Government of Nova Scotia Government of Nova Scotia Nova Scotia, Canada
Natural Resources and Renewables


Module 8: Wood Utilization and Technology



Roundwood products include any item that can be recovered from the tree using a chain saw or other cross-cutting device. For example, saw logs and pulpwood, are roundwood products. If you proceed to the next stage converting sawlogs into lumber in a small mill - you should have a good idea of what affects the quality and value of roundwood. The following list of roundwood products proceeds from most valuable to least valuable: veneer logs, sawlogs, boltwood, posts and poles, pulpwood, and fuelwood, which includes domestic firewood and commercial fuelwood (to be chipped). Other roundwood products that may be exported include softwood logs for plywood, bolts for hard board manufacture, bolts for bentwood products, and furniture bolts.

In addition, a number of special roundwood products are described in Lesson 5, where it seemed the grading and marketing elements were of greatest importance. These include bolts for musical instrument stock, shakes and shingles, cooperage, and spoolwood.

Recognizing Products In The Standing Tree

It may be easier to recognize roundwood products in the standing tree before it has been felled. All faces of the stem can be seen, which allows you to make some preliminary plans on how to best buck the stem. Before looking at individual trees for what they will yield, examine the area to be cut. This will give you an overview of potential products, their quality and the type of defects present. Some of the advantages are as follows:

  1. You may obtain an idea of relative volumes and qualities of products, making it easier to mark trees for removal.

  2. In mixed-wood stands, you may decide which species to favour.

  3. High-quality trees tend to occur in groups, as do low-quality trees. Therefore, consider not only an individual tree but also its neighbours in the stand.

  4. Allows you to identify repetition of tree defects. For example, wood borers, and decay fungi, are often found in infected clusters of trees.

  5. Allows you to identify past logging damage such as wounds at the base of trees. Infection by very aggressive fungi can cause widespread damage in hardwoods.

  6. Allows you to identify repeated damage or evidence of decay fungi in its late stages. Where certain areas are heavily infected, it may be necessary to amend your cutting plans and to remove such trees
    Figure 12
    Figure 12 - Acute branch knot in white pine, indicating prior weevil damage.
    early on.

  7. Allows you to identify damage in white pine by red rot in the stump area, and repeated weevil damage indicated by very acute branching in the stem and crooked stems (see Figure 12). In general, spruces, younger fir, and other softwoods are quite resistant to various fungi and insect damage, such as borers.

  8. In hardwoods, insect damage and decay fungi are more prevalent and can be identified. However, do not over estimate the amount of defect. Northern hardwoods - sugar maple in particular -have a way of sealing off their wounds.

You will also be able to assess the stand in terms of required size specifications for various roundwood products. Are there enough good softwood stems to leave growing for recovery of saw logs? Can you get 13 inch, minimum 10 feet, butts in your hardwoods to qualify for a grade 1 log? Or should they be allowed to grow a little longer?

Silviculture Considerations

Setting future stand objectives are at least as important as looking for products: A preliminary examination of the area to be cut also allows you to think about silvicultural treatments. These treatments may enhance certain properties of wood for specific products. For example, in a vigorous young stand of white pine you might prune the butt logs (16 ft.) of high-potential stems. The effort will more than pay for itself in increased lumber grade and value in the future. Also consider pruning young hardwood to increase veneer log yield.
There are several harvesting systems to consider: clearcutting, shelterwood cutting, selection cutting, seed tree cutting, and commercial thinning. Your choice will depend on the species you have to work with, its condition, available markets, and, most importantly, your objectives. For more information refer to Harvesting Methods in this series. Some systems focus on removing low quality trees initially, which requires finding a market for the low quality wood. As a side note, some poor quality and/or small trees can be left behind to compost into nutrients. They will not be wasted.

Harvesting implies two goals which should be considered:

  1. A supply of timber available at defined intervals, in perpetuity, from the woodlot (ie. it should be sustainable).

  2. Quality of individual trees to be constantly up-graded by various silviculture and harvesting techniques.

Other goals of good management include aesthetic and ecological objectives. Finally, many techniques can be used, within the terms of a specific treatment to enhance certain wood properties already covered. Quality of softwood trees destined for sawlogs can be manipulated by growth rates and spacing treatment. Certain hardwoods, when released by cutting of adjacent trees, are prone to spontaneous branching that reduces value substantially. To avoid this, ensure that release is not too great or abrupt. The formation of reaction wood can to some extent be controlled by ensuring that those factors causing lean are minimized.


You are now ready to determine the products to cut. Review the hardwood log and bolt grading rules (Tables 2, 3, 4 & 5). Reference 5, in Further Reading, provides a white pine saw log grading rule. For other softwoods you will not require grading specifications unless you have a special market; for example, spruce `clears'. In that case, one of the hardwood log grades, or the pine log grades, could serve as a rough guide. At the outset develop your own product priority list. A typical list might be: hardwood veneer log (grades: prime, Select, No. 1); hardwood sawlogs (grade 1) and softwood sawlogs; hardwood veneer logs (grades 2 and 4); various hardwood bolt grades; hardwood sawlogs (grades 2 & 3); pulpwood; firewood.

NOTE: If you are considering poles, contact the utility company, or Canadian Standards Association, Ottawa, with regard to specifications and handling procedures.

Figures 13, 14 and 15 show the procedure for product-grading standing hardwood trees. There are no similar drawings for softwood since, as we mentioned, they are not normally graded. However, the following section does provide a number of guidelines in manufacturing logs and bolts, for either softwood or hardwood.
Harvest your woodlot for a variety of products rather than a single product. This will allow you more flexibility and will usually result in a higher dollar return.
To determine whether your product meets specifications, become familiar with the requirements for each item. A number of these specifications and grading rules are provided. Also, think back to some of the wood properties discussed in Lessons One and Two. Some good references are 4, 5, 7, 8 in Further Reading.
Figure 13 Figure 14 Figure 15
Figure 13 - Product grading a standing hardwood tree. Figure 14 - Product grading a standing hardwood tree. Figure 15 - Product grading a standing hardwood tree.


Veneer Log Specifications and Grading Rules


Veneer Logs
There are no softwood plywood manufacturers in Nova Scotia. However, export markets exist. Softwood peeler log specifications vary with end product. Sheathing grade plywood has minimal log specifications. Decorative plywood panels; eg. white pine, require high quality logs.
There is a ready market for hardwood veneer logs. Three plants - one in Maine and two in New Brunswick - regularly purchase hardwood veneer peeler logs in Nova Scotia. Table 3 provides specifications and grading rules for yellow and white birch veneer logs. Other species purchased include red maple, sugar maple, white ash, and aspen. Veneer logs usually, but not always, occur in the butt section of the tree. These logs must be very carefully harvested with square cuts, and exact lengths, and should be shipped soon after felling. Veneer buyers do not like to see excessive tension wood in the log as revealed by an off-centre core.

1. Softwood - Extreme branching is not permitted and sweep, crook, and rot must be kept to a minimum. There is a good market for sawlogs with a sawmill within a short distance of nearly every woodlot in the province. Again, when you are cutting up the stem, keep in mind other products you may wish to make. It is often easier to visualize these while the tree is standing. Occasionally, softwood mills buy according to log grade with a particular product in mind.

2. Hardwood - Hardwood sawlogs have in the past often been regarded as a by-product, resulting from the harvesting of softwood sawlogs and pulpwood. Today a new interest in hardwood products seems to be pushing that notion aside. Woodlot owners are looking at hardwood trees in their own right and determining their best use. They are also considering the best management system to enhance hardwood growth for future harvests. In general, the best hardwood sawlogs are in the butt section of the tree, with quality decreasing up the stem. It is important to assess the butt section carefully, prior to bucking up the stem. Table 4 provides a widely used hardwood sawlog grading system. It can serve as a guide during log marking. More will be said regarding this system later.

Boltwood is defined as a section of a tree stem, 3 - 8 feet in length, normally for specialized uses. Bolts are usually of fairly high quality and are sawn from both softwoods and hardwoods. In softwood, products include lobster trap lath, snow fence and other lath; and white pine furniture dimension stock. In hardwood, bolts are sawn and further processed into furniture dimension stock, flooring blanks or billets, dowel boards, turning squares, and frame stock. The principal advantage of cutting a tree stem into short pieces is that often sweep and crook can be minimized. Tables 5 and 6 provide bolt specifications for a number of sawn products.

Posts and Poles
Posts are fairly short (8'), usually debarked, sharpened on one end, and sometimes treated with preservatives. In Nova Scotia, spruce and tamarack are the preferred species. They are generally used for fencing and represent a very local market.

Poles are long sections (20' and up) used by telephone companies 'aria -other utilities to carry transmission lines. Poles are always debarked and are pressure treated with a wood preservative. Red pine is the species of choice for transmission poles. The preference for red pine is due to the ease of penetrating the sapwood with the liquid preservative, due to the nature of the cells and their interconnecting pits. Spruce, by contrast, is much more difficult to treat. Poles are structural products, carrying heavy loads and therefore, compression wood should be kept to a minimum.

The forest economy of Nova Scotia in recent years has been highly dependent on harvesting pulpwood. Almost three million cubic metres (less than one million cords) of pulpwood is harvested annually in the province; about 90 percent of this total in softwood species. The highest grades of pulpwood are required for newsprint and therefore green material is preferred. Pulp bolts may be recovered from most trees with the exception of those with large knots and excessive cull.

Firewood and Fuelwood
Hardwood firewood has been a saleable commodity for years. The OPEC oil embargo of the 1960's gave this market a real boost, and it hasn't looked back since. This material may be produced and delivered in 8-ft lengths, or it may be cut into shorter lengths and split. It offers a reasonable return for the energy expended. It is also a good way to use tops, and poor quality material in the stem that cannot be converted profitably into more valuable products.

Fuelwood is that material destined for use as a commercial fuel. This will ultimately be in the form of chips, hogged wood, or as pellets. These markets are growing with the advent of wood burning boilers, and pellet-burning stoves.

A number of other specialty roundwood products are listed in Lesson 5 under Markets.

Guides to Making Better Logs and Bolts

For Sawlogs
  1. Study the log and bolt grade specifications.
  2. Know how to recognize various types of tree quality characteristics and their acceptability for specific products.
  3. It is good practice to cut stumps as low as the quality of the wood will permit. Excessive butt flare may have to be removed from veneer logs, and is not generally acceptable in sawlogs.
  4. If at all possible, use the Humbolt undercut (see Figure 16) during felling to reduce loss due to shorts.
  5. In cutting back cull ends, keep butts as short as possible. Testing the butt for soundness should not exceed 2-foot intervals. Jump butting or jump cutting should stop when 50 percent or less of the cross-sectional area contains rot.
  6. Buck logs at the grade-break or minimum diameter for the best log grade.
  7. Concentrate defective stem portions in lower grade logs (ie. portions containing
    knots, overgrown knots, insect damage, bark distortions, etc.) and clear stem portions in clear or higher grade logs. Follow the log and bolt grade specifications.
  8. Reduce the effect of sweep or crook by cutting a tree stem into shorter, variable length straighter logs and bolts.
  9. Establish a uniform trim or broomage allowance for bucking logs - 4-inches is a safe amount. 10. Buck forked trees to exclude the fork in the top end of the log.
  10. Remove all major log protuberances by cutting them flush with the log surface.
  11. Make all bucking cuts perpendicular to the log axis.
  12. Do not include cull sections between the ends of a log.
  13. Practice jump cutting. Such major cull indicators as stem bulges, canker type fungi, and large holes containing rot, should not be included in logs.
For Veneer Logs
  1. Know the veneer log grades.
  2. Focus on identifying top 3 grades, ie. 11" and up.
    Figure 16
    Figure 16 - Humbolt method

  3. Learn the relative market values between hardwood sawlogs and veneer logs to help you decide which to produce.
  4. In felling a tree containing a veneer log, it is very important to put the undercut on the stump (Humbolt); otherwise the length of the log will be reduced during scaling (see Figure 16).
  5. Make all bucking cuts perpendicular to log.
  6. Measure and cut to exact log length.
  7. Become familiar with your customers' requirements; they may not always be clear in the specifications

More Information On Roundwood Specifications

Learning log specifications can be a real challenge. Generally, correctly bucking up a tree stem is simply common sense. However, there are a few rather specific requirements, particularly in hardwoods.

For hardwood factory sawlogs the minimum diameter and length for grade 1 logs is 13 inches, inside bark (i.b.), small end, and 10 ft., respectively (butt logs only). When you look at a standing tree, visualize these measurements in terms of a cut log.
For grade 1 pine and other softwoods, 10 inches i.b., at the small end would be an equivalent breaking point.

Sweep & Crook
Keep sweep and crook to a minimum by bucking your logs at the maximum point of deviation, or as shown in Figure 17.

Figures 17 to 19, taken from Reference 8 of Further Reading, show how bucking can affect lumber value. In these examples for hardwoods, it is assumed that all portions are being cut for sawlogs. For softwood logs, similar comparisons are not nearly as dramatic. The reason for this is the softwood lumber grades do not have such marked differences in value between grades. Also softwood lumber tends to be allocated to a combination grade, such as: No. l including 15 percent No.2. Defects, such as sweep, affect volume recovery; therefore, it is important to keep these to a minimum for all sawlogs.

NOTE: In figures 17 to 19 the author used the Ontario Log Rule (O. L. R.) to determine volume. The O.L.R. gives slightly higher overrun values than the New Brunswick Log Rule. The object of the comparison, poor bucking versus good bucking practices, is not compromised by the log rule chosen.


Measuring Roundwood Volume

Many woodlot owners accept their customer's measure of incoming roundwood, and are paid on that basis. There is no problem with this, provided both parties are satisfied with the arrangement. With pulpwood, there is usually no alternative. There are a number of good texts on scaling roundwood of all kinds, particularly Further Reading 1,3.

Figure 20
Figure 20 - Measuring stacked pulpwood

The major pulp and paper companies in Nova Scotia use different methods of measurement, which complicates things. One company uses stacked cubic metres, another cords, while a third purchases their requirements on a weight basis.
To determine the volume of a stack of wood 2.44m (8') in length, pile length and height measurements are taken on both sides of the stack (see Figure 20).

The average length and height are computed from these measurements. Defects are assumed to extend half the bolt length and deductions are made on both sides of the pile. Heights are measured at the mid points of equal intervals.
Maximum recommended interval is 1.5m (5').
Gross volume of a stack is calculated as follows:

Gross volume stacked (m3) _ Avg. length(m) x avg. ht.(m) x bolt length(m)

Deductions from gross volume are made for (i) shortwood, and (ii) defects and voids. In terms of shortwood, measure a number of sticks to determine average bolt length. If short, you must adjust volume accordingly. Deducting for defects and voids is much more complicated. See the N.S. Scalers Manual.

Although most wood in Nova Scotia is now scaled in metric units, some is still measured in cords. A cord is 128 cubic feet of stacked wood containing both wood and air spaces. In 8-foot wood a cord would be 8' (bolt length), 4' height, 4' length pile:

(L' x W' x H)l128 = cords

Measuring stacked volume is similar to scaling in cubic metres. Average heights and lengths are taken as before. Deductions are also made for defects, voids and short wood. Although not mentioned previously, all stacked wood is assumed to contain bark.

Weight scaling is used to a limited extent in Nova Scotia and is a quick way to determine the amount of incoming wood to a pulp yard. The truck is weighed in and weighed out, the difference being the weight of wood. Companies using this method have developed relationships between weight and volume, either in cubic metres stacked or cords. Due to moisture content variation, seasonal adjustments to the relationship may apply. Weighing automatically takes care of shortwood and voids; however, deduction for defective wood may still be required.

Sawlogs are usually bought or sold on the basis of board feet. A board foot is, in a piece of lumber, a section 1-inch thick, by 1-foot long, by 1-foot wide or its equivalent in volume. In terms of log scale, it is the volume in board feet of lumber that the log is expected to yield during sawing under a fixed set of conditions.

Many years ago, Nova Scotia adopted the New Brunswick Log Rule for scaling sawlogs. Table 6  shows gross volumes in board feet for various diameter logs (measured inside bark at the small end to the last full inch) and for various lengths. Deduction for log defects are made by reducing scaling diameter, or scaling length, while for some defects, percentage deduction to board footage is made. Because of the large number of possibilities, consult the provincial Scaling Manual.

Figure 21
Figure 21 - Comparison of overrun values for four log rules.

Most log rules underestimate the amount of lumber produced from small logs (over-run) and overestimate it for larger logs (underrun). The New Brunswick rule is one of the most accurate rules used in Canada. (Figure 21) shows the comparison of values for four log rules.

Note how inaccurate the Doyle rule is; this is to the buyers advantage. Log rules are not good measures of sawmill efficiency because of the built-in bias, or inaccuracies noted in the figure.

Weight scaling is also an acceptable method of determining sawlog volume. For softwood logs, it is estimated that between 4.76 and 5.50 metric tonnes of green softwood logs are equivalent to 1000 fbm as scaled by the New Brunswick rule. Corresponding values for green hardwood logs are: 5.67 metric tonnes per 1000 fbm, New Brunswick scale.

TABLE 6 - New Brunswick Log Scale

Further Reading

  1. Anon, 1987, Scaling Manual, N.S. Dept. of Lands and Forests,
  2. Anon, 1980. The Trees Around Us, N.S. Forest Practices Improvement Board, Halifax
  3. Bedard, J.R. 1968, The Small Forest and The Tree Farm, Maritime Forest Ranger School, Fredericton
  4. Calvert, W.W. and F.J. Petro, 1993. Grading Standing Hardwood Trees in Nova Scotia., N.S. Dept. of Natural Resources, Halifax
  5. Calvert, W.W., 1972. A Proposed Sawlog Grade for Eastern White Pine, Forintek Canada Corp., Ottawa
  6. Calvert, W.W.,1963, Factors Affecting Over-run and Its Significance, Foriritek Canada Corp., Ottawa
  7. Petro, F.J. and W.W. Calvert, 1976. How to Grade Hardwood Logs for Factory Lumber, Forintek Canada Corp., Ottawa
  8. Petro, F.J., 1975. Felling and Bucking Hardwoods, Forintek Canada Corp., Ottawa
  9. Shigo, A.L. and E.H. Larson, 1969. A Photo Guide to the Patterns of Discoloration and Decay in Living Northern Hardwood Trees, U.S.D.A. Forest Service, N. E. For. Exp. Station, Washington, D. C.

Lesson 3 Quiz