Waterproof decks – the deck is springy

Causes

There is damage to the substrate and/or framing due to water entry through the membrane or through adjacent wall claddings 

The substrate material is not thick enough to span the rafters/joists

The particleboard used as a substrate has deteriorated

Listed under: Exterior, membranes, timber and wood-based, particleboard, balconies, cladding, decks, framing, moisture, leaks, weathertightness

Cause

There is damage to the substrate and/or framing due to water entry through the membrane or through adjacent wall claddings 

Repair

  • check the deck structure from below for evidence or water leaks and substrate or framing deterioration or engage a well-experienced building surveyor to do this. The source of water entry must be clearly identified before any repair work begins
  • where leaks are through adjacent wall cladding, repairs must be made to the cladding as well as the deck membrane
  • in all cases where significant leaks are found, engage practitioners (building surveyor, builder) who have experience in identifying and remedying weathertightness problems
  • if the deck framing is sound but the substrate is damaged, the membrane and substrate should both be removed and replaced. The new substrate should be appropriate for the purpose, such as H3.2 CCA-treated, minimum 17 mm thick plywood. Ensure the recommendations and requirements of the membrane manufacturer are followed
  • if the membrane was installed in recent years, call the installer back. Deck membranes still under warranty should be repaired by the contractor who carried out the original membrane application or by another applicator approved by the membrane supplier. Homeowners can take action for up to 10 years after building work is completed if implied warranties set out in the Building Act have not been met. This is likely to apply if the leaks are the result of poor membrane installation
  • installation and/or repair of deck membranes is not a DIY job. Membrane manufacturers and suppliers typically train and license applicators in the use of their membranes. A warranty may only apply where application or repair is carried out by someone licensed by the supplier
  • where the membrane has not proved to be weathertight for a minimum 15 years, a building consent is likely to be required for the repairs
  • check the condition of deck membranes at least once a year to ensure there is no debris on the membrane, no damage and no breakdown of the membrane surface

 

Back to top

Cause

The substrate material is not thick enough to span the rafters/joists

Repair

  • as for first repair above. The substrate must be replaced with material thick enough for the spans

Back to top

Cause

The particleboard used as a substrate has deteriorated

Repair

  • as for the first repair. Particleboard is not suitable as a substrate in this situation and must be replaced with a suitable material such as H3.2 CCA-treated, minimum 17 mm thick plywood

Back to top