The LGS Frame Design Process

Introduction

Architects or building designers develop building designs. From these designs, plans are produced, showing the detailed layout and the construction specification. The plans are then given to engineers so that they can complete their structural design which defines the dimensions of structural members such as walls, floors and roofs. Once the architectural and structural plans are completed, they are given to a frame fabricator to undertake the detailing, roll forming, site delivery and installation.

Detailing starts with plans that are typically downloaded from architects’ and/or engineers’ CAD systems into the software systems used by frame fabricators.

These software systems have programable logic that simplify the location and size decisions of frame members and connections. Detailing ensures all structural, and non-structural, elements are in the correct place, the right size and are compliant with National Construction Code (NCC) requirements.

Detailing is an extremely important part of the process, and requires the fabricator and builder to work closely together at the early design stage to ensure the pre-fabricated frame design incorporates details such as larger service ducts, plumbing routing and orientation, air conditioning, accessible grab rail attachments etc. Careful detailing will ensure ease of on-site installation and minimise the need for on-site modifications.

It would be common for one set of plans to be detailed differently by two separate frame fabricators. For this reason, it is important to always refer back to your frame fabricator when there are any changes to load-bearing structures. Remember, the detailed plans are engineered to meet the NCC and relevant standards based on the design and location of the house.

Once detailing is completed, a set of assembly plans is printed showing how and where each component part is connected to make a completed frame. In addition, a second set of drawings is printed which will be used by carpenters to install on-site.

Finally, the files are sent to the manufacturing equipment which automatically rolls each individual element for all frames. Each part is pre-numbered and cross-referenced to the assembly plan to ensure correct assembly into a wall panel or roof truss.

Factory staff use the assembly drawings to screw each element into the final frame.

Frames are stacked at the factory until needed at the site.

Note that frame manufacturers must meet compliance requirements relating to the strength of screws used for assembling frames in the factory including minimum design capacities and pull out capacities. Self-tapping screws (generally hex head or #3 phillips head or special star drive) are increasingly being used by frame manufacturers where holes are pre punched in the factory setting and therefore a higher level of accuracy can be achieved.

NASH also provides guidance on coating classes for durability of screws.

It is worth noting that components can also be disassembled by simply unscrewing or drilling out the connection. This may be necessary if a component is:

damaged on-site or during transport
a design alteration is made after assembly
a large service needs to be accommodated.

Replacing factory assembly fasteners should be done under guidance from the frame fabricators to ensure that the frame connection engineering is maintained.

Resources

Download PDF

NASH Advisory Note. NAN 006 Getting your steel right

This Advisory Note looks at the requirements of AS 1397 as this is the most common steel used in the residential and low-rise steel framing industry. However, the principles discussed apply for all steel products used in building structures.

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NASH Advisory Note. NAN 013 Durability of screws

This Advisory Note discusses some of the issues involved in the correct selection of screw coatings for steel framing and makes recommendations on minimum coating performance to achieve reliable durability in steel framing connections.