# What is boarding?
**Boarding is the cladding of a structure with planks (boards), for example as external wall cladding or as roof sarking (decking beneath the roof covering).** The boards can be fixed horizontally or vertically.
## Application
### Wall cladding
Timber boards are fixed to the facade as a weather-resistant and decorative finish:
– **Weatherboarding (lap boarding)** — boards overlap horizontally
– **Tongue-and-groove boarding** — boards interlock with a tongue-and-groove joint
– **Vertical boarding** — boards fixed vertically, sometimes with cover strips over the joints
### Roof sarking
Boards are nailed to the rafters as a substrate for the roof covering. This forms a closed surface onto which insulation and tiles or felt can be laid.
### Interior lining
In historic buildings, boarding was also used as wall or ceiling lining, sometimes with decorative profiles.
## Materials
Common timber species for external boarding:
– Spruce or pine (with preservative treatment)
– Western Red Cedar (naturally durable)
– Larch (good weather resistance)
– Accoya (modified timber)
## Related terms
– Weatherboarding
– Timber frame construction
– Roof sarking
– Cladding
– Timber
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