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Metal Framing and metal work

Metal Framing and metal work

. 4 min read

Structural Loads:

  • Wind: 150 mph (3-sec gust)
  • Seismic Design Category: E
  • Live Load, LL: 100 psf main floor, 60 psf roof deck
  • Snow Load, SL: 60 psf
  • Dead Load, DL: 15 psf + Water tanks

There are two ways to build this unit, for On-site and mobile. However, the superstructure is built off-site for both cases with different structural requirements.

To build a On-Site superstructure in a factory:

  • Columns: HSS 6”x3”x1/4”
  • Roof Beams: HSS 6”x3”x1/4”
  • Existing Trailer Reinforcement (see figure 2): 2’-0” long 11-5/8” x 3/16” A36 steel plates welded 2” @ 6” centered below columns (1’-0” long at ends) see figure 1 below:

These are based on welded connections.

To build a mobile superstructure in a factory:

For trailer being used to transport complete structure/building,

  • reinforce the main trailer beams the entire length with 11-5/8” x 3/16” A36 steel plates welded 2” @ 12” spacing minimum on each side of the beam such as shown on figure 1 below. This configuration will still allow the proposed pier supports to attach to the beams.
  • The tongue and trailer beam above tongue will have to be replaced with a custom built one in order to support the loads during transit. Our engineers suggest using HSS 10”x4”x3/8” A500 Gr. C steel tube, or similar strength beams.
  • We expect max total weight of 43,200 lbs for the structure, assuming no live loads, empty water tanks, and 15 psf dead load on floor and roof. Max dynamic reactions induced while in-transit are expected to be double the loads shown of stationary.
  • In-Transit Impact: 2G (2 x DLtotal) Transported to site on trailer and existing 5 axles and then set on piers. We expect around 10,000 lbs on tongue hitch, and 3,660 lbs max per side of an axle of one of the 5 axles of the existing trailer, or 7,320 lb per axle.
Figure 1 Stiffner plates
Figure 2. Tailer Frame

Light Gauge Metal Framing is same for both structures (see figure 3):

  • Floor Joists: 1200S250-68 (12” x 2.5” x 14ga) @ 24” o.c.
  • Roof Joists: 600S250-54 (6” x 2.5” x 16ga) @ 24” o.c.
Figure 3. Framing

Pier Spacing and Reactions:

Based on the structure being installed on site and experiencing max forces, we determined that piers shall be placed under each column and spaced no more than 10 feet on center. Approximately 9 piers per side, 18 total.
Maximum reactions, including lateral forces are expected to be 17,000 lbs vertical, 3,200 lbs horizontal, and 1,600 lbs uplift.


Angel Landings system provides a structural design that is easy to assemble and requires minimal leg work to build. We took a trailer chassis from a reputable manufacturer and reinforced it to handle addition vertical load. Once the trailer chassis is fitted with the moment frame it becomes a super structure. By now you must be asking why would I build on top of the chassis? It is quite simple why, first it qualifies for federal agency HUD approval vs local government approval. Second it makes it easy to assemble the super structure off-site and ship it on wheels. Since wheels are attached directly to the structure then in most cases crane is not required to place it on site.  Chassis with superstructure simplifies the construction logistic and cost associated with it.

The light frame is easy to assemble either on site or off-site and requires no scaffolding or heavy lifting equipment. All one needs is a ladder to assemble.

The chassis is built with a tongue hitch so that one can easily ship it using a tractor trailer truck. Additional axial may be required either for incomplete or complete unit to carry additional load. Each axial can carry around 6000LB of weight.


HUD requirements:

Please note to qualify for federal approval there are federal agency inspection requirements and are handle by DAPIA (manufactured housing and HUD). If the state jurisdiction prohibits use of Federal code, then one needs to file and inspection under local state modular building code or IBC.

Please note a builder needs to verify with a local engineer if the structural calculation meets local wind and seismic requirements and some cases soil conditions. Also, to file under federal agency DAPIA one needs signed and sealed drawing from a registerer engineer in the USA. Angel Landings can provide these drawings from our structural engineers for a fee.

Builder installing the structure unit onto above ground piers footing would need to attach the piers after the structure is delivered to its location. However, if the footing is installed below ground level, then the footing needs to be professionally installed by a licensed foundation contractor for trailer buildings/homes.


Additional metal accessories are:

- Retractable steps can adjust up to 44 inches. There are good for offsite living where retractable stairs can prevent unwanted fury guest into the unit at night. Please note retractable steps are not IBC compliant and may be unsafe for young kids. To learn more about retractable steps and details please download the metal frame package.

- For exterior finish we recommend Vesta metal panel system. These are corrosion resistant, built strong and have quality imprinted wood grain textures. They are easy to install.

- We recommend using a standard metal wire railing that can be assembled on site easily.

- Painted corrosion resistant steel angle is used to frame the EPDM roofing and roof insulation.