Measures · Timber floor
Timber floor pre-sizing FREE
Work out the thickness of a timber floor and the size of its joists. Below the result you find the formula and the standard.
Indicative pre-sizing. It does not replace a structural calculation signed by a licensed engineer. For seismic zones with agS (design ground acceleration) > 0.15g, long spans or use classes III/IV → talk to a structural engineer.
Pick a calculation from the list to start.
Formula, example and standard
H ≈ L/20 ÷ L/25 · joist b ≥ 8 cm and ≥ i/8
Example with the starting values (Span L: 4 m; Joist spacing: 0.5 m): Thickness H ≈ 16–20 cm. Joist width: 8.0 cm.
- Thickness includes joist + top boarding (2-3 cm) + any composite concrete topping.
- For public use or heavy foot traffic: an EC5 §7.3 vibration check is required.
- Typical materials: C24 spruce, GL24h glulam for spans > 5 m.
Source: NTC 2018 ch. 4.4 + UNI EN 1995 (EC5) · risponde.promolegno.com
Indicative pre-sizing: it does not replace a calculation signed by a licensed engineer.
The other calculations
Timber beamSteel IPE beamReinforced concrete beamReinforced concrete columnSteel columnTimber columnRC cantilever / balconyLintelClay block and concrete slabPredalles slabLoad-bearing brick wallPartition wallStaircaseMinimum room heightWindow-to-floor ratioEscape route widthNumber of toiletsNTC imposed loadsExternal insulationVentilated crawl spaceRoof pitch