InSite | Timber posts and beams for canopies, porches and bay roofs

Timber posts and beams for canopies, porches and bay roofs

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Provision of information


For warranty purposes, timber posts and beams for canopies, porches and bay roofs:


  • Must have a suitable durability and use class (to BS 8417) for its intended end use or be naturally durable.
  • Must be adequately treated or finished to resist insect attacks (or must be naturally durable to resist attack), and be suitable for the position used within the structure. All timber treatment should be in accordance with relevant British standards and Codes of Practice. For further information, see appendix C of our Technical Manual.
  • Must be designed by a Structural Engineer to withstand all relevant loadings.
  • Must be appropriately seasoned to prevent excessive shrinkage and movement.
  • Timber posts should not be built into the ground.


Please note: Where oak posts and beams are used to form the structural support, canopies must:

  • Not exceed 3m2 in area
  • Should be structurally independent from the dwelling with no timber element built into the external walls
  • The canopy roof must not link with or be part of the roof over the main property.



Contact with the ground


Timber posts should not be built into the ground as this can lead to the timber post absorbing excessive amounts of water or moisture which can lead to decay reducing the service life of the post.


DPC material is often sandwiched around the timber post and the ground as an attempt to protect the buried post, however for warranty purposes this is not a suitable solution. Posts must not be in direct contact with the ground and should be supported off a suitable raised foundation support.


Timber posts should be adequately treated to provide the required durability and where they are cut on site, the ends must also be treated.


In addition, the following should be adhered to:


  • Timber posts should not be built into the ground or sunk into pockets.
  • Metal connectors should be used when timber posts are installed onto brickwork or concrete supports.
  • The metal support must provide a clear air path to prevent the timber post absorbing moisture whilst also providing drainage and ventilation.
  • Timber posts must be raised by at least 150mm from the finished ground level.
  • Timber posts must be supported on suitable foundations.
  • All metal fixings must be made from corrosion resistant materials (such as stainless steel) which have been hot-dipped galvanised.
  • Metal fixings should be verified to be suitable with the treated timber.
  • The same kind of metal for both fixings and connectors should be used.


Warranty stance


Timber posts should be of a suitable durability and use class and be appropriately preservative treated. Timber posts should not be in direct contact with the ground and any metal fixings and supports should be appropriate for their end use.


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Every care was taken to ensure the information in this article was correct at the time of publication (July 2022). Guidance provided does not replace the reader’s professional judgement and any construction project should comply with the relevant Building Regulations or applicable technical standards. For the most up to date Premier Guarantee technical guidance please refer to your Risk Management Surveyor and the latest version of the Premier Guarantee Technical Manual.

Ref: TS-3206

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