Unseasoned Hardwood Shrinkage

Shrinkage rates for some common australian species are provided in table 1.

Unseasoned hardwood shrinkage.

Shrinkage in unseasoned members. An indication of shrinkage rates for individual species is given in technical data sheet 16 species properties and uses. Do not enter decimals or fractions and do not enter the percentage sign after the value. Some other hardwood species can shrink in excess of 10.

Such as hardwood floor joists figures relating to the shrinkage from unseasoned to 12 moisture content are of greater importance. Partially seasoned timber can come from unseasoned timber that has partly dried or from seasoned timber used in a moist environment so that it has taken up moisture and increased in moisture content above 15 mc. Allowance should therefore be made for shrinkage in unseasoned bearers joists and decking and for the gaps that will develop between the decking boards. Unseasoned timber can be expected to shrink as its moisture content reduces.

The amount a piece of wood will shrink lengthwise called longitudinal shrinkage is so small typically about 0 1 to 0 2 that it is usually inconsequential to the volumetric shrinkage however plywood greatly benefits from the low longitudinal shrinkage of wood layers of wood veneer are glued together with the grain direction of each ply oriented perpendicular to the adjacent ply. As the timber dries out seasons shrinkage will occur which varies between species from say 3 12 in the common hardwood species and 3 5 in the common pine species. Seasoning hardwood timber enhances the basic properties of the timber increasing the stiffness bending strength and compression strength. This does not mean unseasoned timber is unsuitable for any use it just means you need to be aware of and maybe detail for any shrinkage that may occur.

Once timber has dried to the moisture content of its environment called its emc it can and will of course continue to swell and shrink as it s environment changes. Wood shrinkage calculator width. Enter the initial moisture content mc. Enter the actual measured width of the lumber in inches and fractions of an inch centimeters if metric.

Also included in the table. Shrinkage 6 mm per 100 mm should be expected for unseasoned hardwood. Consideration must be given in design construction to allow for shrinkage where unseasoned timber is used. Hardwood species of high shrinkage eg.

Solid seasoned hardwood timber tends to have a superior dimensional stability to unseasoned hardwood timber and is much less prone to warping and splitting. The figures in each class represent the average shrinkage that occurs from unseasoned to 12 moisture content. Seasoning refers to the process of removing moisture from timber or drying timber.