The detailed guide below is currently available in English.
Sheets, seams, and why the number rounds up
Drywall is sold in whole sheets, so the answer always rounds up — there is no such thing as 0.75 of a panel. The waste allowance covers cut-offs around doors and windows, broken corners, and the offcuts that never quite fit anywhere else. Ten percent is the usual planning figure for a plain rectangular room; complicated ceilings, many openings, or diagonal walls can push it to fifteen.
Choosing a sheet length
All three sizes are four feet wide, so the choice is about seam count, not coverage per hour of taping. Long walls that match a sheet length exactly — a 12-foot wall with 4×12 panels — finish with a single horizontal seam and less mudding. The trade-off is handling: a 4×12 sheet is awkward solo and often will not turn in a hallway, which is why 4×8 remains the default for most rooms.
Repères pour la France
Repères locaux pour la France, utiles dans les calculs du quotidien :
- TVA: 20 % en taux normal (5,5 % alimentaire, 10 % restauration) ; les prix sont TTC par loi.
- Monnaie & paiements: Euro (€) ; paiement sans contact et carte bancaire très répandus, virement SEPA instantané en développement.
- Unités & nombres: Système métrique ; virgule décimale et espace pour les milliers : 1 234,56 €.
- Santé: Carte Vitale ; l'Assurance Maladie rembourse en base ≈ 70 % des soins, le reste par mutuelle.
- Pourboire: Service compris : aucun pourboire obligatoire ; arrondir suffit.
Mis à jour : octobre 2026 · valeurs 2025, sources officielles ci-dessus.
Questions fréquentes
How do I include the ceiling?
Measure the floor and add that area to your wall total before entering it — a 12×15 room contributes another 180 ft². Many people board ceilings with the same sheet size as the walls.
What waste percentage should I use?
Ten percent is a safe default for typical rooms. Simple garages and basements with few openings can drop to five, while rooms with lots of angles, bulkheads, or window cutouts are happier at fifteen.
Does the cost include tape, mud, and screws?
No — the price row multiplies sheets by your per-sheet price only. A common rule of thumb adds about 15–20% to the board cost for joint compound, tape, fasteners, and corner bead.