Exposure of 3 pilaster bases shows corroded rebar due to moisture intrusion

THIS POST documents the condition of the newly exposed pilaster bases, on the south wall of the sanctuary. I provisionally interpret the findings as evidence of damage due to longstanding water intrusion — but not threatening the stability of the building itself. The structural engineer seems to agree with this assessment, but I believe he is withholding final judgment until he makes an on-site visit.

Here is a map of the south wall, showing which 3 of the 7 pilasters are involved. The labels “1st,” “2nd,” and “3rd” refer to the order in which the structural engineer and I have attended to them, rather than their position on the wall.

(As usual, click/tap on an image to enlarge it.)

Below the jump, I recap the uncovering process, and then show a set of photos for each base.…

Exposure process

A hammer and chisel removed much of the stucco that covered these pilaster bases, because it had already separated from the concrete behind it, due to moisture damage. Some of the stucco, however, still tightly adhered to the concrete, particularly on the stem wall to the left of the 1st base. To remove those sections, hand tools did not suffice. So the handyman and I went to Home Depot and rented a power tool: a 1.5", 20-pound rotary hammer with a chisel bit (4 hrs for about $60). We ran an extension cord from the inside of the sanctuary through the closest window opening.

Pilaster base #1

This base was exposed in December, as documented HERE.

The structural engineer then wanted to ensure that the adjacent stem wall had not cracked due to the weight borne by the post inside the pilaster. So we were asked to remove the stucco 2 ft on each side of the post’s center line. 

The right side is shown first, because it was the easiest to expose.

The only cracks are a horizontal hairline, about 6 inches below the sill plate, and a vertical hairline about 6 inches away from the plaster base. Here is a close-up.

To my untrained eye, those cracks are not signs of strain from the post’s weight.

And here is the left side. I see no cracks on the stem wall itself…

Pilaster base #2

This base was partially exposed in January, and more fully today. In the photo sequence, the viewing position proceeds from right to left.

Termite infestation in the post

There is obvious termite activity at the exposed base of the post inside this second pilaster. I rubbed my fingernail against the wood, finding it brittle; and as I did so, termite frass came pouring out. It troubles me to see this in a weight-bearing member! 😳

The structural engineer recommends that we open up the inside wall at this post and take a closer look at the termite damage (and apply termiticide). That sounds like the prudent thing to do. 🤔

Pilaster base #3

This base was first exposed today. This was helpful in that it reveals how the rebar curves inward, toward the center of the post: this accounts for the curved cracking pattern in the other two bases.

It appears to me that the rebar was installed in that curved configuration. Perhaps the installer thought that this would provide a stronger buttress for the post in the center. 

Again, the photos proceed from right to left.