Jim Klinger, concrete construction specialist The Voice Newsletter September 2022

Question: We are working on a large city public works project that has us placing our first foundation concrete in about a month.  We are inundated with design changes in the form of large "Bulletins" and sketches (aka "SKs") that are returned to us as part of Requests for Information (aka RFIs). In turn, we must transmit all project documents to our subcontractors, which includes detailers for rebar, PT and formwork. Each of those stakeholders must quickly determine if there are any cost or schedule impacts to their scope and, perhaps most important now, if rebar placement drawing submittals are going to be affected. In many cases, the only way we can tell if design drawings have been updated is by checking the dates in the title blocks.  We have advised the GC that we expect all drawing changes to be clouded, and that all changes to our scope be issued with a written narrative describing such changes. Are there any industry standards we can cite that support our expectations?

Answer: The Owner gets maximum time and cost benefit when information flows up and down the food chain in an efficient and professional manner. This includes the design team issuing Bulletins, Addenda, RFIs, sketches and other contract changes with all drawing changes clouded and all changes clearly described in a written narrative. This is true not only during budget and bid time (estimators, take note) but also holds true for all sides during the construction phase as well. For ASCC members, we are aware of two industry references that describe scope revision documents and how they should be prepared by designers and detailers.

According to the Council of American Structural Engineers (CASE) Document 962-F A Guideline Addressing the Bidding and Construction Administration Phases for the Structural Engineer:

"Changes to the construction documents...should be clearly identified with dated revision numbers and "clouding" in the case of drawings.  All changes must be documented in writing and delivered to everyone that has received a copy of the construction documents...including contractors, subcontractors, consultants and Owners.  Prompt issuance and clear description of the changes, communicated to all interested parties, are essential to minimizing their impact on cost and schedule."

On the other hand, concrete contractors and their detailers should be aware that they can be held to the same standard regarding completeness of their rebar placing drawings, formwork shop drawings and other documents prepared for submittal to, and review by the design team. 

According to Joint ACI-CRSI (American Concrete Institute - Concrete Reinforcing Steel Institute) document ACI 315R-18, Guide to Presenting Reinforcing Steel Design Details, section 3.3- "General Cautions," that applies to rebar and PT detailers:

"All revisions to drawings should be clouded. Be as specific as possible when putting a cloud on a drawing.  Place a cloud around each revision, rather than a large cloud around several revisions.  Remove all previous clouds from a drawing before initiating a new revision.  Clearly annotate the revision on the revision list at the side of the drawing".

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Question:  We placed a CIP (cast-in-place) concrete slab two months ago. Part of our scope included placing anchor bolts for some follow-on metal building framing.  Supply, layout and pre-pour anchor bolt location survey checks were performed by others.  Today, we received a substantial backcharge from the GC, stating that the metal building erector had to provide shims to make his framing work. We acknowledge that our concrete finishing work was not perfect, but the slab passed the F-number test performed by the Owner, and there is no way any of our finished concrete top of slab elevation was outside of the ACI 117-10 tolerance envelope of plus or minus 3/4 inch in section 4.4.1.  How should we respond to this backcharge?

Answer:  For structural steel columns and baseplates per se, steel shim packs are routinely used by steel erectors to level column base plates.  This allows steel column erection loads to get transferred to the concrete foundation without loading the anchor rods. Your case is slightly different e.g. a metal building on an elevated concrete slab, not a steel column bearing on a concrete footing.  So does that make a difference and allow one to transmute cheap steel shims into gold?

Not so, according to the Metal Building Manufacturer's Association.  As it turns out, the issue of shims is addressed in straightforward manner in the Metal Building Systems Manual, section 6.10, titled "Correction of Errors and Repairs" as follows:

"The correction of minor misfits by the use of drift pins to draw the components into line, shimming, moderate amounts of reaming, chipping and cutting, and the replacement of minor shortages of material are a normal part of erection and are not subject to claim."

(N.B.  The interface between a steel structure and whatever concrete it sits on is often a murky no-man's land.  Example: grout and grouting under column base plates is a scope item that isn't likely to be found addressed in either steel or concrete design manuals. For ASCC members who have grouting of steel column base plates in your scope, make sure you understand the timing of the grout placement relative to the erection schedule.  This is a design item that should be part of an Owner-approved erection stability plan provided to the concrete contractor.)

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ASCC Webinars:  Thanks to Dr. Ken Hover for presenting the latest ASCC webinar titled "When Does Rebar Corrode in Concrete, and Why?" on Sept. 14.  Previous webinars presented by Dr. Hover include "How Well Do We Know In-Place Concrete Strength" and "Shoring and Re-shoring." More than one hundred past ASCC webinars are archived on our website.  General topics we have covered include Concrete Construction, Decorative Concrete, Polished Concrete, Business Management, Paving and Parking Lots, and Safety.