Ungraded or Graded timber?
As some of you may know, timber is much more than just a piece of wood, it has many different species, grades, shapes, sizes and uses and one of the most important things to know is what is best to be used for a specific job. In this blog I will be discussing the difference between Graded and Ungraded timber and the importance of making the correct choice of timber for the right job, so you don’t find yourself with problems in the future.
What’s the difference?
Ungraded timber is generally sold as a wet, unseasoned, mixed species softwood. It tends to have a rough sawn finish and dimension can vary from +/- 3mm to 5mm throughout the length with some twist and waney edges. Knot size, quantity, and location along with splits/shakes, waney edges and level of twists prevents the timber being suitable for internal construction requirements. On the other hand, softwood graded timber such as C16 & C24 is Kiln Dried and generally appears in a semi-planed finish and regularized to give a slightly more uniform width and thickness. Large knots and slight twists and warps can be present with the odd knot hole, but the timber has been machined tested for strength to meet the grading rules and will carry a stamp mark stating dry C16/C24 or KD C16/C24. This denotes that the timbers have been kiln dried and fit for purpose for the use in construction for internal use. Larger sections such as 100mm or 150mm thick generally are stamped wet C16 or C24 and can be supplied semi-planed or sawn subject to availability at the time of order and will not have deep, long drying cracks but still meet the grading rule.
Uses of Ungraded timber
Ungraded rough sawn carcassing has many uses such as fencing and landscaping posts, rails, pales, raised sleeper beds and packaging and these are offered in various lengths, widths, thicknesses in both untreated and pressure treated. For outdoor usage we would recommend pressure treatment in a tinted green or brown, but please note that shades can and may vary. If no further fence stain is applied, then timber colouring will fade to a lighter colour then weather to a driftwood/silvery grey appearance. Pressure treatment from NWTT will reduce the amount of rot and decay, depending on the location of use as timbers in ground contact will have a shorter life expectancy.
Uses of Graded timber
Graded timber is widely used for many load bearing applications. The “Rule of thumb” if 47mm or 75mm thickness and being used in your home for structural use, a minimum grade of KD or dry C16 should be used or the higher strength of KD or dry C24. Always check with your local building inspector if you are unsure. If you are using it for a garden structure or agricultural building, then a wet graded C16/C24 option should be suitable providing that your intentions are not to carry a heavy load.
If in doubt, check it out and don’t assume as paying a little bit extra can lower risks and save money in the long term.