The surrounding terrain and topography will affect the local conditions at the location for the project. Local conditions can affect drying conditions (through for example shading) or exposure to precipitation (through e.g. shelter from buildings).

Select local conditions:

Open field
Forest
Sheltered by buildings

k₁ = 1.0

Exposed end-grain tend to absorb more water than exposed side-grain. As a result, decay often starts near exposed end-grain.

Side-grain
End-grain

Detailing where different components intersect and join are often problematic as they attract dirt and prevent water from drying out.

No contact face or gap size >5 mm free from dirt
Partially ventilated contact face free from dirt
Direct contact or insufficient ventilation

The term shelter is here used to describe any effect which is may reduce the duration of wetting of a horizontal wood surface. A roof overhang has an obvious sheltering effect on the cladding of a wall, but simply orienting a wooden product vertically will reduce the duration of wetting and thereby increase service life.

Vertical member (subjected to driving rain)
Roof overhang
distance to ground (a)
roof overhang (e)
distance from shelter (d)