Technical Notes: Timber Canopies, carports, pergolas and verandahs




Technical notes which complement the Design guide and the specification for canopies.  Some time around 2005 the councils started to crack down on canopies, especially those attached to houses: as a consequence there was a rapid influx of people seeking structural assessment: some 50 timber canopies arriving in week. Whilst we had the design guide and could cut that up into calculations for specific spans, it wasn’t suitable for handling all the variations and additional features of specific projects. The result was a need for a rapid estimating technique, and this document is a composite of the various technical notes written to address various issues encountered.

Besides containing approaches to estimating the member  sizes it also contains derivation of the frame formulas used in the spreadsheet developed for assessing timber framed doubly pitched canopies. Also included is derivation of the Rutledge formula used for footings.

Contents Include:

  1. Tabulated calculations from zero to 12m in 300mm increments, rafters at 1200mm spacing and roof pitch 22.5 degrees. {NB: Maximum spans most likely limited by maximum 6m length of timber for collar-tie. }
  2. Design charts plotting design-action-effects against member capacities.
  3. The estimating techniques
  4. Derivation of frame formula
  5. Assessment of free standing canopies
  6. Assessment of existing house structure
  7. Attachment of canopy gable end to house
  8. Attachment of canopy to house hip
  9. Capacity Tables for Timber (F4, F5, F7, MGP10, MGP12, MGP15) to AS1720
  10. Capacity Tables for Connections (Nails, Self-drilling screws, Bolts) to AS1720
  11. Capacity Tables for Bolts to AS4100

Individuals seeking development approval will need to get their project documentation certified, by obtaining a Certificate of Structural Adequacy.


Is a pdf file contained in a zip file. It is scanned from our original master printout (mostly hand written), and then edited to replace sheet headers with our current contact details. The document is released under a creative commons attribution, non-commercial, no derivatives license.


The document is a read/print pdf file. As the authors of the document we hold the copyright and choose to release under a creative commons attribution, non-commercial, no derivatives license. Subscribers/Licensees are thus free to share the document with their friends, however such friends will not receive nor have access to updates, nor will they have access to support. Support is by email, and comprises of clarification of meaning.  {NB: If want us to specify and be responsible for the size of structural sections for your canopy, then you will need to supply us with drawings and pay for the services associated with a certificate of structural adequacy.}


Future Releases:

Related Tools:
  1. Footing Calculator using Rutledge Formula
  2. Calculator for Pocket Footings