Installing Steel to Support a Chimney Once Its Base is Removed

The existing basement was only partially finished because of an obstacle blocked from view by this partition.

The obstacle to creating a new, larger media room and custom wine cellar was the massive base of a brick chimney. The chimney base needed to be removed, and our job was to support the upper portion of the chimney and flues--which were to remain--with steel beams.

The engineer's plans called for installing structural steel to support the chimney and flues that were to remain intact above the basement.

Our first logistical challenge was simply getting the beams into the basement, using our boom truck, some furniture dollies, and a pair of one-ton Genie lifts. A few days before the I-beams showed up, we did a test run with a full-length wood mockup to make sure we could get them where they needed to go.

Once we had the beams in the basement, the welder had to do some fabrication — cutting to length, drilling holes for connections, and welding on web-stiffeners at various bearing points. Our brick mason had assured us that the brick chimney would behave monolithically, so that we could install the beams one side at a time without risking collapse.

In preparation, we installed 3-inch tube supports at the end points, where they would be hidden in cabinets and wall framing, while the mason removed the brick to make way for the first beam. The channel created for the beam was about an inch too high, but the space would be filled later with stone shims and nonshrink grout. For now, it gave us the needed clearance to make the installation easier.

We hoisted the first beam with our Genie lifts and positioned it.

We bolted the beam to the post caps at each end while our temporary supports were still in place.

With the beam in place, the next step was to grout the empty spaces above it to ensure even bearing.

We also welded a 5-foot length of 6-by-1/4-inch steel plate along the top flange for securely attaching the brick mass above to the I-beam. The steel  plate was predrilled every 8 inches so that we could embed and epoxy 5/8-inch threaded rod anchors directly into the brick. Once the steel plate was installed, we repeated the whole process on the other side of the chimney with the second 18-foot beam. Next came some pieces of steel angle  that spanned the 30 inches between the I-beams at each end of the chimney. These short members were notched into the brick above and grouted so that they picked up more of the load.

At this point, we were able to begin removing the bottom part of the chimney. The engineer had warned us to expect as much as 3/4 inch of deflection in the I-beams as they took the load. We gradually transferred the weight of the brick onto the steel by slowly lowering the 20-ton jacks we had used for temporary support. We worked our way around the chimney, first removing any loose shims, then removing loaded shims. When the final shims were removed, the beams had deflected about 3/8 inch, causing no damage to the tile and drywall finishes upstairs.

With the brick out of the way, we added a couple of angles from underneath and grouted any remaining voids between the steel and brick.

The area where the chimney base had been was now open for construction.

We finished our phase of the job by framing the walls for the wine cellar. . . .

. . . and the media room, which were completed by the GC.

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