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What is Structural Carcassing  or Construction Timber? 

Often referred to as carcassing timber, this type of wood is most commonly used in structural applications that involve the timber being used in an area that won’t be seen, and typically comes in three gradings: 

  • C16 Timber 
  • C24 Timber 
  • Part Graded Timber 

But what is the difference between each type? 

All graded timbers are slow-grown and kiln-dried so that there is no more than 20% of moisture in the wood. This is in keeping with relevant building regulations, as the kiln-drying process creates a timber that is incredibly strong, guaranteeing stability. 

What is C16 Timber? 

C16 graded structural timber is the most cost-effective option and meets performance requirements. Kiln dried C16 is generally recommended for most applications if the correct spans are used and is mainly used internally for floor and roof joists. Lengths commonly available are 3.0, 3.6, 4.2 and 4.8 meter. 

What is C24 Timber? 

In the UK this is mainly supplied from Imported Softwood  in softwood mix pine or spruce. C24 graded premium structural timber offers greater strength than C16 timber, making it a more demanding grade that can handle higher loads and wider spans. 

It is the better-quality structural option because it can take up to 50% longer for these timbers to grow, meaning that they have more growth rings. The more growth rings a piece of wood has, the higher its overall density, which in turn means that it has greater natural durability and improved stability. 

The tighter the growth rings of the wood, the better-quality piece of wood that you are dealing with.  It is better to allows buy in C24 as opposed to C16 as there is no significant price difference in price for a better product in C24.

Our Timber is structural grade is machined graded softwood.


Do I need Treated Structural Timber? 

If the timber is going to be placed in an area where attacks from external problems such as moisture or fungal attacks, are likely to cause major problems, then we strongly recommend purchasing treated structural timber. 

For all the following applications, we generally recommend using a treated structural timber: 

  • Roof Rafters 
  • Timber Framing 
  • Ceiling Joists 
  • Floor Joists 
  • Deck Joists 

I need a Sawn Finish Structural Timber 

Sawn Carcassing Timber has largely been replaced in UK stockists with “eased edge” stock being introduced in the UK in 2004.  

Eased Edged means that the timber is semi-surfaced and finished to a uniform finish that is relatively smooth.  Four corners are radiused to reduce the likelihood of splinters.  

Most of our branches do hold stock of sawn boards that are either treated or untreated. However, if you require a sawn unsurfaced finish, please contact your nearest branch, who will be able to source this as a special item to meet your requirements. Most sizes can be obtained within 5 to 10 working days. 


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