Cupping of stained or clear-finished timber weatherboards
Listed under:
Exterior,
finishes,
clear finishes,
timber and wood-based,
stain,
timber,
cladding,
walls,
moisture,
wall cladding,
stained or clear-finished timber weatherboards
Cause
Thermal expansion and contraction of timber
Repair
- if cupping is minor and no water is getting behind the cladding the boards may be left
- if the boards have been finished with a clear coating or stain, the finish should be re-applied. Confirm the weatherboards are not damaged before re-applying the finish
- for uncoated timber (such as cedar), apply a clear finish, paint or stain to reduce moisture absorption. Re-apply stain every 2–4 years
- before applying a finish, the weathered timber must be sanded back to sound timber to ensure the coating will adhere to the timber
- where water entry is possible through open laps or joints, replace affected boards
- when replacing boards, check that wall underlay (building paper) and framing behind weatherboards are sound
Cause
Swelling/shrinkage due to moisture absorption
Repair
- if cupping is minor and no water is getting behind the cladding the boards may be left
- if the boards have been finished with a clear coating or stain, the finish should be re-applied. Confirm the weatherboards are not damaged before re-applying the finish
- for uncoated timber (such as cedar), apply a clear finish, paint or stain to reduce moisture absorption. Re-apply stain every 2–4 years
- before applying a finish, the weathered timber must be sanded back to sound timber to ensure the coating will adhere to the timber
- where water entry is possible through open laps or joints, replace affected boards
- when replacing boards, check that wall underlay (building paper) and framing behind weatherboards are sound
Cause
An insufficient gap was left between rusticated weatherboards during installation where boards have been finished with a clear coating or stain
Repair
- if cupping is minor and no water is getting behind the cladding the boards may be left
- if the boards have been finished with a clear coating or stain, the finish should be re-applied. Confirm the weatherboards are not damaged before re-applying the finish
- for uncoated timber (such as cedar), apply a clear finish, paint or stain to reduce moisture absorption. Re-apply stain every 2–4 years
- before applying a finish, the weathered timber must be sanded back to sound timber to ensure the coating will adhere to the timber
- where water entry is possible through open laps or joints, replace affected boards
- when replacing boards, check that wall underlay (building paper) and framing behind weatherboards are sound