We build customized stairs: straight , spiral, helical, staggered and cantilever.
The parameter which differentiates the stairs is essentially the ratio between the riser and the tread or, in other words, the inclination:
- between 75 and 90 degrees they are called stairs by hand
- between 45 and 75 degrees they are called industrial ladders
- between 45 and 25 degrees they are called common stairs.
Normally the riser is generally between 13 and 20 cm. The tread is calculated by empirical relationships based on user’s work in addressing the gap. The formulas used are 2A + P = 62/64 cm (Blondel’s formula) or P + 4A/3 = 52 cm. The Italian law on architectural barriers (D.M. Ministero dei LL. PP. 6/14/89 n° 236) requires the following: ratio between riser and tread (minimum tread of 30 cm): the sum of twice the riser and the tread should be between 62/64 cm (coefficient of Blondel).
In order to ensure the safety of people, the Italian legislation requires:
the parapets must be at least 1 meter from floor plan (D.P. R 4/27/1955 # 547 and D.M. 6/14/1989 # 236)
Inner ledges must be located at a height above the floor that does not facilitate the support of foot and the climb over of children
the parapets must be secured to prevent the passage of objects (10 cm diameter sphere)
the parapets of balconies and terraces must be capable of withstanding a horizontal thrust of 1000 N/m applied on the handrail.