LT7^®

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.

Roll-forming facility location: Wellington and Invercargill

Crimp curving facility location: Hamilton and Christchurch

Manufacturing location for DuraClad®: Auckland

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

DIMOND LT7® LIMIT STATE LOAD / SPAN CAPACITY CHART

(span in mm, distributed serviceability loads in kPa)

Notes

1. In Restricted Access Roof and Non-Access Roof & Wall applications, spans exceeding the maximum values shown should not be used. The maximum spans for Restricted Access Roofs are based on static point load testing as a guide and are further limited by practical experience of roof performance under dynamic foot traffic loads. For Non-Access Roof & Wall applications, the maximum spans are limited to ensure 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 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 ratio of the internal span.
7. Design Criteria for Limit State Capacities
   1. Serviceability Limit State (SLS Design)
      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 (ULS Design)
      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 the roofing or cladding profile is determined from the Load Span Table, using the section of the chart appropriate to the grade and type of material, and the category of serviceability selected from the two categories above. Serviceability loads have been derived by testing according to NZMRM procedures. To obtain an ultimate limit state load, we recommend factoring the serviceability load by 1.4 in line with NZMRM guidelines. 
   Note: The capacities given do not apply for cyclone wind conditions.
   
   Serviceability Requirements
   While these categories are provided for design guidance to meet the serviceability limit state criteria, foot traffic point load damage may still occur if point loads are placed carelessly
   
   Service Category
   Refer to MRMCOP 3.7.4 Roof Traffic. The designer must consider the degree and type of foot traffic expected on a roof. The following equirements are subjective standards and must be considered in line with customer expectations, building use, and type. More robust design than specified below (such as reducing purlin spacing or adding protection from mechanical action) is required for roofs that are regularly accessed, used as staging by subsequent trades, or areas adjacent to access points, particularly step-down access
   
    
9. Wind Pressure Guide
   As a guide for non-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.

When using Stainless Steel screws, an 8mm diameter clearance hole must be drilled through the Aluminium LT7 sheet and an
EPDM seal with an Aluminium washer must be used.

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.
 

Information: Layout Fastenings.

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