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Truss Technical Information

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Chromadek® is specifically developed and tested for harsh South African UV conditions. The Chromadek® African Heritage Colour range is available in exiting colours which is available in Corrugated, IBR and Widespan roofing profiles.

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STAALBEER GALVANISED ROOF TRUSSES TO SANS 517: 2013 ed 1.2

1. DESIGN STANDARD

The complete roof structure including trusses, purlins, brandering, brackets and fasteners is custom designed using specialised engineering software and all design loads are as per SANS 517:2013 Ed 1.2.

Unless otherwise specified the following loads are applied to designs:

  • Top chord dead load: 0.06 KPA – metal roofing / 0.53 Concrete tiles
  • Bottom chord dead load: 0.14 KPA
  • Top chord live load: 0.50 KPA
  • Moving load: 1.0 KPA
  • Wind load: 0.55 KPA
  • Safety factor: 1.5

Trusses can be designed and manufactured in any of following shapes

  • Howe Trusses
  • Parallel cord trusses. (Girder truss)
  • Dual pitched roof trusses.
  • Scissor trusses.
  • Cantilevered trusses etc.

2. STEEL SPECIFICATION

Trusses, purlins and brandering sections are manufactured from steel with the following guaranteed properties:

  • Z200 Galvanised coating
  • 550MPA Guaranteed yield strength
  • 0.80 mm thickness for Truss chords and webs
  • 0.58 mm thickness for Purlins
  • 0.50 mm thickness for Brandering

3. TRUSS PROFILE AND RIVET SYSTEM

The Staalbeer truss is manufactured from a 45x60x8x0.80mm U-shaped lipped channel that is roll formed, punched, notched, lip cut and crimped on a precision roll forming line. This profile is used for both chords and webs to create a strong & durable yet lightweight truss.

After roll forming trusses are factory assembled using a unique 10mm Galvanised hollow core steel rivet which is crimped using a specially designed tool. The rivet ensures structural integrity and dimensional accuracy of the truss.

The truss webs and chords are joined to form a unique overlap with three times material thickness that enhances the strength of the truss.

Depending on design loads, connections can be further reinforced using strengthening plates and factory fitted Class 2 Stitching Screws.

4. CHORD BRACING

When additional bracing of the top or bottom chord is required a specially developed bracing section is supplied. Because of transport considerations the chord braces need to be fitted on site prior to erection of the trusses.

5. SPLICING OF TRUSSES

Staalbeer can legally transport trusses of 15m overall length including overhangs. A height limitation 2.50 m also applies.

When trusses exceed these dimensions it needs to be spliced and then joined on site according to the manufacturers recommendation.

Trusses are spliced with a Galvanised steel plate that is bolted through Rivet Holes and Tex screwed to webs and chords.

6. FASTENERS

Only fasteners with a minimum corrosion coating of Class 2 is used in the manufacture and erection of Staalbeer roof trusses and battens.

Class 2 (Z2) is for use in urban and rural environments away from industrial pollution and marine environments. The corrosion rate for ISO Class2 environments is 0.1 – 0.7 micron zinc per year. Class 2 fasteners are electroplated to SANS1273 specifications with a minimum of 12 micron zinc and can be identified by a Z2 head marking. Recommended for use with Z200 and Z275 galvanized roof sheeting.

The following fasteners are used during the fabrication and erection of Staalbeer roof trusses:

Description
Application
Screw attachment
#12X38MM ZAP S/D SCREW HEX #5 POINT CLASS 2
Corrugated Roof sheeting into Steel Purlins up to 3mm
5/16" A.F. MAG. SOCKET 65MM
#12X50MM ZAP S/D SCREW HEX CLASS 2
Widespan Roof sheeting into Steel Purlins up to 3mm
5/16" A.F. MAG. SOCKET 65MM
#12X65MM ZAP S/D SCREW HEX CLASS 2
IBR Roof sheeting into Steel Purlins up to 3mm
5/16" A.F. MAG. SOCKET 65MM
#12X35MM ZAP S/D SCREW HEX T17 CLASS 2
Corrugated Roof sheeting into Timber Purlins
5/16" A.F. MAG. SOCKET 65MM
#12X85MM ZAP S/D SCREW HEX T17 CLASS 2
IBR & Widespan Roof sheeting into Timber Purlins
5/16" A.F. MAG. SOCKET 65MM
5.5X19MM BONDED WASHER E.P.D.M./GALV.
Corrugated Roof sheeting
5.5X25MM BONDED WASHER EPDM/GALV.
IBR & Widespan Roof sheeting
#14X22MM ZAP STITCHING SCREW HWH + SEAL CLASS 2
Fix purlins, brandering, bracing to Light Steel Trusses
5/16" A.F. MAG. SOCKET 65MM
#10X16MM ZAP S/D STITCH SCREW HEX CLASS 2
Fix purlins, brandering, bracing to Light Steel Trusses
5/16" A.F. MAG. SOCKET 65MM
#6X32MM SELF DRILLING DRYWALL SCREW
Indoor, fix PVC ceiling to LSF Brandering
#2 PHILLIPS BIT 25MM
#8X32MM ZAP S/D SCREW PAN PH2
Outdoor / Indoor, fix Fibre cement & plaster board to LSF
#2 PHILLIPS BIT 25MM
8×70 Chip Board Type 17 point
Fix Concrete Roof Tile into LSF Batten
#2 POZI BIT 25MM
5/16" A.F. MAG. SOCKET 65MM
Hex head fasteners
#2 PHILLIPS BIT 25MM
#8X32MM ZAP S/D SCREW PAN PH2
#2 POZI BIT 25MM
Fix 8×70 Roof Tile Screw into LSF Purlin

A drill with an adjustable clutch and depth gauge should be used to ensure that fasteners are not overtightened.

The corrosive properties of the environment should be considered when a fastener is selected for a Light Steel Roof System.

SANS 1273: Table 12 — Corrosion protection requirements for fasteners
12345
ApplicationLocation in buildingEase of accessaAtmospherebCoating classc
min.
Steel wall framesInside building envelopeDifficultInlandC2
DifficultAggressiveC2
Outside building envelopeEasyInlandC2
EasyAggressiveC3
TrussesVentilated roof cavityDifficultInlandC2
DifficultAggressiveC3
Unventilated roof cavityDifficultInlandC2
DifficultAggressiveC2
Wall frame anchorsInside building envelopeDifficultInlandC2
DifficultAggressiveC2
External claddingOutside building envelopeEasyInlandC2
EasyAggressiveC3
Internal lining, ceilings‘Wet rooms’EasyInternal – Regular condensationC2
All other roomsEasyInternal – DryC1
RoofingOutside building envelopeEasyInlandC2d
EasyAggressiveC3d
a   For inspection and maintenance.
b   ‘Aggressive’: Marine environment (500 m to 10 km from the sea), or industrially polluted atmospheres. ‘Inland’: All other environments.
c   Coating class defines the corrosion resistance requirements. (See 5.14.2.2.)
d   Subject to the requirements of SANS 1273.

7. JOINING OF TWO PLY TRUSSES

Trusses can be used in two ply configurations to increase the load carrying capacity of the truss. Trusses must be securely joined to each other through the rivet holes using an 8x120mm galvanised high tensile bolt with nyloc nut.

8. WALL PLATE

On a masonry structures a 76 x 38mm timber wall plate must be used at the building eaves to isolate the trusses from the structure and to provide a level mounting base for the trusses.

9. FASTENING TRUSSES TO THE STRUCTURE

Trusses with a span of

  • Double twisted 3.15mm galvanised roof wire that is built into the wall at least six brick layers deep.
  • A 25×1.2mm Galvanised hoop iron strap that is built into the wall at least six brick layers deep.
  • A Staalbeer twist strap bracket can be used securely fixed to the wall using 8x75mm coach or equivalent expanding anchors with chemical compounds if necessary. The installer must ensure that the strap is secured on left, top and right hand side of the top chord.
  • On a Light steel or timber structure the trusses can be fixed using 4 off 90deg angle brackets per truss.
  • On steel structures angle cleats can be welded to the structure and bolted to the truss through the rivet holes using a 8mm galvanised high tensile bolt with nyloc nut.

When truss spans exceed 8m an engineer should be consulted to ensure that trusses are sufficiently fastened to the supporting structure.

10. CUTTING AND DRILLING ON SITE

When trusses, battens or roof sheeting are cut or drilled on site, care must be taken to clean all burs and also to remove any swarf and grinding dust from trusses and roofs. Metallic particles that is left on roofs or trusses will cause rust and will decrease the lifespan of the roof.

11. SITE STORAGE PRIOR TO ERECTION

When trusses, purlins and brandering are stored on site prior to erection, it should be kept dry as galvanised material is prone to develop white rust between surfaces that are tightly stacked.

Once the trusses are fixed to the structure it is not affected by moisture.

12. GEYSERS

Standard design loads DOES NOT allow for a geyser to be supported by the trusses.

A conventional geyser that is installed inside the roof must be supported on two internal walls. The truss should be propped up using a 38mm timber member to fill the space between the truss and the internal wall.

If no internal walls are available, it remains the responsibility of the customer to point this out prior to the design and manufacture of the trusses. In this case a special geyser platform needs to be constructed and the trusses carrying this load should be reinforced.

The installation of a solar geyser also requires reinforcement of the truss and should be pointed out in the design phase.

13. PURLINS

Staalbeer produces a unique 30mm top hat section that can be used for purlins and or brandering. Purlins are typically manufactured from 0.58mm 550MPA Galvanised steel. The web features a textured finish to aid with the location of roofing screws.

Purlins are supplied cut to the correct length to avoid wastage on site.

Purlins must be secured to the top chord of each truss using two fasteners at each point. Either of the following fasteners can be used:

  • TEK SCREW #10x16MM HEX CLASS 2 – typically used in low cost applications
  • #14X22MM STITCHING SCREW – A superior fastener

For tiled roofs purlins should be spaced at 320mm c@c. At the eave a Staalbeer Tilting spacer should be installed to lift the bottom purlin by 15mm in order to ensure a level tile.

For Light Steel roofs the following purlin spacing should not be exceeded:

  • IBR 0.50 mm – 1.50m
  • Widespan 0.50mm – 1.20m
  • Corrugated 0.50mm – 0.90m

If a customer requires a purlin gable overhang of >300mm it is recommended that purlins are braced using a second purlin that is fitted on the underside of the overhang and protrudes through the gable wall to support the existing purlin.

If it is necessary to join purlins it should be joined on a truss with a minimum overlap of 150mm

14. BRANDERING

Staalbeer produces a unique 15mm top hat section that are used as brandering.

Brandering is manufactured from 0.50mm 550MPA Galvanised material.

Typicaly brandering is spaced @450mm centres.

Brandering must be fixed to the bottom chord of the truss using the following fasteners:

  • TEK SCREW #10x16MM HEX CLASS 2 – typically used in low cost applications
  • #14X22MM STITCHING SCREW – A superior fastener

If it is necessary to join brandering it should be joined on a truss with a minimum overlap of 150mm

15. BOTTOM CHORD BRACING

If brandering is installed @450mm centres no additional bottom chord bracing is required.

In the absence of brandering the following bottom chord bracing must be installed:

  • A longitudinal brace in the centre of each bay of the truss
  • V-bracing at each gable end of the building and thereafter in intervals of 10m

16. TOP CHORD BRACING

In low cost applications the top chord should be braced using 25×1.0mm galvanised hoop iron.

The hoop iron must be pulled tight to form a cross on the roof using a piece that is at least the length of the top chord at each side of the building.

17. LONGITUDINAL WEB BRACING

Depending on the roof design truss webs needs to be braced in order to reduce the effective length of the web.

The Staalbeer 0.58mm Galvanised top hat section is used as a bracing section and is supplied cut to length.

18. ANCHOR WEB BRACING

Depending on roof design truss webs needs to be diagonally braced to reinforce the roof structure.

The Staalbeer 0.58mm Galvanised top hat section is used as a bracing section and is supplied cut to length.

19. TAIL BRACING

When an eave overhang >400mm is required tail bracing will be added during truss assembly in order to reinforce eave overhangs. A 0.80mm thick U-shaped channel will be used to form a box section that is secured using a TEK SCREW #10x16MM HEX CLASS 2.

20. BOXED SECTIONS

Two pieces of the truss profile (one of them is produced “lip off") can be joined together to form a box section.

This box section is typically used on a hip roof to extend the HR truss to the top of the T – truss in such a design.

21. TIMBER – TOP CHORD EXTENTIONS

Certain customers require a timber finish on the eave overhang of steel trusses.

Trussed can be manufactured with a flat end. A 76x38mm timber section can then be bolted in at least three positions (with 8x120mm galvanised bolt with nyloc nut) to the side of the truss to form the eave overhang.

22. BRACKETS

22.1 Brackets – 45 Degrees

All 45 degree brackets are manufactured from 102x102x1.20mm galvanised steel and is available in lengths of 84, 122, 160 and 200 mm respectively. These brackets are predominantly used to fix jack trusses to HR trusses on a hip roof. The angle of the bracket can be adjusted on site to fit the exact location.

22.2 Brackets – 90 Degrees

All 90 Degree brackets are manufactured from 72x50x1.20 mm Galvanised steel and is available in lengths of 75, 127, 174 and 220mm respectively.

These brackets are used in a variety of applications including but not limited to the following:

  • Fixing of trusses to a steel or timber structure.
  • Fixing of J1-1 to HG truss on a hip roof
  • Fixing of Valley trusses to T trusses

22.3 Twist strap bracket

Staalbeer manufactures a TWIST STRAP – 30X1.2X750/1225 bracket to fix trusses to a masonry wall

  • Strap width: 30mm
  • Material Thickness 1.20mm
  • Overall bracket length: 1225mm
  • Distance below twist section: 750mm (equal to 6 layers of bricks)

The bracket is placed in a snug fitting below the intersection of the truss and wall. The bottom part of the bracket is securely fixed to the wall using 75x8mm coach screws or RAWL bolts. Chemical anchors are required if the wall is of poor quality. The top part of the bracket is then folded over the truss and secured both sides and on the top of the top chord.

22.4 TRUSS HANGER – 90 DEG – 1.2MM

Truss hangers is used to fix trusses against a masonry wall. The truss hanger is used to secure the truss at the bottom to support the truss while a 90deg 127mm bracket is used to secure the truss at the top.

The truss hanger is fixed to wall using coach screws with at least 8x75mm coach screws or suitable Rawl Bolts. If the wall/plaster is of poor quality a chemical anchor should be used to fix trusses to the wall.

22.5 HG TO HR&J Connector 2.0mm Galv

This bracket is used on a hip roof to secure 2xHR trusses and a Jack truss to the HG truss. The same bracket can also be used if the HG is in a 2 ply configuration.

This bracket is also used on when a hip stepdown truss is used to form a hip roof.

On large hip roofs the vertical web that is used to attach the HR truss should be boxed to prevent buckling of the section.

22.6 SPACER 20MM – TILT EAVE ROW OF ROOF TILES

On a tiled roof the bottom row of the eave tiles must be tilted slightly upwards. The 20mm spacer bracket is then secured to the truss prior to fitment of the bottom row of purlins to obtain the required effect.

22.7 Channel with strap bracket

These brackets are used on when a hip stepdown truss is used to form a hip roof. The channel with strap is used to fix boxed sections to the HG Truss and also to the T1 truss

22.8 Fixing of ceilings and facia & barge boards

Interior plaster or PVC ceiling boards are fixed directly to light steel brandering sections using a #6x32mm Self Drilling Drywall screw.

Exterior fibre cement barge boards are fixed to purlins using a 90deg-100X50X1.2X127 – Barge Board Bracket. Boards are fixed to the brackets using a Class 2 #8X32mm self drilling countersunk wing screw.

Fibre cement facia boards are fixed to truss ends with 90deg – 72X50X1.2X174mm bracket. Boards are fixed to the brackets using a Class 2 #8X32mm self drilling countersunk wing screw.

22.9 Valley Angle bracket

On valleys a 90 deg Valley Angle Bracket 56.5x30x0.80×3 000mm Galv is used to support the valley flashing.

Staalbeer Deliveries

Staalbeer uses an inhouse delivery fleet consisting of 48 trucks in various load formats to deliver your product directly to site.