LT7^®

LT7^® Performance

Designed for applications where protection from severe climatic conditions and maximum structural economy is required, the strong section properties of LT7^®allow for wider purlin and girt spacings which add extra economy to building projects. It also has excellent water shedding characteristics as well as being perfect for low pitch roofs.

Sheet Tolerances
Sheet width: ‡5mm
Sheet width for aluminium +0, -15mm. If sheet cover widths are critical, advise Dimond Roofing at time of order.
Sheet length: +10, - 0mm. For horizontal wall cladding where notified at time of order of intended use, tighter tolerances can be achieved +3, -0.

Roll-forming facilities at: Wellington and Invercargill

Crimp Curving facility at: Wellington

Sheet lengths: LT7^® is custom run to order.

Where long sheets are used, consideration must be given to:

• Special transportation licences for sheet lengths over 25m
• Site access for special lifting equipment
• Fixing techniques to accommodate thermal expansion

LT7^® Limit State Load / Span Capacity

(span in mm, distributed serviceability loads in kPa)

Notes

1. In any category, spans above the maximum shown should not be used. Category 1 and 2 maximum spans are based on static point load testing as a guide, and further limited by practical experience of roof performance under dynamic foot traffic loads. Category 3 maximum spans are limited as a guide to achieving satisfactory appearance for wall cladding.
2. Loads given are based on 4 screw fasteners/sheet/purlin.
3. Loads given are limited to a maximum of 3.5kPa. If design requirements exceed this limit, Contact Dimond Roofing for specific advice.
4. Duraclad
   - Serviceability Limit State Load are not applicable to Duraclad material, as it does not experience permanent deformation
   - System must include Safety Mesh it intended for use as a Restricted-Access roof. Refer Section 2.2.1.8 of Technical Manual
5. N/R = not recommended
6. End span capacities given in this table are based on the end span being 2/3 of the internal span.
7. Design Criteria for Limit State Capacities
   1. Serviceability Limit State
      No Deflection or permanent distortion that would cause unacceptable appearance, side lap leakage or water ponding, due to foot traffic point loads, inward or outward wind loads or snow loads.
   2. Ultimate Limit State
      No pull through of fixings or fasteners withdrawal resulting in sheet detachment due to wind up-lift (outward) loads.
8. System Design
   The span capacity of LT7^®/5 is determined from the LT7^®/5 Limit State Load/Capacity Chart using the section of the chart appropriate to grade and type of material, and to the category of serviceability selected from the three categories below. Serviceability loads have been derived by test to the NZMRM testing procedures. To obtain an ultimate limit state load we recommend factoring the serviceability load up by 1.4 in-line with NZMRM guidelines. The capacities given do not apply for cyclone wind conditions.
   
   Serviceability Requirements
   While these categories are given for design guidance to meet the serviceability limit state criteria, foot traffic point load damage may still occur if there is careless placement of these point loads.
   
   Unrestricted-access roof
   Expected regular foot traffic to access the roof for maintenance work and able to walk anywhere on the roof. No congregation of foot traffic expected.
   Restricted-access roof
   Expect occasional foot traffic educated to walk only on the purlin lines, in the profile pan. Walkways installed where regular traffic is expected, and “Restricted Access” signs placed at access point.
   Non-access roof or wall
   Walls or roofs where no foot traffic access is possible or permitted. If necessary, “No Roof Access” signs used.
   
   
9. Wind Pressure Guide
   As a guide for no-specific design the following S.L.S. design loads in accordance with the MRM Roofing Code of Practice can be used for buildings less than 10m high, otherwise AS/NZS 1170.2 should be used
   Low wind zone = 0.68kPa, Medium wind zone = 0.93kPa, High wind zone = 1.32kPa, Very high wind zone = 1.72kPa and Extra high wind zone = 2.09kPa.

LT7^® Fastener Design

LT7^® should be screw fixed to either timber or steel purlins. The use of the appropriate length of 12g or 14g screw will ensure
failure by screw pull out will not occur under loads within the scope of the Limited State Load/Span Capacity Chart.

For screw size range and fastener/washer assembly refer to Section 2.2.3.1 of Technical Manual.

The Limited State Load/Span Capacity Chart for LT7^® is based on 4 screw fasteners/sheet/purlin without the use of load spreading washers. For LT5 Load /span capacity chart is based on 3 screw fasteners/sheet/purlin without the use of load spreading washers.

Profile metal washers are recommended for use:

1. On end spans, or large internal spans where Ultimate Limit State distribution load is limiting. Contact Dimond Roofing for specific advice in these cases.
2. When required to enable the fixing system to accommodate the thermal movement of long sheets – See Section 2.1.3.4 Thermal Movement in
   Technical Manual.
3. Whenever the designer wishes to ensure the risk of fastener over-tightening will not cause dishing in the crest of the profile rib.

Use in serviceability categories (1) and (2) can allow the reduction of fasteners to 3 screw fasteners/sheet/purlin. If this is done, the distributed load capacities given in the chart should be reduced using a multiplying factor of 0.75.

Long spans may require specification and use of side lap stitching screws – Section 2.3.2 C Installation Information: Layout and Fastenings in Technical Manual.

Design Examples

Restricted access roof, 0.55mm G550 steel LT7^® has a maximum end span of 1900mm and a maximum internal span of 2900mm.

The following distributed load capacities apply.

Fixing Layout Options

Product Technical Statement

To help you get through the building consent process as quickly as possible, we have developed the Product Technical Statement (PTS) downloads to make it quick and easy for both Architects and Home Owners to access the documentation required.

The PTS downloads hold all of the information that the council requires for a building consent where Dimond product is specified.

Product Data Sheet

For specific design by profile please refer to the Technical Manual Section 2.1.4 or download the data sheet below

Product Brochure

Need a brochure for one of our roofing profiles? Here you can download one for each of our profiles with the basic information and details you need during the decision process.