Near fatal deck collapse

This time last week we saw another potentially fatal deck collapse in Lane Cove NSW.

Locally in Queensland we have had two recent failures at Morayfield in October 2009 and one at Ascot in November 2008.

Based on inspection sampling results from Victoria 2% of the decks constructed for residential use have serious design flaws which could precipitate a collapse.  8000 decks was estimated Australia wide as a total number of defective or unsafe structures.   That is an enormous level of potential loss, injury or death.

Deck collapses can be fatal but could be prevented with some care and attention.

Should you be concerned?  Queensland with its warm climate is well suited to enjoying outdoor entertaining using an elevated timber deck for parties and family gatherings.

Assess the risk.  A high level deck or veranda 2.5-+3m above the ground is potentially a fatal height if a structural failure occurs – match your need for confidence in the deck with the consequences of failure.

Start with a self inspection

Is there direct bearing support for joists and bearers or limited support?

What is the condition of steel fixings if present?

Conduct a timber rot hammer tap survey.  Rot or termite attack will soften the timber and sound dead and dull.

Are there non-standard connections, extensions and add-on features present - If it doesn't look quite right is probably isn't?
Are there obscured support conditions - look harder if you can’t see how support is provided particularly for bearers.  This can be tricky.  If rainwater can drain into a concealed joint this is a potential problem worth more effort to confirm conditions are ok behind the cladding.
Get a second opinion and some qualified advice if in doubt.

A good deck should comply with the general arrangements offered by the Timber Queensland guides.
See attached diagrams below.

Note the Ledger connection to the house (which was apparently fixed in the Lane Cove deck with only twelve nails) is a connection worth particular attention.  Just because the deck has held-up to date doesn't mean the connections are adequate or offer a reasonable factor of safety.