Stramit TH120 Top Hat Sections



• Large 120 height – big spans
• Range of thicknesses – design efficiency
• Fluted walls – increased strength
• Patented chamfer – easy nesting & laps
• Screw ridges – accurate & easy fixing
• Simple screw fasteners - Quick to install
• No Bridging required - economical 


Stramit TH120 top hat sections are suitable for use in  industrial, commercial or agricultural applications when used as secondary members supporting roof or wall cladding. 


Stramit TH120 top hat sections are manufactured from high-tensile (G550) steel with AZ150 zincaluminium alloy coating conforming to AS1397. 

Adverse Conditions

Stramit TH120 top hats  will give excellent durability in benign locations. Do not use in marine or heavy industrial environments or applications where corrosive or aboveambient-humidity air will be discharged.




Stramit TH120 top hats are generally considered as secondary members and designed in accordance with AS4600. 

Section Properties

Please refer to Table 1 on page 3 of the Stramit TH120 Top Hat Sections Product Technical Supplement.


All building products need to be checked for compatibility with adjacent materials, whether they be part of the current project or pre-existing or planned building elements.Avoid placing on or in conjunction with components made from copper, lead, green or treated timber, stainless steel and mortar or concrete. Contact Stramit for more detailed information. 


Stramit TH120 top hats have been tested at the Cyclone Testing Station at James Cook University in Townsville, North Queensland. 

Architectural Specification

This specification may be used to ensure that required performance and functional needs are met. 

The roof/wall secondary members shall be Stramit TH120 top hats  in XXmm length/s with thickness of  XX (0.70/0.90) mm. Sheet materials shall be protected steel sheet to Australian Standard AS1397, with a minimum AZ150 zinc-aluminium coating.The sections shall be fixed to the structure in accordance with the manufacturer’s recommendations. Suitable fixing screws in accordance with Australian Standards AS3566, Class 3 minimum, shall be used at each connection. All components shall be fixed in a workman-like manner, leaving the job clean and weather-tight. All debris (nuts, screws, cuttings, filings etc.) shall be cleaned off daily. 

Cyclonic Areas

Contact your nearest Stramit office for information on use of Stramit TH120 top hats  in cyclonic regions.


All loadings used in deriving the design data are assumed to either act uniformly along the top central flange of the sections or, for connections to support members, evenly between each of the lower flanges (feet). Foot traffic loadings, where used, are based on AS1562. 


Member, fastener or roof sheeting capacity influences top hat spacing. It is often economical to reduce top hat spacing at the building edge and ends to account for the higher wind pressures encountered on these parts of the building. Additional runs may be required adjacent to roof penetrations or in areas of additional loading.

Capacity tables

Limit-state design capacity tables for TH12070 and TH12090 for use in non-cyclonic areas are located on pages 4 - 9 of the Stramit TH120 Top Hat Sections Product Technical Supplement. 

Contact your nearest Stramit office for information on use of the products in cyclonic areas.

Allowance at ends

End fastenings of top hats are recommended to be at least 25 mm from the section end irrespective of whether this occurs at the structure end or at an internal support. Remember to allow for this additional material over and above the span length/s and laps when specifying, ordering or cutting sections. 


Lapped Stramit TH120configurations require a minimum 10% lap length (i.e. 5% at each end). Section properties within the lap have been assumed to be twice that of a single section rather than the properties of a double thickness section. Data for both 10% and15% laps can be found in pages 6 -9 of the Stramit TH120 Top Hat SectionsProduct Technical Supplement. 



Site Induction

Consideration should be given to include top hats in site induction safety procedures. Specific consideration should be given to handling long items, avoidance of cuts, trips, slips and falls, working at heights. 


For a lap to be considered structural (as per the capacity tables for double lapped and triple lapped spans) a minimum overlap length of 10% of the span (support spacing) is required. In addition to the two screws at the support position two additional screws per side are required 25mm - 50mm from both ends of the lap at the top of the web and bottom flange, a total of ten screws per lap. 

Top hat overlaps (or non-structural laps) are recommended to be a minimum of 100mm in length. In these cases structural continuity must not be assumed. When connecting overlapping top hats, place foot onto upper section to nest sections prior to and during fixing. Laps must be fastened through both webs as shown.


Should cutting be required, use a power saw with a steel cutting blade or a power nibbler.Avoid the use of abrasive discs as these can cause burred edges. Please dispose of any off-cuts carefully. 


Stramit does not recommend the welding of top hats or battens.The heat produced in welding will affect the material properties of the high-tensile cold-formed steel used by Stramit in its top hats. In many instances considerable stress concentrations are likely to arise, even with good quality welding. In addition, welding will locally remove the coating leading to a potential reduction in durability.


Stramit TH120top hat sections must be fixed using a minimum of two No14 screws at every primary member support position, one screw on each side of the section positioned within the pair of screw ridges. All lap fasteners to be No14 self-drilling screws. All fastening screws must conform to AS3566 – Class 3 or better.They are to be hexagon headed and may be used with or without sealing washers. For connecting to purlins or beams use: 

For steel
(1.2mm or greater)
 – No.14 x 25mm self-drilling and threading screws for fixing to primary structural members. Ensure that the point  classification is correct for the member to which the top hat is being fixed. Always use the correct size and quantity of fasteners as specified by the design engineer. Pairs of screws at connections must be directly in line (parallel with the supporting member). 


Stramit TH120sections have been designed to withstand foot traffic load during installation and service. The use of appropriate craddles or cherry pickers is recommended.As a minimum, never walk on purlins without safety mesh in place. Do not walk on girts. 

Good Practice

Stramit recommends that good trade practice be followed when using this product, such as that found in Australian Standards Handbook HB39.




Prices on Stramit TH120 top hat  and accessories can be obtained from your nearest Stramit location or distributor of Stramit® products. As Stramit does not provide an installation service, ask your tradesperson for a supply and fix price. Contact your nearest Stramit location for the names of suitable tradespersons in your area. 

Related Products

Roof Sheeting – wide range of roofing profiles
Ridge Capping – standard or custom dimensions
Purlins – comprehensive range of purlins, girts and accessories
Insulation & roofing mesh – a range of mesh, plain & foil backed blanket 


Stramit TH120top hat sections supplied in made-to order lengths up to a maximum of 9m. When designing or transporting long products ensure that the length is within the limit of the local Transport Authority regulations.The manufacturing tolerance on the length of components supplied is +0, -15mm. 


Stramit TH120top hat sections can be ordered directly or through distributors. 


Delivery times would vary, subject to the delivery location, quantity and material availability, or delivery can be at a pre-arranged date and time. Please ensure that suitable arrangements have been made for truck unloading, as this is the responsibility of the receiver. Pack mass may be up to one tonne. 


Stramit TH120top hat sections and packs should be handled with care. Packs should always be kept dry and stored above ground level while on site. If the sections have become wet, they should be separated, wiped and placed in the open to promote drying.



Further Information

Stramit has a series of Technical Manuals, Installation Leaflets, Case Studies and other promotional literature to aid design. 

These include:
• Top Hats and Battens Technical Manual
• Purlins & Girts Technical Manual 

Please contact your nearest Stramit location for any of these guides or other literature and for information regarding the use of products in cyclonic areas.  

Other Products

Stramit offers a wide range of building products, including: 

• Purlins and girts
• Formwork decking
• Roof and wall sheeting
• Lightweight structural sections
• Gutters and downpipes
• Fascias
• Custom flashings
• Insulating products
• Fasteners



Stramit TH120top hat sections is available from all Stramit branches.
Please contact your local branch for lead times, minimum order quantities and stock length information.