Masonry support solves one of the biggest issues with brick facades used in cavity walls. It allows the insertion of horizontal movement joints to counteract the expansion and contraction of the brickwork itself and prevent cracking. Features, such as windows and vaulted and arched openings, are particularly vulnerable to movement, hence masonry support’s crucial function in these areas.
When it comes to accommodating drops or vertical movements in a building, masonry support systems can incorporate various mechanisms to allow for flexibility and absorb the impact. IG Masonry Support’s Welded Masonry Support system, for example, is specifically designed to allow for drops of up to 1m. It is also suitable for larger-than-average building cavities and has been used to support double cavity walls. In these instances, the masonry support has spanned half a metre from the structure to other parts of the brickwork.
Movement matters
Although a secondary steel structure, from a critical safety point of view, masonry support carries the same level of importance as a building’s mainframe. Correctly designed, support systems allow for movement to be created to an architect or engineer’s precise requirements. Several factors determine the size of movement joints. Temperature variation is one such factor, as it causes movement when brickwork expands and contracts. To absorb expansion, NHBC regulations state a movement joint must be no less than 1.3mm per metre of brickwork. Thus, in respect of a 10m wall, a movement joint of 13mm should be allowed for.
Masonry support design and specification
A masonry support system’s design is defined by two main aspects. Firstly, a unit needs to be capable of being tied back to a structure. By any means, a fixing cannot be allowed to fail, but masonry support manufacturers are highly limited by the nature of the structure itself. When presented with a thin slab, manufacturers can only load brackets with a fixing up to a certain point. Therefore, a unit needs to be sourced that will work with the given conditions and not allow for too much of a deflection. In this instance, the material’s thickness will be key.
When specifying a masonry support system, the main – and very obvious – consideration is to ensure a unit fits a building to guarantee its correct installation. Then there’s the challenge of coordinating the masonry support so that it works with other elements within a cavity. Balcony brackets and connectors, for instance, require space when cast into a slab, as they need to be fire protected. This prevents masonry support brackets from being installed within 100mm of the connectors on either side. When this happens, there is a case for negotiation to have them relocated, or it’s a matter of ‘back to the drawing board’, and a manufacturer being requested to devise a unit that overcomes the issue. Involving a manufacturer at the earliest stage of the design process can prevent the need for building elements to be reworked, which often leads to project delays and additional costs.
Evolving to meet legislation compliance
As masonry support systems have evolved in terms of how and where they can be used, it’s allowed architects to set new parameters in brickwork design. Thanks to the innovation of solutions, such as IG Masonry Support’s prefabricated brick slip soffit ‘B.O.S.S’ system, functionality does not have to concede to a designer’s aesthetic aims for the brickwork. This was certainly the outcome at IIona Rose House, a huge mixed-use development in London. The new building’s facade contained rainwater pipes running through the brickwork. It required IG Masonry Support to bespoke a B.O.S.S solution to facilitate the creation of shadow gaps where the recessed brickwork was used to cover pipework. What might have instigated a complex and lengthy process several years ago, has become a relatively simple masonry support design and manufacturing process.
So, how have masonry support systems adapted to legislative changes that introduced the banning of combustible materials from high-rise buildings in the wake of the Grenfell Tower fire? The insulator shim was the only masonry support element to be impacted by the new fire regulations. IG Masonry Support used to provide a plastic shim that was located between the masonry support bracket and the structure, providing a thermal break to avoid instances of cold bridging. Following the new regulations, the plastic shim has been replaced in IG Masonry Support units with one comprising silica composite material. This new element has the same thermal properties as its predecessor, but most importantly, it’s A1-rated fireproof.
Finite analysis
High-performance masonry support products are vital to a safe, well-designed brick building, but confirming their suitability for a project takes good planning and, sometimes, many hours and days of careful assessment. With safety being our highest priority, IG Masonry Support’s technical experts carry out simulations and tests that match the reality of how a support unit will perform to affirm its appropriateness. This involves finite element analysis involving specialist software, with models being calibrated by testing to guarantee a required result. Painstaking it may be, but this rigorous testing procedure pays long-term dividends, ensuring structural support units match the structural safety requirements.
So, although not a headline consideration when it comes to design, an incorrect or underperforming masonry support system could be very bad news for a building’s structural integrity. Our safety and the sustainability of our future built environment depend on their use and continued evolution.
