WOOD Andrea Wheeler
Week 11 Part 2
CONTENT (Lectures and Lab Thurs/ Friday)
1. Review: The timber yard and supply chain – the
sustainable sourcing of wood.
2. Wood composites, laminated timber and new
3. Wood rot, and insects.
4. Construction uses for wood and timber framing.
5. Fastenings, and connections – more Lab (Friday)
6. Case studies of timber in structure and construction
(throughout) – more Lab (Friday)
Attendance question ?
Describe the stages
involved in the
How can we ensure
the process is
PREPARATION OF TIMBER FOR
COMMERCIAL USE: Manufacturing process of
The production of wood for construction – from
log to board:
• Sourcing – mature trees felled / identified by the forest
Stewart involved sustainable forestry management.
• Stacked for transport to mill (some free water dissipating) -
floated downstream to mill
• sawing/cutting (before logs are sawn debarked and inspected)
• planing/ surfacing,
• preservative treatment,
Sourcing – Sustainable Forestry
• Certified Forest/ Forest Stewardship
Council two types of certification Forest
Management and Chain of Custody. (10
principles, 57 criteria.) FSC-certified
wood was found to be the most specified
green-building product in LEED certified
• Sustainable Forestry Initiative (SFI),
which provides a comprehensive system
of principles, guidelines and performance
standards that balance the perpetual
growing and harvesting of trees with
environmental protection and
conservation. The Sustainable Forestry
Initiative (SFI) is a 'forest certification
Sustainable forestry principles
PRINCIPLE #3: INDIGENOUS PEOPLES’ RIGHTS - The legal and
customary rights of indigenous peoples to own, use and manage their lands,
territories, and resources shall be recognized and respected.
PRINCIPLE #4: COMMUNITY RELATIONS AND WORKER’S
RIGHTS - Forest management operations shall maintain or enhance the
long-term social and economic well being of forest workers and local
PRINCIPLE # 5: BENEFITS FROM THE FOREST - Forest management
operations shall encourage the efficient use of the forest’s multiple products
and services to ensure economic viability and a wide range of environmental
and social benefits.
PRINCIPLE #6: ENVIRONMENTAL IMPACT - Forest management
shall conserve biological diversity and its associated values, water resources,
soils, and unique and fragile ecosystems and landscapes, and, by so doing,
maintain the ecological functions and the integrity of the forest.
PRINCIPLE #7: MANAGEMENT PLAN - A management plan —
appropriate to the scale and intensity of the operations — shall be written,
implemented, and kept up to date. The long-term objectives of management,
and the means of achieving them, shall be clearly stated.
The importance of the supply chain
FSC Chain-of-Custody certification traces the path of products from
forests through the supply chain, verifying that FSC-certified material is
identified or kept separated from non-certified material throughout the chain.
Any company in this supply chain, including harvesters, processors,
manufacturers, distributors, printers, retailers or anyone that is taking
ownership of the forest product before the end user, needs to be FSC certified
to be able to label or promote their products as FSC certified.
The Chain-of-Custody process ensures the consumer that the FSC-certified
products they purchase are coming from responsibly managed sources. For a
consumer to purchase an FSC-certified product, every company that previously
had ownership of the forest product material components of the end product
would have had to be FSC certified.
The requirements for the credit are:
“Use a minimum of 50% of wood-based materials and
products, which are certified in accordance with the Forest
Stewardship Council’s (FSC) Principles and Criteria, for
wood building components. These components include,
but are not limited to, structural framing and general
dimensional framing, flooring, sub-flooring, wood doors
and finishes. Only include materials permanently installed
in the project. Furniture may be included, providing it is
included consistently in MR Credits 3–7.” - LEED NC
Does LEED or FSC certified standards mean
The debarked log is evaluated by scanners with "electronic eyes". The scanners use lasers to
determine the size of the log and the best possible cuts. A computer then sets up the
longitudinal cuts using an edge saw. The sawyer's cut decisions are based on: Species of wood
;Log diameter ;Intended use of the lumber ; Yield ;Market costs for different grades and sizes of
lumber. The sawyer is a very important person at the mill because he determines whether or not
the mill will make money based on his evaluation of the log.
Air drying programs will
take more than a year.
The sustainable timber yard: wastage in the timber yard.
Almost all the parts of a tree are commercially
Bark: used for fuel or mulch
Lower-grade logs are processed into paper
Low grade boards and scraps from sawing
processed into paper.
Finally, machines and workers inspect the lumber and rate it
based on the amount of defects present.
BSW produce strength graded timber to specifications laid down in British Standards - BS4978
for visual grading and BS EN 14081 for machine grading. Timber is graded to strength classes.
The most commonly specified grade for softwood carcassing is C16.
Grading USA – Types of Timber
Boards: 1 to 1.5 inches thick, 2 inches and wider
Dimension Lumber: 2 to 4 inches thick, 2 inches and
wider (Dimension lumber is further subdivided into five
categories based on size classifications. These classes are
structural joists and planks, studs, decking, light
framing, and structural light framing. After the
dimension lumber has been separated, the grader assigns a
Timbers: 5 inches and thicker, 5 inches and wider
Board lumber is graded by evaluating the better face of the
board. Natural and manufacturing defects are considered, but
strength is not a critical factor (unlike the grading of dimension
•The highest classification of board lumber is called select
grade. Select grade is further divided into three categories: B &
Better, C Select, and D Select. B is the best but all of the select
grades are used in demanding finishing applications.
•The next classification is called common grade. Common grade
boards generally contain more knots than the select grade.
Common grade is divided numerically from 1 to 5 with 1 being
the best in appearance. No. 3 and No. 4 common grades are most
frequently used for such applications as sheathing or sub-
Visual Grading is the most common type of grading performed on lumber in
the U.S. A grade stamp on each piece of lumber as it leaves the mill. Visual
grading is done based on both appearance and strength factors. The grader
marks each piece of lumber according to such factors as:
•Number, size, and position of knots and holes
•Bark on edges
•Checks and splits
•Twisting, bowing, and warp
Rules for grading are established by the U.S. Department of Commerce and
maintained by the American Lumber Standards Committee. These standards
are enforced by regional organizations.
Three years of training are required to become a grader.
After kiln drying to an average moisture content of below 20%, the timber is
passed through a highly automated grading line where a combination of
measurements are taken which closely relate to strength. From this, the machine
determines the Strength Class of the piece of timber. The machines are calibrated
DIMENSIONAL LUMBER - Machine graded
(strength is the factor)
The species of lumber is
stamped, and is also
abbreviated. Some common
examples include: •"S-P-F"
represents spruce-pine-fir, a
common grouping for some
of the Eastern softwoods.
"DF-L" refers to Douglas fir
and Western larch. "Hem-
fir" stands for Western
hemlock and true firs.
In the U.S., there are six
develop and publish
grade rules and issue
• Redwood Inspection
• Northern Hardwood
• Southern Pine
• West Coast Lumber
• and Western Wood
name or number
is also included.
The grade itself is indicated. A lumber
grade is the quality-control standard for
lumber that has been in place since such
standards were instituted in 1960. Lumber
is graded using the American Lumber
Standards, which are based on the
structural integrity of a board. These
grades take into account the size and
location of defects, as well as the slope of
grain, in order to predict the load-bearing
capacity of the board.
You'll also find the moisture content of the wood, which
is determined at the mill when the stamp is applied.
Under the National Grading Rule, there are three
moisture-content conditions: "S-GRN" (surfaced
green) means that the moisture content is above 19%.
Most lumber is dried to the "S-DRY" (surfaced dry)
condition, meaning that that the moisture content is less
than 19%. "MC15" means that the moisture content is
less than 15%.
Select" = at least 80% clear wood
"#1 Structural" = at least 75% clear wood;
"#2 Structural" = at least 66% clear wood;
"#3 Structural" ("stud" grade) = at least 50%
"Construction Grade" = at least 57% clear
"Standard Grade" = at least 43% clear wood;
"Utility Grade" = at least 29% clear wood
Preservative treatments (CCA – Copper Chromium Arsenic)
Timber products such as construction, fencing, landscaping and
decking are subject to preservative treatments to enhance durability and
lifespan. When exposed to certain conditions, in particular when the
moisture content is allowed to rise it is susceptible to attack from fungi and
CCA (Copper Chromium Arsenic) Pressure Treated treatment is
effective - for example, extending the life of softwood posts from a few
years to 40 years.
Partial or complete restriction of CCA occurs in a number of countries
including Japan, Indonesia, Sweden and Germany.
The main concern with CCA is that it contains arsenic. While not a
mutagen, arsenic acts as a carcinogen when ingested at rates above certain
tolerable limits. It may initiate skin and liver cancers. A link between
handling CCA-treated timber (using recommended procedures) and cancer
has not been demonstrated,
During CCA treatment, timber is impregnated with
the preservative solution using controlled
Common Chemicals Threaten Our
Brains, Say Studies
WASHINGTON—There exists a “silent pandemic” of toxins that has been
damaging the brains of unborn children, according to a recent study by
researchers from Harvard University and Mount Sinai School of Medicine.
The researchers listed 12 chemicals—substances found in both the
environment and items such as furniture and clothing—that they believed
to be causing lower IQs, as well as ADHD and autism.
Paints, adhesives, preservatives
Timber as a sustainable material and the supply chain?
• Does a certificate mean timber is “sustainable” are
the criteria for our assessment adequate?
• Does LEED = sustainable architecture?
• What is the role of health and wellbeing in
designing sustainable buildings?
• What is the limits of the architects’ decision
making to allow him/her to question the ethics of
the building process or the supply chain? How
green can you be?
The Woodmans’ Cottage. BBC documentaries with Kevin McCloud
The Woodmans’ Cottage
No LEED certification
No FSC certificate
Supply chain – transport minimal
Processing of the wood – minimal?
Labor costs – minimal?
Engineered wood products: Wood composites, laminated timber
and new materials
Characterized by fibres, strands, laminar, veneers – bonded with
adhesives to maximize strength of these products.
1. Orientated strand board (OSB) and plywood panels
2. Structural composite lumber (SCL) includes: Laminated
Veneer Lumber (LVL), Parallel Strand Lumber (PSL)
Laminated Stand Lumber (LSL) Orientated Strand Lumber
3. Structural glued laminated timber / glulam
5. Non-structural products: Particle Board, Hardboard,
Medium density siding, Fiberboard, Medium density fiber
board, Decorative plywood
1. Orientated strand board (OSB) and plywood panels used in
timber framed buildings add stability to the framed structure –
commonly used throughout the US in domestic construction.
Made by gluing wood
veneers under heat
The veneers are glued such
that the grain
direction in each veneer is
oriented at right
angle to the grain of the next
Urea formaldehyde – toxic
glue used in manufacture.
2. Structural composite
lumber (SCL) is
designed to be free from
warping, splitting and
shrinking. Performance can
be predicted with
confidence. The grade and
quality of each layer is
closely controlled in
manufacture. Purpose to
overcome the natural
variability in timber.
Laminated Veneer Lumber (LVL)
Laminated veneer lumber
(LVL) is made
by gluing together dried
The grain runs in the same
the difference with
plywood where the
veneers are cross grained.
Orientated Strand Lumber
Made with wood strands
• Alternate layers of
strands are oriented at
angles to each other
• The several layers are
glued under heat and
• Used only for structural
cannot be stained or
painted). Also OSB
cannot be treated with
Orientated Strand Lumber used in domestic property
3. Structural glued laminated timber / glulam made up of
individual wood laminar or layers. Depths of beams 6 inches to 6 feet
and lengths up to 100 feet. Increasing the predictability of
performance and can be used for large long span structures.
Can be used in domestic properties but also in structurally
innovative building forms – e.g. domed stadium roofs and to
extend the structural potential of timber.
wood (glulam) is
lengths of dimension
lumber that are
glued together to
large cross section.
Niall McLaughlin Architects Bishop Edward King Chapel. Oxford
4. I Joists
like the letter I. Floor
joists and roof
Name some uses for timber in
Peter Zumthor, Brother Claus Field Chapel,
Construction uses for wood
1. Structural framing. Approximately 90% of
buildings constructed in the US each year are
framed with wood, whilst that percentage is only
15 – 20 percent in the UK.
2. Subfloors and roof sheathing.
3. Siding (weatherboards)
4. Finishes/ cabinetry and trim
Historic timber framing
Each joint must be sufficient to carry the
load, and the post must not break.
Traditional joints mortise and tenon.
This tie beam often carries floor loads.
The three-bay, side-
entrance barn, common
New England and New
York after about 1800,
made use of the
plate tying joint. The
rafters were additionally
continuous purlin plates
at their midspan.
barn at great coxwell
“the greatest piece of architecture in england”
joint detail from barn at coggeshall
springton manor barn
1700’s dutch barn
Name Workability Uses Notes
Western Red Cedar - good joinery & cladding weathers to grey, smells good
Douglas Fir - excellent const. to furniture grows fast and straight – in USA
Southern Pine - excellent const. to furniture grows fast and straight – in USA
Spruce - good const. & scrap lower quality and not durable
Yew - difficult furniture & joinery limited availability
Yellow Poplar - medium const. & moldings little grain – paints well
Ash - good joinery & veneer decorative, sim. to oak
Bubinga - medium veneer African exotic, dark red
Cherry - good joinery, veneer, furn. medium color to light red
Elm - medium joinery & furniture wiped out in US by disease
Mahogany - good joinery & furniture dark color, medium grain
Maple - medium veneer & flooring light grain, takes stain poorly
Red Oak - medium veneer, joinery, furn. red to brown, course, strong grain
White Oak - good veneer, joinery, floors lighter brown, hard, stains well
Padauk - good joinery & furniture strong red, limited availability
Teak - medium joinery & furniture warm brown, questionable sources
FOREST STEWARSHIP COUNCIL (FSC) : http://www.fsc.org/en/
CERTIFIED FOREST PRODUCTS COUNCIL : www.certifiedwood.org
Beetles, fungus and other rots
Types of insects that cause deterioration of wood
carpenter ants, beetles, and termites
Carpenter ants prefer higher moisture content and
softer wood that has begun to decay while powder
post beetles prefer low moisture content in both
softwoods and hardwoods.
Meg, the Dry Rot
Sniffs out fungus
Timber is a material with a unique charisma – it
was, after all, once living, and its organic origins
are clear in its appearance and texture. It also has
an historic resonance, since a thousand-year
tradition is still evident in the great frames and
roofs of the medieval period and earlier.
Overall, its appeal to designers is based
principally on its:
• Visual tactile qualities
• Material properties
• Environmental credentials.
Labs: 4 groups
GROUP RESEARCH THEMES
1. Is wood a sustainable construction
material? The case for new innovative
wood based construction materials.
2. Why have we seen a development in
structural connections and fastenings in
timber: From the Old English Barn, log
structures to Shiguru Ban?
3. The structural limits of timber
structures: How high can we go?
4. Designing with wood – new materials
and new methods of engineering,
design and construction.