Structure: Approved Document A

A1/2 THICKNESS OF WALLS IN CERTAIN SMALL BUILDINGS Table 5 C avity wall ties Nominal cavity width mm Tie length mm BS EN 845-1 tie (Note 1) (Note 2) 50 to 75 200 Type 1, 2, 3 or 4 to BSI PD 6697:2010 and selected on the basis of the design loading and design cavity width. 76 to 100 225 101 to 125 250 126 to 150 275 151 to 175 300 176 to 300 (See Note 3) Notes: 1. Where face insulated blocks are used the cavity width should be measured from the face of the masonry unit. 2. The embedment depth of the tie should not be less than 50mm in both leaves. 3. For cavities wider than 175mm calculate the length as the nominal cavity width plus 125mm and select the nearest stock length. For wall ties requiring embedment depths in excess of 50mm, increase the calculated tie length accordingly. Table 6 D eclared compressive strength of masonry units complying with BS EN 771-1 to -5 (N/mm2) Masonry unit Clay masonry units to Calcium silicate masonry Aggregate Autoclaved Manufactured BS EN 771-1 units to BS EN 771-2 concrete aerated conc. stone masonry masonry masonry units to units to units to BS EN 771-3 BS EN 771-4 BS EN 771-5 Condition A (See Diagram 9) Brick Group 1 Group 2 Group 1 Group 2 6.0 – 6.0 9.0 6.0 9.0 Block See Table 7 See Table 7 See Table 7 See Table 7 2.9* 2.9 Condition B (See Diagram 9) Brick Group 1 Group 2 Group 1 Group 2 9.0 – 9.0 13.0 9.0 13.0 Block See Table 7 See Table 7 See Table 7 See Table 7 7.3* 7.3 Condition C (See Diagram 9) Brick Group 1 Group 2 Group 1 Group 2 18.0 – 18.0 25.0 18.0 25.0 Block See Table 7 See Table 7 See Table 7 See Table 7 7.3* 7.3 Approved Document A Structure 23 lliw 5-177 NE SB htiw gniylpmoc tinu ynA C dna B ,A snoitidnoc rof elbatpecca eb O N L I N E V E R S I O N * These values are dry strengths to BS EN 772-1 Notes: 1. This table applies to Group 1 and Group 2 units. 2. For the EN 771 series of standards for masonry units the values of declared compressive strengths (N/mm²) given in Table 6 are mean values. 3. Brick: a masonry unit having work sizes not exceeding 337.5mm in length or 112.5mm in height. 4. Block: a masonry unit exceeding either of the limiting work sizes of a brick and with a minimum height of 190mm. For blocks with smaller heights, excluding cuts or make up units, the strength requirements are as for brick except for solid external walls where the blocks should have a compressive strength at least equal to that shown for block for an inner leaf of a cavity wall in the same position. 5. Group 1 masonry units have not more than 25% formed voids (20% for frogged bricks). Group 2 masonry units have formed voids greater than 25%, but not more than 55%. O N L I N E V E R S I O N