INTRODUCTION TO 1920S FOUNDATIONS
Welcome to the second part of our series exploring how homes were constructed back in 1923. It is important to note that building methods varied wildly during this era, and working in construction, you will see a wide array of historical techniques. The oldest house I have worked on was built around 1922 in Southern California. While we do not see the centuries-old colonial homes found on the East Coast or in the Midwest, the 1920s era still provides a fascinating look into early modern building practices.
Keep in mind that early homes were often built directly on top of the ground. Back then, builders might construct a house on top of wood beams, site-made concrete piers located around the perimeter, or even flat rocks. Sometimes, they would simply roll a boulder into place, level out a hole, set the boulder in, and call it a day. For this breakdown, we are going to look at a slightly more robust design using a concrete footing and brick foundation walls.
CONCRETE FOOTINGS AND BRICK WALLS
In our model of a 1923 home, we are using a concrete footing that is six inches deep and about 20 inches wide, running around the entire perimeter of the house. This six-inch deep footing is also poured for the heavy fireplace base and the interior piers that will hold up the center floor beams.
On top of this perimeter footing, builders constructed brick walls. These walls were typically about eight inches wide, consisting of two rows of bricks running parallel to the foundation line. Every once in a while, a brick would be turned perpendicular to tie the two rows together and add strength to the wall. This was a solid, reliable way of building a foundation at the time. The brick wall would be built up to about 18 inches tall, leaving a crawl space opening to allow access beneath the house.
ATTACHING THE WOOD FRAMING TO MASONRY
You might be wondering how the wood framing and sill plates were attached to this brick and concrete base. Surprisingly, they often were not attached at all. I have seen many instances where the wood sill plates were just sitting right on top of the concrete or brick foundation, held in place purely by gravity.
Sometimes builders might drive a nail through the wood and try to hit the softer mortar joints between the bricks, but there were no modern anchor bolts. The thinking back then was simply to position everything correctly. Once the floor was framed and the wood sheathing was attached, the weight and rigidity of the floor structure would hold everything together. This provided a seemingly solid foundation, but without physical anchors, these homes are susceptible to sliding off their foundations during an earthquake.
SUPPORTING THE INTERIOR BEAMS
For the center of the house, a large wood beam is needed to support the floor joists. This beam sits in a pocket left in the brick perimeter wall so that it sits flush with the sill plates. In the center of the crawl space, this beam rests on concrete piers.
There were a few common ways to attach these center beams to the piers. Sometimes they just sat on top with a nail driven into the side. Other times, builders used a wood block placed on the pier to level the beam. Another less reliable method involved throwing wet mortar on top of the pier and setting the beam into it; over time, as the house moved, this mortar would just crack and fall off.
BUILDING THE FIREPLACE AND PORCH
Back porches in this era could have been framed with wood, but building them out of solid brick was a heavier-duty option. For homes in snowy or wet climates, a brick porch holds up much better to wet boots and winter weather than unprotected wood.
The masonry fireplace is another massive structural element. It is important to point out that builders did not build the entire fireplace from the ground up all at once. They would build it in sections. They built it up as high as they could comfortably reach from the ground, then they would frame the wood floor, stand on the floor to build the next section of the chimney, frame the ceiling joists, and use that as the next platform. The chimney was integrated into the construction process step-by-step.
CONCLUSION: THE STRUCTURAL REALITY OF 1923
Looking back at a building foundation from 1923, it is amazing what they accomplished without modern building hardware. There were no framing anchors, no anchor bolts, and no structural steel rebar inside the concrete.
Even the concrete itself was a gamble. You never know how well it was mixed, where the sand came from, or if it was full of large, weak river rocks. They often used smaller amounts of cement in the mix to save money and make it easier to tear out in the future. While these foundations have stood the test of time for a century, they are simply not as structurally strong as the engineered building foundations we pour today.
THREE KEY TIPS FOR OLDER FOUNDATIONS
Check for foundation shifting: Because 1920s homes were often built without anchor bolts tying the wood framing to the masonry, inspect your foundation walls to ensure the wood sill plate has not shifted or started to slide off the center of the brick or concrete.
Inspect load-bearing blocks: If you have a crawl space with concrete piers, go underneath and check the wood blocks sitting between the concrete and your floor beams. These were often not secured and can easily rot or slip out of place over the decades.
Evaluate the concrete quality: Historic concrete was often mixed on-site with whatever sand and aggregate were nearby. Look for severe crumbling or flaking (spalling) at the base of your footings, which may indicate that the original mix was too sandy or lacked sufficient Portland cement.
FREQUENTLY ASKED QUESTIONS ABOUT HISTORIC FOUNDATIONS
WHY DO 1920S BRICK FOUNDATIONS OFTEN HAVE A WHITE, POWDERY SUBSTANCE ON THEM?
While understanding how these old foundations were built is crucial, you also need to know how to maintain them, which brings us to a common visual issue. The white powder is called efflorescence, which occurs when ground moisture moves upward through the porous vintage brick and mortar, leaving salt deposits behind as the water evaporates. Modern building codes require a capillary break or vapor retarder between the concrete footing and the foundation wall to stop this moisture from wicking upward, a step that was completely skipped in 1923. If you are doing repairs on an older home, applying a breathable siloxane-based masonry water repellent using a standard pump sprayer can help protect the exterior brick from rainwater absorption without trapping dangerous internal moisture.
HOW DO YOU RETROFIT A 1920S FOUNDATION TO MEET MODERN EARTHQUAKE SAFETY CODES?
Speaking of foundational integrity, many homeowners wonder how to bring these gravity-held structures into the 21st century. Retrofitting usually involves bolting the existing wood sill plate to the concrete or brick foundation and adding structural plywood to the crawl space framing to resist horizontal shear forces. Current building codes require seismic retrofitting in earthquake-prone areas to prevent the house from sliding off its base during a tremor, which was a major flaw of simply resting the wood on top of the masonry as done in the 1920s. When upgrading, utilizing heavy-duty retrofit foundation plates and a rotary hammer drill with specialized masonry bits is essential for safely anchoring the old brittle wood to the existing concrete without shattering it.
IS IT SAFE TO ENCAPSULATE A 1920S DIRT CRAWL SPACE?
Beyond structural fastening, modernizing the environment underneath the house is another major concern for historic homeowners. Yes, it is generally safe and highly recommended to encapsulate a dirt crawl space, provided you account for proper moisture and air management. Historically, these crawl spaces relied on passive ventilation through open foundation vents, but modern building science dictates that completely sealing the space and controlling the humidity prevents wood rot and preserves the unreinforced masonry walls. To do this correctly, you will need a heavy-duty vapor barrier, typically a 20-mil reinforced polyethylene plastic sheet, installed completely across the dirt floor and taped securely to the interior foundation walls.
