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Issue #13: April 15, 2015
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Installing an Aerial Rig in a Single-Family Residence
 

There has been some interest/inquires on how to install an aerial rig in a single-family residence. Before I go any further, I want to state for the record that while having many years of experience in both aerial rigging and carpentry, I have never installed an aerial rig in a residence. As with any endeavor which may risk the health, safety and welfare of another individual, expert advice is required. Fortunately, I have free access to an architect who has provided me good information on this subject (my brother Dennis J. Hall is a Fellow with the American Institute of Architects and a former national president of the Construction Specifications Institute). In discussing this subject, I will have two underlying goals for the design of my rig: 1) it must safely support the dynamic load of the performer in motion and the required structure, and 2) it must not damage either the structure of the home or the finish of the walls and ceiling. 
 
The first thing I want to stress is that every house is different and the best solution for one structure, may not be the best for another. In this article I will discuss concepts related to how I would approach installing an aerial rig in a home, and explain terms that you might hear from a building contractor. I strongly recommend that you contact a building contractor or licensed design professional before attempting the installation of any type of aerial rig in a home. Design and construction professionals can assist you in the evaluation of the existing structure and also provide you with options best suited to your home. Remember, damaging your home can be very expense, so hiring a professional could save you a lot of money in the long term. So, let's begin.
 
There are two types of loads imposed upon a structure, dead loads and live (or dynamic) loads. A dead load is the weight of the structure itself and live loads are the dynamic force created by the performer in motion. Both the dead and live loads are transferred through the aerial support structure, to the building/residence framing, and to the foundation of the home. We must ensure that the load path for these loads do not have any negative consequences on the existing structure or finishes. These may include cracking of the gypsum board walls or ceiling, or failure of the existing structural members of the home.  
 
In most single-family homes, floor and ceiling loads are transferred through load-bearing walls to the home’s foundation. Not all walls in a home are designed to be load-bearing, some are partition walls, resting on the floor structure, and are not designed to carry large live loads.  Load-bearing walls, such as the outer walls of a house, however rest directly on the house's foundation and present the best and most direct load path for our aerial rig design. A building contractor or design professional can assist you in identifying the load-bearing walls and determine the best location(s) in the home for installing the aerial apparatus, as well as design options.
 
Once we determine where we want to install our aerial apparatus in the home, we need to think about the apparatus supporting structure (the support beam) and how it is supported on the home's framing members. As we have discussed, I want to place the load from the support beam on the top of the load-bearing walls, so I am going to start in my attic. There, I want to identify 1) the location of the point (or points) where my aerial rig will be suspended, and 2) the points on two load-bearing walls where the support beam will rest. My plan is to use a support beam that will span between the two load-bearing walls. A hole or holes in the ceiling will allow the apparatus to be attached to my beam. This way the dynamic load on the apparatus is transferred directly to the beam, and the load on the support beam is transferred to the double top-plates of my load-bearing walls, and then down the studs to the building's foundation. This is the load path that I mentioned earlier. The support beam should be positioned so that no load from the aerial rig is on the existing ceiling, the ceiling joists or the roof - which might result in damage to my roof or ceiling.
 
This support beam, which is the critical component of the rigging, needs to be very strong and very stiff (have very little deflection under the anticipated load), since it will typically have to span 12 to 15 feet, or more. Depending upon the imposed loads and the span, the support beam may be as simple as multiple 2-bys bolted together, a box beam, an engineered lumber beam, or a steel beam. An architect or structural engineer can quickly help you with the most economical beam design. There are also companies that will design and build a beam that meets your particular requirements, but first you must identify them. They are:
 
  • Maximum height of the support beam (based on the allowable space)
  • Length of the support beam (based on the span distance)
  • Maximum point load and location of that load on the support beam (I would specify at least 1,000 pounds, but you should base your load on the maximum dynamic load that you expect to generate)
 
Note: Do-it-yourselfers can use load charts, such as them ones found on pages 41-42 of Georgia-Pacific Wood Product's Engineered Lumber Residential Guide (www.buildgp.com/DocumentViewer.aspx?
elementid=9548)
to help them determine the height and width of the required beam. These charts show you the Allowable Load per linear foot for different sizes of beams. To determine the maximum allowable point load, I would multiply the Live Load L/360 specification by the length of the beam and then divide the result by 2. I would then apply a design factor of at least 4. Sometimes these charts contain an Fb number. This number describes the bending fiber of the lumber - but do not be overly concerned with it.
 
The support beam manufacturer should design the lightest beam that will meet your needs. In doing this, the maximum height of the beam is very important. Generally speaking, the taller the beam, the less deflection. A shorter beam will need to be much wider, and contain more materials (and therefore be heavier) than a taller beam of the same strength.
 
The support beam manufacturer may recommend a Laminated Veneer Lumber (LVL) or Parallel Strand Lumber (PSL) beam. These engineered lumber beams are very strong. If the height of the beam is insufficient or the span is too great an engineered wood beam will not work, you may need to consider a "flitch" beam. A flitch beam is a composite construction beam, made of both steel and wood. These can have either one or two steel plates, sandwiched between layers of wood. Below are images of two variations of flitch beams.
 
 
A flitch beam that is going to be able to support the required load is going to be heavy - possibly several hundred pounds. However, a flitch beam can be constructed, then disassembled, transported to the attic piece-by-piece, and then reassembled in place. Remember, the heavier the beam, the greater the dead load that the structure must support. This is why you want the lightest beam possible.
 
Do-it-yourselfers can construct their own flitch beams. Information on constructing flitch beams, as well as span tables, can be found at http://www.toolbase.org/PDF/DesignGuides/flitchplate.pdf.
 
Once the support beam is set in place it must be secured to keep it from moving. Installation should also take into consideration the designed deflection of the beam under load. Depending on the height of the beam, it may also need to be braced to keep it from rolling. 
 
The final part of our rig is the attachment point (eye) on the beam. If a flitch beam, with two steel plates (like the one on the right), is used, you can drill down through the center piece of lumber and mount your eye bolt there (put a 1/4" thick steel plate on the top and bottom of the beam so that the load is distributed across all three pieces of lumber and the two steel plates and cannot wiggle and ream-out the hole). However, with LVL and PSL beams, I would not recommend drilling holes in the beam, as the beam is engineered for the load to be placed on the top of the beam. Instead, I suggest that you have a steel hanger, such as the one shown below, that clamps around the top and bottom of the beam.
 

This hanger can be designed so that the bottom of the hanger is about 1/2" above the top of your ceiling, so that it will not hit and damage the ceiling when the beam deflects under load. The hole in your ceiling only needs to be large enough for the washers/spacers to fit into the hole.
 
Note: You might consider using a hoist ring instead of an eye-bolt. Hoist rings swivel, although not as well as the typical ball-bearing swivels used by most aerialists.
 
After the rig is installed and in use, it must be inspected on a regular basis. You want to ensure that the support beam is secure and cracks do not develop in the beam, especially near the hanger. Also check the members that the support beam sits on for any signs of damage. Check to ensure that the hanger is secure, not showing any signs of wear and that there are no cracks in any welds. Inspecting your rig is critical to having a safe rig.
 
So, let’s recap the design/construction steps:
  1. Inspect the existing home construction, understanding locations of load-bearing walls and other framing members, load path the foundation, access for installation of support beam, height limitations, and span of support beam.
  2. Select the location for support beam and design/build beam for loads imposed on beam and span.
  3. Install beam and hanger for aerial apparatus.
  4. Inspect the rig regularly.
 
Albert Einstein said that the best solution to a problem should be as simple as possible, but no simpler.This is good to remember when designing and installing an aerial rig in a home. The beam must be sufficiently strong to support the load and must rest on the structure of the building that is designed to support loads. If designed and installed properly, you can have an aerial point or points that are safe, will not allow damage to your home and will not detract from the appearance of your home. 
 
Safe rigging.
 
-Delbert

 

Need to learn rigging math? Check-out my book. You can purchase a special spiral-bound edition at www.SpringKnollPress.com.
 

Delbert L. Hall

ETCP Certified Rigger - Theatre
ETCP Recognized Trainer

 
Copyright © 2015 Delbert L. Hall, LLC, All rights reserved.


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