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Preservation of Historic WoodStructures
Ron AnthonyAnthony & AssociatesAnthony & Associates
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© The Wood Products Council 2014© The Wood Products Council 2014
The Wood Products Council isa Registered Provider with TheAmerican Institute of Architects
This course is registered withAIA CES for continuingprofessional education. As
Continuing Education Systems(AIA/CES), Provider #G516.
such, it does not includecontent that may be deemedor construed to be anapproval or endorsement by
Credit(s) earned on completionof this course will be reported toAIA CES for AIA members
the AIA of any material ofconstruction or any method ormanner ofhandling, using, distributing,AIA CES for AIA members.
Certificates of Completion forboth AIA members and non AIAmembers are available uponrequest
or dealing in any material orproduct.___________________________________________request.Questions related to specific materials,methods, and services will be addressedat the conclusion of this presentation.
Course Description
Wood structures are often historically significant and provide asense of place to local communities, creating an impetus forrenovation or adaptation providing the structure remainssound. Where good construction practices and appropriatemaintenance have been made a priority, wood structures maylast for generations, a testament to wood's potential long termdurability. This presentation will focus on considerations related
h i f d T i ill i l dto the preservation of wood structures. Topics will includefactors that affect wood performance, the basics of conductinga condition assessment and how to maximize the retention ofhi t i f b i hil t di th lif f th t t R ihistoric fabric while extending the life of the structure. Repairand replacement materials and considerations related tospecifications will also be discussed.
Learning Objectives
1. Review the science behind wood as a constructionmaterialmaterial.2. Understand how to determine the condition of woodstructural elements in an existing structure by learningabout factors that affect performance and the basics of aabout factors that affect performance and the basics of astructural assessment. This will enable the designer tounderstand the structure s ability to perform to currentcodes and regulations.
3. Discuss ways to extend the life of an existing structure,which is a crucial element in effective historicpreservation.4. Learn about considerations for repair and replacementof wood elements and ideas for better specifications.
ContextContext
Frank Lloyd Wright and Wood• Believed wood should be allowed to be
wood, not painted to look like , psomething else
• Believed in simple rather than detailedBelieved in simple rather than detailed millwork
Frank Lloyd Wright and Wood• Grew to think of wood as more of an
architectural than structural material because of perception of shrinking forests
• Not necessarily driven by durability issuesissues
Material Properties andMaterial Properties and Behavior
• Variability
• Durability
Factors Affecting WoodFactors Affecting Wood Performance
• Moisture content
• Durabilityy
Equilibrium Moisture qContent
• Depends upon relativeDepends upon relative humidity
• Is always changing• Affects wood performance• Affects wood performance
DurabilityDurability
•Natural durability due toNatural durability due to extractives
•Chemical preservatives•Remedial treatments•Remedial treatments•Finishes•Detailing
InsectsInsects
•Borers tunnel through wood but d t t itdo not eat it• Bore holes contain frass
•Termites digest wood•Termites digest wood• Bore holes are clean
W h i f W dWeathering of Wood
•Moisture
•Ultraviolet light
•Abrasion
Why do we investigate wood structures?structures?
Primary reasons:
• Concerns about moistureConcerns about moisture• Concerns about deterioration• Questions about material properties• Catastrophic failure has occurredCatastrophic failure has occurred• Performance failure has occurred
Wood Assessment
• Visual• Visual• Probingg• Moisture content• Nondestructive testing
Visual Inspection, Probing andMoisture Diagnostics
B tt j i tButt jointbetweenblocking
Fracture Bolt Strength of lumber and gtimber
O ti F G diOptions For Grading
• Use current grading rules
U hi t i d t• Use historic data
• Destructive testing• Destructive testing
D i V lDesign Values
• Based on species and gradep g• Grade based on defects and
isize• Includes end-use conditionsIncludes end use conditions• Includes factor of safety
Specifications
Why write specifications?Why write specifications?To communicate between parties what is needed toparties what is needed to
minimize waste and expensep
Wood SpeciesWood Species
• Softwoods Pinus strobus• Softwoods – Pinus strobus
• Hardwoods – Quercus spp.
Di iDimensions
• Actual• Actual
• Nominal
M i t C t tMoisture Content
• Deterioration• Deterioration
• Shrinkage and swelling
Structural ConsiderationsStructural Considerations
M t i l P tiMaterial Properties
B di• Bending• CompressionCompression• Shear• Tension
Stiff• Stiffness• ConnectionsConnections
Non structural ConsiderationsNon-structural Considerations
Type of CutType of Cut
• Vertical grain or quarter g qsawn
• Flat grain or plain sawng
• Rift sawn• Rift sawn
AestheticsAesthetics Reclaimed vs NewReclaimed vs. New
TreatmentTreatment
• Wood preservatives
• Fire retardant treatment
• Stains and paints• Stains and paints
What Goes In A Specification?What Goes In A Specification?
• SpeciesDi i• Dimensions
• Moisture content• Grade
T f t• Type of cut• Treatment• Aesthetics