Wall ties should be incorporated within 300mm above and below the support.
It is important to select the correct support system to ensure that building tolerances can be accommodated. Ancon brackets have a slot at the back to provide vertical adjustment. Longitudinal adjustment is provided by an Ancon cast-in channel in concrete structures, or horizontally slotted holes in steel framed structures.
The joint will often incorporate a compressible filler and should be of sufficient size to allow for expansion of the masonry below and any shrinkage or deflection of the structural frame.
The underside of the support system should be positioned around 2mm above the joint to allow for the support leg to settle when supporting the brickwork above.
For these usages, the deflections limits of table 18.104.22.168 have been found to provide additional stiffness.
Typically we are asked to accommodate 15, 20 or 25mm deflection (sometimes more), and realistically when might we expect a concrete slab of perhaps 250mm thick to move that far?The question often arises as to whether it is really required at all; I know of numerous cases of clients asking the drywall contractor whether they need to be used, and if so how big a deflection needs to be accommodated.The answer to whether or not they are needed lies with the structural engineer.The principle of the deflection head is simple: during normal use, all buildings move around, and part of this movement is the deflection of floor elements as they literally bend under the load.Any partition built underneath that floor will have load imposed upon it by the structure above, causing the wall itself to bend, potentially cracking finishes and causing other problems.
The clear joint below should be at least 10mm where there is a single storey height of brickwork below the support system.