Fixing sleepers to pre-existing footings?

[sammisum]

We have eventually started to demolish our current (falling down) retaining wall with an aim to replacing it with a wooden sleeper one with steps cut back into the upper lawn. Having removed most of the wall and finding substantial footings at the base of said wall, we were considering anchoring the new sleepers to this solid base, but the question is "How"?

The new wall is to be 50cm above the patio level, and the footings are approximately 20cm below the level of the patio. The wall is 11metres long with a set of 1m wide steps set in the middle and two raised beds projecting out from the wall down the side of the garden onto the patio (which we intend to keep, but again rebuilt from sleepers). Initially we were planning to use vertical posts behind the horizontal sleepers (10"x5") which to be laid horizontally along their longest edge and tied to it but someone told us they wouldn't move & not to bother with the verticals just to fix to the footings... especially as the previous wall had not moved in all the time its been there

So, what fixings should we use to fix the first course to the footings? Or should we go back to plan A and use the verticals? (which would mean warning my husband that he has a few more weekends ahead of him digging out and concreting in posts!)

 

[sammisum]

So overnight, we've decided to drill holes through the sleeper into the concrete and pin using reinforcing bar approximately 15mm dia.

We were planning on going approx 8" into the concrete with the bar to hold the bottom sleeper in place and stop it shifting. Each sleeper above will be fixed to the one below using Timberlok screws.

Will this be sufficient? We don't really want the wall to move... but it's been a b***ard getting the original wall out and digging through the tonnes of hardcore beneath the patio by hand to make room for the sleepers to lie on their widest side! And at this point we don't want to remove the footings too (we'll probably still be at it at Christmas!).