Avalanche has a towing capacity of 8,300 pounds.  Deasler indicates trailer weight is 2,500 pounds.  Weight can be trimmed by eliminating every other bed board.  20′ 2×6″ boards weigh around 45 pounds.  Boards can be recycled in tiny house structure.

Assuming trailer weighs 2,300 pounds after board removal, that leaves no more than 6,000 pounds for structure.  Fat trimming ideas for structure include:

• Shrink floor height to 4″.
• Use cedar siding on exterior.
• Make weight a priority in selecting windows and doors.
• Use flooring material with less wood density.
• Use deck flooring material with less wood density – cedar decking?
• Use 2x4s when feasible for rafters, deck joists, and cross ties.
• Use steel roofing.
• Use 1/4″ pine as an interior wall material.
• Design cabinets to minimize weight.
• Cut electrical capacity to minimize battery weight.
• Avoid use of ceramic tile and granite in bath and on countertop.
• Avoid heavy appliances.

Wisconsin Law sets a maximum heitht of a trailer of 13’6″ without a special permit.  We want TinyHouse to live within that limit.  This is a diagram of the vertical components of FarinHaus.

In this drawing, height is limited to 160″ allowing 2″ for roof sheating, roof, and roof seam.

Beginning at the bottom:

• Deck is 24″ off the ground – Current assumption is floor will be built on top of the deck.
• 2×6 joist floor sandwich is 6″ high.  Assumes aluminum flashing is used to seal the bottom of the sandwich.  Provides 5 1/2 inches of insulation.  Deflection of cantalevered load bearing wall is less of an issue.  Assuming stake pocket assembly can be adapted to provide deflection support, the joists in the floor sandwich could be reduced to 2×4″  Picks up 2″ of height, saves weight, costs 2″ of insulation.
• Wall comes out to 81″ or 6’9″ under loft rafters and cross tie beams.  Could be 2″ higher if floor height is shrunk.
• Rafters are 2×4″ with 2×4″ loft rafters and cross ties.  Vertical from top of wall is 51″.  Could be a bit less with bird beak cuts.  Might be able to use 6″ rafters with birds beak cuts and stay within 51″.  Note that loft is only 46″ high at peak, less if ties are used.  Question – how does ladder fit in with design?

This height limit can be dealt with as long as:

• Trailer height estimate is correct.
• Ladder can be worked out.
• We don’t need to significantly oversize framing material.

When you live in areas of the country where there is likely to be snowfall, tiny house design needs to consider the snow load for that area of the country.  Snow loads are figured in pounds per square foot.  I found the information on this page by Googling “Wisconsin Snow Loads.”  The following map is from the State of Wisconsin Structural Design Code.  The URL is:

http://dsps.wi.gov/sb/docs/sb-CommercialBuildingsCodeEnrolledReplacV1C.pdf

I am located in Dane County Wisconsin which is the county second from the bottom in the center of the state.  As you can see, the snow load that needs to be considered in structural design is 35 psf.

Of course this structure is on wheels.  Just to the northwest of Dane County is an area where the snow load requirement is 40 psf.  Travel beyond about 75 miles north of madison and the snow load requirement is 60 psf.  At this point we aren’t sure where our trailer is likely to be parked during the winter.  It makes sense to design the structural components to carry a 60 psf load.

As the show load requirement goes up, the structural timbers necessary to support the load go up with the requirement.  This will affect the floor joists, the size of headers over openings like windows, doors, long horizontal windows in dormers, tire fenders, and the size and spacing of rafters and cross ties.

Increasing snow load capacity has tradeoffs in the areas of cost, weight, head clearance in the loft areas of the first floor, and the loft itself.

Now that I know snow load capacity requirements, I need to do additional research into the effects on sizing of structural components.