Framing outline is visible on the cladding on cold mornings

Cause

Condensation is forming on cladding where there is insufficient or no insulation

Repair

  • clean walls to remove any moss or mould growth and reduce pattern staining
  • insulate the walls or replace insufficient insulation when renovating the house. Retrofitting wall insulation requires a building consent
  • if internal plasterboard linings are in poor condition, or a very old house still has its original timber wall lining, it may be cost effective to replace the linings and install insulation at the same time. Replace the old wall underlay with new (or install wall underlay if there is none) at the same time
  • check that the wall framing is dry and in good condition
  • when retrofitting wall insulation and underlay, take care to ensure that any rainwater that reaches the back of the wall cladding is not transferred to the insulation or wall framing
  • BRANZ researchers investigated insulation retrofit options for timber-framed walls with direct-fixed weatherboard cladding and without existing wall underlay. The most effective option at preventing moisture transfer was to install drainage plane mesh in conjunction with an underlay. You can find more details in BRANZ Study Report 484 Assessing retrofitted external wall insulation techniques and in a shorter fact sheet

Cause

Condensation forming at the framing locations when the wall is well insulated due to thermal bridging of the framing

Repair

  • if the house is well insulated and the walls are washed down on a regular basis to prevent mould or pattern staining, further action is not required