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Seeking the Best Balcony Choice for Multifamily Buildings
What are the Different Types of Balconies?
What Construction Material is Available for Balconies?
What Details Should You Know for Balcony Design?
Which Balcony Type is Best?
What are the Different Types of Balconies?
Many balcony options exist for today’s multi-family construction projects. Use this guide to figure out the right balcony type for your architectural design.
Cantilever Balconies
The purpose of a cantilevered balcony is to give clear span space without any columns or brace. In other words, this balcony type has no visible means of support, for these cantilever balconies need a support beam within a wall. Thus the install rate for a typical concrete and wood cantilever balcony is about 5 to 10 a day.
The size allowed depends on the joist size and building material type. In general, a cantilevered balcony has a 24″ size limitation. Typical construction materials for the cantilever style are timber, steel, and concrete. The use of concrete or steel is popular for structural use, but thermal conductivity is an issue. For this reason, a cantilevered balcony requires thermal bridging knowledge. Usually, thermal break connectors must be cast into the building during mainframe construction. For this reason, timber joists are popular for low thermal conductivity. However, the timber risks rot over time. So a cantilever style can deteriorate hidden from the eye, as recent news stories show. It’s important to realize errors in cantilever construction mean disastrous future consequences.
“Stacked Balconies”
A stacked balcony has vertical support pillars or posts. This pillared balcony method is simplistic with minimal building load implications. To do this, posts hold the balconies in place, and the weight transfers to the concrete pads on the ground. The resulting vertical support structure gives a stacked balcony look. However, this method does need design consideration to avoid an unpleasant appearance.
Bolt-On or Hung Self-Supporting Balconies
A bolt-on balcony bolts on to the building without the need of inside joists. In other words, a hung or bolt-on balcony style is self-supporting. To do this, a bolt-on balcony system connects with bolts, sag tension rods, and knife plates to the building. The balconies can arrive prefabricated and ready to bolt-on without onsite assembly. As a matter of fact prefabricated means, the balconies can lift off a truck and onto the building. Before balcony arrival, the building gets prepped with connection points. Then a crane lifts the assembled balcony, and the balcony bolts into place. On average, a bolt-on balcony install takes about 20-minutes per balcony. This type is usually limited to either steel or aluminum, with an option of glass railing. In contrast, aluminum is the better option. Currently, timber is not an option. With this bolt-on method, the rate of install is about 15 to 24 balconies within 4 hours. Altogether quick install and increased safety make bolt-on balconies a popular choice.
Post Tension Slab Balconies
Post tension slabs use high strength steel to stabilize and strengthen concrete. The result is more capacity to resist tensile forces. This allows the architect to design with thinner concrete slabs and greater spans. This post-tension slab construction requires special skill and knowledge.
Juliet Balcony
A juliet balcony is a faux balcony with a railing and may be ornamental in nature. Sometimes a juliet balcony may feature a very small standing area.
What Construction Material is Available for Balconies?
Concrete Balconies
Concrete balconies often use a combination of steel and concrete. To prevent steel corrosion, a precise pour of concrete needs to occur. Furthermore, over time, concrete may crack due to element exposure. And water exposure may speed up safety issues. Moreover, a corrosive galvanic response may occur with aluminum railings on concrete. And a large city with a lot of carbon dioxide may also lead to corrosion. Being that, sometimes this type can last 50 years with proper maintenance, or 5 years without. So a property owner needs diligent inspections of this type to prevent litigation.
Wood Balconies
The design of a wood balcony either attaches to a wall or cantilevers through the building facade. Moisture is a big concern for wood balconies, as rot can go undetected. Also, maintenance costs can be higher with staining and frequent safety inspections. As well the exposure of a waterfront property may shorten the lifespan of a wood balcony. Sometimes when a wood balcony fails, it can affect a dwelling inside, which is very costly to repair. Another cost may include code induced sprinkler protection for wood balconies. So on one side, wood seems like a cost-savings option until you account for all the details.
Steel Balconies
Steel balconies can attach to a building in a variety of ways. With this in mind, the support will depend on the architectural design. Being that design affects support, steel balconies may need extra weight support elements. Moreover, the weight may increase the installation time. Over time steel is strong and long-lasting if maintained from rust and corrosion. Steel is generally painted. And steel railings will need a fresh coat of protective paint every few years. Once steel rusts, it may drip onto the building facade.
Aluminum Balconies
An aluminum balcony is about half the weight of a steel balcony. This reduced weight also reduces the number of anchor connections. And aluminum is ‘maintenance-free’ from corrosion and rust. Generally, aluminum is powder-coated. So a good hose down should be all that’s needed for aesthetic purposes. Considering all aspects, aluminum will cost less in the long run as compared to other options. For instance, steel requires long term maintenance, and aluminum does not.
What Details Should You Know for Balcony Design?
Flashing for Water Protection
Flashing provides water protection and is important to preserve wood cantilever balconies. The flashing areas for balcony waterproofing include the door and the balcony perimeter.
Types of Balcony Connections
How a balcony connects to the building is the most important element in balcony safety. For example, corrosion, thermal breaks, and water are all connection concerns. Additionally, balcony connections relate to deflection or a feeling of rigidity or bounce. New options for balcony connections seem to change daily to solve these concerns. Some companies have proprietary connections. In any case, an engineer will make sure of the use of appropriate connections. Whatever the choice, it’s important to use the same metal-to-metal type.
Currently, some common types of balcony connection are:
- Cast-in balcony anchors—cast into the edge of a concrete slab
- Bracket system—installed after floor substrate and anchor to load-bearing exterior walls
- Stubs and arms—joins within the building and supports the whole balcony
- Knife plates—designed to be a minimum horizontal presence with ease of waterproofing
- Lag bolts—tough fasteners that can bear heavy loads
- Threaded or sag rods—diagonal support rods that anchor one story up
Balcony Deflection
Jump up and down on a balcony, and you may learn about deflection. Deflection is how much the surface bends against weight or movement. Too much deflection can either make the surface feel safe or unsafe. Thus a balcony requires minimal deflection to feel safe.
Thermal Breaks and Thermal Bridge
Cantilever balconies act as a thermal bridge between the outside and inside air. So cantilever balconies need thermal breaks to prevent heat loss and mold growth. Thermal breaks help maintain temperature control between the outside and inside air; thus, temperature imbalance forms condensation and creates mold growth. And mold growth may result in litigation risk. Thus the fixing detail needs insulation to break the transfer of heat.
Codes and Regulations to Consider with Balcony Construction
Any balcony poses a safety risk with fire, falls, and rot. So codes and regulations are critical when it comes to balconies. And the type of materials allowed depends on the number of building stories. Note that building codes for guards and rails change about every three years. Particularly, certain Type V buildings need sprinklers over balconies to prevent combustion.
LEED Certification Requirements for Balconies
Sometimes the use of aluminum contributes to LEED certification. LEED certification is an ever-changing criteria list and requires a process to complete. In particular, aluminum may certify the areas of energy, sustainable materials, and environment.
Which Balcony Type is Best?
And the winner is…prefab bolt-on aluminum balconies! We are a little biased, but this option holds steady when you compare the other alternatives. A short term investor may want a wood or steel option, but a long term investor would do best with bolt-on balconies.
First, the removal of water is a major consideration for property owners—bolt-on balconies pitch for water removal. In contrast, concrete is not waterproof, and sealers do not add waterproof protection. A concrete balcony requires flashing, a drip edge, and a drainage mat for water removal.
Furthermore, wood balconies can rot undetected and pose a well-known safety risk. Even a small nail hole can pose a risk of water damage. Finally, steel balconies can show rust that drips along the face of the building.
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