NEW ZEALAND TIMBERS

Hokitika Guardian, 27 November 1930, Page 2

NEW ZEALAND TIMBERS

A SUMMARY SUPPLIED BY THE FOREST ENGINEERING BRANCH, STATE FOREST SERVICE.

RIMU (OR RED PINE)

Distribution.

Rimu, or red pine as it is commonly known in some districts of New Zealand, is the most widely distributed softwood in New Zealand. It grpws, in abundance in the North on the West Coast and. Southland "districts of the South Island.

Properties and Uses

Rimu is moderately hard and possesses ■ a fine uniform' and dense • texture, being easy to work and of considerable strength. Though slightly inferior to Dougins Fir (or, as it is commonly but erroneously termed, “Oregon”) in some strength properties, Rimu is superior in others, and the following comparative results of tests carried out on small clear specimens of each timber are supplied:— : , . Rimu. Douglas Fir • • MpunCoast , tain

ijfardness (side surface) 620 4 470 - 400 • ,Eor the purposes, however, for which they are used, it can be genuinely claimed that Rimu is far stronger than the imported .Douglas. Fir with which it competes, owing to the large loose knots and defects, apparent in most grades of the imported timber, which considerably decrease its strength particularly as a beam.

In beauty of appearance, Rimu is far superior to the timbers with which it is in competition, and for general building utility purposes its ease of working, high nail-holding power, and * its ability to easily take all types of artificial finish have caused Rimu to be" the most widely used timber in the Dominion. Its field of application is large, and it is used with equal success for framing joists, studs, linings, flooring, weatherboarding, sashes, doors, and all types of interior finish and furniture. • Farmers are particularly referred, to the high general use value of Rimu. and are recommended to adopt it for general building work about the farm, for rails, and for stock yards. In these instances, however, it is considered that the life, appearance and utility of the buildings could be considerably increased if the structures were freely painted with hot creosote, which can now be purchased in drums at a cost as low ns 1/6. per gallon. This inexpensive and effective treatment will be amply 1 renaid by the increased life of the structure on which it is used.

j Classes of Rimu, Tlie new National Grading Rules issued by the Government Special Timber Committee allows for the marketing of Rimu as follows:—' ... .. .... . Clause. (26) For thq, purpose . of. marketing building timbers, Rimu shall be • classed in the following qualities: “Heart,” “Medium,” an,d “Qrdih- : ary.” (27) “Heart” shall contain! 100 per cent, heartwood. (28) “Medium” shall contain not less than 50 per cent, heartwood in any piece, and not less than 25 per cent, in any cross-section. (29) “Ordinary” need not necessarily contain any heartwood. The basis for the introduction of the new quality of “Medium”, Rimu is sound, scientific, economic and practical, and has only been instituted after considerable microscopic research into the character of the timber cells and the deposits therein. These investigations proved, inter alia, that Rimu, instead of developing, as most timbers do, only a central heartwood cord and an outer sapwood zone, formed, in addition an intermediate or transition zone. In the latter, it has been definitely proved that the cells contain considerably less sapwood products than do the outer white sapwood, while a marked proportion of heartwood products is present, the latter increasing as the true heartwood is approached, In consequence, there is no d’oubt that timber from the intermediate zone, although not so valuable as that from the central heartwood core, is more durable and more generally useful than that from th* outer sapwood. Uses of the Different Classes. Heart Rimu is sawn from the central heartwood core of the tree, and should be all heart, except as is provided for in the grading rules to allow for exigencies in sawing. Timber sawn from the heart of the log has long lasting, qualities, and for the general purposes for which it is used is superior to imported timbers. In general home construction Heart Rimu is specially recommended for sleepers, stringers, verandah floors, joists, for flooring, weatherhoarding and exterior joinery and trim below the ground floor level, for all timber in contact with the ground, and for natural finish, interior joinery and trim.

Medium Rimu, containing as it does at least 25 per cent, heartwood on any cross-section and at least 50 per cent, heartwood by volume of any piece jfyillj in actual practice, generally con-

tain from 70 to 80 per cent, heartwood. This class is specially recommended in general building for lower plates, floor joists, (studs in outer wall and in loadbearing and partition walls, flooring, weatherboard!ng and exterior joinery and,'trim above the ground floor level, ceiling joists and all roof-framnig timbers.

; Ordinary Rimu does not necessarily contain any heart, and will, in practice, . consist mainly of timber from the intermediate zone. This class is considered suitable for studs in non-bear-ing, .partitions, sarking, rough linings, kitchen and bathroom joinery, trim and lining. The timber, however, obtainable in this class, if thoroughly seasoned and Well painted, would be suitable for many of the purposes foi which nil heart or medium class is ro commended above. • > Grades of Rimu. The three classes in which Rimu is marketed can be obtained in six different grades, as follows, the differentiation between the latter being on a basis of the defects occurring: Clean. Dressing “A”. Dressing “B”. Building “A”. Building “B”. Common. =

Clean grade is provided specifically for jbiriery' and furniture, and is a superfine grade containing practically defect free timber." The requirements of the grade are rigidly defined in the standard Classification and Grading Rules and are such as to guarantee clear, well-cut and full-sized timber. Dressing “A" grade is intended for all interior work of a natural finish charaoter. For partition work where two good faces are required, this grade will supply suitable timber. For unonved flooring requiring a special finish -this, grade should appeal, containing as it does one clear face and edge, with permissible small sound defects on the reverse or hidden side.

Dressing “B” grade is. supplied specially for all work which is to be covered or have a paint finish. Bedroom and kitchen floors,' painted partitions, weatherboarding, etc., sizes are stocked in this grade. The face side of a piece may contain a maximum of four small defects per twelve linear feet of face and edges.

Building “A” grade is included to supply sound.timber,. well manufactured arid suitable for superior construction purposes. The. grade is free from loose or . rotten knots,-knot holes, shakes, rot and other defects which materially impair the : strength of timber, due allowance being always made for the purpose for which it is to be used. The grade generally is- suitable for floor joists, studs, principal framing members, cheap or temporary weatherboarding'and flooring, etc.

Building “B” grade is intended chiefly for sarking, rough lining, and covering, or .framing, purposes where strength is not the deciding factor. It is sound . timber, free from rot or large holes, , but allows .large, firm knots, wane, bark pockets, open shakes net exceeding iin. Ip width, and, generally, defects wliich will allow the use of a shipment with little waste. Common :/iTimber in . this grade may contain all types and sizes of defects, and is the lowest, grade of timber produced. It should find a special use on farms for rough sheds, pigsties, fowlhousea, etoV;

(lbs. square inch) Type. Type. Strength ns a Beam 7740 7800 6400 Strength ns n Column or Post 3290 8940 3000 Strength Perpendicular 590 450 to the Grain ... 390 Tension Perpendicular ■' 200 v to the Grain ... 620 — 1 (lbs.)