External staircase - calculate slope


There are many formulas to calculate the slope of stairs. However, external staircases with their manifold characteristics are often completely forgotten. For them, the slope should not be as high as in the interior stairs. Which slope is sensible and customary for an external staircase is shown here in the overview.

Requirements for external stairs

Although the state building regulations do not differentiate between indoor and outdoor stairs, the requirements are very different. In addition to the need to use materials that withstand the weather, the steps should also have a slight slope towards the step edge. So the moisture can drain away without water puddles forming on the stairs.

With various small tricks, such as a second handrail, steep external stairs can be mitigated a bit. If possible, however, the slope should be kept slightly lower.

Plan slope

Commonly used are the following ratios of pitch per step and tread on an outside staircase:

  • 16/31 centimeters
  • 15/33 centimeters
  • 14/35 centimeters
  • 12/39 centimeters

The models listed above have always complied with the familiar calculation formula for stairs, which is used for both indoor and outdoor staircases. Because that says:

Twice the step height plus step depth is equal to 63 centimeters

Insert intermediate platforms

The outdoor space is usually much more space than inside the house. Therefore, one usually has the freedom to reduce the slope of a staircase by intermediate platforms. Outdoor stairs, which open one or two stories without interruption, are uncomfortable and uncomfortable for most people. Therefore, it is important to incorporate a pedestal after about ten to twelve steps or halfway up a floor.

Fire escape

A staircase can also be built without a building. Their dimensions are regulated by the DIN 18065 as well as those of an escape staircase. Also escape routes which are attached outside and are provided with a roof, are subject to this DIN regulation.

Tips & Tricks

If you need to install a continuous exterior staircase or if you need to use a clearer grade for the stairs, you should add two handrails. These not only ensure a perceived safety, but also visually soften a steep staircase.


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