Design Considerations for Durable Structures “The Wood Products Council”is This course is registered with a Registered Provider with The AIA CESfor continuing American Institute of Architects professional education. As Continuing Education Systems such, it does not include (AIA/CES), Provider #G516. content that may be deemed or construed to be an approval or endorsement by the AIA of any material of Credit(s) earned on completion or any method or of this course will be reported to manner of handling, using, AIA CES for AIA members. distributing, or dealing in any Certificates of Completion for material or product. both AIA members and non-AIA ______members are available upon Questions related to specific materials, request. methods, and services will be addressed at the conclusion of this presentation. Course Description

With proper design, detailing and specification, wood structures can provide long and useful service lives while also offering a reduced environmental footprint. The key is careful planning and understanding of environmental loads and other external factors likely to impact a building over its lifetime. This presentation provides an overview of considerations related to durable wood design, including moisture management techniques, preservative treatment specification, and details for controlling termites. Learning Objectives

1. Determine methods for controlling moisture infiltration into the exterior assemblies. 2. Review good building envelope detailing practices including guidance on the use of water, air and vapor barriers. 3. Discuss specification of preservative treated and naturally decay resistant wood material. 4. Introduce termite prevention strategies. Outline

• Building Examples • Potential Building Hazards • Understanding Wood • Moisture Control • Durable Materials • Controlling Termites • Service Life Outline

• Building Examples • Potential Building Hazards • Understanding Wood • Moisture Control • Durable Materials • Controlling Termites • Long Service Life Borgund Stave Church Borgund, Norway Built between 1180 - 1250 Tōdai-ji, Buddhist Temple Nara, Japan Built 752 and Rebuilt 1709 Butler Brothers Building Architect: Harry W. Jones Built 1906 and Renovated 1974 The Cathedral of Christ The Light, Oakland, CA, USA Design Team: Skidmore Owings & Merrill, Craig W. Harman, Webcor Builders Photo Credit: Timothy Hursley, Cesar Rubio, and John Blaustein, Arena Stage, Washington, DC Architect: Bing Tom Photo Credit: Nic Lehoux Outline

• Building Examples • Potential Building Hazards • Understanding Wood • Moisture Control • Durable Materials • Controlling Termites • Long Service Life Potential Hazards

MOLD • Fungi • Does not significantly effect structural properties of wood • Some associated with occupant health concerns MOLD effects all materials! Potential Hazards

DECAY • Fungi • Can degrade structural capacity • Do not cause health concern

RUST and ERROSION are potential hazards too. Potential Hazards

INSECTS Wood Boring • Wood boring beetles Beetles • Carpenter ants • Termites • Damp-wood termites – rarely a Carpenter problem for buildings Ants • Dry-wood termites – only in extreme southern US and Mexico Formosan • Subterranean termites – very Ter m i t e controllable risk § Formosan termites–more aggressive, exist in southeastern US Know your risk based on geography and design for it. Not Hazards

Staining Fungi Weathering Potential Hazards

Mold Decay

All Organic Life Requires: Insects

1. Oxygen 2. Food Source 3. Moderate Temperature 4. Moisture Outline

• Building Examples • Potential Building Hazards • Understanding Wood • Moisture Control • Durable Materials • Controlling Termites • Long Service Life Understanding Wood: Hygroscopic

Free Water VS Bound Water

Fiber Saturation Point: Point at which cell are completely saturated, cell cavities are empty (i.e. no free water but still has all its bound water) Understanding Wood: Hygroscopic

Moisture Content • Fiber Saturation = 28% MC • Code required to be < 19% MC at building close • Wood still has ability to absorb water between 19- 28%

Picture Source: Panshin, A.J. and de Zeeuw, C., (1980) Textbook of Wood Technology, Fourth Edition, McGraw-Hill, inc. Understanding Wood: Orthotropic

Wood is orthotropic, meaning it behaves differently in its three orthogonal directions: Longitudinal (L), Radial (R), and Tangential (T) This is a direct result of the arrangement of wood cells Outline

• Building Examples • Potential Building Hazards • Understanding Wood • Moisture Control • Bulk Water Intrusion • Air flow Current • Vapor Diffusion • Durable Materials • Controlling Termites • Long Service Life Moisture Control

Wetting Drying

Bulk water intrusion Evaporation or diffusion

Air current induced moisture vapor movement Directionally effected by humidity, temperature Vapor migration by and pressurization diffusion Moisture Control

Wetting Drying

Bulk water intrusion Evaporation or diffusion

Air current induced moisture vapor movement Directionally effected by humidity, temperature Vapor migration by diffusion and pressurization Durability By Design Deflection

Source: Moisture and Wood Framed Buildings by CWC Deflection

Source: Moisture and Wood Framed Buildings by CWC Deflection

Overhang Overhang Width Ratio Wall Height

Source: Moisture and Wood Framed Buildings by CWC Deflection

Source: Moisture and Wood Framed Buildings by CWC Barrier Wall System

Example: Commonly masonry (veneer) facades are face sealed and may not have a path for drainage behind. Source: Moisture and Wood Framed Buildings by CWC Concealed Barrier Wall System

Example: All joints and seams in sheathing sealed with compatible and durable tape and façade directly attached.

Source: Moisture and Wood Framed Buildings by CWC Rainscreen Wall System

Example: In addition to furring strips, dimpled mats, crinkled housewrap or textured mesh can also provide a drainage plain an capillary break.

Source: Moisture and Wood Framed Buildings by CWC Vented Rainscreen Wall System

Example: Furring strips fastened to through insulating sheathing with openings at top and bottom provided with screen to prevent insect entry. Source: Moisture and Wood Framed Buildings by CWC Durability by Design - Guide to Barriers

• Address bulk water that gets past cladding • Applied at exterior Weather Barrier • Ex: building /wraps (NOT all) • Limits liquid water passing through

• Stops movement of air under pressure Air Barrier • Applied at interior or exterior • Ex: Board stock, tapes

• Slow movement of water vapor by diffusion Vapor • Installed on warm side of insulation Barrier/Retarder • May not be required or desired • Low level of permeability Weather Barriers

Perforated Unperforated Building Felt/ House wraps House wraps

Water Resistant Less than Yes Yes, varies greatly unperforated Vapor Permeable Yes Yes Yes Air Resistant Yes Yes Only if penetrations are all sealed Moisture Absorptive No No Yes, varies greatly Tear Resistant Yes Yes Varies greatly UV Resistant Varies greatly Varies greatly No Moisture Tolerant Yes Yes No Durability By Design – Reservoir Cladding

Reservoir cladding systems need an airspace to dry and eliminate capillary action. Durability by Design - Stucco

Moisture load at window header, sills and corners

Need to minimize ability to store water Durability by Design - Stucco

Ensure clean sand is used in Stucco mix. Specify building wrap with built in drainage or two layers of building wrap. Durability by Design – Brick Veneer

Provide minimum 1” airspace behind brick veneer. Durability by Design – Brick Veneer

Provide a path for drainage get out from behind the wall. Durability By Design – Detailing

DO NOT X-cut Building Paper at Window. Durability By Design – Detailing

http://www.apawood.org/buildabetterhome-walls Durability By Design – Detailing

Avoid Horizontal Valley’s.

2000 sq ft of 1250 gallons 1” of RAIN ROOF of WATER Durability By Design – Detailing

Flash at roof and wall intersections. Moisture Control

Wetting Drying

Bulk water intrusion Evaporation or diffusion

Air current induced moisture vapor movement Directionally effected by humidity, temperature Vapor migration by diffusion and pressurization Moisture Control - Condensation

Change in relative humidity (rh) of air at 70F cooled to 35F (with no moisture added or removed) Moisture Control - Condensation

Dew Point Location

70 Degrees F 30% Relative Humidity

INSIDE OUTSIDE

Dew Point

0 Degrees F Moisture Control – Air Current

Source: Building Science Corporation Moisture Control – Insulation

Steel may be hard to insulate: Wood insulation example: Moisture Control – Air Sealing

Exterior Air Interior Air Barrier Barrier Ease of No intersecting More intersecting installation walls and fewer walls and penetrations penetrations to detail around Addresses Prevents wind- Using semi-rigid Wind- washing of the insulation can prevent washing cavity insulation the need to address wind-washing Controlling Control entry of Control entry of moisture exterior hot humid interior moisture loads air into insulated laden air into cavities in hot insulated cavity humid climates. during heating Moisture Control

Wetting Drying

Bulk water intrusion Evaporation or diffusion

Air current induced moisture vapor movement Directionally effected by humidity, temperature Vapor migration by and pressurization diffusion Moisture Control - Vapor Diffusion

Vapor Diffusion • Moisture transfer through a material moving from wetter to dryer • Vapor Pressure is the weight of the water in the air. • Higher humidity air weighs more creating a pressure that move water from wetter to dryer Moisture Control – Vapor Retarders

Vapor Retarders: • Class I - 0.1 perm or less • Class II – less than (or equal to) 1.0 perm and greater than 0.1 perm • Class III – less than (or equal to) 10 perm and greater than 1.0 perm “Vapor Barrier” = Class I

Source: Building Science Corporation Moisture Control – Vapor Retarders

Source: IECC Climate Zone Map Moisture Control – Vapor Retarders

• Do not require any class of Vapor retarder Zone on the interior surface of insulation in insulated wall and floor assemblies 1-3

• Do not require any class of Vapor retarder Zone 4 (except on the interior surface of insulation in Marine) insulated wall and floor assemblies

• Class II or III (or lower) may be required depending on permeance of sheathing Zone 4 and cladding. Higher class can be applied (marine), 5-7 if dew point is controlled (requires modeling). Moisture Control – Climate Zones

Source: Build America US Department of Energy (http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/4_3a_ba_innov_buildingscienceclimatemaps_011713.pdf) Moisture Control – Good Example

Applicable to • Mixed-humid • Hot-humid • Mixed-dry • Hot-dry • Marine • Some colder regions (5/6)

NOT applicable to: • Very cold • Subarctic/arctic

Source: Building Science Corporation Moisture Control – Good Example

Applicable to • Mixed-humid • Hot-humid • Mixed-dry • Hot-dry

NOT applicable to: • Marine • Cold • Very cold • Subarctic/arctic

Source: Building Science Corporation Moisture Control – Good Example

Applicable to: • Cold • Very cold

NOT Applicable to • Marine • Mixed-humid • Hot-humid • Mixed-dry • Hot-dry • Subarctic/arctic

Source: Building Science Corporation Moisture Control – Good Example

Applicable to: • Marine • Cold • Very cold

NOT Applicable to • Mixed-humid • Hot-humid • Mixed-dry • Hot-dry • Subarctic/arctic

Source: Building Science Corporation Outline

• Building Examples • Potential Building Hazards • Understanding Wood • Moisture Control • Durable Materials • Preservative Treatment • Naturally Decay Resistant • Controlling Termites • Long Service Life Preservative VS Pressure Treated Preservative Treated

As defined by the IBC in Chapter 23

2303.1.8 Preservative-treated wood. , timber, , piles and poles supporting permanent structures required by Section 2304.11 to be preservative treated shall conform to the requirements of the applicable AWPA Standard U1 and M4 for the species, product, preservative and end use. Preservatives shall be listed in Section 4 of AWPA U1. Lumber and plywood used in wood foundation systems shall conform to Chapter 18.

However code compliant preservative treated products can also follow: • 104.11 Alternate materials and methods • ICC reports can also be provided for proprietary treatments and products under this provision Source: Guide to Pressure Treated Wood, WWPI Preservative Treated - Specification Preservative Treated - Specification

ICC reports can also have a lot of information that can be useful in specification for both proprietary and non proprietary treatments. • Conditions of use • Fastener recommendations • Structural capacity

http://www.icc-es.org/Reports/index.cfm Preservative Treated – Treatment Types

Waterborne Copper Based: • ACQ – Alkaline Copper Quat • ACZA (Chemonite) – Ammoniacal Copper Zinc Arsenate • CA – Copper Azole • CCA – Chromated Copper Arsenate • PTI and EL2 – Carbon-based preservatives • MCA –Micronized Copper Azole Borate Based: • SBX – Inorganic Boron Oil based • Pentachlorophenol • Copper Naphthenate Creosote Preservative Treated - Incising

Pressure-treated Pressure-treated Douglas- Southern

Photo from University of Tennessee Forest Products Extension Preservative Treated –Spec Examples

1. Sill plates shall be treated in accordance with AWPA Standard U1 to the requirements of Use Category 2 (UC2). 2. Sill plates shall be treated with waterborne preservatives in accordance with AWPA Standard U1 to the requirements of Use Category 2 (UC2). 3. Sill plates shall be treated with waterborne preservatives in accordance with AWPA Standard U1, Commodity Specification A, to the requirements of Use Category 2 (UC2). 4. Sill plates shall be southern pine lumber, treated with waterborne preservatives in accordance with AWPA Standard U1, Commodity Specification A, to the requirements of Use Category 2 (UC2). 5. Sill plates shall be southern pine lumber, treated with inorganic boron (SBX) in accordance with AWPA Standard U1, Commodity Specification A, to the requirements of Use Category 2 (UC2).

Proprietary Treatments specification guidelines are usually very clearly provided by the treated product supplier on their website. Preservative Treated - Fasteners

IBC 2304.9.5.1 • Hot-dipped galvanized steel § above grade • Stainless steel § below grade, § salt-water exposure, § severe conditions • Silicon bronze § Special use • Copper § Special use Preservative Treated – LCA Comparison

Source: Conclusions and Summary Report on an Environmental Life Cycle Assessment of Borate –Treated Lumber Structural Framing with Comparisons to Galvanized Steel Framing, Treated Wood Council 2012 Preservative Treated – Field Treatment

Copper Napthenate At least 2% copper solution Available field treatment products • Copper-Green • Copper-Green Brown • Wood life Copper Coat • Copper Care Cu-Nap Concentrate • Armor All End Cut Wood Preservative Preservative Treated – Wood Products

• Solid Sawn • Plywood • Glulam • Parallel Strand Lumber Naturally Decay Resistant Species

Source: US Forest Products Lab Wood Handbook Chapter 14 Biodeterioration, Clausen 2010 Cell Structure: Heartwood & Sapwood

Sapwood: Outer, lighter colored band which conducts moisture and sap, stores biochemicals and carbon, and is the metabolically active zone (living sapwood cells are agents of heartwood formation) Cell Structure: Heartwood & Sapwood

Heartwood: darker colored core, long term storage of extractives which are biochemicalsthat provide natural durability to wood. They are formed at the heartwood-sapwood interface and infiltrate cells throughout the heartwood region Outline

• Building Examples • Potential Building Hazards • Understanding Wood • Moisture Control • Durable Materials • Controlling Termites • Long Service Life Controlling Termites Controlling Termites: Subterranean

2006 Map Subterranean Termite Hazard Severity

Subterranean Termites—Their Prevention and Control in Buildings, US Forest Service 2006 Controlling Termites: Formosan Territory

Source: www.termite.com Durability Detailing

The 6S Approach to Subterranean Termite Control

Soil and Site Suppression Physical Management Barriers

Slab and Surveillance Structural Foundation and Protection Details Remediation Controlling Termites: Site Management

Remove from site • tree stumps • all wood/ containing debris • Formwork (don’t leave embedded in foundation) Soil Work • Do not use excavation spoil under wood frame elements • Drain water away from building (slope 5% for 10’) • Keep non-treated wood away from soil (6”-8”code minimums) Controlling Termites: Barrier/Foundations

Physical Barriers • 4” thick sand or crushed stone (1/16-1/10” Dia) beneath slab and/or along inside and outside of foundation wall • Install sheet metal between top of foundation and sill plate • Wrap perimeter foundation in mesh to protect at/below grade penetrations (1/32” grid spacing) • Marine grade stainless steel mesh has 20yr service life • Openings in slab/stem wall sealed with non-shrink grout Slabs and Foundations • Slabs control joints and cracks don not exceed 1/25” • Stem walls exposed for 8” above grade to allow inspection • Keep crawl space access in floor instead of foundation walls Controlling Termites: Details

Brick Veneer

Ground clearance: Floor Brick Veneer

Plate/sill

8”

Foundation Controlling Termites: Details

Approx. 1” Controlling Termites: Details

Wood Veneer

Ground clearance: Floor Joist Plate/sill

8” 6”

Foundation Controlling Termites: Details

Approx 1-1/2” Controlling Termites: Details Controlling Termites: Details

Wood Veneer

Floor Joist Concrete clearance: Wood veneer Plate/sill

6” 2” Porch, walk, etc Foundation Controlling Termites: Details Controlling Termites: Details

Source: American Wood Council WCD 6 Controlling Termites: Details

Floor joist

Ground clearance: Girder Crawl space Wood Post Moisture barrier 8” Controlling Termites: Details

Wood Post

Ground clearance: Wood column 1” Impervious Moisture Barrier

6”

Moisture barrier Controlling Termites: Details

Wood Post

Ground clearance: Wood column

Moisture 6” barrier Controlling Termites: Details

Source: American Wood Council WCD 6 Controlling Termites - Details

Source: American Wood Council WCD 6 Controlling Termites - Details

Source: American Wood Council WCD 6 Controlling Termites – Structural

Preservative Treated Wood • CCA for interior damp, exterior above ground and exterior ground contact applications • Borate treatments for interior dry and interior damp applications Termite Resistant species • Yellow Cedar • Cypress • Redwood • Western/Eastern Red Cedar Outline

• Building Examples • Potential Building Hazards • Understanding Wood • Moisture Control • Durable Materials • Controlling Termites • Long Service Life Service Life and Durability

47

18 19

12 7 Number of Buildings of Number

0-25 26-50 51-75 76-100 100+ Age Class – Years

Source: Demolition Study – Forintek Canada Corporation, Vancouver, B.C., Canada 2004 Service Life and Durability

60%

Concrete

40% Steel Wood

20% Percent of Buildings of Percent 0% 0-25 26-50 51-75 76-100 100+ Age Class – Years Source: Demolition Study – Forintek Canada Corporation, Vancouver, B.C., Canada

Source: Demolition Study – Forintek Canada Corporation, Vancouver, B.C., Canada 2004 Service Life and Durability Percent of Buildings of Percent

Age Class – Years Source: Demolition Study – Forintek Canada Corporation, Vancouver, B.C., Canada 2004 Service Life and Durability

Demolition study (service life of buildings) • Findings suggest no significant relationship between the structural system and the actual useful life of the building.

Reasons for demolition: 1. Changing land value 2. Building does not meet current needs 3. Lack of maintenance of non-structuralcomponents

Lessons: • Determine realistic service life § Resources: ISO 15686, CSA 478-95 • Find balance between building’s intended use and adaptability § Buildings designed for all purposes don’t lend themselves to efficient/sustainable design http://www.woodworks.org/wp-content/uploads/2012/02/fpi-survey- actual-service-lives.pdf Service Life and Durability

Fulton County Stadium, Atlanta, Georgia, 1965-1997 Questions?

This concludes The American Institute of Architects Continuing Education Systems Course

Wood Project Assistance

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