Is your shed safe?
Consumers should be aware that many shed companies are falsely advertising that their respective sheds are safe when in fact they are potentially unsafe. Furthermore, they claim to comply with the Building Codes of Australia (BCA) by inferring that a Low High Low (L/H/L) wind test has been endorsed and approved by their respective suppliers. What the public are not aware of is that the L/H/L testing has very little to do with the total structural integrity of the building. For example the L/H/L testing only applies to the "immediate members" namely, the roof battens, roof cladding, and fixing screws. The BCA ruling does not state that unless an L/H/L testing certificate is produced, the shed is unsafe. Unfortunately, ordinary everyday people, particularly those in tropical cyclonic areas are being misled into a false sense of security.
At the end of the day, the design certificate should be endorsed by a competent structural engineer who takes the whole structure into account; Including:
What makes a shed safe?
(a) The integrity of the portal itself.
(b) Portal or Stud Frame Tie downs.
(c) Connection of base plate to column.
(d) Knee plate and Apex plate connections.
(e) Roof bracing, fly bracing and wall bracing.
(f) Wind locks in high wind areas are needed as an essential item to protect the "Immediate members"
NOTE: Unless all the above components are acting together, the "immediate members" are not protected
While the above components are not classified as "immediate members" however the L/H/L testing should include the dependence and strength of the whole structure just as an umbrella needs the frame and spokes to hold the canopy intact. If the umbrella spokes are made from straw, then the umbrella collapses just as the L/H/L testing would mean nothing once the inside is exposed to wind. In the same way, engineers taking shortcuts by using the diaphragm method* are putting lives at risk. The L/H/L testing is powerless without the other components holding it together.
Decision makers within the many individual building and planning departments should be made aware as a duty of care that those individuals who appear to be the gatekeepers of the cold form shed industry are in fact opening doors and allowing potential weapons of destruction to dot the landscape, especially industrial sheds that are built in areas that fringe on or are within reach of suburban residential areas where the concentration of most damage will be evident.
*Diaphragm method. This method takes into account the use of the entire frame tied together with wall and roof battens and bracing which acts as a diaphragm once the sheeting is fixed to the members. This method is limited, and only works when the structure is fully enclosed without the possibility of being exposed to inside wind pressure. Many structural engineers within the cold form section industry are now pushing the boundaries with "engineering tricks" that take little notice of the safety factors. Many incidences of the larger portal failures are "covered up" with various excuses as to why the structure has failed.
Fact 1 - Domestic Sheds
When wind pressure forces in a roller door or a larger opening, the roof battens and roof cladding are solely dependent on the fixing screws through the rafter. The truth is, both the batten material and the high tensile galvanized “C” section rafter, whether Australian or Imported Steel, is simply too thin to hold the screw when subjected to a violent twister such as the illustration below.
Roller doors should be braced or wind locks approved by a certified engineer to avoid wind from doing damage. The damage shown here was caused by the failure of the roller door.
The top photos show that after the roller doors were blown in, the roof was peeled from the rafters.
The complete roof was blown more than 300 meters from the structure. Notice that the rafters are still in tact : Therefore using the LHL tested product as an endorsement is questionable as to the "safeness" of the structure.
Consumers and Building Inspectors should be more concerned about the points listed above.
The shed is not safe once the underside of the roof is exposed to extreme wind forces.
Forces such as cyclone Yasi show that the L/H/L testing alone does not mean that the shed is safe. When the inside of the structure is exposed to high winds, the "immediate members" simply blow away.
Fact 2 - Larger Sheds
The result of incompetent engineers who use unethical practices at the cost of the end user :
21m span failure during construction
21m span failure during construction
25m span collapsed
25m span collapsed
If you are concerned about safety factors that may impact on your neighbourhood, or have evidence of failures during or after construction please have your say.
Report Shed Damage
The disregard for the more important structural components, particularly the larger Industrial spans over 20 meters that are failing during construction and becoming hazardous with potential for death and injury is becoming increasingly a concern for many structural engineers, especially those associated with this "false security" of the L/H/L testing.
Regional councils, suppliers, and those who advertise that their sheds as safe because of the L/H/L testing, should be held accountable if their sheds are proved to be unsafe.
If consumers have any concerns regarding the structural integrity of their building, structural engineers are available “free of charge” to advise if the shed is in fact safe.
Have your say
- Should there be a registry of engineers' names in the likely event of failures?
Should responsibility fall on the structural design engineer who is responsible for the structural integrity of the building?
If an independent body claims that they have the expertise to endorse or make legitimate the safety of a building, should each individual engineer engaged or associated with that body sign his or her name on the endorsement presented by the independent body so that responsibility rests on both the body and the individual engineer?
Should Regional Council Building Inspectors be aware, or at best, made aware, that a number of engineers are using questionable methods, especially with the larger portal frames, not excluding methods of construction that call into question serious safety issues?
When doubts arise as to the safety of the structure or concern for safety while under construction, or should doubts arise with regard to the safety of residents living close to industrial and commercial sites in the event of destructive winds, should a Building Inspector have the authority to have the individual engineers calculations verified either by having the engineer in question submit the calculations, or, if still in doubt, have an independent evaluation done by a competent engineer or panel of competent engineers not associated with the cold formed steel section?
Should engineers with doubtful reputations, those involved with failures and potential failures involving larger portals that have failed during and after construction have their respective professional engineering licence suspended?
Should insurance companies be made aware of potential damage bills that may be avoided with the likelihood of injury due to failures during construction and after construction of the larger portal frames?
Should regional councils be held personally accountable if there is evidence they have ignored issues with regard to the danger of larger portals failing, and causing injury and or fatalities?
Should emergency services be notified and have a registry of suppliers wherever and whenever larger industrial portal frames are being erected close to residential areas?
Should residents be made aware of the dangers concerned with the larger industrial and commercial buildings and have precautions in place to protect themselves from potential injury and fatalities?
Should those involved with L/H/L testing disclose the results of the testing and disclose a list for public viewing, showing the endorsement from the laboratory conducting the testing.
In the event of structural damage, injury, or death, should those associated with the endorsement of unsafe structures be prosecuted and held criminally negligent?
Have your say
Those with concerns, including structural engineers and portal frame fabricators, are invited to report shed failures by emailing us using the form below or posting to ShedFailures.com.au, P.O. Box 758 Gympie 4570.