Dimond Purlin Systems are intended for use as structural support to roofing and wall cladding. The systems provide for bolted connections to primary structural framework and include Dimond Hi-Span (DHS) Purlins, Fastbrace, Dimond Brace Channels and Top Notch purlins.

/ Environment

General Environment

The durability of galvanised zinc coated products is dependent on:

  • the environment it will be installed in.
  • the grade or weight of the zinc coating used.
  • the degree and extent of the maintenance that will be undertaken over the life of the product.

Performance of galvanised zinc coated products is affected by:

  • the cumulative effects of the weather.
  • the amount of dust that settles on the product (which can hold moisture).
  • any other wind-blown deposits that may settle on the product, promoting corrosion.

If these deposits are not removed, they will greatly lessen the durability of the product. Regular maintenance should be carried out on these area.

Standard zinc coating weight is used on most buildings where components are kept dry, protected from exposure to moisture and corrosive environments. Inside the building the galvanised zinc coated products can be used in the temperature range of +60ºC and down to a minimum of -30ºC.


In high risk areas such as the underside of canopies, exposed purlin systems used above underslung canopies or exposed purlin systems around large door openings facing the prevailing wind direction, attention should be given to specifying a suitably protective paint coating on the purlin and bracing. The special grade Z450 material may also be specified for the purlins. Bracing Channel and cleats are supplied standard as Z450 galv weight.

Limitations of use

Avoid the use of galvanised steel purlin systems without the additional protection of an appropriate coating in the following environments:

  • Swimming pool covers, where high concentrations of chlorine are combined with a high humidity environment. In this situation the purlin system remains wet for long periods of time, causing a rapid consumption of the galvanised zinc coating and eventual red rusting of the base metal.
  • Any use where the galvanised surface is being exposed to continuous moisture, without a chance for the surface to dry out.
  • In or near marine environments, where the prevailing wind may deposit marine salts on the galvanised surface.
  • In areas surrounding chemical or industrial storage buildings where any chemical attack may lessen the life of the structure or wind-driven chemical fumes may attack the galvanised coating.
  • When in contact with the ground (e.g. soil or clay) or where embedded in concrete.

Avoid the use of galvanised steel purlin systems:

  • When in contact with timber and especially treated timber such as CCA (copper chrome arsenic) without the use of an isolating material such as Malthoid (DPC) between the timber and galvanised steel flooring sheet. This avoids any moisture or chemical reaction between the two materials.
  • When in contact with the ground (ie soil or clay) or where embedded in concrete.
  • When used in sub-floor areas with less than 450mm ground clearance.
  • When used in sub-floor areas where ventilation does not comply with NZS 3604 Clause 6.14.
  • When used within 50mm of the concrete ground slab.

/ Maintenance

Dimond Purlin Systems require a minimum degree of maintenance in order that the expected performance is achieved by ensuring the galvanised surface is free from dirt buildup.

Careful maintenance can extend the useful life of the Dimond Purlin System.

  1. As a guide the following should be carried out as often as is needed (this could be as often as every three months).
  2. Keep surfaces clean and free from continuous contact with moisture, dust and other debris. This includes areas such as exposed undersides of canopies.
  3. Regular maintenance should include a washdown programme to remove all the accumulated dirt or salt buildup on all the galvanised surfaces with a soft brush and plenty of clean water or by water blasting at 15 MPa (2000 psi).
  4. Periodically inspect and replace where necessary any bolts or fasteners that have deteriorated to the extent that red rust has become obvious over most of their surface.
  5. Periodically inspect the Purlin, Girt, Fastbrace Brace Channel, Sag Rod members and all connections for signs of surface corrosion. Remove any surface corrosion and spot prime corroded areas that exhibit exposed steel substrate, and repaint to an appropriate paint manufacturer’s recommendations.

Any case of severe damage or corrosion must be reported to the design engineer.

/ General Material Specification

Dimond Purlin Systems are manufactured from galvanised coil in the following protective galvanised zinc coating weights.

  1. Standard grade (typically used for interor use) Z 275, i.e. 275 g/m² total zinc coating weight, for DHS Purlins. Fastbrace channel standard is Z450, i.e. 450 g/m² total zinc coating weight.
  2. Special grade (typically used for exposed external use) Z450, i.e. 450 g/m² total zinc coating weight, for DHS Purlins and Fastbrace channel and cleat ends.

Refer to Section 2.1.3 of the design manual on the selection of the appropriate grade.
Refer to Section 2.1.3.1 of the design manual where extra paint protection may be required

The special grade Z450 usually requires a three-month lead time from date of order to supply for all sizes of purlins and quantities.

For detailed purlin material specification see:

TOP
NOTCH

Dimond’s range of Top Notch purlins
are compact, lightweight and easy to install.

/
Scope of use

Dimond Purlin Systems are not intended to be used as members to which fall arrest anchor points are attached.

Dimond purlin systems are not intended to be used as vertical studs or horizontal wall girts where plaster board is fixed directly to the DHS purlin and a level 4 finish or above is required. Where a level 4 finish or above is required, Dimond recommend fixing a secondary adjustable grid framing system to the DHS purlins prior to lining with plasterboard to ensure a tighter alignment and fixing tolerances, to achieve the required finish.

It is critical to product performance that the loads applied, member spans, member sizes and bracing points are designed within the appropriate Limit State Loads and limitations published in this manual. Before commencing a project using a Dimond Purlin System, the designer must ensure relevant information is available to the end user. Failure to observe this information may result in a significant reduction in product performance. Dimond accepts no liability whatsoever for products which are used otherwise than in accordance with these recommendations.

The information contained within Purlin Systems is only applicable to Dimond Purlin and Bracing Systems – it cannot be assumed to apply to similar products from other manufacturers.

Use outside the stated guidelines

If the need arises to use a Dimond Purlin System outside the limitations and procedures given in this manual or if there exists any doubt on product handling or use, written approval should be obtained from Dimond for the specific project, before the project is commenced.

Load Span Tables

Top Notch load span tables for single, end and internal spans can be found below.

/
Material Specification

Dimond Top Notch are manufactured by roll forming galvanised steel coil produced to AS 1397:2001.

Mas eMEtal Thickness (BMT) (mm) Steel Grade Yield Strength Zinc Weight (Z) (g/m2)
0.75 G550 550 275
0.95 G550 550 275
1.15 G500 500 275

Z 450 zinc weight coil can be supplied with order lead times of up to 12 weeks. Please discuss with Dimond on 0800 DIMOND.

Tolerances

Top Notch Size Overall Width (mm) Overall Depth (mm) Top Web Width (mm)
60 ±1 ±1
±1
100 ±2
±2
±1
120
150 ±3
±3
±1

Short Form Specification - Top Notch

The light steel section will be Dimond (1) Top Notch (2) mm BMT to a galvanised zinc weight of (3) g/m2.

The sizes, lengths, span configuration, lap length where required and thickness variations are as shown on the drawing.

Fixings to rafters to be (4) (5) self-drilling screws.
Choose from
(1) 60, 100, 120, 150
(2) 0.75, 0.95 (and if using the 150) 0.95 or 1.15
(3) 275 or 450
(4) 2 – 12g, 4 – 12g, 6 – 12g, 2 – 14g, 4 – 14g, 6 – 14g or 8 – 14g (Refer Section 2.4.6)
(5) Type 17 self-drilling screw (timber), metal self-drilling screw (steel).

/
Design considerations

Data presented in this section is intended for use by structural engineers. Load situations other than
uniformly distributed loads will require specifc design.

Design capacities in the limit state format have been derived by the application of a capacity factor, Φb = 0.90 for bending.

A design yield stress as outlined in Section 2.4.9 has been used for Top Notch Purlins.

Uniformly loaded bending capacities (kN/m) are given for Top Notch purlins and girts for Inward and
Outward cases.

The serviceability linear load, Ws (kN/m), is the load at which the midspan deflection equates to span/150. As deflection is proportional to loading, Ws loads may be factored by the deflection ratio for any deflection within the limit of the linear load capacities.

These tables are intended for use where roofing or cladding provides full restraint to the top flange of the Top Notch purlin or girt. Loads are assumed to be applied about the major axis of symmetry
(X-X). Loads for intermediate spans may be calculated by linear interpolation.

The fixing type and size is critical to achieve the outward design loads. Refer Section 2.4.7 Fasteners of the design manual.

Dimond Top Notch do not require bracing to provide restraint. Therefore the loads are represented as inward and outward cases.

However bracing battens can be screwed transversely along the underside of the purlins to enhance the performance of the Top Notch purlins and are recommended where supports/restraints are further than 30 times the Top Notch depth apart.

Gravity type loads can be assumed to act perpendicular to the roof plane for pitches up to 10 degrees. For pitches greater than 10 degrees, load components about the minor axis of symmetry (Y-Y) should also be considered.

When designing Top Notch to be used as girts, it is assumed cladding and girt gravity loads are taken by a stiff eaves member such as a DHS Purlin.

For combined bending & compression design, section properties and conversion formulae see Structural Design Manual.

/
Installation

General

The fixing of Dimond Purlin Systems is generally carried out by steel fabricators and riggers who are familiar with installation of the Dimond Purlin range.

Handling & Storage

  • Correct handling and storage is critical to ensure the Dimond Purlin System is not damaged on site.  The following points must be adhered to for maximum product durability and performance over the expected life of the product.
  • Site storage must be clear of the ground on dunnage to allow the free movement of air around each bundle. When product is stored on site, it must be kept dry using covers over each product bundle.
  • A visual inspection should be carried out, when delivery is taken on site, of all the material supplied to ensure the product is free from damage and the galvanised coating is in good condition.
  • Damaged product resulting in a distorted or buckled section shape must not be installed and should be replaced.
  • Wear protective gloves when handling the product. Treat all cut edges as sharp. 
  • Product must always be lifted when moved and not dragged as damage to the galvanised coating will occur.

General Fixing & Workmanship

  • Bundle labels should be checked to ensure the correct size and type is used for the designated area.
  • Top Notch purlins are placed at premarked centres, and fixed onto the rafter.
  • Additional strapping for Top Notch purlins may be required as specified by the design engineer.
  • The purlin system must not be subject to or installed on spans that are excessive for the loads imposed during construction, or in the serviceable life of the product. All construction loads must have the design engineer’s approval, prior to loading.
  • All connections including those between the purlin system and primary structural framework must be fully fixed and tightened before any loads are applied. Similarly bracing members must be correctly positioned and fastened prior to installation of the roofing or cladding.
  • The recommended method for cutting of Top Notch is either by hacksaw or shear cut such as tin snips. If using abrasive disc blade, care must be taken to ensure the swarf doesn’t fall on other products causing rust stains, and the burred cut edge must be cleaned off and primed after cutting.
  • Gas cutting of holes, or welding of members, or connections are not recommended, as these may causes an unacceptable loss of member strength capacity.  In addition gas cutting or welding will remove the galvanised coating locally around the welded area, reducing the product’s durability.
  • Top Notch purlins are not designed for walking on as manufacturing lubricant may still be present on these components. In additional Health and Safety requirements prohibit “walking the purlins”. All on-site Health and Safety requirements must be adhered to.
  • Roofing and wall cladding sheets cannot be installed until the roofing contractor is satisfied that the support structure is complete, sound, and correctly aligned.  This includes support around penetrations and openings.
  • Curved roofs (whether drape/rolled or crimped) require purlin alignment within ±5mm to minimise risk of unacceptable finished appearance.
  • Dimond Top Notch purlins are not intended to be used as members to which fall arrest anchor points are attached.

Fixings

Self-drilling screws should be installed as per engineer’s specification, and tightened with mechanical drivers set to a preset torque setting. Avoid over tightening as this may damage the galvanised coating.

Support Condition Support Member - Material Support Member - Grade Support Member - Min. Thickness (mm) Purlin Size -60x0.75 and 60x0.95 Purlin Size -100x0.75 and 100x0.95 Purlin Size -120x0.75 and 120x0.95 Purlin Size -150x0.95 Purlin Size -150x1.15
End Cold-Formed Steel
Steel
Timber
G450
G300
1.45
3
37*
2/12g
2/12g
2/12g
2/12g
2/12g
2/12g
2/14g
2/14g
2/14g
2/14g
2/14g
2/14g
2/14g
2/14g
2/14g
Internal Cold-Formed Steel
Steel
Timber
G450
G300
1.45
3
37*
4/12g
2/12g
2/12g
6/12g
4/12g
4/12g
6/14g
4/14g
4/14g
6/14g
4/14g
4/14g
8/14g
6/14g
6/14g

*Minimum screw embedment into timber support.

Notes to table

  • Cold-formed option - 2/14g indicates 2 of 14 gauge self-drilling screws fastened into a cold-formed steel (grade G450) support member of 1.45mm minimum thickness. the same rationale applies where 12 gauge screws are required.
  • Steel/timber option - 2/12g indicates 2 of 12 gauge self-drilling screws fastened into a Grade 300 hot-rolled steel support member of 3mm minimum thickness, or 2 of 12g x 50mm long Type 17 screws fastened into timber to achieve a minimum embedment length of 37mm. The same rationale applies where 14 gauge screws are required.
  • Outward loads shall be adjusted to a lower value if less screws or thinner support members are used.
  • A minimum distance of 20mm from the fastener to the end of the Top Notch purlin is required
  • Lap end fasteners shall be:
    2 screws for the 60 and 100 Top Notch or 
    4 screws for the 120 and 150 Top Notch
    positioned at each end
  • Lapped Top Notch purlins require additional fixings to be installed in the lapped region. 
  • When the number of specified fixings above cannot be fixed into the Top Notch  and/or Top Notch is being installed in cyclonic regions, an additional hold-down strap should  be used (Strap capacity 20kN)  - refer drawing A below.

DHS
PURLIN

The Dimond Hi-Span purlin range is available in 12 sizes from DHS 150/12 to DHS 400/20 to suit commercial applications from 5m to 18m spans. Speed of installation is assured as Hi-Span purlins and girts are supplied complete with brace channels ready for site assembly.

/
Scope of use

Dimond Purlin Systems are not intended to be used as members to which fall arrest anchor points are attached.

Dimond purlin systems are not intended to be used as vertical studs or horizontal wall girts where plaster board is fixed directly to the DHS purlin and a level 4 finish or above is required. Where a level 4 finish or above is required, Dimond recommend fixing a secondary adjustable grid framing system to the DHS purlins prior to lining with plasterboard to ensure a tighter alignment andfixing tolerances, to achieve the required finish.

It is critical to product performance that the loads applied, member spans, member sizes and bracing points are designed within the appropriate Limit State Loads and limitations published in this manual. Before commencing a project using a Dimond Purlin System, the designer must ensure relevant information is available to the end user. Failure to observe this information may result in a signifi cant reduction in product performance. Dimond accepts no liability whatsoever for products which are used otherwise than in accordance with these recommendations.

The information contained within Purlin Systems is only applicable to Dimond Purlin and Bracing Systems – it cannot be assumed to apply to similar products from other manufacturers.

Use outside the stated guidelines

If the need arises to use a Dimond Purlin System outside the limitations and procedures given in this manual or if there exists any doubt on product handling or use, written approval should be obtained from Dimond for the specific project, before the project is commenced.

Load Span Tables

DHS Load Span tables for Single, End and internal spans can be found below

/
DHS Material Specification

Dimond Hi-Span Purlins are manufactured by roll forming galvanised steel coil produced to AS 1397:2001.

Base Material Thickness, BMT (mm) Steel Grade Yield Strength fy (Mpa) Standard Zinc Weight, Z (g/m2)
DHS Purlins and Grits < 1.5 G500 500 Z 275
>1.5 G450 450 Z 275
Tolerance Depth +/-2mm
Width +/-2mm
Hole Centres +/-1.5mm
Length +/-6mm
Web/Flange Angle 89-93 degrees

Z 450 zinc weight coil can be supplied with order lead times of up 12 weeks. Please discuss with Dimond on 0800 DIMOND.

Short Form Specification - DHS Purlins and Grits

The purlin system will be Dimond DHS (1), manufactured from G450-G500 grade steel with a (2) g/m2 galvanised zinc weight.

The sizes, lengths, span configuration and lap lengths (where required) are as detailed on the drawings.

All hole sizes, hole shapes and positions are as shown on the drawings.

The bracing system is to be (3). The bracing channel size is 89mm x 1.2 thick galvanised with a (2) galvanised zinc weight.

All bolts to be (4) grade, (5) diameter, (6) finish.
Choose from
(1) 150/12, 150/15, 200/12, 200/15, 200/18, 250/13, 250/15, 250/18, 300/15, 300/18, 350/18,
400/20
(2) Z 275 or Z 450
(3) Fastbrace or bolted channel bracing
(4) 4.6 or 8.8
(5) 12mm or 16mm
(6) Electro galvanised or hot dip galvanised.

/
Design Considerations

Data presented in this section is intended for use by structural engineers. Load situations other than
uniformly distributed and axial loads will require specific design.

Design Capacities in the Limit State format have been derived by the application of a capacity factor, Φ:

Bending Φb = 0.90
Compression Φc = 0.85

A design yield strength of 500 MPa has been used for DHS purlins and girts. This is in line with the
minimum specified yield for G500 material and is significantly less than the consistent minimum yield stress in the G450 material used in manufacture.

Design capacity of the DHS Purlin System is largely dependent on the amount of restraint provided to the purlin section. These design tables assume that bracing prevents both lateral movement and rotation of the section at that point.

It is also assumed that screw-fixed cladding significantly prevents lateral movement of the flange to
which it is attached. Where this assumption does not hold, it is recommended that the number of braces required is specified such that the purlin load capacity, ΦbWbx is not less than the capacity for the Fully Restrained case (FR).

Uniformly loaded bending capacities (kN/m) and axial compression capacities (kN) are given for purlins and girts with 1, 2 or 3 braces. The Fully Restrained (FR) case may be used when the compression flange is fully restrained against lateral movement.

The Serviceability Linear Load, Ws (kN/m), is the load at which midspan deflection equates to span/150. As deflection is proportional to loading, Ws loads may be factored by the deflection ratio for any deflection within the limit of the linear load capacities.

As a guide to acceptable deflection limits for serviceability of DHS used as purlins or girts, for wind and dead load actions, Dimond recommend the following limits:

• Where there is no ceiling:
– Deflection for Ws >l Span/150
– Deflection for G >l Span/300
• Where there is a ceiling:
– Deflection for Ws >l Span/200
– Deflection for G >l Span/360.

For specific deflection limits reference must be made to AS/NZS 1170.0:2002.
These tables are intended for use where roofing or cladding is attached to one DHS purlin or girt flange.

Loads are assumed to be applied about the major axis of symmetry (X-X). Loads for intermediate spans may be calculated by linear interpolation.

For roofs, the dead load of roofing and purlins is assumed to be tied across the ridge or into the
ridge beam for monoslope roofs. This avoids purlins sagging out of plane down the roof slope.

For walls, the following table gives the maximum allowable wall heights for Dimond bracing systems,
where the dead load of cladding and girts is assumed to be carried in tension to an eaves beam by
Fastbrace or brace channels. Specific design of the brace system and connections is required for wall heights greater than the limits shown or where the bracing is designed to carry compression loads.

Maximum Wall Height
Purlin Thickness BMT (mm) Fastbrace Bolted Channel Bracing
1.15,1.25 5.0m 15.0m
1.45 6.5m 15.0m
1.75 8.0m 15.0m
1.95 - 15.0m

Basis to Table

  1. Spacing between bracing lines and/or portal frames not greater than 3.5m.
  2. Weight of cladding not greater than 6.7kg/m2.


In order to minimise deflections in the girt member, we recommend a maximum spacing between bracing lines and/or portal frames of 3.5 metres.

Gravity type loads can be assumed to act perpendicular to the roof plane for roof pitches up to 10 degrees provided the DHS purlins are placed with their flanges facing up the slope. For pitches greater than 10 degrees, load components about the minor axis of symmetry (Y-Y) should also be considered.

Specific design is required for loads suspended from DHS purlin systems (such as ducting and piping). Hangers must be connected to the web of the purlins or to the bottom flange within 25mm of the web. Under no circumstances should loads be hung off the purlin lips.

Specific design is required to AS/NZS 4600 when designing DHS purlins as truss or portal members.

The following table lists design capacities and distortional buckling stresses that were used in determining the load span tables.

Compression Bending Shear
DHS ΦcNs ΦbMsx Φodx(TW) ΦbMbdx kv ΦvVvy
size (kN) (kNm) (MPa) (kNm) (kN)
150/12 94.7 6.93 413 5.82 7.80 14.03
150/15 133.4 9.60 526 7.93 7.53 27.27
200/12 101.2 9.85 321 8.62 7.62 10.6
200/15 142.8 14.15 409 11.82 7.45 19.78
200/18 188.9 18.96 498 15.21 7.33 34.31
250/13 123.3 115.00 290 13.36 8.03 10.75
250/15 153.6 18.82 339 16.40 7.89 16.53
250/18 203.3 25.29 412 21.18 7.73 28.54
300/15 161.9 23.85 271 21.39 8.00 13.83
300/18 214.6 31.89 330 27.74 7.83 23.85
350/18 222.4 38.37 301 33.48 7.70 19.97
400/20 270.1 53.28 300 45.29 7.51 23.50
  • ΦcNs: Design section capacity in pure compression, determined in accordance with AS/NZS 4600:1996 Clause 3.4.1 with Φc = 0.85.
  • ΦbMsx : Design section capacity in pure bending about the major (x) axis, determined in accordance with AS/NZS 4600:1996 Clause 3.3.2 with Φb = 0.95 and the web modelled as a single stiffened flat element.
  • ΦbMbdx : Design member capacity in pure bending about the major (x) axis based on failure by distortional buckling, determined in accordance with AS/NZS 4600:1996 Clause 3.3.3.3 with
  • Φb = 0.90. The corresponding distortional buckling stress (Φodx(TW)) is determined using a rational elastic buckling analysis of the whole cross-section.
  • kv: Shear buckling coefficient for the web following the procedures outlined in Section R6.2 of the ECCS document entitled European Recommendations for Steel Construction: The Design of Profiled Sheeting (ECCS, 1983). The ECCS procedures provide a sound basis for determining kv where a stiffening swage is present in the web.
  • ΦvVvy: Design shear capacity for a shear force in the direction of the y-axis, determined in accordance with AS/NZS 4600:1996 Clause 3.3.5 with Φv = 0.90.

For combined bending & compression design, section properties and conversion formulae see Structural Design Manual.

/
Components

Fastbrace

Fastbrace is a lock-in bracing system which uses cleats with specially shaped lock-in tabs attached to each end of a 89 x 12 bracing channel, for use with DHS purlins up to and including DHS 300 series.

Pairs of Fastbrace are fitted from each side of the DHS purlin through prepunched 18mm diameter
round bracing holes and are locked together, minimising erection time.

When a line of Fastbrace has been installed, the system provides resistance to restrict lateral
movement of the DHS purlin and also supports the purlin flange.

Limitation for use

The end brace at the first and last bracing points is secured using the standard bolted connection on the outermost cleat end.

To ensure straight alignment of the bracing system, the bracing holes can be offset by 25mm over
the last purlin spacing to accommodate a bolted cleat. If this is not achieved, an angle of less than
2 degrees from a straight alignment is created, which in most cases is negligible and acceptable.

At the ridge, the lower bolt position is used to tie the bracing lines each side together using a sag rod.

Where back to back DHS purlins are used, bolted end brace components are required each side.

The durability of zinc coated products is dependent on the environment it will be used in, the
grade of the zinc coating and the amount of maintenance that will be carried out over the life of the
product. Refer Section 2.1.3 Environments of structural design manual for further guidelines.

Maintenance

Must be carried out in accordance with Section 2.1.6 Maintenance of structural design manual.

Handling & Storage

The Fastbrace system is delivered to site, usually strapped together, marked in bundles for installing
in the same area of the roof structure. Refer to Section 2.6.2 Handling and Storage of structural design manual.

Material Specification

Base metal Thickness (BMT) mmSteel gradeYield Strength Φy(MPa)Standard zinc weight Z (g/m2)
Bracing channel1.15G250250275
End cleats2.00G250250275


Tolerances:
Length ± 2mm
Depth ± 1mm
Width ± 1mm
Web/flange angle 89 to 93 degrees

/
Bolted Channel Bracing

The Dimond bolted channel bracing system uses cleats, clinched at each end of a 89 x 12 bracing

channel, which are fastened through the DHS purlin with two bolts each end. Bolted channel bracing
is used with the full DHS purlin range (DHS 150 to DHS 400 series).

This system uses bolted channel bracing between all purlins in the bracing line. Refer Section 2.3.9.1 of structural design manual for design basis.

At the ridge, the lower hole position is used to tie the bracing lines each side together using a sag rod.

Limitations of use

The durability of zinc coated products is dependent on the environment it will be used in, the grade of the zinc coating and the amount of maintenance that will be carried out over the life of the product.
Refer Section 2.1.3 Environments of structural design manual for further guidelines.

Maintenance

Must be carried out in accordance with Section 2.1.6 Maintenance of structural design manual.

Handling & Storage

The channel bracing system is delivered to site, usually strapped together, marked in bundles for installing in the same area of the roof structure. Refer to Section 2.6.2 Handling and Storage.
For the material specifications of the bracing refer to Section 2.3.15.1 of structural design manual.

Bolted Channel Brace

This is the standard component used in the bolted channel bracing system and is used almost everywhere.

Adjustable Bolted Channel Brace

This is the adjustable component in the bolted channel bracing system and is used where some level of adjustment on the purlin line is required. The purlin is adjusted into line and the 12mm diameter hex flange bolts on the brace tightened. The adjustable brace offers up to 20mm of adjustment.

Portal Cleats

These are typically supplied by the fabricator or installer and welded on to the portal frame. Cleat thicknesses range from 6mm to 12mm thickness. The hole centres are laid out to suit hole punchings in the DHS purlin, refer to Section 2.3.16.3 Hole Locations of structural design manual for details. The cleat height may need to be increased where an expansion step in the roof is detailed.

Sag Rods

Alternating sag rods and channel have been superseded by the use of Fastbrace and the bolted channel bracing as the preferred bracing method. However the rods are still used as a cranked sag rod at the ridge to join each side together. Usually supplied by the steel erectors and fabricators in 12mm diameter engineering round bar grade 250 MPa, galvanised or electroplated finishes, with double nuts and washers each end. Where loads require, 16mm diameter engineering round bar can be used. 

Timber Strip

Timber strip battens are fi tted once the netting is in place to avoid roof insulation squashing down, over the purlin, as the roofi ng is screwed down.

Usually supplied and fi xed on site by the fabricator. However Dimond recommend using an ex 50mm x 50mm timber batten or a depth of batten equal to the thickness of the insulation gauged two sides and treated to H3 timber preservation such as boric or LOSP (low, organic solvent preservative). The CCA treatment process should be avoided, due to chemical contact with galvanised surface.



The batten is fixed onto the top fl ange of the DHS Purlins, once the netting or safety mesh has been laid on the structure. Fixings to be 10g – 16 x 75mm. Countersunk rib head – wingtek. The coating finish is a zinc plated AS 3566 class 2 finish. Longer, other types of fixings may need to be considered when the timber depth is greater than 65mm.

Spacing of the wingteks is dependent on the DHS material thickness it is being fixed into. Refer to
the following table.

DHS Purlin BMT (mm)Max. screw centres (mm)
1.15250
1.25 to 2.0300


At these centres, the maximum outward load on the nailing strip is 5.0 kN/m.

/
Installation

General Fixing & Workmanship

  • Bundle labels should be checked to ensure the correct size and type is used for the designated area.
  • Purlins are placed on the upside of the portal cleat (or at premarked centres for Top Notch), and fixed onto the cleat or rafter.
  • Installation of DHS Purlins relies on the correct bolt type, diameter and washer being located through each cleat hole and tightened.
  • Washers should be used under the bolt head or nuts against the DHS Purlin.
  • Bolts should be tightened using the part turn tightening method, commonly termed snug fi t. There are two stages, the fi rst involves bringing the mating surfaces of the joint into effective contact by initially tightening the bolt. The second stage involves marking the bolt and nut relative to each other and then completing a further half turn.
  • Self-drilling screws should installed as per engineer’s specification, and tightened with mechanical drivers set to a preset torque setting. Avoid overtightening as this may damage the galvanised coating.
  • Lapped purlins require additional fixings to be installed in the lapped region. 
  • Additional strapping for Top Notch Purlins may be required as specified by the design engineer.
  • The purlin system must not be subject to or installed on spans that are excessive for the loads imposed during construction, or in the serviceable life of the product. All construction loads must have the design engineer’s approval, prior to loading.
  • All connections including those between the purlin system and primary structural framework must be fully fi xed and tightened before any loads are applied. Similarly bracing members must be correctly positioned and fastened prior to installation of the roofi ng or cladding.
  • Gas cutting of holes, or welding of members, or connections are not recommended, as these may cause an unacceptable loss of member strength capacity. In addition gas cutting or welding will remove the galvanised coating locally around the welded area, reducing the product’s durability.
  • The recommended method for cutting of Top Notch is either by hacksaw or shear cut such as tin snips. If using an abrasive disc blade, care must be taken to ensure the swarf doesn’t fall on other products causing rust stains, and the burred cut edge must be cleaned off and primed after cutting.
  • DHS Purlins and Top Notch Purlins are not designed for walking on as manufacturing lubricant may still be present on these components. In additional Health and Safety requirements prohibit “walking the purlins”. All on-site Health & Safety requirements must be adhered to. 
  • Roofing and wall cladding sheets can not be installed until the roofing contractor is satisfied that the support structure is complete, sound, and correctly aligned. This includes support around penetrations and openings.
  • Curved roofs (whether draped/rolled or crimped) require purlin alignment within ±5mm to minimise the risk of unacceptable fi nished appearance.
  • Hanging of fixtures from the purlin lips, brace channel lips or brace channel flanges is not recommended. All fixtures must be attached to the web of the member they will be connected to and are subject to specific design by the engineer.
  • Dimond Purlin Systems are not intended to be used as members to which fall arrest anchor points are attached.

DHS Bracing Installation

Prior to the purlin system being fully tensioned up and loads applied, the bracing system must be installed.

Fastbrace Installation

Installation of Fastbrace is started from the ridge and works down the roof slope, but the first row of Fastbrace must be bolted off on the top purlin before beginning the next row.

Standard Installation Procedure

Note: As the eaves and ridge braces are bolted, there is a 25mm offset to the bracing line. This offset can be aligned.

1. The end cleat is bolted to the purlin at the ridge.It is vital to make sure that the bolted cleat at the ridge is on the left of the brace (looking from the ridge down)

2. The locking tabs at the other end of the brace are then fitted into the second purlin and pushed to the right to lock (looking from the ridge down).

3. The second brace is then held at a 45° angle and inserted into the other side of the second purlin. Now rotate the brace until square to the purlin.Ensure all locking tabs are fitted into the purlin holes.

4. Fit the other end of the brae into the next purlin. Steps 3 and 4 of this process are then repeated until the last cleat is bolted to the eave purlin.

NOTE: Due to the versatility of the system, the process can be started at the ridge or the eaves.

Adjustable Fastbrace allows up to 20mm adjustment to be made anywhere in the Fastbrace system, simply by installing this adjustable brace and fully tightening two bolts.

Purpose-made cranked sag rods, installed in the lower holes of the DHS ridge purlin at the bracing line, tie each roof plane together at the ridge. These rods should be fitted with washer and double nuts and fully tightened up prior to loading.

Bolted channel bracing relies on placing and tightening one bolt top and bottom through the brace cleat/purlin assembly. Hence the installation time required for bolted channel bracing is much longer than for Fastbrace.