Plate compactor risk to footings?
BrunoF
| Posted in General Questions on
I need to build up my garage slab base with 57 gravel in my builder says that he does not compact it and has never had an issue.
It seems that it would be beneficial to compact the gravel, but I’m concerned about banging around with a plate compactor on top of my footings and next to my CMU foundation block. Is there a risk to my footings by using a plate compactor on top of the gravel which is on top of the footing projection in my garage?
thx!
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Replies
BrunoF,
The fill under every slab gets compacted (or should). You are fine.
If you tried hard enough you might be able to nudge a long footing a little by pushing the compactor against it for a long time. But the usual approach is to move around and I've never seen or heard of a problem. Standard practice is to compact/consolidate the crushed stone (or sand), as Malcolm wrote.
Crusher run (graded aggregate base or aggregate base course), which has many fines, will compact.
Sand, which is only fines, will compact.
#57 stone, which should be clean stones that are all about 3/4" in size, does not compact much. It is often considered "self compacting." If you try to compact it, you really just reorient the stones and that sometime provides some "compaction" in the form of moving them around to take less space. But if you don't compact, the stones are unlikely to reorient themselves over time - this material simply does not settle like sand or crusher run. You can probably achieve the same reorientation by getting it proof rolled with a concrete truck or any dump truck (for dirt or dumpsters, full or empty)
User ...022,
" If you try to compact it, you really just reorient the stones and that sometime provides some "compaction" in the form of moving them around to take less space. But if you don't compact, the stones are unlikely to reorient themselves over time"
That's really useful advice. I knew, and had experienced, the first part - that you can consolidate almost any shape of rock - but hadn't thought through that it really didn't matter.
"#57 stone, which should be clean stones that are all about 3/4" in size, does not compact much. It is often considered "self compacting." If you try to compact it, you really just reorient the stones and that sometime provides some "compaction" in the form of moving them around to take less space. But if you don't compact, the stones are unlikely to reorient themselves over time - this material simply does not settle like sand or crusher run"
I don't really disagree, especially under something like a frost protected slab.
It's also obvious it does compact/ consolidate when you hit it with a big enough packer.
I also wonder if the type of stone would have any effect? Limestone being much softer than say granite....
Is anyone aware of any research comparing say driveways on similar prepped subgrade with the same depth packed vs unpacked open graded stone in areas with frost?
BrunoF,
The one thing you can damage is ABS or PVC drain lines. Go easy on them if they are close to the surface.
Thx folks! The only drain I have is a 6”, solid core SCH40 pipe that is part of the foundation drain which runs across the front of the overhead doors. It is pretty deep though.