Visually Graded Lumber

7/29/2019 Visually Graded Lumber

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Lumber Visually Graded Lumber Machine Graded Lumber

Fingerjoined Lumber Decking Timber

Milliken Park Community Recreation Centre

Scarborough, ONPhoto: Patrick KennedyArchitect: Shore Tilbe Irwin & Partners
http://www.cwc.ca/products/lumber/visually_graded/index.phphttp://www.cwc.ca/products/lumber/machine_graded/index.phphttp://www.cwc.ca/products/lumber/finger_joined/index.phphttp://www.cwc.ca/products/lumber/decking/index.phphttp://www.cwc.ca/products/lumber/timber/index.phphttp://www.cwc.ca/products/lumber/timber/index.phphttp://www.cwc.ca/products/lumber/decking/index.phphttp://www.cwc.ca/products/lumber/finger_joined/index.phphttp://www.cwc.ca/products/lumber/machine_graded/index.phphttp://www.cwc.ca/products/lumber/visually_graded/index.php


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Visually Graded Lumber

Current Issues

Moisture Content Measurement and Control

Building codes specify that structural wood building products should be at dry at time of installation.Dry is defined as 19% moisture content (MC) on a dry weight basis. This number has been derived fromexperiences and has been used by the construction and wood products industry over the last 100 years.It is intended to ensure that wood will perform well in construction, under varying end use conditions.

Measurement of moisture content of wood products can be difficult, particularly if done in variable siteconditions. Guidelines should be followed to measure and interpret results to correctly assess whetherwood products are dry at installation time. For example, when measuring the moisture content of apiece of wood the following factors affect the individual result.

Type of test (oven dry is most accurate) Type of meter (dielectric, DC resistance) Product type Temperature Species Variation of wood (wet pockets) Frequency, location and depth of sampling to correctly represent the entire piece

When assessing whether a structure composed of different types of wood products will performsatisfactorily under given end use conditions, the following factors should be considered

Moisture distribution Where moisture will accumulate Number of storeys Location in structure Construction type and orientation Sampling and analysis of individual results

Practices to help control moisture content during construction phase

Proper storage of building products (off the ground and covered) Early close-in of walls and roof Allow venting as long as possible but balance with local climate Sequence of weather-resistant barrier installation Sequence of flashing installation Sequence of cladding installation Sequence of vapour barrier installation

Further information will be provided in the near future.

For related info, see www.durable-wood.com or www.forintek.ca or www.cmhc-schl.gc.ca
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New Shear Values

Shear Design Values for Lumber Shear design values for lumber have recently been revised andapproved by the American Lumber Standard Committee, in accordance with changes to ASTM StandardD 245, Establishing Structural Grades and Related Allowable Properties for Visually Graded Lumber.These new lumber shear design values are higher than earlier assigned values. To obtain moreinformation on new lumber shear design values, contact any of the following agencies:

American Wood CouncilSouthern Pine Inspection BureauWest Coast Lumber Inspection BureauWestern Wood Products Association

Design provisions, including requirements for shear design of lumber, are published by the AmericanForest & Paper Association (AF&PA) in the National Design Specification for Wood Construction(NDS )

, an ANSI national consensus standard. NDS shear provisions are being revised in the nextedition of the NDS in order to utilize new lumber shear design values. However, until revision of theNDS has been completed, 1997 NDS design provisions are only to be used with design values in the1997 NDS Supplement: Design Values for Wood Construction, or similar values.

Until appropriate revisions to the NDS can be fully implemented, the American Forest & PaperAssociation recommends the following as guidance when using new shear design values with the 1997or earlier editions of the NDS:

The shear stress adjustment factor, CH, for splits, checks, and shakes does not apply to the newshear design values.

Tension-side notching equations (3.4-3 & 3.4-4) are only to be applied with 1997 NDSSupplementdesign values. These equations are being revised to permit the use of higherlumber shear design values. Until these design provisions are approved, tension-side notchesshould be designed using existing 1997 NDS design procedures and 1997 NDS Supplementdesign values.

Provisions in 3.4.5 on shear design for bending members at connections, including equations(3.4-6 & 3.4-7), are only to be applied with 1997 NDS Supplementdesign values. Theseprovisions are being revised to permit the use of higher lumber shear design values. Until thesedesign provisions are approved, shear design for bending members at connections should be inaccordance with existing 1997 NDS design procedures and 1997 NDS Supplementdesignvalues.

Alternate design procedures in 4.4.2 do not apply to new shear design values.New Horisontal Shear Values for Canadian lumber used in the US.Applicable to all grades.

Species Group Fv(psi)

Spruce - Pine - Fir: 135

Douglas Fir - Larch(N): 180

Hem - Fir (N): 145

Northern Species: 110

For more information on the new shear design provisions for lumber, contact the American WoodCouncil (AWC) Helpdesk at 202/463-4713 or email [email protected].
http://www.awc.org/http://www.spib.org/http://www.wclib.org/http://www.wwpa.org/http://www.awc.org/Standards/nds.htmlhttp://www.awc.org/Standards/nds.htmlhttp://www.awc.org/Standards/nds.htmlhttp://www.awc.org/Standards/nds.htmlmailto:[email protected]:[email protected]://www.awc.org/Standards/nds.htmlhttp://www.awc.org/Standards/nds.htmlhttp://www.wwpa.org/http://www.wclib.org/http://www.spib.org/http://www.awc.org/


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Molds

Good information on molds can be found in the FAQ section ofwww.durable-wood.com Answers to thefollowing questions can be found there

Are all molds bad?

Do molds grow only in buildings? Are all discolored areas mold?

Because Forintek has often been asked to investigate such questions a fact sheet has been prepared toassist buyers and users of wood in understanding the nature of wood discolorations and decidingwhether or not action is required.

The fact sheet can be downloaded in PDF format from the FAQ page of www.durable-wood.com.
http://www.durable-wood.com/http://www.forintek.ca/http://durable-wood.com/faqs/mould.phphttp://durable-wood.com/faqs/mould.phphttp://www.forintek.ca/http://www.durable-wood.com/


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Introduction

Canadian Forests

Covering nearly half of Canada's land area of 2.5 billion acres, the Canadian forest offers ampleopportunity for tourism, parks and the provision of forest products. This massive resource accounts for

15% of the world's softwood timber from which Canada produces 11% of the world's lumber. The bulkof Canadian softwood lumber is exported to the United States, where it represents 1/3 of U.S.consumption.

Forestry is such a substantial industry in Canada that it is of particular importance that the forest becapable of providing products on a sustainable and perpetual basis. The Canadian forest industry is aworld leader in forest management techniques, improving recovery in lumber manufacturing, wastereduction, and new products that maximize resources and species.

In 1996, Canada became the first country in the world to have a national standard for SustainableForestry Management developed by the Canadian Standards Association (CSA) through an open andinclusive process. To be granted forestry certification under the standard, companies must demonstrateforest management systems based on long term environmental objectives.

This map appears courtesy ofNatural Resources Canada.

Canadian forests have several features that provide desirable structural wood products. Some of thoseinclude: a favourable northern climate, a majority of the species (spruces) have small knots and manyof the western species grow to 30m or more in height providing long sections of clear straight grain.The majority of the structural products come from a spruce-pine-fir grouping which has the followingadvantages for structural applications:

straight grain good workability light weight moderate strength small knots holds nails and screws well
http://www.nrcan-rncan.gc.ca/homepage/index.htmlhttp://www.nrcan-rncan.gc.ca/homepage/index.html


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Canadian Species

There are more than a hundred softwood species in North America. To simplify the supply and use ofstructural softwood lumber, species in major lumber producing areas having similar strengthcharacteristics are combined. Having a smaller number of combinations makes it easier for a buildinginspector to ensure that products having the design strengths specified by the building designer are

installed. Because non-structural products are graded solely on the basis of appearance quality, non-structural products are usually sold as individual species (for example, eastern white pine, Western RedCedar, Douglas fir).

The four species groups of Canadian lumber and their characteristics are shown in Table 1

Table 1 Canadian Lumber - Commercial Species

Species Combination: Douglas Fir-Larch (N)

Abbreviation: D.Fir-L (N)

Species Included in Combination Growth Regions

Douglas fir Western Larch

Characteristics Colour Ranges

reddish brown to yellowish

high degree of hardness good resistance to decay


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Species Combination: Hem-Fir (N)

Abbreviation: Hem-Fir (N)


Pacific coast HemlockAmabilis Fir


yellow brown to white

works easily takes paint well holds nails well good gluing characteristics


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Species Combination: Spruce - Pine - Fir

Abbreviation: S-P-F


WhiteSpruce

EnglemannSpruce

RedSpruce

BlackSpruce

JackPine

LodgepolePine

BalsamFir

AlpineFir


white to pale yellow

works easily takes paint well holds nails well good gluing characteristics


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Species Combination: Northern Species

Abbreviation: North


Western Red Cedar


reddish brown heartwood, light

sapwood

exceptional resistance to decay moderate strength

high in appearance qualities

works easily takes fine finishes lowest shrinkage

Also Included in Combination Growth Regions

Red Pine


works easily reddish to pale brown heartwood


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Ponderosa Pine


takes finish well holds nails well holds screws well

seasons with little checking or

cupping

pale yellow color sapwood


Western WhitePine

Eastern WhitePine


creamy white to light straw brown

heartwood, almost white sapwood softest of Canadian pines works easily

finishes well doesn't tend to split or splinter

holds nails well low shrinkage

takes stains, paints, varnishes well


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Trembling

Aspen

Largetooth

Aspen

Balsam Poplar


works easily finishes well

holds nails wellalmost white to greyish-white

The Spruce-Pine-Fir species group makes up by far the largest proportion of dimension lumber since thespecies in this group grow throughout most of Canada. The other major species groups for dimensionlumber are Douglas Fir-Larch (N)and Hem-Fir (N). Northern Species include the other commercialspecies for Canadian lumber.


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Lumber Properties

Lumber is a general term which includes boards, dimension lumber, and timber. The product ismanufactured by sawing logs into rough size lumber or cants (square timbers) which are edged, resawnto final dimension and cut to length.

This section deals with lumber products used for structural framing. In the context of North Americanconstruction materials, it usually refers to wood originating from softwood species of trees. In thesmaller sizes it is known as "dimension lumber," and in the larger sizes as "timbers."

Testing

For many years, the design values of Canadian dimension lumber were determined by testing smallclear samples and applying appropriate adjustments depending on grade, size, moisture and safetyfactors. Although this approach has worked well in the past, there were some indications that it did notalways provide an accurate reflection of how a full sized member would behave in service.

Beginning in the 1970s, new data was gathered on full-size graded lumber. In the early 1980s, thewood industries in Canada and in the United States embarked on a joint comprehensive testing program

which involved testing thousands of pieces of dimension lumber to destruction to determine their in-service characteristics. It was agreed that this testing program should simulate, as closely as possible,the structural end use conditions to which the lumber would be subjected to. This is called in-gradetesting.

Results

The in-grade design values resulted in new relationships between species, sizes and grades. The changereflects the importance of wood characteristics in predicting strength properties. The presence andlocation of characteristics such as knots influence wood strength.

This is also shown in the size factor for lumber. There are significant differences in strength propertiesbetween 2 by 4 and 2 by 12 lumber. The difference relates to the size of characteristics permitted in for

each lumber size as established by grading rules. Full size testing has resulted in size factors for eachsize of lumber.

Design values for different grades have changed. Based on the two major testing programs, researchershave concluded that no consistent difference could be found between No. 1 and No. 2 grades forCanadian dimension lumber. As a result the same design value is applied for both grades No.1 and No.2. Select Structural grade, which is sometimes available, has higher design values.

On a species level, the effect of the in-grade testing raised S-P-F and Hem-Fir values while Douglas Fir-Larch values decreased slightly, when compared to design values based on previous small clear testing.

The data which resulted from the in-grade testing programs has been used to update the design valueswhich are applied in Canada and the United States.

For more information on the Lumber Properties program please refer to the Canadian Lumber Propertiesbook.
http://www.cwc.ca/publications/books_for_sale/canadian_lumber_properties/index.htmlhttp://www.cwc.ca/publications/books_for_sale/canadian_lumber_properties/index.html


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U.S. Design Value acceptance

Following the testing program, a new ASTM Standard D1990 ("Establishing Allowable Properties forVisually Graded Dimension Lumber from In-Grade Tests of Full-Sized Specimens") was approved. Datafor bending, tension parallel to grain, compression parallel to grain, and modulus of elasticity wereanalyzed in accordance with this Standard.

The Canadian lumber design values based on this data are published in the 1997 "National DesignSpecification for Wood Construction" (NDS) ANSI Standard and are also published in the NationalLumber Grades Authority's "NLGA Standard Grading Rules for Canadian Lumber". These values havebeen approved by the American Lumber Standards (ALS) Board of Review. Design values published inthe NDS are adopted in all U.S. model building codes including ICBO, BOCA, NCSBCS, SBCCI.

Canadian Design Value Acceptance

The Canadian Design values for wood were developed in a limit states design format. The CSA O86Technical Committee on Engineering Design in Wood approved these design values in 1989. They weregenerated with a reliability-based design approach that incorporated the in-grade testing data togenerate specified strengths. The procedures are described in Canadian Lumber Properties
http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/PAGES/D1990.htm?L+mystore+mwpt5421http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/PAGES/D1990.htm?L+mystore+mwpt5421http://www.awc.org/Standards/nds.htmlhttp://www.awc.org/Standards/nds.htmlhttp://www.nlga.org/newbooks.htmlhttp://www.icbo.org/http://www.bocai.org/http://www.ncsbcs.org/http://www.sbcci.org/https://secure.cwc.ca/cwc.ca/ecommerce/https://secure.cwc.ca/cwc.ca/ecommerce/http://www.sbcci.org/http://www.ncsbcs.org/http://www.bocai.org/http://www.icbo.org/http://www.nlga.org/newbooks.htmlhttp://www.awc.org/Standards/nds.htmlhttp://www.awc.org/Standards/nds.htmlhttp://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/PAGES/D1990.htm?L+mystore+mwpt5421http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/PAGES/D1990.htm?L+mystore+mwpt5421


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Size Adjusted Design Values for Canadian Species used in the United States

Design values for lumber presented in this section are based on ASTM Standards in accordance with therequirements of American Softwood Lumber Standard PS20-99 , as applied to species grown withinCanada.

Design values are in pounds per square inch (psi)

Grade SizeBending

Fb

Tensionparallelto grain

Ft

Shear

parallelto

grainFv

Comp.perp.

tograin

Fcperp

Comp.parallelto grain

Fc

Modulusof

ElasticityE

2x2

2x3

2x4

1875 1050 1610

2x6 1625 910 1540

2x8 1500 840 1470

2x10 1375 770 1400

Sel. Str.

2x12 1250 700

135 425

1400

1,500,000

2x2

2x3

2x4

1310 675 1320

2x6 1135 585 1265

2x8 1050 540 1205

2x10 960 495 1150

No.1 &

No.2

2x12 875 450

135 425

1150

1,400,000

2x2

2x3

2x4

750 375 745

2x6 650 325 715

2x8 600 300 680

2x10 550 275 650

S-P-F

No.3

2x12 500 250

135 425

650

1,200,000

These size adjusted values are intended for use by qualified designers and can be used in conjunctionwith the appropriate adjustment factors from the tables below.
http://www.alsc.org/greenbook%20collection/ps20.pdfhttp://www.alsc.org/greenbook%20collection/ps20.pdf


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Size Adjusted Design Values for Canadian Species used in the United States(Cont)


Grade SizeBending

Fb


Ft

Shearparallelto grain

Fv

Comp.

perp.

tograin

Fcperp

Comp.parallelto grain

Fc

Modulusof

ElasticityE

2x2

2x3

2x4

2025 1235 2185

2x6 1755 1070 2090

2x8 1620 990 1995

2x10 1485 905 1900

Sel.

Str.

2x12 1350 825

180 625

1900

1,900,000

2x2

2x3

2x4

1725 1125 2070

2x6 1495 975 1980

2x8 1380 900 1890

2x10 1265 825 1800

No.1 &

Btr.*

2x12 1150 750

180 625

1800

1,800,000

2x2

2x3

2x4

1275 750 1610

2x6 1105 650 1540

2x8 1020 600 1470

2x10 935 550 1400

No.1 &

No.2

2x12 850 500

180 625

1400

1,600,000

2x2

2x3

2x4

710 450 945

2x6 615 390 905

2x8 570 360 865

2x10 520 330 825

DouglasFir-

Larch(North)

No.3

2x12 475 300

180 625

825

1,400,000

*New 1&Btr Design Values

Thesesize adjusted values are intended for use by qualified designers and can be used in conjunction with theappropriate adjustment factors from the tables below.



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Grade Size

Bending

Fb

Tension

parallelto grain

Ft

Shearparallel

tograin

Fv

Comp.perp.

tograin

Fc

perp

Comp.parallel

tograin

Fc

Modulus

ofElasticity

E2x2

2x3

2x4

1950 1160 1955

2x6 1690 1005 1870

2x8 1560 930 1785

2x10 1430 850 1700

Sel. Str.

2x12 1300 775

145 405

1700

1,700,000

2x2

2x3

2x4

1800 1085 1780

2x6 1560 940 17052x8 1440 870 1625

2x10 1320 795 1550

No.1 &

Btr.*

2x12 1200 725

145 405

1550

1,700,000

2x2

2x3

2x4

1500 860 1665

2x6 1300 745 1595

2x8 1200 690 1520

2x10 1100 630 1450

No.1 &

No.2

2x12 1000 575

145 405

1450

1,600,000

2x22x3

2x4

860 485 975

2x6 745 420 935

2x8 690 390 890

2x10 630 355 850

Hem-Fir(North)

No.3

2x12 575 325

145 405

850

1,400,000

*New 1&Btr Design Values




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Grade Size

Bending

Fb


Ft

Shearparallel

tograin

Fv

Comp.perp.

tograin

Fc

perp

Comp.parallel

tograin

Fc

Modulusof

Elassticity

E2x2

2x3

2x4

1500 675 1265

2x6 1300 585 1210

2x8 1200 540 1155

2x10 1100 495 1100

Sel.

Str.

2x12 1000 450

110 350

1100

1,100,000

2x2

2x3

2x4

900 410 975

2x6 780 355 9352x8 720 330 890

2x10 660 300 850

No.1 &

No.2

2x12 600 275

110 350

850

1,100,000

2x2

2x3

2x4

525 225 575

2x6 455 195 550

2x8 420 180 525

2x10 385 165 500

Northern

Species

No.3

2x12 350 150

110 350

500

1,000,000



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Flat Use Factors (Cfu) - For Use Where Lumber is Loaded FlatwiseApply to Tabulated Design Values for Extreme Fibre Stress in Bending

N om i n a l T h i ck n e s s N o m i n a l W i d t h

2 " & 3 " 4 "

2" & 3" 1.00 -

4" 1.10 1.00

5" 1.10 1.05

6" 1.15 1.05

8" 1.15 1.05

10" & wider 1.20 1.10

* N o t e: These factors apply to all dimension lumber except decking grades. Bending design values for deckinggrades have already been adjusted for flat usage.

Wet Use Factors (CM) For Tabulated Design ValuesThe recommended design values are for applications where the wood does not exceed 19%. For useconditions where the moisture content of dimension lumber will exceed 19%, the Wet Use Adjustment

Factors below are recommended:

Property Adjustment Factor

Fb Extreme Fibre Test in Bending 0.85*

Ft Tension Parallel to Grain 1.0

Fv Horisontal Shear 0.97

Fc perp Compression Perpendicular to Grain 0.67

Fc Compression Parallel to Grain 0.8**

E Modulus of Elasticity 0.9

* Bending Wet Use Factor = 1.0 where Fb x CF (Base Value x Size Factor) does not exceed 1150 psi.** Compression Parallel Wet Use Factor = 1.0 where Fc x C,F (Base Value x Size Factor) does not exceed 750 psi.

Duration of Load Adjustment (Cd) For Tabulated Design Values

Load Duration Factor

Permanent 0.9

Ten Years (Normal Load) 1.0

Two Months (Snow Load) 1.15*

Seven Days 1.25*

Ten Minutes (Wind, Earthquake) 1.6

Impact 2.0

Confirm load requirements with local codes. Refer to Model Building Codes or the National DesignSpecification for high-temperature or fire-retardant treated adjustment factors.

For more information get the NDS supplement from www.awc.org
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Design Values for Canadian Species used in Canada

These specified strengths and modulus of elasticity are based on lumber that is graded in accordance withNLGA Standard Grading Rules for Canadian Lumber. Lumber should be identified by a grade stamp inaccordance with the provisions or the CSA Standard CAN/CSA-O141. These values are referenced in the

NBCC or the provincial equivalent.

These values are intended to be used by qualified designers and can be used in conjunction with theappropriate adjustment factors found in the CSA O86 Standard . Design tables, examples and backgroundinformation can be found in The CWC's Wood Design Manual which includes a copy of CSA O86supplemented with commentary material.

Specified strengths and modulus of elasticity for Structural Joists and Planks, Structural LightFraming and Stud Grade Lumber

Design Values are in Megapascals (MPa)

Species Grade

BendingatExtreme

FibreFb

Longitudinalshear

Fv

Compression

Parallelto Grain

Fc

Perpen-dicularto Grain

Fcp

TensionParallelto

GrainFt

Modulus ofElasticity

E E05

Sel Str 16.5 1.1 19.0 10.6 12,500 8,500

No.1/No.2 10.0 1.1 14.0 5.8 11,000 7,000

Douglas Fir- Larch

No.3/Stud 4.6 1.1 4.6

7.0

2.1 10,000 5,500

Sel Str 16.0 0.9 17.6 9.7 12,000 8,500

No.1/No.2 11.0 0.9 14.8 6.2 11,000 7,500

Hem-Fir

No.3/Stud 7.0 0.9 7.0

4.6

3.2 10,000 6,000

Sel Str 16.5 1.0 14.5 8.6 10,500 7,500

No.1/No.2 11.8 1.0 11.5 5.5 9,500 6,500

Spruce-Pine-Fir

No.3/Stud 7.0 1.0 7.05.3

3.2 9,000 5,500

Sel Str 10.6 0.9 13.0 6.2 7,500 5,500

No.1/No.2 7.6 0.9 10.4 4.0 7,000 5,000

Northern Species

No.3/Stud 4.5 0.9 4.5

3.5

2.0 6,500 4,000

Note:Tabulated values are based on the following standard conditions:(a) 286 mm larger dimension;(b) dry service conditions; and(c) standard-term duration of load.
http://www.csa-intl.org/onlinestore/GetCatalogItemDetails.asp?mat=2002896&Parent=1638http://www.csa-intl.org/onlinestore/GetCatalogItemDetails.asp?mat=2005007&Parent=1721https://secure.cwc.ca/cwc.ca/ecommercehttps://secure.cwc.ca/cwc.ca/ecommercehttp://www.csa-intl.org/onlinestore/GetCatalogItemDetails.asp?mat=2005007&Parent=1721http://www.csa-intl.org/onlinestore/GetCatalogItemDetails.asp?mat=2002896&Parent=1638


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Physical PropertiesPhysical properties of commercially available Canadian softwood species are summarized in table formatbelow.

Species Density

Hardness*

Side (N) End (N)

Thermal Conductivity

W/(m.K)@ 15%M.C.perpendicular to grain

D.Fir-Larch (N) 0.49 2990 4020 0.151

Hem-Fir (N) 0.46 2355 4060 0.144

S-P-F 0.42 2169 2976 0.130

Northern 0.35 1676 2675 0.115

*Note: Hardness data was collected by Forintek Canada Corp with a loadrequired to imbed 11.3mm. sphere to half diameter (N).

Thermal conductivity is given as a coefficient. To calculate its resistance (RSI value), divide length bythermal conductivity. For example one inch of S-P-F would give 0.0254 / 0.13 = 0.195 W / (m2 K) or1.1 BTU / (ft2 hr F)

Species Resistance to Decay Apsorption of Treatment

D.Fir-Larch moderate low to moderate

Hem-Fir low moderate

S-P-F low low to moderate

high low

moderate good

Cedars

White PinesNorthernSpecies Other Pines low good

Note: Information in this table applies only to the heartwood of the species.

Surface Smoothness

There are three general levels of surface smoothness to which lumber is manufactured. Rough lumber islumber which has been sawn, trimmed, and edged. The saw blades used for mass manufacturing arecoarse toothed for speed of production and, as a result, rough lumber is usually characterized bystriations or saw lines.

Surfaced lumber is lumber which has been surfaced after sawing by passing through a planing machinefor the purpose of adding smoothness and uniformity of size on one side (S1S), two sides (S2S), foursides (S4S), or a combination of sides and edges.
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Quality ControlThe Grading System

To ensure the quality of each piece of lumber, Canadian millshave each piece of lumber graded and grade stamped by

lumber graders approved by the grading agency. The gradingagency is required under the CLSAB regulations to perform aminimun of twelve (12) inspections per calendar year atapproximately monthly intevals at each facility. This gradestamp can only be used if the mill is a member of the gradingagency. The Canadian Lumber Standards Accreditation Board(CLSAB) is the regulatory body that oversees the lumbergrading system in Canada. Membership in the CLSAB includeslumber manufacturers' associations and independent gradingagencies in Canada that have been accredited by the CLSAB. Most Canadian grading agencies have alsobeen accredited by the American Lumber Standard Board of Review for lumber shipped to the US. Thisis possible because lumber grades and sizes have been standardized in Canada and the United States.Other sizes and grades may be produced for offshore markets. Examples of CWC member agency gradestamps are shown below.

Lumber Grade stamps


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Standards

Canadian dimension lumber, timbers and boards are manufactured according to the Standard GradingRules for Canadian Lumberpublished by the National Lumber Grades Authority. This NLGA rule is whatis used by graders to assign a grade to lumber, timbers and boards. The NLGA rule is approved by theCanadian Lumber Standards Accreditation Board in Canada and by the Americain Lumber StandardsBoard of Review in the U.S.. Approval in both countries is possible because grades and sizes ofCanadian dimension lumber are identical to those in use throughout the United States. ThereforeLumber manufactured and measured according to NLGA grading rules is considered Standard Lumber inCanada and in the United States and meets both the provisions of American Softwood Lumber StandardPS 20-99 and those of the Canadian Softwood Lumber CSA Standard CAN/CSA-O141. These productstandards both reference the NLGA grading rules to ensure consistent product quality.

NLGA is a rules writing agency responsible for writing, interpreting and maintaining Canadian lumbergrading rules. Grading rules exist to maintain a standard or measure of value between millsmanufacturing similar woods so that uniform quality is ensured to the public.

Canadian Lumber Standards Accreditation Board (CLSAB)

CLSAB performs normal monitoring of agencies to ensure the visual grading system maintainsstandards expected by lumber users. CLSAB's membership consists ofCanadian grading agencies,which are subject to accreditation and inspection to ensure that they carry out their functions properly.In turn, these agencies conduct qualification and inspection of the mills to ensure the grading is doneproperly on a day-to-day basis.

Re-inspection

Grading of lumber is based upon grade, moisture content, size and manufacture at the time of grading,shipment and unloading by the buyer. If questions arise the agency whose grade stamp appears on thelumber and/or NLGA should be contacted. Contact information can be found at Canadian gradingagencies listing on NLGA's website. For additional information on Canadian lumber quality controlcontact the NLGA at (604) 524-2393 or visit their website at www.nlga.org
http://www.nlga.org/newbooks.htmlhttp://ts.nist.gov/htdocs/210/215/ps20-99.pdfhttp://www.csa-intl.org/onlinestore/GetCatalogItemDetails.asp?mat=2002896&Parent=1638http://www.nlga.org/http://www.nlga.org/newgrade.htmlhttp://www.nlga.org/http://www.nlga.org/newgrade.htmlhttp://www.nlga.org/newgrade.htmlhttp://www.nlga.org/http://www.nlga.org/http://www.nlga.org/newgrade.htmlhttp://www.nlga.org/newgrade.htmlhttp://www.nlga.org/http://www.nlga.org/newgrade.htmlhttp://www.nlga.org/http://www.csa-intl.org/onlinestore/GetCatalogItemDetails.asp?mat=2002896&Parent=1638http://ts.nist.gov/htdocs/210/215/ps20-99.pdfhttp://www.nlga.org/newbooks.html


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Uses

The predominant use of dimension lumber in building construction is in framing of roofs, floors,shearwalls, diaphragms, and load bearing walls. Lumber may be used directly as framing materials ormay be used to manufacture engineered structural products, such as light frame trusses or

prefabricated wood I-joists. Special grade dimension lumber called lamstock (laminating stock) ismanufactured exclusively for glulam.Dimension lumber is categorized into the following four groups: Structural Light Framing, StructuralJoists and Planks, Light Framing, and Studs. The table below shows the grades and uses for thesegroups.

Dimension Lumber - Grades and Uses

Grade Category Size GradesCommon

Grade Mix Principal Uses

Structural Light Framing 38 to 89mm (2"to 4" nom.) thickand wide

SelectStructural,No.1, No.2,No.3

No.2 andBetter

Used for engineeringapplications such as fortrusses, lintels, raftersand joists in the smaller

dimensions.Structural Joists andPlanks

38 to 89mm (2"to 4" nom.) thickand 114mm (5"nom.) or morewide

SelectStructural,No.1, No.2,No.3

No.2 andBetter

Used for engineeringapplications such as fortrusses, lintels, rafters,and joists in thedimensions greater than114mm (5" nom.).

Light Framing 38 to 89mm (2"to 4" nom.) thickand wide

Construction,Standard,Utility

Standardand Better(Std. &Btr.)

Used for general framingwhere high strengthvalues are not requiredsuch as for plates, sills,and blocking.

Studs 38 to 89mm (2"

to 4" nom.) thickand 38 to 140mm(2" to 6" nom.)wide and 3m(10') or less inlength

Stud, Economy

Stud

Made principally for use in

walls. Stud grade issuitable for bearing wallapplications. Economygrade is suitable fortemporary applications.

Notes:

1. Grades may be bundled individually or they may be individually stamped but they must be groupedtogether with the engineering properties dictated by the lowest strength grade in the bundle.

2. The common grade mix shown is the most economical blending of strength for most applications whereappearance is not a factor and average strength is acceptable.

3. Except for economy grade, all grades are stress graded which means specified strengths have beenassigned and span tables calculated. Economy and utility grades are suited for temporary construction or forapplications where strength and appearance are not important.

4. Construction, Standard, Stud, and No. 3 grades should be used in designs that are composed of 3 or moreessentially parallel members (load sharing) spaced at 610mm (2") centres or less.

5. Strength properties and appearance are best in the premium grades such as Select Structural.


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Grades

Dimension Lumber Grades

Canadian dimension lumber is manufactured to conform to grading rules meeting Canadian and USrequirements. Each piece of lumber is inspected to determine its grade and a stamp is applied indicating

the assigned grade, the mill of origin, a green or dry moisture content at time of manufacture, thespecies or species group, and the grading authority having jurisdiction over the mill of origin.

Lumber has traditionally been graded by visual inspection. The grade of a given piece of lumber isbased on visual observation of such characteristics as slope of grain and the location of knots. Mostsoftwood lumber is assigned either an appearance grade or a structural grade based on visual review bya lumber grading who is an integral part of the lumber manufacturing process. Based on correlationbetween appearance and strength, lumber graders are trained to assign a strength grade to lumberbased on appearance criteria such as the presence of wane (bark remnant on the outer edge),presence, size and location of knots, the slope of the grain relative to the long axis and several others.The table below shows a sample of a few of the criteria used to asses grade for a 2x4 as structural lightframing or as a structural joist and plank.

Grades

CharacteristicSelect

StructuralNo. 1 & No. 2 No. 3

Edge of wide faceknots

3/4" 1 1/4" 1 3/4"

Slope of grain 1 in 12 1 in 8 1 in 4

Dimension lumber is generally grade stamped about 600mm (2') from one end of each piece so that thestamp will be clearly visible during construction. (Specialty items such as lumber manufactured formillwork or for decorative purposes are seldom marked).

To keep sorting cost to a minimum grades may be marketed by being grouped together. For example,there is an appearance difference between No.1 and No.2 Canadian dimension lumber but not astrength difference. Therefore the product mix No.2 and better is commonly used where the appearance

of No.1 grade lumber is not required, as, for example, in the case of joists and rafters or trusses.

Unless regraded, graded lumber should not be ripped or resawn lengthwise for engineered applications.This changes the location of knots and grain slope relative to the areas of high stress concentration andtherefore changes the grade.


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Sizes

Dimension Lumber Sizes

Standard dimension lumber sizes produced in North America are listed as surfaced dry sizes (19 percentmoisture content or less) in the table below. The availability of lumber sizes varies somewhat according

to the area of the country from which the raw material originates. Lengths up to 6.1 m ( 20' ) arecommonly available from western Canada and up to 4.9m (16') from eastern Canada. Longer lengthsare available on special order. They are also available in the form of fingerjoined lumber.

Dimension Lumber - Sizes

Surfaced Dry(S-Dry),Size, mm

Surfaced Dry(S-Dry),Size, in.(actual)

Rough SawnSize, in.(nom.)

SurfacedGreen

(S-Grn)Size, in.(actual)

38 x 38 1-1/2 x 1-1/2 2 x 21-9/16 x 1-

9/16

x 64 x 2-1/2 x 3 x 2-9/16

x 89 x 3-1/2 x 4 x 3-9/16

x 140 x 5-1/2 x 6 x 5-5/8

x 184 x 7-1/4 x 8 x 7-1/2

x 235 x 9-1/4 x 10 x 9-1/2

x 286 x 11-1/4 x 12 x 11-1/2

64 x 64 2-1/2 x 2-1/2 3 x 32-9/16 x 2-

9/16

x 89 x 3-1/2 x 4 x 3-9/16

x 140 x 5-1/2 x 6 x 5-5/8

x 184 x 7-1/4 x 8 x 7-1/2x 235 x 9-1/4 x 10 x 9-1/2

x 286 x 11-1/4 x 12 x 11-1/2

89 x 89 3-1/2 x 3-1/2 4 x 43-9/16 x 3-

9/16

x 140 x 5-1/2 x 6 x 5-5/8

x 184 x 7-1/4 x 8 x 7-1/2

x 235 x 9-1/4 x 10 x 9-1/2

x 286 x 11-1/4 x 12 x 11-1/2

Notes:

6. 38mm (2" nominal) lumber is readily available as S-Dry.7. S-Dry lumber is surfaced at a moisture content of 19 percent or less.8. After drying, S-Green lumber sizes will be approximately the same as S-Dry lumber.9. Tabulated metric sizes are equivalent to Imperial S-Dry sizes rounded to the nearest millimeter.10.S-Dry is the final size for seasoned lumber in place and is the size used in design calculations.


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Moisture Control

Moisture content (MC) is the weight of water contained in the wood compared to the wood's oven-dryweight. A change in the size of a piece of lumber is related to the amount of water it absorbs or loses.For moisture contents from 0 to about 28 percent, the moisture is held within the walls of the wood

cells. At about 28 percent MC the cell walls reach their capacity or fibre saturation point (FSP) and anyadditional water must be held in the cell cavities.

Moisture Content and Shrinkage ofManufactured Wood Products

Moisture Control in Dimension Lumber

Lumber stamped S-Grn (surfaced green) is lumber which had a moisture content exceeding 19 percent(unseasoned) at time of manufacture.The designation S-Dry on the grade stamp stands for surfaced dry and means that the lumber wassurfaced at a maximum moisture content of 19 percent (seasoned) or less. The grade stamp will not

indicate whether seasoning resulted from air drying or kiln drying. Some mills apply a voluntary stampindicating that the lumber was kiln dried but service performance is the same for kiln dried lumber asfor lumber dried by seasoning.

Regardless of whether S-Grn or S-Dry at the time of manufacture, careless storage can lead toabsorption of water which reverses the seasoning process and therefore increases the possibility thatdimensional change will take place when the lumber has been placed into service which of course is notdesirable.


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Shrinkage Coefficients for Canadian Softwoods

Shrinkage (% of green wood) to:

SpeciesDirection ofshrinkage 19% 15% 12% 6%

Radial 0.9 1.2 1.4 1.9Cedar, WesternRed

Tangential 1.8 2.5 3.0 4.0

Radial 1.8 2.4 2.9 3.8Douglas Fir,Coast

Tangential 2.8 3.8 4.6 6.1

Radial 1.4 1.9 2.3 3.0Douglas Fir,Interior

Tangential 2.5 3.4 4.1 5.5

Radial 1.5 2.1 2.5 3.4Hemlock,Western

Tangential 2.9 3.9 4.7 6.2

Radial 1.7 2.2 2.7 3.6Larch, Western

Tangential 3.3 4.6 5.5 7.3

Radial 0.8 1.0 1.3 1.7Pine, EasternWhite

Tangential 2.2 3.0 3.7 4.9

Radial 1.4 1.9 2.3 3.0Pine, Red

Tangential 2.6 3.6 4.3 5.8

Radial 1.5 2.0 2.5 3.3Pine, WesternWhite

Tangential 2.7 3.7 4.4 5.9

Radial 1.5 2.0 2.4 3.2Spruce, Eastern

Tangential 2.5 3.6 4.4 5.8

Radial 1.4 1.9 2.3 3.0Spruce,Engelmann

Tangential 2.6 3.6 4.3 5.7

Careful storage and handling of S-Dry lumber will ensure that it remains in seasoned condition whenput into service. Careful storage of S-Grn lumber will allow further drying after service, therebyminimizing dimensional change which might occur after going into service.

S-Dry lumber is up to 15 percent more expensive than S-Grn lumber owing to packaging and dryingcosts.


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Links and Other Information

Fire Safety

Dimension lumber is commonly used for Wood-Frame construction in floor, wall, and roof assemblies.

Building codes provide guidance on how Wood-Frame construction can be used to meet fire safetyrequirements Dimension lumber can of course be used in assemblies which do not require a fire-resistance rating. Where a rating is required, the required level of performance can be met by sheathingthe wood framing with materials such as gypsum wallboard to protect the wood and retard the spreadof fire. The Fire Safety Design in Buildings book outlines the potential for using dimension lumber for alltypes of buildings both for structural and decorative purposes while meeting fire safety requirements.

Links

CWC Members

Alberta Forest Products Association www.albertaforestproducts.ca

APA - Engineered Wood Systems www.apawood.org

Quebec Forest Industry Council www.cifq.qc.ca

Canadian Institute of Treated Wood www.citw.org

Canadian Lumbermen's Association www.cla-ca.ca

Canadian Plywood Association www.canply.org

Coast Forest & Lumber Association www.cfla.org

Council of Forest Industries www.cofi.org

Maritime Lumber Bureau www.mlb.ca

Structural Board Association www.osbguide.com

Other Organizations

Forintek Canada Corp. www.forintek.ca

National Lumber Grades Authority www.nlga.org

FERIC www.feric.ca
http://www.cwc.ca/design/tech_topics/fire/index.htmlhttp://www.cwc.ca/design/tech_topics/fire/index.htmlhttp://www.cwc.ca/publications/books_for_sale/fire_safety_design/index.htmlhttp://www.albertaforestproducts.ca/http://www.apawood.org/http://www.cifq.qc.ca/http://www.citw.org/http://www.cla-ca.ca/http://www.canply.org/http://www.cfla.org/http://www.cofi.org/http://www.mlb.ca/http://www.osbguide.com/http://www.forintek.ca/http://www.nlga.org/http://www.feric.ca/http://www.feric.ca/http://www.nlga.org/http://www.forintek.ca/http://www.osbguide.com/http://www.mlb.ca/http://www.cofi.org/http://www.cfla.org/http://www.canply.org/http://www.cla-ca.ca/http://www.citw.org/http://www.cifq.qc.ca/http://www.apawood.org/http://www.albertaforestproducts.ca/http://www.cwc.ca/publications/books_for_sale/fire_safety_design/index.htmlhttp://www.cwc.ca/design/tech_topics/fire/index.htmlhttp://www.cwc.ca/design/tech_topics/fire/index.html

Documents

Visually Graded Lumber