The construction industry has minimum requirements for graded timber which are suitable for their end use. There are 2 main types of timber used in construction, kiln dried and unseasoned timber.
Stress graded unseasoned timber (Wet Graded) can be used for some load bearing applications e.g Agricultural Purlins and can be used for other uses where the thickness is 100mm or above.
Timber for use in load bearing situations is typically required to be graded to strength classes usually C16, C24 and TR26 in the UK (TR26 and C24 are a higher structure grade than C16). Graded timber is generally kiln dried (moisture content is reduced to required levels in a kiln), although can also be wet graded (which is moisture content at ambient levels and not kiln dried). It is increasingly being specified as regularised which means that the product has a machined finish, giving a regular consistent section size.
British carcassing (often referred to as Home Grown) is typically only available to strength class C16, due to faster rate of growth, due to its warmer climate.
Imported carcassing is widely available to C24 as it tends to have a slower rate for the same size tree.
Unseasoned sawn timber can vary in size as the timber is generally cut from the log. It is typically used in fencing and landscaping applications and it will contain differing amounts of moisture as it has not been kiln dried, this will cause more movement but is not particularly a problem due to its end use. This does not require grading and is usually sourced from British sawmills.
When timber is graded by machine, it has to pass certain tests the main one being a test of the deflection of the piece under applied pressure, once it passes this test it is given a grade stamp which identifies the grade, producer, identification number and condition. A similar stamp is used when visual grading takes place. An example of the grade stamp is every piece of graded timber must have a stamp similar to the one shown which is visible to enable a user or inspector to assess the quality of the timber.
Treatment of carcassing timber is becoming increasingly popular in the construction, landscaping and packaging industry. We can offer a service to treat the timber to various pressure impregnation cycles, which relate to a user class or end use required.
Softwood timber is one of the most environmentally friendly building products available to us. It exceeds all the current building regulations when used in the correct application and with the correct specification and grade.