Room additions & extensions in 5e Arrondissement (Quartier Latin / Panthéon)
5e Arrondissement (Quartier Latin / Panthéon) is 5e arr. — Panthéon's medieval fragments + 17th-19th c. quartier latin + haussmannien infill submarket. The 5e contains some of the oldest residential cellars in Paris — many rue Mouffetard buildings have 13th-14th century cave foundations that show up on the cadastre as patrimoine archéologique, and any deep excavation triggers a Service Régional de l'Archéologie diagnostic before earthwork begins.
What a room additions & extensions project looks like here
The 5e contains some of the oldest residential cellars in Paris — many rue Mouffetard buildings have 13th-14th century cave foundations that show up on the cadastre as patrimoine archéologique, and any deep excavation triggers a Service Régional de l'Archéologie diagnostic before earthwork begins.
Because the quarter sits on the geological Bièvre alluvium, sub-grade groundwater is shallow — most basement-conversion projects require permanent dewatering pumps and a SAGE / hydrogeology declaration that adds 6-10 weeks to the dossier.
Paris extensions are rare in the historic core — typically attic / combles conversion or rooftop addition (surélévation). PLU governs maximum hauteur plafond, Permis de Construire required, ABF veto on PSMV-listed faubourgs. In 5e Arrondissement (Quartier Latin / Panthéon) specifically, medieval fragments + 17th-19th c. quartier latin + haussmannien infill stock means room additions & extensions scope is shaped by the neighborhood's dominant construction typology. Baily's Paris scoping flow factors abf avis and medieval cellar (caves) preservation orders on rue mouffetard cohort into the estimate before a contractor is involved.
Start your 5e Arrondissement (Quartier Latin / Panthéon) scope — Baily asks the right questions.
Pre-seeded for room additions & extensions in 5e Arrondissement (Quartier Latin / Panthéon). Mention your 45-180 m² appartements + townhouses, your timeline, and any known constraints — Baily factors the mairie du 5e + mairie de paris (du) + abf review queue into the scope.
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Who is Baily?
Baily is named after Francis Baily — an English stockbroker who retired at 51, became an astronomer, and in 1836 described something on the edge of a solar eclipse that nobody had properly articulated before: a string of bright beads of sunlight breaking through the valleys along the moon’s rim.
He wasn’t the first to see them. Edmond Halley saw them in 1715 and barely noticed. Baily’s contribution was clarity — describing exactly what was happening, in plain language, so vividly that the whole field of astronomy paid attention. The phenomenon is still called Baily’s beads.
That’s what we wanted our AI to do. Every inbound call and text has signal in it — a homeowner’s real question, a timeline, a budget, a hesitation that means “yes but.” Baily listens to every one, 24/7, and finds the beads of light.
Baily was a businessman before he was a scientist. That’s our vibe too.
Questions LA homeowners actually ask
5e Arrondissement (Quartier Latin / Panthéon) room additions & extensions projects typically run $75K–$385K. 5e Arrondissement (Quartier Latin / Panthéon)'s medieval fragments + 17th-19th c. quartier latin + haussmannien infill stock, combined with abf avis — panthéon + sorbonne + notre-dame perimeters, puts most mid-complexity projects in the $230K range. Baily scopes the exact band once you describe the work.
Nearest neighborhoods
Same service, adjacent Paris submarkets.