1.hand-tamper and plate compactor Compaction requirements vary

but I’ve hand tamped thousands of SF of subgrade for building footings and they usually test for 90% compaction. Achieving that by hand, with PROPER 6″ LIFTS, proper hydration, and using other methods, and I’ve never failed a compaction test. And in some cases, machines are hard to work with, even dangerous – like when you’re doing hillside work.

2. hand-tamper and plate compactor depends on the job.

If you’re just doing 500 SF, 24″ or less of sub-grade compaction / recompaction under a new house for instance, you can do it by hand no problem. But if you’re doing a couple thou SF, then by-god, get yourself a plate compactor. ALSO, if you’re compacting more than 24″, you should use a plate compactor. The reason is that you really should not hand-compact more than 6″ lifts, and that can take a lot of time. You really cannot hand compact a 12″ lift, but a plate compactor can. Some fools will sometimes try to “jet” soil in a large lift, and come back the following day and compact the top. This method may pass a test, but has a lot of potential for subsidence down the road. Jetting should only be used for compacting 12 – 36″ of backfill material – usually clean sand, and it works great – but not for structural subgrade prep.

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