Exceptions

The NHLA grading rules have been the standard for hardwood lumber transactions throughout North America for over 100 years. Within this standard framework, companies have been seeking ways to tweak their grading standards thus elevating their lumber products into a more custom, added-value product. The following notes and exceptions are a collaboration of NHLA rules and current marketing standards.

Exceptions by species

Red Alder: The grading rules are unique for this western USA hardwood. Key points include the following: The lumber is kiln-dried, surfaced, and then inspected from the better face. Pin knots are a natural characteristic and are not considered a defect. The primary grades include Superior (Select & Better), Cabinet (No.1 Common), and Frame (No.2 Common), which adapt themselves to similar uses as the standard NHLA grades. Your best option is to work closely with your red alder supplier to find the best grade that will work for you.

Ash: When the purchasing specifications call for a white (sapwood) or brown (heartwood) colour in the clear cuttings, I always refer buyers to the colour specifications for hard maple. These can be found in the back pages of AHEC’s Illustrated Guide to American Hardwood Lumber Grades (click to order), as well as in the NHLA’s Rules for the Measurement & Inspection of Hardwood & Cypress

Aspen: Regionally referred to as popple and is not to be confused with American tulipwood (Liriodendron tulipifera). Light brown mineral streaks are naturally occurring and are not considered a defect.

Basswood: Often produced in 9/4 (57.15mm) thickness for Venetian blinds. Black and brown mineral streaks are admitted in the clear-face cuttings. Dormant twig buds are not considered a defect.

Beech: Standard grading in all respects with an occasional brown mineral streak which is not considered a defect.

Yellow birch: This northern species is often sorted for sap (sapwood) or red (heartwood) clear cuttings. Again, I refer you to the grading specifications for hard maple colour sorts. When sorted for colour, the FAS grade will allow a 5 inch width. Paper birch is a much softer birch species, which is lighter in colour with scattered brown flecks and should not be mixed with yellow birch.

Cherry: This premium wood has naturally occurring pin knots and gum streaks which are not considered defects. Sapwood is admitted without limit. Because of this NHLA rule, cherry is often sold with a heartwood specification such as 90/50, which means one face will be 90% heartwood and not less than 50% heartwood on the back side. Consult your supplier about how their cherry is being sold.

Cottonwood: Sometimes regionally referred to as white poplar and is not to be confused with American tulipwood or yellow poplar. Sometimes sawn in 9/4 (57.15mm) thickness for Venetian blinds.

Elm: Purchase orders should specify American red or grey elm. Bird pecks and the purple mineral streaks, which are often present, are admitted in the clear-face cuttings.

Gum: Often sold as sap gum and no colour specification is required. When sold as red gum, each clear cutting is required to have one red (heartwood) face.

Hackberry: Sometimes regionally referred to as sugarberry and used as an ash substitute. It is best to purchase surfaced lumber, as an interior blue stain is not uncommon.

Hickory and pecan: Typically referred to as hickory in the North and pecan in the southern USA. Bird pecks and the purple mineral streaks extending from the peck are naturally occurring and are not considered a defect. This heavy hardwood can be susceptible to interior blue stain and purchasing surfaced lumber is recommended to ensure good colour throughout. The FAS grade allows a 4 inch minimum width.

Hard maple: Most often sorted for the white (sapwood) colour. More information is available in AHEC’s Illustrated Guide to American Hardwood Lumber Grades (click to order).

Eastern soft maple: Typically red-leaf maple in the North and silver-leaf maple through the Midwest and southern USA. It is essential to discuss this with your supplier, as they are very different in appearance. The red-leaf tends to resemble hard maple and is much more consistent in colour, while the silver-leaf has a wide range of colours and can have a slightly softer texture. Both species can produce a highly figured wormy variety which is sold WHND or Worm Holes No Defect. All soft maple varieties can be sorted for colour according to the specifications in the grading guide.

Pacific coast maple: This western USA species follows the grading guidelines for red alder. The main grades are Select & Better, No.1 Common, and Frame. It is sold kiln-dried, surfaced, and graded from the better face with naturally occurring pin knots, which are not considered a defect. For best results, consult your supplier for the grade that will suit your needs.

Red oak: Red oak is graded true to the NHLA standard allowing naturally occurring mineral streaks in the clear-face cuttings. Red oak is becoming more readily available in fixed widths.

White oak: Tends to be consistent in colour throughout its wide northern to southern range. Certain areas of the Appalachian Mountains produce a highly figured wormy variety and this is sold as Sound Wormy. Sapwood is admitted without limit in the NHLA rules, but usually sorted with a minimum of one heartwood face for export. Consult your supplier about their grading standards for sapwood.

Quartered and rift sawn red and white oak: When specified, 90% of the clear-face cuttings must show figure or straight grain respectfully. The FAS grade will allow a 5 inch minimum width.

Sassafrass: Not readily available as lumber, and is graded true to the NHLA standard.

Sycamore: This species tends to move during the drying process and it is recommended that it should be graded after kiln drying.

Tulipwood: Widely known as yellow or tulip poplar in the USA. Burls and swirls in the grain are a common occurrence and are not considered defects. A heavy purplish-blue mineral colour is limited in the upper grades and unlimited in the Common grades. Tulipwood is becoming more readily available in fixed widths. Because the Common grades are generally stained or painted in finishing, a grey colour is allowed in the wood after surfacing.

Walnut: The NHLA grades have been altered for this species because of the limited availability and nature of the timber growth. The FAS grade allows a 5 inch minimum width and 6 foot minimum length. When steamed, the sapwood will turn a darker colour to assist blending in the finishing process and is admitted without limit. Discuss with your supplier how they do this steaming process for best results.

Willow: Burls and swirls are very common and are not considered a defect.

Color sorting

In addition to sorting for grades or selecting specific widths, various species are commercially sold at an added value when colour is also considered. It is important to note, colour in this explanation refers to sapwood and heartwood.

Number 1 and 2 white

A colour selection typically made on hard maple, but can be applied to any species where sapwood clear cuttings are desired, such as ash, birch, and soft maple. Number 1 white means both faces and edges of the clear cuttings must be all sapwood. Number 2 white means that one face and both edges of the clear cuttings must be sapwood and not less than 50% sapwood on the reverse face.

Sap and better

Commercially sold when only one face of the board needs to be sapwood. Usually applied to the same species as Number 1 and 2 White, although just a little less stringent. In Sap and Better every board should have a minimum of one sapwood face in the clear cuttings.

Red one face and better

Commercially sold when a minimum of one face of the board needs to be heartwood. Usually applied to species such as cherry, oak, walnut, gum, and even birch and maple in certain applications. What the producer is looking for in this specification is that all clear cuttings must have a minimum of one heartwood face.

There is a wide range of additional options open to American hardwood producers in sorting and selecting specific lengths, widths and even grain patterns. If these can be agreed individually between producers and buyers, there can be benefits by making modifications to the standard grades shown in this guide. This may also assist with improving the yield from each log and thus contribute to the sustainability of the forest. It may also reduce costs to both sides or add value to the delivery.

Cherry sorted 90-50 red

Refers to 90% heartwood on the better face and not less than 50% heartwood on the reverse face.

Red oak color sorting

American red oak encompasses nearly 35% of the hardwood timber stand throughout North America from Maine through to Louisiana. Because of weather-related differences in growing conditions, a wide range of colour is apparent in the heartwood of the tree. Some common colour sorts include: wheat, rose and pink as well as regional sorts of Northern, Appalacian and Southern. Northern tends to be most consistent in colour, leaning to the lighter wheat colour ranges, generally slower growth, tighter growth rings producing on average narrower widths and shorter lengths than the other regions.

Appalacian encompasses all the growing regions because of the vastness of the area and diversity of climate, elevation and soil conditions. The higher elevations tend to produce a more Northern colour, but with larger widths and lengths. The lowlands most resemble Southern timber producing the largest average of width and lengths and a wide band of colour ranges. Southern red oak tends to consistently produce the largest timber sizes yielding the best lumber widths and lengths. A more varied colour range is also present. The importance of the diversity of red oak and its origin is key to its success with any hardwoods manufacturer. If long lengths and wide widths are vital to a manufacturer, then Southern or South-Appalacian could be purchased. If a consistent colour is needed, seek out a Northern supplier or one that includes colour-sorting in their grading. Any possible combination of colour, widths or lengths can be achieved from almost all regions with the proper communication between buyer and supplier.

Quarter and Rift Sawn lumber

A type of sawing referring to the angle of the growth rings to the face of the board. Quarter sawn boards will have the growth rings, seen from the end of the board, run at or near 90 degrees and in oaks will produce a spotted figure or tiger stripe. Rift sawn will have the growth rings, seen from the end of the board, run at or near 45 degrees and will produce a consistent straight grain. When grading quarter and rift sawn red or white oak, 90% of the clear cutting yield must show figure or straight grain respectively. The FAS grade will allow a 5 inch (12.7cm) minimum width.