Extra heavy duty Thermally Broken Lintels
Extra heavy duty steel lintels, like their heavy duty counterparts in the Catnic Thermally Broken Lintel (TBL) range, provide support where concrete floor loads or attic truss roof loads act on masonry cavity walls. The range of applications is generally the same, but extra heavy duty TBLs achieve the greater safe working loads (SWL) over larger opening spans.
Catnic TBLs are designed to give equivalent load-bearing performance to ‘conventional’ steel lintels for masonry cavity walls, while delivering improved thermal efficiency and lower psi values. Nevertheless, structural openings should always be assessed on an individual basis and loadings calculated accordingly in case heavy duty lintels or extra heavy duty lintels are required instead.
To aid lintel specification, manufacturers produce safe working load (SWL) tables, giving the maximum loads for given lintel lengths.
Safe working load tables for extra heavy duty TBLs
| TX90/100 | |||
|---|---|---|---|
| 90-105 mm Cavity. 100-115 mm inner leaf. | |||
| Standard lengths (mm) | SWL 1:1/19:1 (kN) | Weight (kg/m) | Nominal height (mm) |
| 900 - 2100 | 60 | 16.7 | 229 |
| 2250 - 2700 | 60 | 21.6 | 229 |
| 2850 - 3000 | 55 | 21.6 | 229 |
| 3300 - 3600 | 50 | 21.6 | 229 |
| 3900 - 4800 | 32 | 21.6 | 229 |
| TX110/100 | |||
|---|---|---|---|
| 110-125 mm Cavity. 100-115 mm inner leaf. | |||
| Standard lengths (mm) | SWL 1:1/19:1 (kN) | Weight (kg/m) | Nominal height (mm) |
| 900 - 2100 | 60 | 16.9 | 229 |
| 2250 - 2700 | 60 | 21.7 | 229 |
| 2850 - 3000 | 55 | 21.7 | 229 |
| 3300 - 3600 | 50 | 21.7 | 229 |
| 3900 - 4800 | 32 | 21.7 | 229 |
| TX130/100 | |||
|---|---|---|---|
| 130-145 mm Cavity. 100-115 mm inner leaf. | |||
| Standard lengths (mm) | SWL 1:1/19:1 (kN) | Weight (kg/m) | Nominal height (mm) |
| 900 - 2100 | 60 | 17.0 | 229 |
| 2250 - 2700 | 60 | 21.9 | 229 |
| 2850 - 3000 | 55 | 21.9 | 229 |
| 3300 - 3600 | 50 | 21.9 | 229 |
| 3900 - 4800 | 32 | 21.9 | 229 |
| TX150/100 | |||
|---|---|---|---|
| 150-165 mm Cavity. 100-115 mm inner leaf. | |||
| Standard lengths (mm) | SWL 1:1/19:1 (kN) | Weight (kg/m) | Nominal height (mm) |
| 900 - 2100 | 60 | 17.1 | 229 |
| 2250 - 2700 | 60 | 22.0 | 229 |
| 2850 - 3000 | 55 | 22.0 | 229 |
| 3300 - 3600 | 50 | 22.0 | 229 |
| 3900 - 4800 | 32 | 22.0 | 229 |
What is the load ratio shown in the extra heavy duty SWL tables?
The loads imposed on masonry cavity walls are, generally, distributed unequally between the inner leaf and the outer leaf. As a result, they are referred to as ‘asymmetric loads’ and steel lintels for masonry cavity walls must be capable of bearing them.
The load imposed on the inner masonry skin is usually higher, and the difference is expressed as a ratio of the inner leaf load to outer leaf load. As the tables above show, a standard duty Catnic TBL is capable of bearing inner to outer load ratio between 1:1 and 19:1.
The 19:1 load ratio occurs in eaves applications. The 3:1 ratio reflects timber floor loads, and concrete floor loads generate the 5:1 load ratio. Where the Thermally Broken Lintel is supporting only masonry, the load ratio is simply 1:1.
Catnic’s technical support page provides more information and advice about specifying Catnic TBLs.