Try some of the smaller businesses our small sand and soil place is cheaper than the big B especially with the sleepers, you might save a few bob to offset the H beams may get some better quality too.Actually going to use 2400 x 200 x 50 sleepers - I need about 11 joiners / end pieces all up - Could use these but designed for blocks or the actual wall inserts
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Should use these but should not do a 2.4m run on them so would have to got to 1.8 sleeper at longest - The advantage to these is I might get away with just hammering them in over digging holes - Would need 1 x corner and 2 x end pieces so if you worked on 11 x 70
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I used some of them on the garden and they worked fine, grabbed some sleepers from the local joint so grabbed some joiners there similar prices but heavier gauge and a touch longer worked well.
I still used rapid set for each one as well, don’t want any movement even with one sleeper I don’t want to redo it later.