Permanent Truss Bracing

July 2025

Rev E

Gary Baxter

The Necessity of Proper Roof Bracing (Granbury May 2013)

Approach to Prescribed Truss Bracing

• Habitat Houses make extensive use of common roof elevations types
• Used repetitively across many elevations
• That commonality allows us to apply bracing methods without engineering drawings for every floorplan
• Instead we are using elevation outlines to determine what bracing is required

Roof Types - Gables

Small:

• Smallest wind exposure
• Smallest height and span

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Large:

• Have largest areas exposed to wind - Tallest
• Span anywhere from 2/3 of the house width to full
• Usually found over garage or across the back

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Medium:

• Smaller wind exposure than large gable
• Not as tall
• Span is less than 2/3 of house width
• Often found on porches

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• Typically found on bedrooms and bumpouts

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Roof Types - Hip

Hip Roof Areas - No Diagonal Braces Required

Full Hip – Spans Full House

Partial Hip

Two Types of Permanent Truss Bracing

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• Diagonal Bracing
• Determined by Amount of Windswept Exposure
• Diagonal bracing connects gable truss web to rat-run
• Diagonal bracing is simple and volunteer friendly…. and very strong when well-nailed (no air-nails)

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• Longitudinal Bracing
• Runs from front of house to back
• Attaches to webs on

common trusses (shown at right)

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Rat-runs

Diagonal Brace

Fortified Standard

6 – 8’ spacing

Diagonal Bracing

Attached to truss webs and rat-runs

Longitudinal

Attached to truss webs

Full Rat-run spacing

6’ – 8’ (Fortified Standard)

Diagonal Bracing

Trusses joined together as a group with only longitudinal bracing are unstable

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Without diagonal brace, group is

free to move either direction

Diagonal brace restrains group

Important: Only install 5 trusses at a time and then install diagonal bracing.

Failure to adhere to this method violates both OSHA and Trinity HFH policy

In order for Diagonal�Bracing to be effective:��It must in conjunction with�other framing (rat-runs and truss webs) �Form a triangle

A Note About Rat-Runs

• There are two kinds of rat-runs
• Full length – Runs the length of the building and includes 36” Simpson straps and thrust blocks on the ends and are spaced across the building every 6 – 8’
• Partial length – at least 8’ long - Used to tie diagonal braces to truss bottom chords
• Don’t need thrust blocks or straps
• Diagonal braces may be attached to either full or partial rat-runs
• Often, it is necessary to locate a diagonal brace where a full rat-run does not exist
• Add partial rat-runs as needed

Full length rat-run

Partial length rat-run

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Nailing Practices

Air Nails are not acceptable

Diagonal Brace is too high:

Nails catch only the edge of

the rat-run

Diagonal Brace is dropped

down allowing nails to be

fully embedded in rat-run

Diagonal Brace Locations

Diagonal Brace Locations

Front Elevations - Upper Gable with Hip Porch

Hip Roof

self-braced

Hip Roof

self-braced

Windswept Area

Field Guide Sample - 1

Back Elevations – Medium Size, Full Size

Diagonal Brace Locations

Windswept Area

Garage Cross Gable

Diagonal Brace Locations

Garage

Diagonal Brace Locations

Back Elevations – Medium Size, Small

Field Guide Sample - 2

How to Attach a Diagonal Brace when a vertical web does not exist

Attach all elements

shown in red with

3” long construction

screws - NOT Nails

If Gable Truss Looks Like This

Longitudinal Bracing

• Not all Longitudinal Bracing will be called out on Truss drawings but industry standards recognize it is required
• To overcome inconsistencies in truss drawings, use the following approach:

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Central portion of house receives Longitudinal braces on common trusses only – Longitudinals don’t have to tie to gable trusses but if a gable truss web lines up with common truss web, tie them together

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Porches and bedroom bumpouts don’t need longitudinal braces, but if a gable truss web lines up with common truss web, tie them together

Gable

Common

Gable

Gable

Gable

Common

HVAC

Truss Layout Drawing

Central Part of House

(light blue dashed outline)

Front Porch

Bedroom Bumpout

Common

Common

HVAC

Longitudinal Braces (shown in red)

No Longitudinal Braces on Bumpouts

required but, if webs align, continue

Longitudinal bracing as far as possible

CeCentral Portion of house (dashed blue line)

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Front Porch

Bedroom Bumpout

No Longitudinal

Braces on Porches required but, if webs align, continue Longitudinal

bracing as far as possible

Place middle set of short diagonals (shown in orange) midpoint of house length

Accomplished by connecting to other common trusses

Short Diagonal sets placed across three trusses in three locations along length of Longitudinal

Longitudinal Brace Locations

Longitudinal brace

does not need to tie

to gable truss web

Main portion

of house

Two sets of Longitudinal

Required – Only one set

shown here

Longitudinal Brace�with Short Diagonal�Bracing Sets

Short Diagonal Brace Placement

HVAC Truss

1. For two HVAC trusses: Tie one to the other. If no common truss webs lie in plane, run the longitudinal

brace thru them with no tie in

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2) For one HVAC truss and if no common truss webs lie in plane: Run the longitudinal brace thru them with no tie in

Single HVAC Truss

Double HVAC Truss

Common Truss

Common Truss

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No

Braces

in this

area

Hmm, I wonder who’s installing the bracing?