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U d t di W d Sh i kUnderstanding Wood ShrinkagePresented to:
C S2014 Chicago Wood Solutions Fair Presented by:
Doug Steimle | Schaefer
“The Wood Products Council”is a Registered Provider with The American Institute of
This course is registered with AIA CES for continuing professional education. AsThe American Institute of
Architects Continuing Education Systems (AIA/CES), Provider #G516.
professional education. As such, it does not include 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
the AIA of any material of construction or any method or manner ofhandling, using, distributing, or dealing in any material or ( ) p
of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-
g yproduct.___________________________________________
Questions related to specific materials, AIA members are available upon request.
p ,methods, and services will be addressed at the conclusion of this presentation.
Copyright Materials
This presentation is protected by US and International copyright laws. Reproduction, distribution, display and use of the presentation without written p p y ppermission of the speaker is prohibited.© Schaefer 2014
schaefer-inc.com
Course Description
• For condominiums, apartments, hotels and dormitories, multi-story wood construction is viewed by many as a way tostory wood construction is viewed by many as a way to achieve higher density at lower cost, while reducing the project’s carbon footprint. One of the challenges, in designing these taller buildings is how to calculate and address woodthese taller buildings, is how to calculate and address wood shrinkage, which occurs as the wood dries from its ‘green’state to its in-service equilibrium state. This session will examine shrinkage associated with wall and floor design, and g g ,demonstrate how to minimize effects of both shrinkage and differential movement with proper detailing. The discussion will include how to prevent shrinkage induced construction issues such as drywall cracking, window frame wracking, and compromised plumbing lines.
Learning ObjectivesLearning ObjectivesIdentify wood shrinkage characteristics of commonly used dimensional and engineered wood productsdimensional and engineered wood products
Identify expansion/contraction characteristics of other materials in common buildings including veneers and PVC plumbing stacks
Identify conditions where differential movements within a building occur including window locations and plumbing stacks
Identify effective methods for limiting problems associated with differential movements
Condominiums
ApartmentsApartments
HotelsHotels
Student Housing
Low Income HousingLow Income Housing
Mixed Use
The Banks
Why Design With Wood Framing?Why Design With Wood Framing?
Economical
Availability of material
It’s GreenIt s Green
Familiarity of owners, contractors and end users
Speed of construction
Future modifications can be made with relative ease
POLL QUESTION #1POLL QUESTION #1
• True or False:The root cause of the majority of shrinkage within a wood• The root cause of the majority of shrinkage within a wood building is due to compression/crushing of the wood members as a result of the applied combination of dead and live loadslive loads.
False:The compression of a properly engineered and constructed wood structure should be relatively minimal The majority ofwood structure should be relatively minimal. The majority of shrinkage in a wood structure is due to a loss of moisture content in the wood members.
Understanding Wood ShrinkageUnderstanding Wood Shrinkage
• Why does wood shrink?
Trees are living organisms, needing water to stay alive
A large component of wood is moistureA large component of wood is moisture
Most “green” wood has a moisture content equal to 30% of its weightof its weight
Understanding Wood ShrinkageUnderstanding Wood Shrinkage
• What happens when wood loses moisture content?
Wood shrinks
This is the main reason why wood warps checks cupsThis is the main reason why wood warps, checks, cups, etc.
Characteristics of WoodCharacteristics of Wood
Wood shrinks most in the radial and tangential directions. Very little shrinkage occurs in the longitudinal direction.
Characteristics of WoodCharacteristics of Wood
Characteristics of WoodCharacteristics of Wood
Characteristics of WoodAmount of Shrinkage for 30% Change in MC
Characteristics of Wood
Radial 4-5%
Tangential 7-8%
Longitudinal 0.1-0.2%
• 30% change in moisture content is the maximum moistureis the maximum moisture change possible. This is from green (30% MC) to no moisture (0% MC).
Characteristics of WoodCharacteristics of Wood
• Moisture Content
The amount of shrinkage experienced by a wood member is dependent upon the change in moisture content
Kiln dried lumber – typically 19% or lower moisture content
The drier the member is when installed, the less moisture will be lost in a finished structure and the less the member will shrink
Characteristics of WoodCharacteristics of Wood
Code Required Shrinkage CalculationCode Required Shrinkage Calculation
• IBC 2304.3.3 Shrinkage. Wood walls and bearing titi h ll t t th t fl d fpartitions shall not support more than two floors and a roof
unless an analysis satisfactory to the building official shows that shrinkage of the wood framing will not have adverse effects on the structure or any plumbingadverse effects on the structure or any plumbing, electrical or mechanical systems, or other equipment installed therein due to excessive shrinkage or differential movements caused by shrinkagemovements caused by shrinkage…
S l Sh i kSample Shrinkage Calculation for Typical StoryStory
Typical Components
(1) 2x Sill Plate
StudStud
(2) 2x Top Plate
2x12 Joist
¾” Floor Sheathingg
Sample Shrinkage Calculation for Typical StoryTypical Story• Spruce Pine Fir 2x4 Plate (Sill or Top Plate)
Shrinkage perpendicular to grain affects change in height
Direction of grain in a member is dependent upon how it is milled
Therefore, take the average between tangential and radial shrinkage for shrinkage calculation (6% average)
Assume initial moisture content to be 16%, final moisture content to be 10%
Sample Shrinkage Calculation for Typical StoryTypical Story• Spruce Pine Fir 2x4 Plate (Sill or Top Plate)
Average Amount of Shrinkage for 30% Change in MC
Radial 4-5%
T ti l 7 8%Tangential 7-8%
Average for Shrinkage Perpendicular to Grain 6%
h2x4sill = (1.5 )(0.06)(6/30)
h2x4sill = 0.018Change in MC (16% to 10%)/30%
Sample Shrinkage Calculation for Typical StoryTypical Story
• Spruce Pine Fir 2x4x9’-0” Tall StudAverage Amount of Shrinkage for 30% Change in MC
Parallel to Grain 0.15%
h2x4stud = (108 )(0.0015)(6/30)
h2x4stud = 0.032Change in MC (16% to 10%)/30%
Sample Shrinkage Calculation for Typical StoryTypical Story
• Southern Yellow Pine 2x12 JoistAverage Amount of Shrinkage for 30% Change in MC
Radial 4-5%
Tangential 7-8%
Average for Perpendicular to Grain 6%
h2x12 joist = (11.25 )(0.06%)(6/30) h2x12 joist = 0.135 Change in MC (16%
to 10%)/30%
Sample Shrinkage Calculation for Typical StoryTypical Story
• ¾” Tongue and Groove OSB Floor SheathingExposure 1Exposure 1
Floor sheathing can swell up to 25% of its thickness during construction depending on the amount of moisture duringconstruction depending on the amount of moisture during construction (0.188” for ¾” sheathing)
No published testing performed by APA regarding how much p g p y g gthe product shrinks after the product swells and a load is placed on the sheathing (below a bearing wall)
Sample Shrinkage Calculation for Typical StoryTypical Story
• ¾” Tongue and Groove OSB Floor SheathingExposure 1Exposure 1
APA help desk indicated to estimate a 50% reduction in swell thickness after drying and loadingswell thickness after drying and loading
• h floor sheathing = (0.75”)(0.25)(1/2)
• h floor sheathing = 0.094”
Sample ShrinkageSample Shrinkage Calculation for Typical StoryStory
¾” Tongue and Groove OSB Floor Sheathing - Exposure 1Sheathing Exposure 1
Swelling of floor sheathing is very real. The shrinkage can also be assumed to gbe very real as well.
¾ Tongue and Groove OSB Floor
Sample Shrinkage Calculation for Typical Story
Sheathing
p g yp y
¾ Tongue and Groove OSB Floor
Sample Shrinkage Calculation for Typical Story
Sheathing
p g yp y
Sample ShrinkageSample Shrinkage Calculation for Typical StoryTypical Story
Three 2x4 Plates 0.054”
One 9’ 0” Stud 0 032”One 9 -0 Stud 0.032
One 2x12 Joist 0.135”
Floor Sheathing 0.094”
Total Shrinkage Per Story 0.315”
Consider revising gcalculation based on
conditions experienced while at
the site
Sample Shrinkage Calculation for Typical Storyp g yp y
POLL QUESTION #2POLL QUESTION #2
• True or False:In a multi story wood framed building the majority of• In a multi-story wood framed building, the majority of problems associated with wood shrinkage are observed at the lowest level of the building.
False:The shrinkage of a building is cumulative, the total shrinkage in a building increases the higher the structure extendsa building increases the higher the structure extends.
DiscussionDiscussion
• Where does shrinkage become a problem in the field?
Window ProblemsWindow Problems
• When a brick veneer is used in combination with a wood t t bl ft f llstructure, problems often follow.
Windows are typically fastened to the wood structure.
The windows move as the wood structure moves.
What happens when the windows move down and theWhat happens when the windows move down and the veneer is moving up?
Window Problems
Properties of BrickProperties of Brick• Brick is a clay product and can change size dependent
upon temperature and moisture content Brick arrives atupon temperature and moisture content. Brick arrives atthe site with the lowest moisture content it will ever have.
Thermal expansion can be as much as 0.028” for 11’ height e a e pa s o ca be as uc as 0 0 8 o e g tof brick
Moisture expansion of brick can be as much as 0.040” for 11’height of brick
Estimated total expansion of brick per story is 0.068”
Window ProblemsWindow Problems
• Window Sill
Accommodations need to be made to allow for the differential movement. Otherwise, window will have operational difficultiesoperational difficulties.
Remember that caulk is typically only 50% compressible.
Window Sill
Window Problems
Window SillWindow Sill
Window Problems
Window Sill
Window Problemsdo ob e s
Window Sill
Window Problems
Dimension needs to be two times estimated shrinkage
Window ProblemsWindow Problems
Joint is expandingJoint is expanding (widening)
Window ProblemsWindow Problems
Moving Down
Moving Up
Moving Down
Shear cracking in caulk jointj
Window Problems
Window Head and Jambs
This is the second story of a residence, the caulk joint has failed in both the jamb and head conditions
Window ProblemsWindow Problems
Wi d J bWindow Jamb
Window ProblemsWindow Problems
Window ProblemsWindow Problems
Window ProblemsWindow Problems
Solutions to Window ProblemsSolutions to Window Problems• Window Head and Jambs
The caulk joint needs to be designed for the potential differential movement or the caulk will fail. The caulk joints tend to fail on higher stories where differential movement is larger.
Consider specifying timeline for when to install caulk. The later the caulk joint is installed, the closer the building will be to its final moisture content and heightmoisture content and height.
Contractor may not be able to delay the caulk joint as it may prevent the ability to dry-in the building.
Solutions to Window ProblemsSolutions to Window Problems
• Window Head and Jambs
Inform owner of potential problems with these joints. Maintenance should be expected on these joints due to differential movementdifferential movement.
Code Take on Window ProblemsCode Take on Window Problems
• Building Code Empirical Limits for Masonry Veneer Height
• Addressed in Chapter 21 of IBC which refers to Chapter 6 of ACI 530/ASCE 5/TMS402
Prescriptive height limitations of anchored veneer with wood backup is 30 feet at height of plate and 38 feet at a gable.
Limits differential movement between wood structure and anchored veneer
Limits brick stressesLimits brick stresses
Limits anchor stresses
Code Take on Window ProblemsCode Take on Window Problems• Building Code Empirical Limits for Masonry Veneer Height
Addressed in Chapter 21 of IBC which refers to Chapter 6 ofAddressed in Chapter 21 of IBC which refers to Chapter 6 of ACI 530/ASCE 5/TMS402
Anchored veneer can be engineered to exceed theAnchored veneer can be engineered to exceed the prescriptive height limitations.
The primary concern with exceeding the prescriptive limits is in regards to detailing for the differential movement between the wood structure and the masonry veneer.
Building Skin ProblemsBuilding Skin Problems
• Siding/Hardi-plank/plaster located over anchored brick veneerveneer
Often used by architect to change look of outside of building.
Has similar potential problems as at window sills
An expansion joint is required above the veneer and below p j qthe hardi-plank or stucco to avoid problems with the hardi-plank or stucco
Building Skin ProblemsBuilding Skin Problems
Building Skin ProblemsBuilding Skin Problems
Building Skin ProblemsBuilding Skin Problems
Thin Set Veneer ProblemsThin Set Veneer Problems
Thin set veneers are adhered directly to the exterior h thisheathing.
When the wood structure experiences shrinkage, the veneer moves with the woodveneer moves with the wood.
Check with the manufacturer for how much movement the thin set veneer can handle and the potential need forthin set veneer can handle and the potential need for expansion/control joints.
Thin Brick over Anchored VeneerThin Set Veneer
Anchored Veneer
Other Common ProblemsOther Common Problems
Thin Set Veneer
Here is the result
Thin Set Veneer
Other Common ProblemsOther Common Problems
Plumbing Stack ProblemsProblems
What problems occur when the plumbing stacks travel vertically fromplumbing stacks travel vertically from the slab on grade through the roof?
Plumbing Stack ProblemsProblems
The horizontal tees that drain into the plumbing stacks typically travelthe plumbing stacks typically travel through holes in the stud wall. If the holes are too big, there may be a structural problem with the stud. If the holes are too small thethe holes are too small, the plumbing tees may shear off as the wood structure shrinks and the plumbing stack does not go down.
Plumbing Stack ProblemsPlumbing Stack Problems
Another potential contributing factor to possible problems ith l bi t k i i th th l i f thwith plumbing stacks is in the thermal expansion of the
plumbing stack itself.
Consider when plumbing stacks are installed on a projectConsider when plumbing stacks are installed on a project. If it is very cold outside and the building is not enclosed or heated, the plumbing will be very cold when installed as wellwell.
Plumbing Stack ProblemsPlumbing Stack Problems• Assume we have a PVC plumbing stack.
If the plumbing is installed in 20 degree weather and the final temperature of the building is 70 degrees, then there is a 50 degree Fahrenheit change in temperature
Resulting increase in the height of a plumbing stack = 0.19” per 11 foot height.
The same increase in temperature would result in a 0.02” increase in height of the wood structurethe wood structure.
This movement acts in the opposite direction as the wood shrinkage and exacerbates potential plumbing tee problems.
Plumbing Stack SolutionsPlumbing Stack Solutions• Incorporate differential vertical movement into the design of the plumbing
system.y
Vertical expansion joints
Require gap around horizontal plumbing runsRequire gap around horizontal plumbing runs
Avoid horizontal plumbing runs in structural studs
I f th l bi iInform the plumbing engineer
Masonry Stair or Elevator Tower ProblemsProblems• CMU stair and elevator towers shrink very little compared
to the wood structure.Similar iss es can present themsel es hen steel framingSimilar issues can present themselves when steel framing is introduced in a wood structure.
Floor framing parallel to and adjacent to the CMU towerFloor framing parallel to and adjacent to the CMU tower will shrink with the wood structure.
Result is a sloped floor in the first joist space adjacent toResult is a sloped floor in the first joist space adjacent to the CMU tower.
This slope increases as the floor framing then deflects s s ope c eases as t e oo a g t e de ectsmid-span.
Masonry Stair or Elevator Tower ProblemsProblems
Masonry Stair or Elevator Tower RecommendationRecommendation
• This is a problem that does not have a great solution.
Inform owner/construction manager of issue to manage expectations.
Minimize span of members framed parallel to CMU walls.
Minimize amount of shrinkage in buildingMinimize amount of shrinkage in building.
Ways to Reduce ShrinkageWays to Reduce Shrinkage
Floor Trusses
AdvanTech
Protected WoodProtected Wood
During ConstructionDuring Construction
• Construction Observation Recommendations
Make sure the mason is aware of the amount of space required between the brick sill and the window sill
Check the dimension between the window sill and the masonry sill
Check the size of holes for plumbing penetrations made through vertical studs to ensure there is some ability to allow for differential movement
During ConstructionDuring Construction• Construction Observation Recommendations
Specify that all lumber be protected from weather prior to installation
Make sure Structural Engineer gives you anticipated shrinkage movements per floor for window detailing purposes
Be willing to take extra measures during wet seasonsBe willing to take extra measures during wet seasons
Window Sill
Window Solutions
Shrinkage Summary• Anticipated Shrinkage Per Story Shrinkage Reducing
Recommendations
Shrinkage Summary
Three 2x4 Plates 0.054”
One 9’-0” Stud 0.032”
Recommendations
One 9 0 Stud 0.032
One Floor Truss 0.036”
Floor Sheathing 0.020”
Total Shrinkage Per Story 0.142”
Shrinkage Summary• Anticipated Differential Movement at Windows With
Shrinkage Reducing Recommendations
Shrinkage Summary
Three 2x4 Plates 0.054”
One 9’-0” Stud 0.032”
Shrinkage Reducing Recommendations
One Floor Truss 0.036”
Floor Sheathing 0.020”
Brick Expansion 0 068”Brick Expansion 0.068
Total Differential Movement at Windows Per Story 0.210”
Shrinkage SummaryShrinkage Summary• Anticipated Differential Movement at Plumbing Stacks
With Shrinkage Reducing Recommendations
Three 2x4 Plates 0.054”
One 9’-0” Stud 0.032”
With Shrinkage Reducing Recommendations
One Floor Truss 0.036”
Floor Sheathing 0.020”
PVC Plumbing Thermal Expansion (If installed at 20ºF) 0 165”PVC Plumbing Thermal Expansion (If installed at 20ºF) 0.165
Total Differential Movement at Plumbing Stacks Per Story 0.307”
Thank you for your time and your attention!attention!
Q ti ?Questions?
h f ischaefer-inc.com
This presentation was developed by a third party and is not funded by WoodWorks or the softwood lumber check-off.y