Don’t take our word for it.
A qualification is easy to display. It is just as easy to check — provided you are given the means. Here they are.
Our RGE (French ‘reconnu garant de l’environnement’ label) Qualibois Air module qualification bears the number QB/48106. You can check it yourself, with our SIRET (French company registration number) 528 048 069 00025, in the official France Rénov’ directory or that of Qualit’EnR, which issues it. There you will see our active qualifications and their validity dates — the source is authoritative, not this page.
Our professional liability insurance and our garantie décennale (ten-year liability insurance, compulsory in France) are covered by a single contract, MMA IARD no. 125 388 562, for the activities ‘Fumisterie – Chemisage – Tubage’ (flue work, relining, flue liners), including the construction of hearths and fireboxes, in mainland France. Certificate on request, within 24 hours.
The vocational qualification of Mason (titre professionnel de Maçon) held by the founder, Guillaume Dejeux, bears the number 10/21/626, issued by the French Ministry of Employment on 5 August 2010. Added to this is the C.O.S.T.I.C. chimney sweep and flue installer diploma.
A masonry heater involves the structure of your house, your safety and decades of use. Here, precisely, is what covers ours — and yours.
Ten-year guarantee
Ten-year liability: for ten years after handover, for damage that compromises the soundness of the structure or renders it unfit for its purpose.
RGE Qualibois Air
Reconnu Garant de l’Environnement, independent wood-burning appliances.
Mason
Founder’s vocational qualification of Mason (2010).
C.O.S.T.I.C.
Founder’s chimney sweep and flue installer diploma.
4 manufacturers
Certified by Biofire, Brunner, Ortner and Ecostove.
AFPMA
Founding member, former president, treasurer on the board.
Insurance
Thermasse is covered by MMA liability and ten-year insurance (MMA IARD, contract no. 125 388 562, Semur-en-Auxois agency): for ten years after handover, damage compromising the soundness of the structure or rendering it unfit for its purpose is covered, anywhere in mainland France.
The insured activities are those of the trade, named as such in the contract: flue work, relining, flue liners — including the construction and installation of hearths and fireboxes, the laying of refractory and ceramic tiles, and flue sweeping. The current year’s certificate is supplied with every quote — and can be viewed right here:
→ 2026 ten-year liability certificate (PDF, 256 KB)
→ 2026 professional liability certificate (PDF, 161 KB)
→ RGE Qualibois Air module certificate 2025-2026 (PDF)
Trade qualifications
Building a masonry heater brings together two regulated trades, and we are qualified in both:
- Masonry qualification — the heater body, the accumulator, the renders. The founder holds the vocational qualification of Mason (2010);
- Sweeping and flue work qualification — the flue, the draught, flue gas safety. He also holds the C.O.S.T.I.C. chimney sweep and flue installer diploma.
RGE Qualibois Air module
Thermasse is RGE Qualibois Air module (Reconnu Garant de l’Environnement, independent wood-burning heating appliances). This qualification is a condition of access to certain public grants — eligibility depends on your situation and on the appliance: we look into it with you, with no blanket promise.
Manufacturer certifications
We are certified by the manufacturers Biofire, Brunner, Ortner and Ecostove: training on the manufacturer’s systems, installation to its specifications, access to its parts and technical support.
Commitment to the trade — AFPMA
Guiom is a founding member of the AFPMA (Association Française du Poêle Maçonné Artisanal, the French association of artisan site-built masonry heaters), former president of the association and currently treasurer on the board. In 2026, the heater at the école maternelle du Bois-Perrier (Rosny-sous-Bois) won both categories of the AFPMA photo competition: ‘best photo (unusual)’ and ‘most beautiful heater’.
Site equipment
Thermasse is registered for lifting equipment (Manitou-type telescopic handler): the tonnes of bricks, grog and accumulators reach your room without improvisation.
In short — ten-year guarantee, dual masonry and flue work qualification — founder qualified in both trades —, RGE Qualibois Air, four manufacturer certifications, and a founding role in the national trade association. Every term above is used exactly — never stretched.