Roof Decking: Thicker is not better

Improvements in the technology and performance of high tensile steel roof decking products have effectively made the old 0.60mm base metal thickness decking obsolete. Heavy gauge decking today is a throwback to the 22ga soft steel products used in the 1960s and 1970s.

If you are specifying metal deck roofing, you should be aware of the following comparisons. 
 

Materials Handling

Thicker decking is more expensive in terms of product (more steel to purchase), weight (more steel to carry), freight (higher cost to move) and handling (more fatigue or more labour to install).


Durability

The life of roof decking is determined by the coating, not the steel thickness. Corrosion protection is provided by the self-sacrificing effect of zinc-aluminium layer, which is the same thickness regardless of the base material. The thinner the base steel, the greater the relative thickness of the coating. Therefore, 0.42 bmt material is more corrosion resistant than 0.60 bmt. 
 

Foot Traffic

In terms of foot traffic loads, the advanced Stramit Speed Deck Ultra® concealed fixed decking in 0.48 bmt outperforms the older Stramit Speed Deck® 500 concealed fixed decking in 0.60 bmt material.

For example, on large shopping centres where purlins are commonly at 1200mm centres to accommodate ceiling grids, Stramit Speed Deck Ultra® concealed fixed decking in 0.42 bmt easily carries all but the heaviest foot traffic loads. 
 

Wind Load Comparison

Roof Decking Thickness Strength (kPa) at Internal Spans Shown
    1200 2400
Stramit Speed Deck® 500 0.42 2.94 0.89
0.48 6.21 1.69
0.60 4.53 1.45
Stramit Speed Deck Ultra® 0.42 6.16 3.36
0.48 6.65 3.63


The higher wind load performance of Stramit Speed Deck Ultra® concealed fixed decking allows reductions in thickness at all spans. Additionally, Stramit® Speed Deck Ultra® concealed fixed decking has full cyclonic performance, tested under repeated load cycles.  


Cost

For a typical commercial roofing system, Stramit Speed Deck Ultra® concealed fixed decking in 0.48 bmt can produce a lower roof cost than Stramit Speed Deck® 500 concealed fixed decking in 0.60 bmt material (15% lower at 1200mm spans and 14% lower at 2400mm).

Therefore, using 0.60 bmt decking means paying 15% more for a lower performing product. 
  

Installation

Older style decks rely on the fixing clip being trapped in the side lap and the side lap being forced into place - in some cases requiring a rubber mallet. The unique fixing clip and side lap of Stramit Speed Deck Ultra® concealed fixed decking allows higher performance levels to be achieved, without having to use thicker sheets with interference-fit side laps. 
  

Conclusion

Older technology products do not use the full potential of newer high tensile materials. Today, 0.60 bmt decks are no longer required because the new generation decking products provide better performance from thinner materials.
For further information, contact your local Stramit Architectural Representative.