Support & FAQs
Box lintels are structural elements that have been designed for use in external and internal solid walls as well as in some instances with cavity walls. Catnic offers two kinds of box lintels – a rectangular shape internal solid wall box, and an external solid wall box with a toe.
Read more: What are box lintels?
Internal box lintels are used for supporting loads over internal openings in load-bearing walls. These lintels are designed to support masonry, floor, roof, and point loads. Insulated internal box lintels (an option offered by Catnic) can also be used to support the inner leaf in cavity wall constructions.
External solid wall box lintels are used for 200-215 mm exterior solid walls. These lintels are also designed to support masonry, floor, roof, and point loads.
All box lintels can be used over large spans. Catnic offers them in various lengths, with heavy duty boxes reaching a length of 4.8 meters
Box lintels should be fully bedded on bricklaying mortar. In the case of an external solid box lintel, there should be a drip on the lintel toe facing the outside of the building. The lintel should be levelled along the length and width. Floor and roof loads should not be applied until the masonry cures.
Read more: From start to finish: How to install a Catnic lintel
The size of lintel you need is mainly determined by the structural opening span you have to cover, plus an additional 300 mm. This can vary from project to project, meaning accurate measurements are key to a successful installation.
Read more:Lintel size guide: How to specify lintel dimensions
Calculating the load imposed on lintels depends on a variety of factors, including the wall type in which the lintel is installed, and whether floor or roof loads need to be accounted for in addition to masonry loads.
Lintels are primarily designed to support uniformly distributed loads (UDLs), but on occasion, when point loads occur, they also need to be considered. This guide only provides an overview of how the loads on the lintel are established and should not be used as a substitute for obtaining loading calculations directly from the lintel manufacturer or a qualified structural engineer.
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Video Guides
When selecting a lintel, there are three factors that should be considered to ensure the correct specification: the type of wall construction, the dimensions of the structural opening and the total load on the lintel. In this video, we run you through the lintel selection process.
Once you have chosen the correct lintel for your project, it is crucial that the lintel be installed properly – if it is not, it could lead to serious issues for the building. In this video, we explain the installation considerations for cavity wall lintels.
Catnic’s Thermally Broken Lintel is the only lintel on the market to provide a complete thermal break between the inner and outer leafs. In this video, we outline the key benefits of Thermally Broken Lintels and explain the installation process.
Steel lintels, and specifically Catnic's thermally broken lintels, have a significant role to play in reducing thermal bridging and achieving carbon gains. They represent one of the simplest and most economical ways for building fabric to be designed and constructed to help achieve the carbon gains necessary to meet current and future building regulations.
