How do I achieve solid bed fixing?

Under BS 5385, solid bed fixing must be achieved for: all floor tiling; wall tiling with tiles greater than 0.1m²(316mm x 316mm); and all tiling in all wet, external or swimming pool locations. To ensure you’re achieving solid bed fixing on floor tiles, use a semi-pourable or pourable tile adhesive such as ARDEX X 325 PTB,ARDEX MICROTEC X 78orARDEX MICROTEC X 7001. To ensure you’re achieving solid bed fixing on walls, or when using a slump-free adhesive on floors, back buttering is usually required.