MAKING TEST CUTS into the south wall will be an adventure in discovery. (Best case: we find that the wall’s structural integrity is in good shape. Worst case: we find that there’s significant structural damage due to water damage, dry rot, termites; and maybe there’s mold, as well.) The point of this exercise is to be able to develop reliable cost estimates for structural repair and waterproofing later this year.
There are many issues to consider in advance, in order to ensure that we get useful and reliable answers to our questions. To me, the pending discovery stage feels a bit like sending an unmanned mission to Mars—we’ve got to get it right long before the probe lands on the unexplored surface of interest.
 |
| An American probe sent to Mars |
Below the jump, this post discusses the various considerations.…
Executive Summary
In order to get a reliable cost estimate for performing test cuts that will reveal the conditions inside the south wall, the following considerations need to be attended to:
- Providing enough room to work on the wall (DONE)
- Proving that asbestos-abatement measures are not needed (DONE)
- Deciding whether to open from the inside or from the outside (DONE)
- Planning for the prospect of mold inside the wall (DONE)
- Specifying the size, number, and placement of the openings (DONE)
- Rebar corrosion? (DONE)
- Specifying the nature of temporary wall closure (DONE)
- Providing a toilet for workers (DONE)
- Coordinating with restoration of the windows
- Pulling a building permit
Interspersed below are a number of lingering questions that I would like to see addressed by the president, the executive director, the structural engineer, the contractor, and a mold inspector.
Issues to be Investigated
Our starting point is the findings of the Historic Structure Report (2003, p. IE-105):
There are multiple issues in regards to the water penetrating the building. The wood sills [i.e., bottom of the frame wall] along the top of the concrete foundation walls were observed to be deteriorated by fungal rot and termite infestation at some locations. The [termite] frass and mud tunnels were found in the space over the kitchen. The south concrete wall was wet.… Due to the condition of the exposed wood mud sills, it is expected that the wood sill studs and possibly some of the joists have been damaged.
In addition, as documented in other blog posts, there are other reasons for concern along the south wall: a stair-step crack that runs from floor to ceiling has since appeared on the interior; evidence of prior repair of long cracks in the stucco suggests systemic problems with drainage in the wall; and large cracks can be seen outside at the base of a steel pillar, where stucco has flaked off. All of these phenomena need to be better understood before waterproofing work can be undertaken.
Room Enough to Work
So far, the most visible step taken has been to remove a token 4 seats from near the wall.
 |
| In Rows 1 and 2, the two seats closest to the wall have been temporarily moved. (As usual, click/tap on a photo to enlarge it.) |
This was done soon after Yom Kippur as a proof of concept. We now know what effort, tools, and logistics are needed to clear enough space for workers to deal with the wall, halfway back—that is, to the 20th row—which is how far the water intrusion has extended. But that is a later step. In the meantime, to prepare for the test cuts, Tom Sorter and I have removed the equivalent seats in 4 more rows.
Asbestos Testing Gives a Green Light
Both the interior and exterior wall components have now been tested. Happily, no asbestos was found!Open Mainly from the Inside
Given that it’s easier and cheaper to patch interior plaster/drywall than to repair stucco, and less risk of water intrusion from a rainstorm, we will make the test cuts on the inside of the wall.
Perhaps one reason to hesitate in making the cuts indoors is the possibility of mold within the wall. However, both the contractor and a mold inspector seem unconcerned about the prospect of mold. The contractor said, “If there was a serious mold problem, you would probably already smell it.”
Although there is the high likelihood that one or more old coats of paint contains lead, the duration of time that the room is occupied is too occasional to be of concern to service attendees. However, to protect our staff, I have asked that dust shrouds and HEPA vacuuming be used on the cutting equipment during the removal of plaster.
Size, Number, and Placement of Openings
This is the desired configuration, as explained below:
SIZE: Both the structural engineer and the contractor are thinking in terms of 2’ x 2’ openings “as a starting point,” in order to be able to see what’s going on well enough.
NUMBER and PLACEMENT: Given the various phenomena of interest, I have asked for the following wall cuts:
- Upward from the sill: 3 holes = 1 at the base of the stair-step crack (between the 4th and 5th rows of seats), 1 where termites were visible in the wall in 2021 (under the center of the easternmost star, at approx. the 4th row of seats), and 1 under the left edge of the stair-step crack.
- At a cross-brace: 1 hole, halfway up between the foundation and the window sill, along the stair-step crack.
- At prior exterior patching of easternmost window corner: 1 hole, while avoiding cutting into the horizontal belt (plaster frieze band). (NOTE: Although termiticide foam was recently injected just below that band, as part of a perimeter treatment, it poses no danger to the workers to open up the wall there, according to the termite inspector. He adds that it has since been absorbed into the nearby wood and is no longer visible.)
Rebar corrosion?
Regarding the serious cracks at the base of the exterior post,
the structural engineers are concerned about the prospect of rust in the rebar within the concrete. As they explain,
structural safety gets triggered when the rebars start to corrode. Because of the cracks and water intrusion that have been observed, it is a good thing to check if any rebar has started to corrode.
I just now (10/17) realized that this cracked base on the outside is located exactly where the stair-step crack meets the foundation wall on the inside. That correspondence might not be a coincidence! If the base of the steel post has become unstable, could that pull a section of wall along with it? Might that account for the stair-step crack? 😮 The consulting engineer responds,
There are many reasons why the cracks at the post pilasters may have happened, and these may correlate or not to the presence of the step-shaped crack in the wall. At this point it is still early to say, but because the wall cracks are on one side of the wall, and the spalling on the opposite side, it leads us towards the impression these are independent damages.
The structural engineer has reassured me that if the rebar is corroding, “there are many different ways of repairing it, depending on what really is affected, where and its configuration.” Our instructions from the structural engineers (11/4 and 11/8) are:
On the exterior sides of the cracked concrete stem wall/pilaster under the post, chip out the concrete in two places, going in about 3” as needed to expose a 6” length of rebar in each place. Observe whether or not there is rebar corrosion. • Do not cut into the rebars. Do not chip out concrete right below the steel column, but rather on the topmost foot of the vertical face of the concrete pier. • After observation, in the event that the rebar is not corroded, clean out the concrete section and repair it with non-shrink grout or equivalent. If the rebar is corroded, cover it temporarily with a water-impermeable material, such as clay caulk.
They note that any demolition of a bigger extent at the pier would require shoring of the post.
Achieving adequate temporary closure
For the interior cuts, temporary closure is a matter of cutting pieces of drywall to fit, and affixing them with removable screws.
Reasonable temporary closure for the concrete base of the steel post is probably rope caulk.
Toilet for workers
The contractor quite reasonably asks: Is there a restroom that my workers can use? For those who are working inside the sanctuary, yes. And those who are working on the exterior will have a fairly easy way to get to our indoors toilets (without disturbing the preschool), now that our office staff has located the missing key to the sanctuary front doors. Hence we do not need to rent a portable toilet for $200. (Anyway, I’m not sure where it would go. Perhaps our neighbor would allow it to sit in their parking lot. If we put it in the alley, chances are that some homeless people would break the padlock in order to get in, according to our contractor’s sad experience.)What about the windows?
As part of the eventual waterproofing effort, the joints between the window frames and the stucco will need to be sealed. (In at least once case, the filler between the window bay and the metal frame is termite damaged.) To avoid messing up those seals, it would be prudent to have the window restoration work done prior to the waterproofing.
Regardless, the test cuts can proceed before the windows are redone. So the condition of the windows is not a reason to hesitate.
No comments:
Post a Comment