What diagnostics are required to sell in 2026? The Complete Guide
Contents
"Mrs. Durand, I'm sorry, but we can't sign the deed today."
Sophie Durand, 42, a Swiss border worker, turns pale. His buyer is waiting for him in the next room. Its move to Zurich is scheduled in 10 days. The truck is reserved. "Your ERP diagnosis is 8 months old. He must be less than 6 months old. And your DPE was done in 2013... It is no longer valid since 2023."
2 expired diagnoses = 2 weeks minimum delay + 400€ extra + maximum stress.
This (real) story illustrates why this guide exists: in 2026, selling without up-to-date diagnoses = major legal risk. Here's EVERYTHING you need to know.
How many mandatory diagnoses are there in 2026?
Full answer : it depends on 4 criteria:
- Year of construction (pre-1949, pre-1997, etc.)
- Type of installation (gas >15 years, electricity >15 years)
- Location (termite zone, radon zone, seismic zone)
- Type of sanitation (collective vs. autonomous)
The 10 possible diagnoses in 2026
- House 1985 in Saint-Genis, gas+electricity 1990 → 8 diagnoses (DPE, ERP, asbestos, electricity, gas, termites border area, sanitation if ANC, audit if DPE F/G)
Has the DPE changed in 2026? (Spoiler: yes!)
MAJOR NEW January 2026 : electricity coefficient increases from 2.3 to 1.9.
What it changes in concrete terms
- Electric heating apartment
- Annual consumption: 15,000 kWh/year
- Primary energy displayed: 15,000 × 2.3 = 34,500 kWh → class E
Since 2026 :
- Same apartment, no work
- Consumption: 15,000 kWh/year (unchanged)
- Primary energy displayed: 15,000 × 1.9 = 28,500 kWh → class D
Result : +17% of properties go up a class without doing anything!
Can your old DPE be updated for free?
YES! If your DPE dates from 2021-2025, you can have it recalculated for FREE on observatoire-dpe.ademe.fr with just the 13-digit number. No new visits necessary.
Why it matters: an F-rated property can no longer be rented since 2025. If it goes back up to E thanks to the new coefficient, it becomes commendable again!
Which diagnostics cost the most ?
Average total budget Pays de Gex (house 120 m² 1980s): 500-700 €
Details of the costs 2026
The scam to avoid : "cheap" diagnostician at €50 the DPE → botched report → buyer's dispute → lawsuit → you lose €10,000.
The right strategy : multi-diagnostic pack at certified pro = -20% vs unit rates.
What happens if a diagnosis is missing on the day of signing?
Real case 2025, Divonne-les-Bains
Buyer's Options :
- Cancel the sale without penalty (diagnostic suspensive clause)
- Demand a price reduction (negotiation: -€15,000 accepted)
- Postpone the signature (cost: 2 weeks + bank file fees)
Marc chose option 2: -15 000€ for a diagnosis at 100€. Catastrophic ratio.
Legal sanctions
- If the diagnosis is deliberately hidden→ nullity sale + damages
- If outdated diagnosis not noticed → price reduction or sale resolution
Construction Code Article L271-4 :
- Fines of up to €300,000 (very rare, extreme cases)
- Civil liability systematically incurred
Do all diagnoses have the same validity period?
NO, and that's the catch!
Summary table 2026
- DPE: 10 years (if done after 01/07/2021)
- Asbestos: unlimited if absent (if done after 01/04/2013)
- Lead: unlimited if absent
Average validity (3-5 years):
- Electricity: 3 years sale, 6 years rental
- Gas: 3 years sale, 6 years rental
- Sanitation: 3 years
Short validity (6 months):
- Termites: 6 months ⚠️
- ERP: 6 months ⚠️
The Common Fatal Mistake
Problem: the sale takes 4 months (normal). On the day of signing at the notary's office:
- Expired ERP (made 8 months ago, valid for 6 months)
- Expired termites (idem)
Solution : order termites + ERP LAST, 1 month before scheduled signature.
How to choose your diagnostician without being scammed?
The 5 mandatory verifications
1. Up-to-date COFRAC certification
Official website: diagnostiqueurs.din.developpement-durable.gouv.fr
Type name + city → check active certifications for EACH diagnosis (DPE, asbestos, separate lead).
Red flag : "certified all diagnostics" without details → false.
2. Valid professional liability insurance
Ask for a certificate dated <3 months. Minimum amount: €300,000 per claim.
3. Full independence
- Be linked to the agency that sells
- Have an interest in the transaction
- Also do work at your home
Example of a foiled scam : agency offers "its" diagnostician → DPE class C (fake) → quick sale → 6 months later, real DPE per buyer = F → lawsuit → agency + diagnostician jointly and severally convicted.
4. Detailed written quotation
- Each diagnosis separately
- Estimated intervention time
- Reporting deadline
- Cancellation conditions
Price too low = red flag : DPE serious house 120m² = minimum 120€. At 50€ → sloppy guaranteed.
5. Mandatory physical presence
A diagnostician who offers to do the DPE "on plans" or "on photos" = ILLEGAL. On-site visit mandatory: 1h-2h for a complete house.
Pays de Gex specificities: what to look out for?
Frequent non-collective sanitation
Rural communes (Échenevex, Crozet, Chevry, Thoiry) = many septic tanks / ANC.
Mandatory on-site sanitation diagnosis
- Cost: 100-150€
- To be requested from the SPANC (Public Service for Non-Collective Sanitation)
- Lead time: 2-4 weeks → anticipate!
Demanding Swiss customers
80% Pays de Gex buyers = Swiss cross-border workers used to Swiss rigor.
Consequence : incomplete or approximate diagnoses = deal that jumps immediately.
Tip : "premium" diagnostic pack with detailed photo reports → reassures CH buyers.
Final checklist: don't forget anything before selling
8-6 months before sale :
✅ Identify necessary diagnoses according to well
✅ Request 3 certified diagnostic quotes
✅ Order long-term diagnostics (DPE, asbestos, lead, electricity, gas, sanitation)
2 months before sale :
✅ Check validity diagnostics already done
✅ Update DPE free of charge if done before 2026 (new coefficient)
1 month before scheduled signature :
✅ Order ERP (free, do it yourself on Géorisques.gouv.fr)
✅ Order termites (valid for 6 months only)
✅ Check that ALL diagnoses will be valid on D-Day
D-Day at the notary's office :
✅ Providing ALL original diagnoses
✅ Check validity dates one last time
Conclusion : invest €600 to save €15,000
- Avoids buyer disputes (-10,000 to -30,000€)
- Speeds up signature (no last-minute delays)
- Legally protected (liability covered)
The mistake to NEVER make: saving €200 on diagnostics → losing €15,000 on negotiation.
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Posted on 28/04/2026 by
Antoine Lanfranchi
Je mets mon expertise du marché immobilier du Pays de Gex au service de vos projets, avec une approche rigoureuse, personnalisée et orientée résultats. Ma parfaite connaissance du territoire et de ses spécificités me permet de vous accompagner efficacement à chaque étape, de l’estimation à la concrétisation de votre projet.
J’interviens sur :
- la transaction (achat et vente de biens immobiliers)
- les programmes neufs
- le conseil juridique immobilier
Mon objectif est de vous offrir un accompagnement transparent et efficace, en valorisant votre bien et en sécurisant chaque étape. En me confiant votre recherche ou la vente de votre bien, vous bénéficiez d’un réseau solide, d’une expertise éprouvée et d’une connaissance fine du marché local.
