Steel roof weight per m2 - How light?

[sybie99]

Hi,

Having worked in the UK and now in South Africa, I have noticed a difference in the steel weight engineers design to for steel roof structures. QS's are very strict and will inform a client if an engineer over designs, as they have learnt from experience what tonnage will work for a specific roof structure.

I am talking about steel portal frames spanning between steel columns, or trussed roofs spanning between concrete columns. Of course in the UK there is an allowance for snow loads which explains why in the UK tonnages are heavier.

Here in SA a roof, including purlins (generally cold formed lip channels) should not be more than 20kgs per m2. More like 15 kgs/m2 to keep the client happy. That is a VERY light roof and takes some time to refine, but it is designed to BS5950 code requirements.

Can anyone who designs structures in a warm climate area with no snow loading tell me what they use as a rule for steel tonnage per square meter for steel framed soft roofs?

This is purely for interest sake, as a guideline.

Thanks

 

[BAretired]

What is a QS?


BA

 

[dik]

Quantity Surveyor was one term for QS?

Dik

 

[BenAustralia]

Depends heavily on location here in Australia. I work in Queensland, so no snow loads, but the wind pressures vary greatly from Brisbane to far north. In the cyclonic areas we see very high suction values from wind, wind speeds exceeding 300 km/h mind you.

Maybe someone from a non-cyclonic state in Aus could help you

 

[BAretired]

An engineer should not be overly concerned about a Quantity Surveyor informing a client that a particular design exceeds the tonnage expected based on the QS's experience. An engineering design must satisfy the appropriate building code provisions.

If a particular design turns out to have a substantially larger weight of steel than typical, then it is a good idea to review the design to find out why, but meeting the QS's expectation should not be the primary focus of the design engineer.



BA