A Truss hanger is a pre-formed metal connector that supports and fixes a roof truss (or joist/beam) to another structural element—typically a wall plate, steel/timber beam, or a girder truss. Think of it as a small, engineered cradle that provides bearing and secure load transfer without bulky cleats or time-consuming carpentry. In modern roof construction—especially with plated timber trusses—hangers are indispensable for speed, safety, and compliance.
Why truss hangers exist
Roofs aren’t just heavy; they’re also subject to wind uplift, live loads from maintenance, and vibration. A Truss hanger solves three problems at once:
- Safe bearing – It supplies a defined seat for the truss heel, preventing crushing of timber fibres and local splitting.
- Positive connection – Factory-punched nail/screw holes create a tested, repeatable joint that resists vertical load, lateral slip, and uplift.
- Geometry control – Because hangers are dimensionally consistent, the truss line stays straight and the soffit, eaves, and ceiling levels align.
The result: faster installation, fewer site errors, and a connection that has known structural capacity rather than a “rule-of-thumb” fix.
Common truss hanger formats
- Face-mount hangers
The most common type. The hanger’s flanges sit flat against the supporting member (girder truss, timber or steel beam), while the “seat” cradles the incoming truss. Good general-purpose option for roofs and floors. - Top-flange (concealed-flange) hangers
The flanges sit on top of the supporting member, hiding the fixings for a cleaner look and improving edge clearance where wall plates are narrow. - Skewed and sloped hangers
Pre-formed to suit oblique angles or pitched connections—handy at hips, valleys, or when secondary trusses meet a girder at something other than 90°. - Heavy-duty / girder-truss hangers
Built for higher reactions where multiple trusses frame into a single girder. Often have thicker steel, longer seats, and more fastener holes. - Masonry/steel interface hangers
Variants with extended side plates or chemical anchors that allow fixing to brickwork or steel beams (using bolts or shot-fired pins, as permitted).
How a truss hanger actually works
A Truss hanger converts the truss reaction at its heel into forces in the hanger’s seat and side flanges. The load path is:
- Roof loads → truss → seat bearing (compression).
- Seat and strap legs → shear and tension in fixings.
- Fixings → supporting member (girder/beam/wall plate).
Engineering details that make this reliable:
- Bearing length: The seat must give enough bearing (often 35–50 mm minimum for timber) so the compressive stress in the chord end stays within limits.
- Edge/End distances: Pre-punched holes maintain safe spacing so nails/screws don’t split timber or tear out under load.
- Uplift resistance: Dedicated holes for angled nails/screws provide “clamping” action to counter wind suction in coastal and escarpment zones.
- Stiffness: Wrap-around side plates and return lips limit deformation, keeping geometry true.
South African considerations when specifying a truss hanger
1) Environment & corrosion
Local climates range from Highveld thunderstorms to salt-laden Cape winds. Match coating to exposure:
- Inland residential: Hot-dip galvanised hangers are typically sufficient.
- Coastal/industrial atmospheres: Upgrade to heavier galvanising or stainless steel.
- Fasteners must match the hanger’s corrosion class (e.g., class 3 galvanised or stainless screws) and be compatible with timber preservatives (ACQ/borate).
2) Timber treatment & compatibility
Most plated trusses are kiln-dried SA pine, UC2-treated for roof spaces. Copper-based preservatives can accelerate corrosion in mild steel; hence the push for appropriate coatings and stainless options at the coast. Always re-treat cut ends.
3) Load cases & SANS compliance
Connections should be sized for SANS 10160 wind loads (note higher suction at edges and corners). Don’t assume one hanger size suits the whole roof—girder junctions often need heavier units and denser fastener schedules.
4) Fixings and tools
Use the fasteners specified by the hanger supplier:
- Correct diameter and length to develop the rated shear/withdrawal capacity.
- Full nail/screw schedule—skipping holes reduces rated capacity.
- Avoid mixing nails and screws unless the design allows it.
5) Buildability
For speed and fewer site mistakes:
- Choose hangers with locator tabs or speed prongs that hold position while fixing.
- Use concealed-flange hangers where visible side flanges clash with finishes.
- Order skewed/sloped models rather than bending standard hangers on site (never bend unless the datasheet explicitly allows it).
Step-by-step: installing a truss hanger
- Set out & mark
Snap a line along the support to mark hanger centres. Check setbacks from edges and ensure the truss heel will land fully on the seat. - Position the hanger
Hold the hanger to the line so the top of the seat is flush with the truss underside line. Use locator tabs if provided. - Fix the hanger to the support
Drive the specified nails/screws into all face (or top-flange) holes. Do not substitute smaller diameter fixings. For steel beams, use approved bolts/pins as specified. - Seat the truss
Lower the truss so its heel bears flat on the seat. No gaps. If the top chord plating fouls the hanger, swap to a plated-truss-rated model with clearance slots rather than trimming the truss. - Wrap and finish fixing
Drive nails/screws through the side-wrap holes into the truss. Install uplift/angle nails where indicated. Fill every required hole to achieve the published capacity. - Inspect & document
Check bearing, fastener fill, and alignment. Photograph critical connections; note any substitutions. This protects warranties and simplifies sign-off.
Two big don’ts:
• Don’t notch or birdsmouth a plated truss to “make it fit”—ask for a different hanger.
• Don’t bend hangers on site unless the manufacturer says it’s permissible.
Truss hanger sizing—what to look for
- Seat width must match (or exceed) the truss chord thickness (e.g., 38/50/63 mm timber).
- Depth of hanger should suit the truss heel depth and required bearing.
- Load rating (kN reaction, uplift, and download) must exceed design reactions with safety factors.
- Fastener schedule dictates how many and what type of nails/screws are needed; capacity assumes a full schedule.
- Special angles (skew/sloped) should be ordered factory-formed to the specified degrees.
Dezzo’s team selects hangers as part of the full roof model—trusses, girders, purlins/battens, fixings, and cladding—so each connection is right-sized for its zone.
Quality assurance on South African sites
- Edge & corner zones: Increase fastener count or move up a hanger size—wind suction peaks here.
- Girder stack-ups: Where multiple secondaries frame into one girder, verify cumulative reactions and spacing.
- Coastal jobs: Inspect coatings before install and touch up cut/abraded edges with compatible systems.
- Fire strategy: In non-combustible roofs (steel truss/metal deck), use hangers and fasteners that maintain performance at elevated temperatures as per the overall design.
The Dezzo difference
We don’t treat hangers as an afterthought. Our engineers model support reactions, wind zones, uplift, and geometry before selecting each Truss hanger—then issue fixing schedules, coastal-ready coatings, and on-site QA checklists. With the right connector in the right place, your roof goes up faster, looks better, and stays safe for decades. Ready to spec your next roof the smart way? Chat to our technical team for an engineering-backed recommendation.
FAQs
What is a truss hanger?
A Truss hanger is a pre-engineered metal connector that supports and fixes a roof truss to a beam, wall plate, or girder truss. It provides bearing, resists slip and uplift, and delivers a connection with known, tested capacity for structural safety.
What size are truss hangers in South Africa?
Sizes vary with the supported member. Typical seats fit 38 mm, 50 mm, or 63 mm timber chords, with depths to suit heel height and load. For heavier reactions (e.g., girder junctions), deep, heavy-duty hangers with larger seat and more fasteners are used. Always size by design reaction, not by appearance.
How to install a truss hanger?
Set out positions, fix the hanger to the support with the specified nails/screws, seat the truss fully on the hanger, then wrap-fix through the side legs and install uplift/angle fixings. Fill every required hole and verify bearing, alignment, and corrosion class. Never cut or notch the truss to suit the hanger.
What are the 4 types of truss bridges?
Different context, but common textbook types are Pratt, Howe, Warren, and K-truss. Roof trusses use similar triangular principles, but components and load paths are tailored for buildings rather than bridges.