Structural Design shed – cold-formed steel – greater than 9m and less than 12m


Price given above is notional. Contact us to get a quote, based on the needs of your project.


Structural Design of shed – cold-formed steel (c-section) – span greater than 9m and less than 12m  : drawings and calculations.

The shed will typically have a gable roof, with main frames having moment connections comprising of welded end plates, bolted across the joints. Other materials, roof shapes, and connections are possible except typically at higher price as we have less spreadsheet automation for the calculations.

It should be noted that gusset plate (bracket) connections typically require testing. Whilst non-linear finite element analysis (FEA) can be used to assess such connections, such modelling needs to be calibrated against testing, therefore testing cannot be eliminated altogether, it merely allows fewer tests. We have had both end plate connections and gusset plate connections tested at the University of South Australia. The location of web stiffeners and flange doubler plates is important to the structural adequacy of end plate connections. Whilst location of lateral bracing is important to prevent distortion of frame when gusset plate connections are used. Note that some bracket connections are proprietary products and there are no technical specifications or design manuals available, so these brackets are limited in use to the suppliers own sheds.

Shed Design & Documentation

One person produces the drawings and calculations, this is typically faster and more efficient than alternating between engineer (calcs) and drafter (drawings). Drawings and calculations feedback into one another and drive one another. Cannot determine the size of structural sections until know the size and shape of the building. Cannot detail connections until know the size and shape of structural sections used. Whilst the final shape and size of connection cannot be determined until calculations have assessed its structural adequacy. So there is a repetitive cycle going from drawings to structural calculations and back round to drawings and repeating the whole cycle. One cycle is rare, two to three cycles would be common for simple projects, whilst five of more cycles would be required for more complex projects.


The drawings are typically drawn on A4 or A3 drawing sheets. The A4 sheets can be enlarged by doubling to A2 and A0 sheets, whilst the A3 can be enlarged to A1. Steel details typically drawn at a scale of 1:10, and concrete details at scale of 1:20.  Whilst plans and elevations are drawn at a standard scale (eg. I have a scale rule that is suitable) to fit the paper, since these are typically stick diagrams there is no loss of information at smaller scales and no gain of information at larger scales.  The drawings are provided in pdf format, though if required we can produce paper prints at A4 or A3 size. If desire larger prints then you will have to arrange such with a printing/plotting service.

The drawings can comprise of the following, as far as possible we place one object or view per drawing sheet.

  1. General Notes
  2. Material & Connection Schedules
  3. Footing Plan
  4. Framing Plan
  5. Elevations 1 to 4 {Typically on one sheet. Top: Front adjacent to right side. Bottom: Back adjacent to left side}
  6. Sections (stick format) each location that the section changes
  7. Typical Detail Section
  8. Footing Detail
  9. Knee/Eaves Detail
  10. Ridge Detail
  11. Additional Details as required.


Calculations start with simple synopsis explaining purpose. Then can comprise of the following:

  1. Calculation of Dimension & Geometry as required for Structural calculations
  2. If map available, then circle on map representing the 1000m averaging distance for wind terrain category with judgement of terrain in 8 cardinal directions.
  3. Site Design Wind Speed (checked in 8 directions, reduced to 2 orthogonal directions, and then maximum)
  4. Calculation of Live loads and Dead Loads
  5. External Wind Pressure Coefficients
  6. Printouts from Multiframe/Microstran of the Frame Analysis (presented as either diagrams or tables)
    • Structural Model
    • Loads & Load Cases
    • Design-Action-Effects
  7. Main Member Design Checks
  8. Column Base Connection Check
  9. Knee/Eaves Connection Check
  10. Ridge Connection Check
  11. Other Connection Checks
  12. Roof Cross Bracing and struts
  13. Wall Cross Bracing and Struts
  14. Roof Purlin check (including local pressure extents)
  15. Wall Girt check (including local pressure extents)
  16. Wall Girt (end wall) check (including local pressure extents)
  17. End Wall Column (mullion) Check
  18. Footing Check (typical column, end wall column, braced columns)

Most calculations are done using MS Excel structural design workbooks all produced in-house. Occasionally we may have to produce some hand written calculations or produce a new Excel worksheet/workbook.

Duration depends on the details. If building is simple construction, then maybe possible to confirm member sizes in 24 hours, there after take at least 2 days to produce documentation (drawings and calculations). If there are complicating factors then will take at least one to two weeks.  If we have a lot of work on then there could be a 8 to 12 week wait. Currently 2019 week 11, we can start as soon as given go ahead.

NB: The web store has pricing for: 3, 6, 9, 12, 15, 18m sheds. Subject to certain constraints the design effort is the same as long as the structural form doesn’t change as the building increases in size.  Typically as a building increases in size, the number of features also increases and this interferes with the common structural from. For example for a small shed the end wall doesn’t have any doors, whilst a large shed may have multiple roller doors and PA doors, this in turn requires end wall columns spaced to suit, which in turn then affects the spacing of roof struts. The result is that there is a minimum fee, which cannot be made lower by reducing the size of the building. It is thus preferable that small buildings are designed once and built multiple times. However, we try our best to keep fees low to accommodate DIY and owner-builders.



  1. [03/03/2019] : Original
  2. [14/03/2019] : Revised Fees, expanded description.