Contractor Jake Lewandowski details how to replace structural columns and upgrade footings in older homes to improve structural integrity and level floors. He highlights the importance of accurate engineering plans, proper shoring, and careful lifting techniques to avoid damaging wall finishes during the process.

Lewandowski explains how to tune the girder beam to achieve a flat plane and discusses the installation of new steel columns, emphasizing the use of shims and nonshrink grout for stability. The article offers practical insights into managing the logistics of such repairs, including site preparation, soil testing, and concrete pouring, ensuring a thorough and effective structural upgrade.

Column Conundrums

I work for Great Lakes Builders, an Illinois-based company that specializes in structural repair. We regularly swap out columns on older houses in the Chicago area. This basic Victorian home was likely built in the late 1800s or early 1900s, and it is not uncommon for a home of this age to have been designed without much understanding of soil mechanics or structural engineering.

Some structural failures are due to age and overloading posts, beams, and other framing members. Some are due to undersized footings. And sometimes long-term moisture exposure is the culprit. When a home has tree-trunk columns, like this one did, engineers will typically call to replace them.

My understanding is that without knowing the species and grade of the wood, they cannot determine the load capabilities. Here, the telltale signs that the footings and columns were not up to the task were the dips and slopes that the homeowners were living with in the floor above. And we could see the rot at the bottom of these columns.

Layout and Lasers After staging the work site with plenty of lighting, a site-built air scrubber, a project-management station, and a material storage area, we mark out the new footing locations based on the engineer’s plans, cut the slab at the perimeter of the new footings, and use a laser level to find the differences in the beam elevation at both beam pockets and each column. This gives us an idea of how much we will need to lift or lower the beam.

Start with a Structural Engineer

As most projects like this go, we start with a drawing that is designed and stamped by a structural engineer. These plans included specs for new 3-in. schedule-40 steel columns, top-plate and base-plate dimensions, proper sizing for steel-reinforced concrete footings, and fastener and anchor-bolt specifications.

Often column locations change based on the engineer’s plan, with the exception being at the beam ends. (On this project, the beam lands in beam pockets in the foundation.) Depending on the loads, the engineer typically will specify a maximum clear span of 4 ft. to 5 ft.

This sometimes means that we’re adding a bunch of footings and columns. In this case, the new column locations were actually pretty consistent with the existing columns. We did move one column just a bit to avoid a drain line, which is allowable as long as we don’t exceed the maximum spacing requirements.

Elevation Upgrades

Often when installing new columns, we have the opportunity to improve the elevation of the existing girder beam. This was one of our clients’ goals here, to help fix their wonky floor above. I call this “tuning” the beam, which most of the time means raising it, like we did here, though there are circumstances where we may lower it. The goal is the same in either case—to get all the bearing points to a flat plane.

There is a risk of damaging wall finishes during this process. It’s especially common for previously filled cracks in plaster and drywall to open back up when a beam is lowered. When a beam is raised, it’s possible that if cracks have formed and haven’t been repaired, they will shrink and sometimes almost disappear.

If the cracks have been filled, however, the wall finish may buckle when we raise a beam. Keep in mind that we are typically trying to lift a floor system to its original elevation. There are a ton of caveats, and this is a longer discussion, but generally we try to take about 50% of the deflection out of a beam.

Shoring Comes First

We do a bit of prep work when we first arrive to mobilize the site. For this project, we brought in temporary lighting so we could see better in the basement. We also brought in a shop-built air scrubber to help with dust control. We then established a management station and a material staging area.

The management station included a stamped set of the engineer’s plans, a first aid kit, and a fire extinguisher, along with miscellaneous consumables such as garbage bags, various tapes, and all the personal protective equipment (PPE) we might need for the job. We picked a location to stage material that has enough space and is out of the way of the work area.

Once a site is prepared, we can lay out the locations and cut the perimeter of the new footings in the existing concrete slab. Doing this first means we won’t put any of the temporary shoring in the way of where we need to work. While this work is being done, I set a horizontal laser and document the beam-end elevations, along with existing elevations at the current column locations.

Goodbye Failing Columns When we install the shoring, we make sure to avoid the new footing locations. We set it on blocks like the LVL cutoffs seen here to spread the load. We also make sure that it is plumb and is tightened snug up to the beam. With the shoring in place, we can cut the old columns with a demolition blade in a reciprocating saw and remove them.

An Important Reminder

Keep in mind that sometimes a beam’s dimensions vary greatly along its length. It’s a good idea to identify that early on. If the girder beam does vary, it may be helpful to take measurements from the top of the beam/bottom of the joists. Of course, it is also possible that the joist height varies, so we look at all of this while planning how to tune the beam.

Once all the footing locations are cut, we set up heavy-duty shoring. We avoid the new footing locations, and we snug shoring to the bottom of the existing beam. The goal is to take the load off the existing columns. If needed, we set up additional cribbing to help distribute the load without interfering with the work.

Typically, however, failure occurs at the slab when the loads are not distributed. Keep in mind that beams, columns, and footings are designed to handle live and dead loads. The actual amount of weight you are temporarily holding up may be less than what the structure is designed to support.

Though our shoring may look like sections of scaffolding, it is not. The shoring you see here, called ladder sections or ladder frames, are designed and built for this purpose. They are available from a few manufacturers and can also be rented.

Time to Tune

After we install the shoring and the existing columns are no longer loaded, we can safely remove them and start the tuning process. It’s important to lift the beam uniformly. This can help minimize cracking wall finishes. And remember: bigger is not necessarily better with jacks.

For this project we set 30-ton and 35-ton hydraulic jacks on the original footings. We have rented super-heavy-duty jacks for large commercial projects, like big parking garages. They can be rated for as much as 80 tons each and connect to a manifold that controls all of them at the push of a button, either simultaneously or individually.

Going Up When the beam needs to be raised in most places, as here, we set hydraulic jacks on the existing footings and use a laser to mark the lifting posts so that we can monitor how much we have raised the beam as we go. As we lift, we keep the shoring snug to the beam. Because it is unlikely that the beam pockets are level to each other in an old house, we run a stringline from pocket to pocket with the goal of getting the beam straight and the floor above flat.

Lifting the Beam

While people do use them for residential structural work, I don’t believe they are needed. Smaller hydraulic jacks with a hand pump, or screw jacks, give you immediate feedback about how the structure is handling the lift. Between the jacks and the beam we put 4×4 posts. With a horizontal laser level as a guide, we mark the 4x4s to give us a baseline that allows us to see how much we have lifted at a particular area.

We lift the beam a little at a time, always checking for collateral damage and anything that needs to be braced, and snugging up the shoring as we go. Once we are close to the final beam elevation, we run a stringline from bearing pocket to bearing pocket. We opt to run a string at this point because bearing pockets on vintage homes are rarely at the same elevation.

It’s not uncommon in 100-year-old homes to see readings that differ in elevation from ½ in. to 1-1/2 in. at the beam pockets. Tuning the beam to match our stringline means that it will be straight, if not level. A drop of 11/2 in. over 50 ft. of floor is not likely to be noticed. The floor will feel flat.

Concrete Concerns

Once the beam is tuned to its final elevation, we remove our jacking equipment and start digging for the new footings. I recommend that anyone doing similar work invest in a pocket penetrometer. We use this device to verify that the soil meets or exceeds the engineer’s design specifications. You can usually find these specifications in the general notes of the engineer’s drawings.

If the soil reading does not match the engineer’s expectation, consult the engineer before proceeding. After our footings are dug and our rebar is cut, tied, and placed in the footing holes on chairs, we are ready to have an inspection with the building official and then to pour concrete.

Prepare and Pour Before we can pour the new footings, we need to remove the existing concrete slab from the footing locations, excavate the soil, and cut a bunch of rebar as specified by the engineer. We mix concrete on-site, vibrate it, and trowel-finish the tops of the new footings so that they are about 2 in. below the top of the existing slab. When we pour more concrete on top of the footings, we will even out the slab and bury the footing bases, removing a trip hazard and getting them out of the way if the homeowners ever want to finish the basement.

Concrete Considerations

Typically we mix a high-early concrete on-site for projects like this for a few reasons—logistics often play a roll, along with hot-mix concerns, the issue of concrete trucks leaking oil on a customer’s driveway, and the need to find a place to dump any excess concrete/washout water when cleaning the truck.

When we do order concrete, it’s with a company that uses a volumetric concrete truck. That’s because we know we’ll end up with fresh concrete and less waste, and we can verify exactly how much product was used. A high-early bagged mix makes sense because these footings are typically designed for a 3000-psi mix.

With a typical bagged mix, you will achieve 3000 psi or 3500 psi after 28 days. By using a high-strength mix, you can reach 3000 psi after approximately 72 hours. It’s not feasible for us to wait a month before we return and finish the job.

We usually pour the footings to the bottom of the existing slab. This slab was only 1 in. thick, though, so we poured the top of the footings 2 in. below the top of the slab. Once the footings are cured and the new columns are installed, we pour a concrete pad on top of each footing and finish it flush with the slab. This eliminates a tripping hazard, and burying the column base makes it easy to encase the new columns in a wall if the homeowners decide later to finish the basement.

Steel Does It Again Once the concrete has set up, we can install the new steel columns. We order them a bit short of the actual distance between the footing and the beam so that they can be maneuvered into place. We fill the space at the top with site-made wood shims before fastening the columns to the beam with 1⁄2-in. lag screws. At the base we use a few steel shims and then a high-strength, nonshrink grout. To fasten the columns to the footing, we drill out the concrete and drive 1⁄2-in. Simpson Titen HD concrete anchors. Once the footing concrete has reached full strength, we remove the shoring and do the final concrete pour and finish.

Finally, the Columns

The steel columns here were ordered to the length we needed, but at this point it’s necessary to verify the dimensions. The columns should be about ½ in. shorter than the overall length. Before installing the columns, we clean up the underside of the beam at the column locations. We typically use a Festool RO 150 sander connected to a Festool vac. I like this setup because it seems to be the most dust-free approach, while still being powerful enough to remove a high spot in the beam quickly.

Now we can stand the columns and then take measurements from the column top plate to the existing beam. This tells us how many steel shims we’ll need to install between the footing and the column base plate. Once the steel shims are installed, the columns are pinned in place. Any gaps that are present between the column top plate and the existing beam are filled with site-made shims, generally from clear Douglas fir, which we trim flush with the top plate.

After a column is shimmed at top and bottom, we fasten it with ½-in. lag screws, as called for in the engineer’s plans. When we are using large-diameter lag screws in 100-year-old beams, it can be critical to drill pilot holes in two passes so we don’t split the beam. For ½-in. lags, that means drilling ½-in. holes to a depth that matches the screw’s shoulder length and then using a 3/8-in. bit driven to the depth of the fastener.

At the base of the column, we use a high-strength, nonshrink grout to fill the approximately ½-in. gap between the column base plate and the footing, where we installed the steel shims. Having a ½-in. gap is critical because you will need to tool in the nonshrink grout. A smaller gap would make this more difficult to do well. After the grout sets, we install anchor bolts to fasten the column to the footing.

Once our columns are installed and our nonshrink grout and concrete have reached the required working strength, we can finish the slab, remove all the shoring, and start the demobilization process.

— Jake Lewandowski (@jakemlewandowski) is a construction manager with Great Lakes Builders, a contracting company in Elk Grove Village, Ill., that specializes in structural repairs. Photos by the author.

From Fine Homebuilding 328

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