Cheaper Faster Lighter Concrete Buildings

The Real Estate Espresso Podcast

Cheaper Faster Lighter Concrete Buildings

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Cheaper Faster Lighter Concrete Buildings

Welcome to the Real Estate Espresso Podcast, your morning shot of what’s new in the world of real estate investing. I’m your host, Victor Menasce.

On today’s show, we’re taking a look at a construction technology that could revolutionize the way concrete buildings and light gauge steel structures are built. The technology is called HamBRO, spelled H A M B R O. Currently, we’re implementing it in six apartment building constructions. The methodology applies two different techniques for walls and another basic approach for floor slabs.

Before we discuss the new technology, it would be best to talk about the way traditional form concrete is constructed. This will provide a point of comparison. In a traditional form concrete structure, you erect forms for your slab and your foundation. You also erect forms for your columns and walls. Concrete construction consists of stages. You set forms for the floor, you insert steel reinforcing bars with spacers to ensure correct positioning in the concrete slab. Any required conduit for future infrastructure to penetrate the concrete slab is inserted. You then pour the concrete and let it set. The finishing steps like screeding, floating, troweling, polishing will be identical either in conventional concrete or in HamBRO.

You follow the above sequence for the walls and columns as well. The change comes in with the next step. After removing the forms from the walls and from the columns, you erect the forms for the floor above with a grid of jack posts. They support the form and the concrete while still wet. Steel rebar is then inserted and concrete poured as before. However, the critical task is waiting for the concrete to harden fully before removing the form’s supporting jack posts. While the result is sturdy, the entire process is labor-intensive and not fast paced. The complexity is amplified further if dealing with winter concrete where insulation is required for proper curing.

In conventional concrete, the slab for each floor is 6 to 8 inches thick. Mechanical and plumbing equipment hang below the concrete ceiling. This often results in numerous bulkheads along the window walls to create space for the ducting. You’d typically find a 9 feet ceiling height in the center of the room and 8 feet wherever ducts are enclosed in a bulkhead. This process is repeated for each floor in the building.

In contrast, HamBRO uses a foundation and main floor slab formed from Styrofoam insulation. It’s the traditional ICF foundation used in higher-end construction for numerous decades. The latest building code calls for a higher degree of exterior continuous insulation, generally rigid Styrofoam. Considering you’ll be purchasing Styrfoam anyway, it’s more efficient to use it to form the concrete, sparing the step of removing the form and later applying the Styrofoam on the exterior of the building.

The forms for the walls, columns, and the outside of the exterior wall are made from a combination of light gauge steel and Styrofoam. Once the concrete is poured, we immediately start prepping the form work for the next step. The forms are permanent, with the light gauge steel remaining. Within a day of the previous concrete pour, you’re already working on forms for the next step.

The implementation of the next level floor is quite advanced. Instead of forms, we install open-web steel trusses spanning from one structural wall to the next. Then, you lay down a light gauge steel sheet across these trusses. This forms the base of the concrete floor. Contrary to a six inch slab, we pour a lighter four inch concrete slab. The strength of this floor assembly comes from the combination of the steel trusses in tension and the concrete slab on top in compression. Consequently, the trusses are tall, with the combination with a concrete slab resulting in an 18-inch floor and ceiling assembly. This is significantly thicker than the traditional 12-inch formed concrete assembly.

If your zoning can tolerate a taller building, then you just make your building six inches taller per floor. Otherwise, you can have an eight and a half foot finished floor to ceiling in your apartments instead of nine feet. My own experience assures that an eight and a half foot ceiling height is very acceptable. It doesn’t have the confined feel of an eight foot ceiling and closely approximates the expansiveness of a nine-foot ceiling.

The larger ceiling cavity, courtesy of the open web trusses provides the flexibility to route all of your mechanical, electrical, and plumbing in the ceiling cavity without needing additional bulkheads. This results in a cleaner, finished look. The beauty is that the forms are permanent. They become part of the permanent structure and part of the installation of the building. There are fewer steps involved in construction. The time savings are significant and the reduction in labor saves you money.

Since you need the Styrofoam insulation anyway, you might as well use it as a permanent form. Currently, HamBRO does produce cost savings for buildings of nine stories or less. The maximum height you can achieve with HamBRO today is 12 stories, making it unsuitable for high rise buildings. However, for a mid-rise building, the time and cost savings merit its consideration. Benchmarks suggest savings between 20 to $40 a square foot compared with traditional formed concrete. We’re big fans of the HamBRO technology, having implemented it in diverse buildings and expecting to continue to do so in the future.

As you think about this, have an awesome rest of your day. Go make some great things happen. We’ll talk to you again tomorrow.

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