Deck balusters/posts, balustrades and barriers – insecure when pressure is applied

Cause

Rotten timber

Repair

  • replace all rotten or damaged timber. If using Pinus radiata, it should be treated to minimum H3.2, otherwise use a timber that is naturally durable. For framing, use timber grade of at least SG8 (wet in service). Infill members may be SG6 (wet in service)

  • select metal fixings with at least the same durability requirements as the timber they connect. (NZS 3604:2011 Timber-framed buildings has the details in section 4.4). Steel fixings in ‘sheltered’ locations – open to airborne salts but not rain washed – must typically be galvanised as a minimum. Those in ‘exposed’ locations – open to airborne salts and rain – require Type 304 or 316 (for marine exposure) stainless steel

  • details for deck barriers can be found in this Build magazine article and in this MBIE publication

Cause

Fixings have pulled out or corroded

Repair

  • replace all missing or corroded fixings. Check that the timber around the fixing is sound – if timber is damaged by fixing corrosion, replace the timber (see details above)

  • select metal fixings with at least the same durability requirements as the timber they connect. (NZS 3604:2011 Timber-framed buildings has the details in section 4.4). Steel fixings in ‘sheltered’ locations – open to airborne salts but not rain washed – must typically be galvanised as a minimum. Those in ‘exposed’ locations – open to airborne salts and rain – require Type 304 or 316 (for marine exposure) stainless steel

  • details for deck barriers can be found in this Build magazine article

Cause

The barrier structure is inadequate (undersized framing or framing support too far apart)

Repair

  • add new framing members to strengthen the existing structure (replace damaged timber as necessary to ensure a safe and secure barrier)

  • barrier details can be found in the MBIE guidance document Guidance on Barrier Design

  • some details for deck barriers can be found in this Build magazine article

  • if using Pinus radiata, ensure it is treated to minimum H3.2 – otherwise use a timber that is naturally durable. For framing, use timber grade of at least SG8 (wet in service). Infill members may be SG6 (wet in service)

  • select metal fixings with at least the same durability requirements as the timber they connect. (NZS 3604:2011 Timber-framed buildings has the details in section 4.4). Steel fixings in ‘sheltered’ locations – open to airborne salts but not rain washed – must typically be galvanised as a minimum. Those in ‘exposed’ locations – open to airborne salts and rain – require Type 304 or 316 (for marine exposure) stainless steel

Cause

Deck baluster/balustrade/post fixings are loose

Repair

  • check and retighten all bolt fixings to the balustrade or posts – fixings can become loose as a result of timber shrinkage (or they were not particularly tight in the first place)

  • where access is available, check and tighten as necessary all other bolts on the deck structure at the same time

Cause

The baluster/balustrade/post fixings to the deck are inadequate

Repair

  • the posts should be fixed with M12 bolts and 50 x 50 mm washers with at least two bolts per baluster or post
  • select metal fixings with at least the same durability requirements as the timber they connect. (NZS 3604:2011 Timber-framed buildings has the details in section 4.4)

Cause

Deck barrier does not meet with current Building Code requirements

Repair

  • if a barrier is unsafe it should be repaired or replaced. Where a deck barrier is being completely replaced, the new barrier must meet Building Code requirements, and in particular clause F4 Safety from falling. F4 requires that where people could fall 1 metre or more there must be a barrier. Among other requirements, barriers must be of adequate strength to withstand the impact of people and the pressure of people against them
  • the minimum height of a deck barrier in a home is 1 m (Table 1 in the acceptable solution F4/AS1). There are particular requirements to protect children under 6 (also given in F4/AS1, Figures 1–4) including that the maximum vertical gap in a balustrade is 100 mm to restrict the passage of children
  • barriers with full height vertical members are difficult for small children to climb
  • where pinus radiata timber is used for the replacement barrier, it should be treated to minimum H3.2
  • barrier fixings should meet the requirements of exposed locations, open to airborne salts and rain. These are type 304 or 316 (for marine or geothermal exposure) stainless steel
  • if part of an existing barrier is being repaired, the finished work must comply with the Building Code to at least the same extent it did before the repairs. (The details are in sections 42A and 112 of the Building Act.) In other words, repairs cannot reduce things such as the structural integrity or durability of the barrier
  • you can find more details in this Build magazine article