FMS Masonry Support

There are a number of different types of concrete frame, however the fixing types are largely universal.

With a concrete frame, the masonry support system can be fixed in place either using the FIRMA Cast-In Channel systems, or post-fixed with site drilled fixings such as expansion bolts. This is specified in line with site specific structural requirements.

For steel frames, there are two main options available. Where it is possible to access both sides of a fixing surface, a Hex Screw (or Set Screw) is generally suitable. Where access is only possible from one side, for example with a hollow section beam, a Blind Bolt is usually suitable.

With masonry panel design, allowances must be made for differential movement between materials. This is particularly critical when combining clay brickwork with concrete blockwork and a concrete frame, as these elements expand and contract at different rates.

• For buildings up to four storeys or 12m in height (whichever is less), the outer leaf may typically remain uninterrupted for its full height.
• For taller structures, the outer leaf should be supported at vertical intervals not exceeding 9m or three storeys (whichever is less), in line with the guidance of BS 5628: Part 1, which, despite its withdrawal, is still recognised as best practice.

To accommodate vertical movement (typically ~1mm per metre), movement joints are generally introduced at every storey or every second storey. These joints are also commonly incorporated in buildings of less than four storeys to ensure long-term stability and façade performance.

Masonry Support systems should be installed directly above horizontal movement joints. These joints provide the necessary allowance for brickwork expansion below the support and for any shrinkage or deflection of the structural frame.

There are some points to consider:

• Joints typically contain a compressible filler sized to suit expected movement.
• The support angle should be set 1.5–2.5mm above the filler to avoid deflection into the joint under load.
• On completion, the open joint at the panel face should be sealed with mastic.
• Thin support angles can be hidden within a standard mortar joint; thicker angles may require a rebate or pistol cut in the brick. Pistol bricks should be bedded on mortar not exceeding 5mm.
• To prevent excessive deflection, build no more than 1.5m of masonry on a support angle per day.
• The clear joint beneath the support should be ≥10mm for single-storey brickwork, or sized to suit anticipated movement for two or more storeys.
• Expansion of brickwork should be considered in the movement joint design to allow for 1mm of expansion per metre height of brickwork.
• This should be added to the potential deflection of the masonry support and the compressible filler to compress to 50% of its original thickness.
• Damp-proofing is typically placed at the support level, with wall ties installed within 300mm above and below.

Structural and masonry tolerances must be considered before finalising support design.

Standard systems offer limited tolerance, so adjustments must be built in prior to manufacture.

• Cavity width: Adjustments can be made with full-height stainless steel shims between the structure and FMS bracket. Maximum shim thickness per project is 12mm. Shims may also be placed between bracket and frame up to 16mm or the fixing bolt’s outside diameter (whichever is less). Greater shimming requires approval from Firma’s technical team.
• Vertical adjustment: The bracket slot allows ±15mm vertical tolerance. The slot depth suits standard FIRMA fixings (Ø12mm). Smaller bolts must not be positioned at the slot’s extremities.
• Fixings: Only supplied fixings should be used. Serrated washers must be installed horizontally, with nuts tightened to the specified torque.
• Lateral adjustment: Systems are designed with a 10mm nominal gap between angle lengths. Continuous lateral adjustment can be achieved by fixing to cast-in channels.

FIRMA Masonry Support Systems are manufactured from grade 1.4301 (304) stainless steel, suitable for most building applications. In particularly aggressive or visible environments, grade 1.4401 (316) stainless steel can be specified.

Bi-metallic corrosion may occur where stainless steel components are in contact with carbon steel in damp conditions. While the stainless steel is unaffected, the carbon steel may experience slightly accelerated corrosion.

To prevent this, the stainless steel support system should be isolated from the structural steel. This can be achieved using:

• Insulating or isolating washers, or
• Moisture exclusion at the connection detail.

FIRMA provides isolation solutions where required to maintain the durability of both stainless steel and adjacent structural steel components.

FIRMA Masonry Support systems carry a UKCA certificate of conformity and are designed to the requirements of EN1993, Eurocode 3 and manufactured to the standard EN1090-1:2009+A1:2011 execution class 2. FIRMA Limited are also certified to ISO9001 and ISO14001 and internal monitoring is done through the FIRMA QC Portal and RopeWeaver prioritisation software.