level 200 truss installation - dallas area habitat
TRANSCRIPT
Level 200 Truss Installation
Mike Proch
1
July 2019
Agenda
Course objectives
Safety & quality
Organization & tools
Truss overview, issues, repair
Truss layout (front wall & porch)
Brace preparation (~ qty / plan)
Alternate Loading of large trusses
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Agenda (cont’d)Minor truss repair
Setting back gable truss
Issues and solutions
Setting & securing common trusses
Bracing overview
Ladder panel build & install
Sub fascia install
Truss team leadership elements
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Vision for the end of the day
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Vision for the end of the day
Requires:▪ Preparation
▪ Team effort
▪ Repeatable processes
▪ Serial/parallel tasks
▪ Appreciation to volunteers
Course Objectives
Expand information from 100 series
Expand FPE implementation
Key area refresher
Install techniques, tips
Common problems and solutions
Assumes familarization with 100 series course
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Safety & QualitySafety on the ground
Correct lifting and ladder use
Spatial awareness
Safety on the top
Secure everything
Constant communications
Quality is a process
¼ of an inch matters
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Fall ProtectionMust be used when working over 6’HUGS best solution roof workFPE harnessed trained personnel for truss settingLadders
Do not lean A frame ladders – new ladders purchased are designed to lean
Extension ladders –claws in dirt, pad on concrete
Extend at least 3’ beyond roof
“tie off” at top to prevent slipping
Do not carry shingles on ladders
FPE Usage
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▪ Inspect equipment
‐ Rips, loose, stitching, cuts
‐ Damaged casing, components
‐ Ensure all function properly
▪ Ensure harness is properly fitted / fastened
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Tools
Ladders
Tool belt, hammer, 12D and
duplex nails
Tape measures & speed square
Impact driver & screws
8 foot level
Push sticks
Clamps
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Common truss components
Bottom ChordKing Post
Truss
Webbing
Metal
Gussets
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Large truss gusset- Top Chord plane
may be impacted
Note:a) Tag does NOT indicate truss install direction
b) Large trusses (e.g. Hawthorne) have non-
symmetrical web bracing over garage/living room
Truss layout
Check wall bracing & alignment/plumb
Double check level for accuracy
Review truss plan (included with trusses)
Use 100 foot tape for measurement
Working back to front (house sides and center caps))1 (first common) to #? (last common before gable), label gable (GG)
Working front to back (porch)Continue sequential label numbering
Marks visible & consistent
Snapping a 1” line on the longer wall
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Label on cap plate inside dimension on non 24” O.C. trusses
Gable nailer for back gable truss
R01
Back
Gable
R02
Large
Common
Truss
R03
Garage
Gable
R04
Small
Common
Truss
R05
Porch
Gable
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Pull line to ensure layout is
consistent from living room
across the garage wall
Truss layout issuesCrown in slab impacting truss install
String across outside walls to determine
impact (also see back gable issues tip)
Tip: Mark truss layout to hall walls in case
cap plate “dado” is required.Common truss lays on Front wall and “rocks”
Move to front of wallEnsure front wall is secured (Hint: use 2x6 scraps
as deadwood and truss nailer – secures wall)
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Brace preparationUse house plans to determine brace needs prior to build day
Reuse bracing from other builds if possible
Build while truss staging and/or earlier (day 1)
Typical “Magnolia Plan” needs:
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Plan Strong
-backs
Ext.
Lats.
Int.
Web
Rat
Runs
K-
Brace
*T-
Blocks
Push
Sticks
12’ Ext Brace(1)
Magnolia 2 10 10 10 5 14 Min. 6 10
Based on 16’ 2x4s(1) External diagonal bracing
Internal diagonal bracing may vary in size but typically runs 7-8’ (see later slides)
* Make T-Top at least 6”
Staging trusses
Identify truss staging destinations
Use enough volunteers
Review lifting mechanics & flow
Sort trusses by type
Make 1” mark (1) (bottom chord) and 9’ (topchord). 9’ for external lateral brace placementMove trusses to staging locations
Inspect trusses before / during movement for issues
Repairing truss (see chart) before loading is easier
than repairing once erected
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Note (1): (Bottom chord – house width)/2 + 1” measured from top chord end
Staging trusses
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Suggested Loading Pattern
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Porch
Garage
Gable
Back
Gable
Note: Ensure porch beams installed before loading trusses!
Gable + 6
commons
Gable +
~17
commons
Spacing permits
push stick lift
effort
Load after main
trusses erected
Check gable
labels to ensure
which is front
and back!
Alternative Loading Process for Large Trusses
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Step 1: Prepare the bracing to holdthe trusses.
Step 2: Lay the truss on the bracing rails with thebottom cord resting in the "V" of the stakes
Alternative Loading Process for Large Trusses
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Step 3: Using push sticks, push the trusses up thebracing
Step 4: As the top of the truss reaches the top of the wall, guide the truss along the wall for thevolunteers
Truss repair
During truss delivery, staging and/or loading, truss elements may be cracked or truss gussets have separated
Contact Construction Supervisor
Repair magnitudeMinor: crack/break permitting at least 8’ scabs centered on the crack
Major: Minor criteria not possible or gusset separation (mfgr. direction)
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Truss Repair (cont’d)Minor web / chord repair
Install 2x4s on the front and back of the element that extends at least 4’ on either side of the crack/break.
Add construction adhesive and nail with 12 D nails alternating from front and back scabs at 6” max. intervals. Similar to wall nailing pattern.
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Construction adhesive (both sides if available)
6”
6”
Setting back gable truss
Installation of strongbacks
Raising of gable into position
Placement with gable nailer
Overhang alignment
Bottom chord nailing pattern
Attach to strongbacks
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Strongback and Gable Installation
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Secure to wall studs with screws
Raise back gable
Use screws to attach gable to strongbacks
Leave strongbacksinstalled until back K / Internal bracing is complete and ladder panel install start
Back gable install issues
Slab crown results in rocking trussCheck before loading trusses (string across outer corners)Tip: Check for back wall crown before installing the backwall cap plates (ref. truss layout crown)
SolutionsGaps 3/8” or less use shimsLarger gaps require trim of cap plates
Pop line from outside corner to outside corner to identify area to remove
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Setting Common Trusses
Assemble 3 teams
Raising, wall attachment, top chord bracing
Temporary bracing inventory
Following the quarterback
Aligning in two dimensions
Bottom chord center set to 24” intervals
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Setting common trusses
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Secure
temporary
bracing
with
Duplex
nails
Securing Common Trusses to Wall
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Figure 5-12
Install:▪ 3 nails (2 one side, 1
opposite) – 12D
▪ Gusset placement may
require nailing through the
gusset
Nail ~1” up to prevent
chord
splitting
Truss Bracing Overview
Purpose
Temporary (external) and Permanent (internal) bracing to support truss
location and provide stability against unintended forces / movement
(e.g. gravity, wind, seismic, etc.) and secure for FPE
Internal K braces to provide lateral force support to gables
Lateral and Diagonal bracing shown below:
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Figure 5-14
May be needed for 38’+ trusses
A A
AB
C C
D D
E
E
E
E
F
F F
F
BA
Temporary Laterals
Permanent Laterals
Rat Runs
Subfascia
Temporary Diagonals
Permanent Diagonals
A
B
C
D
E
F
External Truss Bracing (FPE)
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Strongbacks
Laterals
Diagonals
10 truss spaces
/ 20’ max
~45o
2 bay overlap
FPE used
after first 5
trusses
installed
Common truss temporary braces
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Use DUPLEX nails for easy removal
External Braced Trusses
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FPE Usage Tips
Where possible, have two harnessed
volunteers per side to install bracing and
help move Safety Bar (“red bar”)Use two “safety bars” per side in hop scotchmanner to facilitate easier movement and
truss alignment (if qualified people & bars
available)
Keep “safety bars” above ext. lateral whenpossible
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Internal Permanent Bracing
Rat Runs / “Cal” corner
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Laterals
2 bay overlap
“K” braces Lateral braces Diagonal braces
Rat Runs
2 bay overlap
Internal diagonals
installed every 10 truss
spaces (20’ max)
Lateral and
Diagonal
bracing on both
center webs
Use duplex nails top lateral
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Back of house
Permanent Internal Bracing
Interior PermanentBracing
Purpose
Ensure trusses and roof structure won’t rack when subjected to strong winds
2 types: Diagonal (K and web) and lateral
Installation
K Diagonal (perform first)Large gable trusses have 3 K braces (center, 4-6’ left and right of center)Attached typically to California corner or King Post (depends on house plan) K Brace (Magnolia)
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Figure 5-17
Figure 5-18
Interior Permanent Bracing
Installation (cont’d)Lateral Bracing
Attached to truss interweb ~ 4’ from bottom bottom chord. Start on first common truss
Diagonal BracingTwo 8’ 2x4s (top / bottom) start on first common angled to lateral brace from the back. Repeat every 10 truss spaces. Front diagonals start on last common toward lateral (NOTE: use duplex nails on first common top diagonal to ease ladder panel install
CheckK brace down 2” from peak to clear ladder panelBraces adequately nailed (12d, fully seated)
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Hurricane TiesPurpose:
A connecting tie to provide structural load path to resist high winds
Installation1 tie/truss installed to wall or porch beam with Simpson nails only
NEW: add tie to every other truss on longest hall wall
Where truss is too close to interior wall, do not install
Check:Vertical position (wall board issue), 10 nails and fully seated (not proud)
Ensure truss is straight up and not slanted before installing
TipNeedle Nose pliers and/or a palm nailer makes install for volunteers easy
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Ladder Panels (aka Lookout Ladders)
Purpose
Provides strong overhang structure for the
eave of the gables
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Figure 5-23
Ladder Panel construction
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Lookout rung length derivation
5.7.1 BUILDING LADDER PANELS
Ladder Panel construction (cont’d)
Roof Pitch Tail Peak Tie-In Tail*
4 18½° 18½° 53°
5 22½° 22½° 45°
6 26½° 26½° 37°
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Figure 5-26. Ladder Panel Rung Placement
Table 5.1 Angles for Cuts
Ladder Panel Construction (>16’)
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Extension ConstructionTips:• Ensure flyrafters have minimal
warpage
• Screw rungs (in addition to
normal nailing) to flyrafters to
minimize separation on install
Figure 5-27. Ladder Panel Longer than 16 Feet
Figure 5-28. Ladder Panel Extension
Install extension
after the large
ladder is installed
and secured.
Ladder Panel Bullen Board
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Tips:• Ensure Bullen board material is
straight as possible
• Mark each rung separately for
board placement – DO NOT use
a chalk line
• Pull diagonal measurements to
ensure squareness before
nailing Bullen boardMeasurements based on
trusses spaced 24” O.C.
Bullen Board purpose – secure ladder to
gable and assist in ladder straightness,
particularly with warped gable or first
common trusses
Figure 5-30. Bullen (Stop) Board
Ladder Panel Install Sequence
Align inside flyrafterpeak to 1st common peak, nail common side and ladder side
After outside flyrafterpeaks are aligned and nailed, nail gable to “bullen” boardLarge ladders, add extension (slide down to align with house rafter tails)
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Figure 5-31. Installation of Ladder Panels
Ladder Panel Install Issues/Fixes
Panel is not level “Pagoda Effect”
Typically caused by gable out of plane with roof (slab, positioning, etc.)
If gable position is corrected or OK
Minor adjustment of inside flyrafterposition height may allow reasonable alignment to roof plane
For more severe case, make a small notch to the ladder rungs where they sit on the gable
Use 8’ level to determine notch height (align to plane of roof)
DO NOT MODIFY the truss
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Not Level
Common Gable
Ladder Panel Install Issues/Fixes
Ladder peaks out of alignment horizontally
Typically driven by gaps in rung to flyrafters or twisted flyrafters
If rungs are nailed tightly, consider driving 1-2 2” roofing nails to achieve plane for fascia install or add shim
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¼” or less
Ladder Panel Blocking
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Before blocking, ensure rung toe nailed to gable
Add 2x4 blocking between ladder rungs
Note: Blocking is on top of the gable (not side of)
Figure 5-30. Ladder Panel Blocking
Placement
Subfascia
PurposePermanent truss tail bracing enabling fascia and soffit installation and support to the roof deck
Installation2”x4” - 16’ nailed (2) to truss tail positioned with speed square (see photo)Must be straight down eave, shim/cut tails as required (process follows)
Note: truss bottom chord “nib” may drive averaging subfascia install from tail to tail
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Figure 5-21
Subfascia Install Prep
It is critical that the subfascia is as straight as possible going down the length of the
house
Aesthetics, decking and minimize soffit gaps
Recommend a quick string line check to ensure straightness.
Issues corrected with shims or trimming
Suggested procedure follows
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Stringing Rafter Tails
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1st
ba
ck c
om
mo
n
Cap Plate
StringMark or
measure gap
when square
touches line
Bent 12D
nail, string
attached
Process:• Drive 12D nail into end of rafter tail and
bend up, hammer flush with tail end
• Slide square to mark cut or measure
gap
• Use 8’ level for remaining truss tails
1st
fro
nt
com
mo
n
Front/Back common
Shim gap
Truss team leadership elements
Trusses are a team effort
Drafting your teams
Finding your quarterbacks
Clearly explain tasks and context
Repeatable processes
Serial & parallel tasks
Say thanks
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Questions?
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Slope tailed common truss
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Bottom Chord “Nib” varies 0” – ½”
Nib Issue:
- May affect roof plane
- Impacts sub fascia install
Eliminate slide?
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Marking temporary/permanent lateral bracing
Marking flat truss overhang
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Figure 5-7
Loading trusses
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Figure 5-11
Rat Run Layout
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Figure 5-19
Smaller trusses (~30’) = 2 Rat Runs @ 1/3 spacing (e.g. Trinity & Magnolia)Larger Trusses (~38’) = 3 Rat Runs @ ¼ spacing (e.g. Hawthorne & Hickory)
Add 3rd Rat Run
for large truss
~10’ spacing
Stringing Rafter Tails
60
1st
ba
ck c
om
mo
n
Cap Plate
String
Mark or measure
gap when jig touches
line
Bent 12D
nail, string
attached
Process:• Drive 12D nail in and up, hammer flush
with tail end
• Make jig, 2x4 cut 22.5o attached to
scrap 2x4
• Slide jig to mark cut or measure gap
• Use 8’ level for remaining truss tails
1st
fro
nt
com
mo
n
Front/Back
common
Shim or
scab gap