Unusual Corner Capstone To Low Ret Wall

henhen11417

I built a low gravity retaining wall (five 4" courses of 12x8x4inch HD block), with an acute corner of 75 degrees (10.5 feet long, then 3.0 feet). nice trench, nice base, nicely level. All good.
I expected matching 2" flat capstones (also from HD). EXCEPT, homeowner has a small rock /boulder (gneiss or schist, kinda squarish 14 x 15 x 3-5 inch thick) from old quarry where he grew up (and where he did certain things??). This ROCK LOOKS GREAT as the corner capstone. It fits the 75 degree corner! Very nice design idea this unmatched corner capstone.
Problem: the special rock is close but not solidly level on the blocks (it rocks a little), so, do I
(a) use a "small puddle" of construction adhesive,
(b) use construction adhesive with shim pieces of broken block,
(c) use a small puddle of mortar, or
(d) make small attacks at the rock for leveling with a pitching chisel and hope I get it much closer to level.
Or is the better answer a little (d) plus less of (a), less (b) or less (c)?

The risk of breaking this irreplaceable rock, is scary. Cuts for leveling go with/parallel to the "grain" or foliations of this rock.

Besides getting the rock solidly set, I sure would like to chip off a 2 inch x 4 inch triangular protrusion along one outer edge. These cuts perpendicular to grain. Is this pushing my luck, or just proceed with smaller hammer and chip chip chip away.

Suggestions and help please.
(11 years ago I started cuttin grass, and now look where we are!).

Thanks. Henry

Tscarborough

I would not use construction adhesive. It doesn't have enough body and it is a bitch to remove. Use plain old mortar and shim if you have to. Rather than puonding on the rock, can you cut it, then gently beat it to match the finish?

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CJKarl

What he said. If the bump is on the bottom, saw it off. Then mortar it in.

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