Choosing The Right Timber for Floor and Roof Joists
The C16 vs C24 Showdown.
20:36 06 July 2020
Softwood timbers, which are very commonly used in load-bearing structural applications, always need to be stress graded, classified and clearly marked for strength in order to ensure that they comply with the guidelines established by building codes and regulations. Some companies use X-ray scanning and imaging technology to make sure the timber complies with the set grading guidelines, while some still follow the conventional visual grading system wherein a timber grader makes an assessment of things including natural factors like knots, wange, splits, shakes, and slope of grain etc.
Timber comes in an assortment of grades ranging from C14 to C40 and D30 to D70. There are several species of timber out there and each species demonstrate different strength properties, which is an important thing that needs to be factored in at the time of narrowing down on your options. Although there are quite a few strength classes to pick from among softwood and hardwood timbers ,the C16 and its slightly stronger counterpart the C24 timber are believed to be the most popular and widely used softwood timber classes with extensive applications in several commercial and domestic installations.
What is C16 timber? What is C24 timber? Let’s try to understand the convention of naming the strength grades first. The letter C denotes the species of timber and the ensuing number points to the strength grade. For example, the ‘Ç’ in C16 or C24 refers to conifer, a softwood tree species whereas the number 16 or 24 is the actual indicator of the strength class. Put simply, the higher the number the denser and stronger the timber board is.
It’s difficult to say for sure which is better. The right softwood timber for your project essentially depends on your specifications and the features that matter to you. Read this through and consider your structural requirements thoroughly before you decide which timber to buy.
Having said that, here are a few important things you should know about the C16 timber and C24.
C16, the Cost Effective Option
Obtained from fast-growing trees, C16 grade timber is believed to have more knots than the C24 grade which is primarily sourced from slow-growing trees. As a result, they’re less dense and are not suitable for projects that require wider span.C16 boards may be the preferred choice for most construction projects involving roof, walls and floor joists, but strength-wise, they’re inferior to C24.
A constituent of a lower strength grade, C16 boards have good compression and density numbers but they also come with a number of defects which make them ineffective for heavy load-bearing applications. A swift examination of a C16 grade softwood board will reveal some serious defects such as wanes, grain deviations and perhaps a bit of a bending too. These are not at all insignificant and supposedly have a definite impact on the overall strength and the amount of load a board can bear. Besides, some C16 grade boards might have some odd sap stains which are trivial defects that don’t have any kind of impact on the amount of load they can bear in service. Don’t get us wrong. C16 timber is still going to be strong and good enough for most projects. In fact, it’s the preferred choice for contractors who’re after good performance at a cheaper cost.
But when you bring strength and aesthetic looks into the equation, C24 grade boards, clearly, score well over C16 boards.
C24, the Premium Option:
C24 Timber, being stronger than C16, doesn't have as many defects. As was mentioned earlier, C24 boards are made from slow-growing trees and are more dense in comparison with bog-standard C16 boards. And that translates to better strength, longer life and great structural stability overall. Goes to show why C24 is the go-to choice for applications where it’s required that the timber remains strong enough for the load being placed on it, and in those instances where structural calculations indicate that it’s necessary. For example, projects where the strength of the boards is too crucial such as balconies, terraces, bridges and decking projects that require wider span. Contractors who focus on aesthetic appeal pick C24 boards as well, particularly for the wider rafter center of these boards which lets them shape the final aesthetic in an eye-catching manner.
Choosing the right structural timber for your projects is no small matter. Looking for quality softwood C16 and C24 timber made to certain specifications that provide better life and better protection against decay and insect attack? You must talk to Armstrong Supplies, the UK based timber suppliers that provide a wide assortment of timber from different species and grades to meet your timber needs. Head over to their website today to leaf through their long list of carcassed, strength graded timber, which come in different lengths and cross sections.