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I recently had contractor build several retaining walls ranging from 12" to 20" high.

They dug a shallow one inch trench then filled it with mortar, upon which they laid and leveled first row of blocks.

No drainage behind the walls, just soil.

Blocks were all glued, so the walls are basically one solid piece.

Is this ok? Will the walls hold up over time?

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    A little more info would help. what kind of Blocks ? Mortar as a foundation, are you sure it was mortar, ? One inch trench ? Glued how. Please add as much detail and info as you can so you can get an informed answer. – Alaska Man Jun 5 at 16:16
  • Do you live in a place where you get freeze/thaw cycles? If so, and if there is no drainage, the wall will tilt bit by bit with each cycle. Also the glue will not be strong enough to resist those forces and will probably break. – jwh20 Jun 5 at 16:48
  • not ok ... at least the first row of blocks should be almost completely in ground – jsotola Jun 5 at 19:25
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I have built walls just like that small ones with no weep holes larger over 24” I start adding weep holes , the mortar base is a plus some only use gravel if anything at all. Some of the terrace walls at my cousins house we did 25 years ago 8 each 2’ walls all 100’ long almost identical with chicken wire in the bottom with the mortar , she mows it every week with a lawn tractor it has held up quite well.

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I doubt your contractor installed “mortar” 1” deep on the ground. They probably used a fine mix of sand and pebbles.

If the wall doesn’t extend below the frost line, then a dry set rock wall is probably best.

Any mortar between the rocks/stones will crack because of movement. Movement can be from settlement (because of inadequate base) or frost. When you see cracked mortar, it looks like the wall is failing. That’s why a “glued” wall (as you call it) is better than mortar.

It’s better to install a dry stacked wall like this:

https://www.finegardening.com/article/build-a-dry-stacked-stone-retaining-wall

I like a few cavities on the face where plants can grow, bloom, etc. and soften the rock face. However, I’d install a filter fabric or gravel curtain behind the wall to slow the movement of soil through the wall.

Note: A 24” high wall is not high enough to apply a significant enough load to cause it to tip (fail). In addition, the wall has sufficient holes and cracks to allow water to deep out and relieve any horizontal pressure.

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