I am installing bevelled retaining wall blocks, 17 inched long, 6 inches high and 12 inches deep.

Trying ti understand material to order.. can i use the same base rock that I use for the back fill? What type of rock shoukd be used. I have a lot of river rock from french drain i wanted to back fill wall with.

I am also looking to put rock tamped as a 4 inch base for pool with foam pad (24ft by 52inches intex) Was hoping to use all the same rock, to get one order... or at least same rock to use for pool base, but not sure of the types to use for each.

This is a dug out on slope for pool, and retaining wall is going around inside wall for pool.


  • It's hard to visualize what you're trying to do. Could you add a sketch?
    – fixer1234
    May 7, 2017 at 17:37
  • Sure i can draw one up, for now i sm attaching some pictures. Retaining eall and pool will be inside dug out area
    – eaglei22
    May 7, 2017 at 17:59

1 Answer 1


The rock under the "stack block" wall is different than the rock behind it.

The rock under the wall needs to be crushed rock and compacted. In my area around here, we'd use 1 1/2" minus (with fines) or just 3/4" minus. Compaction is important. Tamp it down or drive on it. (Usually the stack block manufacturers recommend a base course of 8" - 12" deep and a width equal to or greater than the blocks. Read their instructions.)

The rock behind the wall needs to have lots of voids so water can flow through it. So, we use river rock (or some call drainrock). It's smooth (from tumbling around in a river for a few centuries) and does NOT compact.

  • I know nothing about pool rock, but I suspect you want to compact the rock under your pool.
    – Lee Sam
    May 7, 2017 at 21:26
  • Thanks lee. Does the river rock need to be tamped at all when adding? Also, what rock would you recommend under pool?
    – eaglei22
    May 7, 2017 at 21:28
  • 1
    River rock can't be compacted. It's like marbles. Just make sure it's contained (in a pit or depression). Otherwise it will ooze out. The pool is going to weigh a ton...it needs to sit flat and level and I'd use crushed rock, compacted. Make sure you compact in 6" lifts. That is to say, if you put 12" under your pool, install about 6"" and then compact it. Then do the rest and compact it.
    – Lee Sam
    May 8, 2017 at 2:41
  • What is the minimum base height I can use for pool base? Is 4 inches not enough? The dirt is clay, and almost level, just slightly off from dig. And I can use the type of rock for pool base that I am using for retaining wall base correct? I was thinking of the stuff used under asphault driveways, the crushed rock that is gritty and usually tan in color.
    – eaglei22
    May 8, 2017 at 2:45
  • 1
    @eaglei22 The fill must be "contained". That is to say, the fill can't allow water to flow through the fill or it will wash away. Usually, the fill is placed in a hole that has been dug down below finish grade.
    – Lee Sam
    May 10, 2017 at 14:05

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