Buying an existing house and building a new one are two processes that share a common vocabulary (budget, loan, land, warranty) but differ radically in terms of expenses, timelines, and risks. This article compares these two paths to identify the concrete gaps that impact the success of a home project.
New construction or existing purchase: cost and timeline differences
The choice between construction and purchase determines the financial structure of the project well before the first visit or the first shovel of dirt. Here are the main differences to anticipate.
| Criterion | New house construction | Purchase of existing house |
|---|---|---|
| Land budget | Separate item, often half of the total cost | Included in the sale price |
| Average time until move-in | 12 to 18 months after signing the builder’s contract | 3 to 4 months after signing the preliminary agreement |
| Notary fees | Reduced (around 2-3% on new) | Higher (around 7-8% on existing) |
| Work to be expected | No short-term work (builder’s warranties) | Varies depending on the condition of the property and the energy performance diagnosis (DPE) |
| Ten-year warranty | Yes, covers structural defects for 10 years | No (except for recent work covered by the contractor) |
The difference in notary fees favors new construction, but the land item, purchased separately, often rebalances the overall budget. In construction, the land frequently represents half of the total budget, which forces a trade-off between location and living space.
For those looking to compare new house models and customization options, it is possible to find out everything about Maisonea.fr before finalizing a specifications document with a builder.
DPE and energy audit: what changes for home purchase in 2025-2026
Buying an existing house now requires a close look at the energy label. Regulations have tightened significantly in recent years, and the thresholds continue to evolve.
Since April 1, 2023, the sale of a single-family home classified F or G on the DPE requires a regulatory energy audit. This audit details the work scenarios and their estimated costs. From January 1, 2025, the obligation extends to properties classified E, and homes classified D will be affected starting in 2034.
This timeline concretely changes the negotiation. A buyer interested in a house classified E has leverage: the audit quantifies the energy renovation work, justifying a discount on the asking price.
Correction of the DPE for small areas and electric heating
Since July 1, 2024, the DPE thresholds have been adjusted for homes under 40 m², allowing some small townhouses to improve their label without work, simply by updating the diagnosis. A new revision of the calculation method is announced for January 1, 2026, for homes heated with electricity. About 850,000 homes are expected to exit the thermal sieve status thanks to this recalculation.
In new construction, this issue does not arise: the current thermal standards (RE2020) guarantee an A or B label upon delivery. The energy performance gap between new and old remains one of the most underestimated factors in calculating the overall cost of a real estate project.
Choosing a home builder: warranties to check before signing
The individual house construction contract (CCMI) offers a protective legal framework, provided that a few points are checked before signing. Not all builders present the same level of reliability on site.
- The guarantee of delivery at agreed price and deadlines, issued by an external guarantor (bank or insurer), protects against the builder’s failure during the project. Without it, the CCMI is worthless.
- The ten-year warranty covers defects affecting the solidity of the work or rendering it unfit for its purpose for ten years after the completion of the work.
- The perfect completion guarantee obliges the builder to repair all defects reported in the year following delivery, including finishes.
- The damage insurance, taken out by the project owner, allows for rapid pre-financing of repairs without waiting for a court to designate the responsible party.
Checking the existence and validity of these four protections before signing the CCMI avoids the vast majority of construction disputes. A builder who hesitates to provide their insurance certificates is an immediate warning signal.
Mortgage budget: simulate before looking for land or property
Households’ borrowing capacity has significantly decreased in recent years due to rising rates. This makes the financial simulation phase even more crucial than before.
In construction, the financing plan must include three distinct items: the land, the house itself, and ancillary costs (connections, development, planning tax). Forgetting one of these items skews the budget from the start.
For a purchase in the existing market, the renovation budget is the most difficult item to estimate. Getting a professional to estimate the renovation work before signing the preliminary agreement protects against unpleasant surprises, especially if the energy audit reveals inadequate insulation or an obsolete heating system.
Personal contribution and debt ratio
The maximum debt ratio remains set at 35% of net income by the High Council for Financial Stability. A personal contribution covering at least the notary fees and the bank guarantee fees remains the norm expected by lending institutions. In new construction, some banks accept a gradual release of the loan as the builder requests funds, which limits interim interest if the project progresses as planned.
The factor that most often distinguishes a successful project from a stressful one is neither the choice of property nor that of the builder. It is the financial margin retained after finalizing the financing plan. A budget that leaves no reserve for unforeseen events turns every construction mishap or every defect discovered after purchase into a source of lasting tension.
