Ensuring a Buildable Masonry Facade: Overcoming Design Challenges and Common Clashes in the Cavity

When you look up in major cities in the UK, you'll often spot mid-rise buildings with brick facades. In fact, approximately 70% of new constructions in the UK opt for masonry as their external facade material. Given its widespread use, it's crucial for design managers to grasp the intricacies of incorporating masonry support in their designs, ensuring both feasibility and compliance with evolving regulations.

A key challenge lies in ensuring that masonry facades can be completed on schedule and within budget, despite common issues such as clashes in the cavity. This has become more important for design managers to get right much earlier on given the impact of the new BSR regulations in the UK.

Several factors have contributed to the increasing complexity of masonry facade designs:

1. Thinner slabs: modern construction techniques often utilise thinner slabs to reduce material costs and improve structural efficiency. However, thinner slabs can limit the available space for installing masonry supports, leading to potential clashes in the cavity.
2. Increased fire performance requirements: With growing awareness and stringent regulations around fire safety, there is a need for enhanced fire performance in building materials. This often results in stricter rules around the barrier penetration, reducing the space available for other elements and increasing the likelihood of clashes.
3. Larger cavities: to meet higher thermal performance standards, cavities have become larger. While this improves the thermal performance of the building, it also creates challenges in supporting the masonry and accommodating all necessary components without conflicts.

To reduce the risk of programme delays and variation costs I have highlighted a checklist of 5 things that should be considered.

1. External facade clashes: key considerations include avoiding interference between brackets and external features (e.g., rainwater pipes, balcony supports), managing intersections between bricks and other facade elements. Furthermore, checking to ensure the positioning of the SFS and any necessary bracket adjustments. Effective early coordination reduces the risk of design errors and unexpected costs.
2. Accurate load calculations: ensuring load paths are correctly analysed can prevent issues related to bracket centres and channel sizes. Using higher capacity materials, such as duplex steel, can offer a solution that balances structural integrity and cost efficiency.
3. Fire barrier integration: ensuring that fire barriers are correctly integrated into the design from the outset can prevent last-minute adjustments that may disrupt the build schedule and budget. Coordination with fire safety specialists is essential to achieve compliance without compromising on space. Some fire barriers now all 100% penetration with masonry support systems. However, this needs to be confirmed against the manufacturers fire test.
4. Addressing corner challenges: corners often pose significant challenges due to concentrated loads and limited substrate for fixing. Pre-emptive design strategies and additional structural support can mitigate these risks.
5. Downstands and upstands: introducing concrete downstands or upstands early in the design process creates more space for façade fixings. This reduces issues with fitting the fire barrier against the slab, rather than higher against the SFS, which can be complex with current testing standards.

Insights from a previous project:

We are presently working on a project in the UK where the initial design indicated that the SFS extended 25mm from the slab, as shown by the detail below.

The original design concept significantly inflated the cost of the masonry support due to the bracket's inability to fully rest on the slab. Consequently, the bracket spacing had to be decreased, and the channel size increased. This complexity was magnified by the plan to support every two levels, which already large the load requirements.

Removing the notch and placing the SFS inline with the bottom of the slab resulted in a 30% cost reduction. This highlights that even a small change in the design concept can have a large impact on costs. It is therefore crucial that these design details are captured early on.