Crack in bricks in retaining wall

[weswebb]

25 foot long retaining wall, 3 feet high. There is a gap between two bricks which is one inch wide and 7 inches deep. Layer of bricks sits on concrete blocks. All other joints look good. Maybe this was caused by settling or movement. Should I just fill in with mortar mix? Pic is looking down at gap. Sidewalk on left (3 feet below) and soil is on right.

 

[oldognewtrick]

If it were mine, I'd use a flexible masonry caulk and fill the void after cleaning out all the old mortar.

 

[Guzzle]

Almost certainly there is another gap somewhere, maybe subsurface, that hints at the cause.
Possible causes might be soil freezing/thawing/heaving, soil expanding & contracting, a one time high force on the wall toward the right, other. . .?

It could be the row was under tensile force & one joint finally gave, but where would this horizontal force come from? Shrinking bricks?

I'd check the gap size vs. the seasons for more clues. How old is this wall?

Maybe open up other joints & distribute the gap over several joints to make it less obvious & caulk with pliable material as mentioned above. You're making your own expansion joints but I don't know that retaining wall designs call for this.

This is baffling.

 

[weswebb]

Thanks for the replies. Sounds like flexible material might be better than mortar. I don't really care about the look, just hoping no major structural problem.

 

[Guzzle]

Almost certainly this indicates a major structural problem due to a one-time event or some continuing process.

 

[weswebb]

Almost certainly this indicates a major structural problem due to a one-time event or some continuing process.

Manufacturer of one brand of flexible masonry caulk replied (via Lowes website) it should not be used for gap of more than one half inch. So maybe I should use mortar (just to keep rain out) and further widening of gap or other gaps will indicate deeper problem needing professional attention. Is it critical to remove the old mortar which as you can see in picture is still intact but displaced. It is firmly in there so would require chisel to remove but i don't want to do any damage. Or could I just fill the whole opening with mortar; gravity will pull it down into the gap. Or other ideas?

 

[Guzzle]

What you're up against is at least 40,000 lbs separating a brick from its mortar bond. If this structural issue is progressing you need to find the root cause.
But it may just be opening & closing over time so a cosmetic repair may do it.

There was an OP in Colorado whose floor sunk because of the silt & clay soil expanding & contracting; same problem but his problem might have been unsolvable b/c the whole neighborhood did that.

 

[weswebb]

What you're up against is at least 40,000 lbs separating a brick from its mortar bond. If this structural issue is progressing you need to find the root cause.
But it may just be opening & closing over time so a cosmetic repair may do it.

There was an OP in Colorado whose floor sunk because of the silt & clay soil expanding & contracting; same problem but his problem might have been unsolvable b/c the whole neighborhood did that.

I probed the crack with a wire and it goes deeper than I thought, indicating cement blocks below separating. I am trying to find pro as i decided not to mess with it. No freezing temps where I live but there are earthquakes and water made worse by ill placed sprinklers which I have capped off. Also fence 18 inches behind it although post is not near area of separation. Having trouble finding a pro; only hope I can find someone competent.

 

[Guzzle]

If 1/2 are competent & 1/2 are honest then your chance is 1/4 to find someone who is both.
Actually, I think 1/3 are not crooks & 1/3 are competent, so 1/9.

Get several written bids.

 

[tomtheelder2020]

The capping layer of bricks was likely laid level. Run a level string line along the length of the wall, just above the brick. Is the crack at a high spot? That would indicate differential settlement or, less likely, something like a root pushing up from below. If you don't know the cause, your repair may turn out to be cosmetic and the problem could recur.