation, replacement of common networks)
- Identify the planned calls for funds over the next three years to avoid accumulating two heavy expenses at the same time
- Coordinate your own interior insulation or heating work with the collective schedule to avoid redundant interventions
The PPT is not just a regulatory document. It now structures the order and pace of energy renovation in co-ownership, and ignoring its content exposes one to poorly sequenced financial decisions.
Logical Order of Renovation Work: Why Sequence Matters More Than Budget
Most guides list the steps in a standard order: structural work, insulation, networks, finishes. The real trap is not forgetting a step, but reversing them.
Installing a floor covering before finishing plumbing work means accepting its deterioration if a redo is necessary. Installing a high-performance heating system before addressing insulation means sizing the unit for a leaky home, then oversizing it once the envelope is corrected.
Technical Sequence That Limits Rework
The structural work (structure, roofing, waterproofing) conditions everything else. Insulation comes immediately after, before choosing the heating system, as the required power directly depends on the performance of the envelope.
The networks (electricity, plumbing, ventilation) are then installed, before closing the partitions. Exterior carpentry, if replaced, ideally fits in during insulation to ensure continuity of air tightness.
The finishes (painting, floor coverings, kitchen and bathroom fixtures) close the project. Any intervention on a network after this phase generates costly rework.
RGE Craftsmen and Energy Performance: A Non-Negotiable Selection Criterion
The RGE label (Recognized Guarantor of the Environment) is not just a mark of quality. Without an RGE craftsman, no public aid like MaPrimeRénov’ is accessible for energy renovation work. It is a binary filter, not a bonus.
However, holding the RGE label does not guarantee competence in all areas. A craftsman certified for attic insulation is not automatically certified for boiler replacement. Checking the exact scope of certification avoids unpleasant surprises when assembling the financing file.
Control Points Before Signing the Quote
- Check the validity of the RGE certificate on the official directory (the label is renewed periodically and may expire between the quote and the start of the work)
- Compare at least three detailed quotes item by item, distinguishing supplies and labor
- Require a valid ten-year insurance certificate, specifically covering the type of work planned
- Include a penalty clause for delays in the contract, indexed to the exceeding of the agreed timeline
The choice of craftsmen determines both the quality of the work and eligibility for financing. Addressing this issue upfront, even before finalizing the project, significantly reduces the risk of administrative blockages during execution.
A well-sequenced renovation project, aligned with the PPT in co-ownership and entrusted to professionals whose certifications precisely cover the planned areas, absorbs the majority of unforeseen events. The rest relies on weekly project monitoring, comparing quotes against actual work.
