Balcony and Deck Structure Design Considerations

Deflection and Live Load Play a Part in Ultimate Deck Structure Design

Balcony and deck structure design needs several considerations for ultimate design. You have the design, and the color to evoke feeling, but what about the see, touch, and feel part of design. Deflection and live loads definitely play a part in how occupants feel.

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What are live loads?

Live loads factor in the number of people, planned objects, or unplanned objects like snow, can hold without structural compromise. This can also apply to balcony railings, if you think about the number of people who can lean against a railing without structural compromise.

 

What is deflection?

Deflection is the amount of bend in deck or railing.

—Balcony Deflection, Not for the Faint at Heart

Visualize a balcony with a small table, chairs, planter, and an occupant hosting a dinner party. Attendees of the dinner party go out to the balcony and take in the city view. A few remark, “did you feel that (bounce)?” They’re referring to the feeling of deck movement, or the movement of railing as they lean against. Balcony deflection is not for the faint at heart.

 

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—Deck Structure Design Options to Avoid Deflection and Increase Live Load

A springy floor may be fine in an overall sense for capacity, but if the users of the structure are uncomfortable with a bouncing deflecting floor, the structure has “failed” from a serviceability standpoint. Though the balcony structure may be considered safe, ideally, safety shouldn’t be a question. One option of a welded railing to deck will eliminate most railing deflection, like that in prefabricated bolt-on balconies. A thicker aluminum choice versus wood or thinner aluminum can also serve to eliminate most deck and railing deflections, as well as increase live load amounts.

 

The make and composite of a balcony can be the difference of feeling like you’re standing on a desk versus standing on a piece of plywood and sawhorses. Any balcony rails built beyond the standard 200 lb lateral load will feel more sturdy. Sturdy will feel like a quality design, and will give occupants safety confidence. It helps to understand the engineering aspects of design, so your design doesn’t go away because of engineering factors.

 

 

Items to think about for the feel of balcony and deck structure design:

 

  • Plan for a greater load to provide a greater level of safety feel
  • Review IBC code for balconies
  • Understand how design can minimize deflection
  • Type of substrate (e.g. wood, steel, aluminum)
  • Cantilever versus bolt-on self-supporting balcony design
  • Thickness of material
  • Attachments of balcony railing to deck (e.g. welds, screws)
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Safety is More Than Just a Great Design

Property owners should never depend on a great design as a one and done aspect to safety. Awareness of all potential building structure dangers are necessary, as well as a plan for inspection and maintenance programs for decks and balconies.

If you would like to have a preliminary balcony structure design discussion start here.

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Commercial projects only.

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howard@mwstairs.com

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