How steel supports strengthen cantilever structures

For a variety of architectural reasons, upper portions of buildings may be built to extend out farther than lower parts of the building. It’s not uncommon, but it requires particular structural provisions to allow the building to extend out beyond a structural load path directly below. Gravity works in relatively simple ways, and for the most part it makes the simplest most pragmatic direct common sense to just build a structural support for an elevated portion of a building directly below the elevated portion of the building.

In some cases though, it’s actually functionally useful to have a lower portion of the building set inward away from the remainder of the upper facade of the building. The picture below shows an example of an entry door into a building which would be much harder for a vehicle to approach in the city alleyway, had the door been set at one side or another of a 90° right angle corner of the building. From either side of the 90° corner, it would be very difficult for a vehicle to turn in the radius to access that door.

Instead, setting the door at an opposing angle helps a lot. Directly from the intersection, a vehicle can make a 45° turn directly from the center of the intersection. If the door were set on the side of a 90° corner, they wouldn’t be able to turn from the direct center of the intersection and instead would have to get into a street beside the intersection which gives them much less area to turn the vehicle.

In this case, from an architectural perspective and a simple functional perspective, it makes a lot of sense to install the door at a corner and set the door opening underneath of the more typical 90° corner of the wall above. However, there’s a complication here.

To create a wall that’s inset inside of that 90° corner of the remainder of the building facade, the entirety of the building has to lose some of its usable interior property space, off of the acceptable property line, or instead, in this case they did something that is pretty smart and they cantilevered the upper portion of the building out to the original property line. That’s complicated though because it requires structural support from the inner part of the building to extend outward and carry that load all the way up above.

You can’t see a steel support, because it’s hidden behind the exterior finish of the building, but the steel support runs horizontal, from farther within the side to side to the outer corner.  That cantilevered support hold up the upper two levels at the corner.

Cantilevers like this and spanning supports are very common in masonry construction and often they are built with either masonry units such as bricks set into sequences that form archways which are self-supporting or assisted by other elements with greater overall tensile strength.

Here on our website, we’ve looked at several of these different types of arches, particularly ones that are common here in Washington DC historic buildings built with historic brick masonry. Some of the examples include the ubiquitously common segmented arch which is partially assisted by internal framing and the Roman Arch which when built to true form is in fact independebtky self-supporting along with the gothic Arch which happens to be less common here in the historic architecture of our city.

In this coming week, we’ll take a look at a projecting canopy that extends out over the entryway of a commercial building. But unlike the buildings we normally look at, the one we’ll look at this coming week has a spanning support that includes no masonry. Instead, the structural elements are framed with both hot rolled structural steel and cold rolled light gauge steel.

We can Help

Our company focuses on historic restoration more than modern building upkeep, maintenance, and construction, but our company understands both types of construction very well and a full picture well-rounded approach is needed in any niche in the construction industry.  Although we focus on historic restoration, repointing, tuckpointing and historic brick repair, our company also has technical knowledge and competencies in the areas of modern and contemporary construction as well as we become one of the leaders in that area of the market today.  Understanding both historic and modern or contemporary construction is useful because both aspects help understand the challenges and potential solutions for challenges in building science and construction.

We can help with a variety of historic masonry restoration needs and upkeep, from modest tuckpointing and or repointing to complicated and extensive historic masonry restoration. Infinity Design Solutions is a historic restoration specialist contractor specializing in both historic masonry restoration such as tuckpointing our repointing, and brick repair. If you have questions about the architectural details or facade of your historic building in Washington DC, reach out and say hello and if we can help we’ll be glad to assist you. You can email us or call us on the telephone at the following link: contact us here.