My last post provided some of the basic philosophical reasoning behind my journey to build a tiny hacker house. It also featured a rough model of the house at a very early stage in its conception. Well, after a couple more months of research and a dash of Burningman inspiration, I’ve completed what I consider to be the beta version of the design.

Overview Right
Enough hacker space to squeeze in 3 or 4 curious nomads.

Design Goals

Although it’s on a 16’ trailer, I want my house to be practical enough to comfortably shelter 4 adults for weekend ski trips, tiny dinner parties, and the occasional road trip or two. I also want to be fairly independent of grid-tied scenarios; I suspect I’ll be dancing around from place to place as I navigate the legal contours of living in a tiny house in greater San Francisco. As a result, my soft goal for the house is to support a decent living without resupplies for 4 person-weeks. That means electricity, showering, dishes, drinking water, food, and propane for 1 person for 4 weeks, or 4 people for 1 week.

I believe one of the primary reasons folks get hassled for living full-time in RVs is because they are, for the most part, unsightly. Airstreams are beautiful feats of engineering, but even they don’t blend in well as a full-time dwelling in an urban or suburban environment. I was originally planning to use a maintenance-free material for the exterior siding such as corrugated aluminum or Corten RustWall panels, but I’ve decided to stick with the standard cedar planks. The less my house stands out, the easier it’ll be to find permanent parking.

Since I make my living on my computer, I want to be able to work comfortably anytime, anywhere. The electrical system will need to power a laptop, a few lights, and internet equipment for up to 12 hours, in the case of a winter all-nighter. It will also need to handle power spikes of a few hours at a time, such as running toaster oven, lights, range fan, and A/C simultaneously.

I also want to be able to maintain a comfortable 68 - 78°F whether I’m in Austin for the summer or Colorado for the winter. Closed-cell spray foam insulation seems to be the most practical solution here, if a bit pricey. Along with rigid foam insulation, a radiant heat barrier, and the interior / exterior siding, I’m looking at an insulating R-value in the mid 30’s. An 8,000 BTU window air conditioner should cool the 100 sq ft nicely.

For heating, I’ve seen a lot of folks go with Dickinson Marine’s propane fireplace, but I wanted something that provides more ambient heat as opposed to a single point-source of toasty air. Because if your toes are cold, it doesn’t matter how warm the rest of you is – you’re still cold. So I’m planning to integrate a closed-loop solar in-floor heating system.

I spent a couple days crunching numbers trying to size the system, but it’s difficult given the amount of thermal variables in a mobile tiny house. I plan to use 4 solar heating panels on the roof, anti-freeze coolant, variable-voltage DC pump, and PEX tubing snaked under the hardwood floor boards to heat my home. I can adjust the amount of heat exchanged into the home by dialing up or down the speed of the pump. Frigid nights will prove challenging, however – an insulated coolant storage tank may be necessary to collect the day’s heat. If all else fails, I can always light the oven to double as a makeshift fireplace.

Towing

Physics dictates that you’ll need a truck or SUV to safely tow a tiny house at highway speeds. Heavy duty trucks work best due to their weight, braking system, and long wheelbase. Most wood-framed tiny houses seem to come in at a dry weight of 4,000 - 7,000 lb, but mine will be substantially heavier at a maximum 11,000 lb due to its beefier construction and off-grid goodies. That significantly narrows my choices available for tow vehicles – most SUVs are limited to 8,000 lb and even full-size trucks won’t cut it with a maximum towing capacity of about 10,000 lb. Because of this, I chose a Chevy 2500 HD with a maximum towing capacity of 14,500 lb. Its price, lengthy wheelbase, 7500 lb curb weight, and single rear wheel make for the best combination of features given my budget.

Overview
My tow vehicle is a 3/4 ton Chevy truck. Ironically, it's longer than my house.

The front axle of my tandem-axle trailer almost perfectly bisects the house foundation, making it straightforward to estimate the weight distribution to achieve a desired tongue weight of 10-15% total trailer weight. The heaviest items will be located low and towards the front of the house, so I chose a wedge shape for the frame to balance the batteries, water tanks, etc that will sit close to the tongue. A tongue-supported storage shed and rear hitch-mounted luggage tray will provide flexibility for fine-tuning the weight distribution.

Knowing the estimated dry weight of my house, I can roughly calculate the forces involved in an emergency maneuver such as coming to screeching stop. According to MotorTrend, my truck has a 60 to 0 mph stopping distance of 134 ft. That translates to about 1 G-force, and will be less when fully loaded and towing. So the total lateral shear force acting between the house and the trailer could be up to 10,000 lbs, or 5 tons. I’ll probably want to use high-grade bolts to attach the subfloor and reinforce the corners of the frame with angle iron.

Framing

If I’m going to do all the work to build a tiny house, I want the full experience of architecting it too. I didn’t realize, however, how much tedious work is involved just to get an accurate model finished. I’ve been researching and working on it for the past 4 months part-time, and just now getting to the point where I feel comfortable ordering materials. If you haven’t noticed already, I’m using the fantastic and free Sketchup Make to draw these up.

Overview Frame
Measure twice, cut once. Accurately precut frame members will save me time.

I’ve decided to go with 12-gauge steel studs fastened with pan head screws and welded together at the joints. I’ve also chosen the more rust-resistant G90 galvanization in case I decide to live in humid or coastal climates. That puts the total weight of the frame at around 3000 lbs. It’s heavy, but without a solid frame, I’m worried the rest of the house could literally fall apart after a few years of highway jostle. And, I can always peel back and replace siding and sheathing but replacing a frame stud after it’s been welded and sealed in with spray foam would be a nightmare.

Local drywall supply stores usually have access to light gauge metal studs in various sizes and types from the manufacturer, and can have them ready for you in a few business days’ notice. Most will even precut them for free if you give them the desired lengths. Ideally, you could send them a list of the exact members you need and simply assemble them like Legos, no cutting necessary.

I’ve reinforced points where the frame needs to remain perfectly aligned or where I anticipate flex. This will keep the door hinging smoothly, and hopefully prevent any gaps or creaks from developing in the siding and floor boards.

Layout

The kitchen consumes the whole forward bit of the trailer, and features 18” deep counter tops. I like to cook, and I didn’t want my transition to a tiny life to undermine that. The sink is 18” x 16” x 8” inches deep – large enough to hold water for mopping the floors and washing large kitchenware. I’ve yet to find a decent propane-powered stove / oven however. Most seem to be built for either restaurants or camping. This Camp Chef outdoor oven comes close, but it’s lacking a broil option and automatic thermostat.

Overview Top
From left to right: kitchen, living room, bathroom. Not pictured: loft.

The living room / office / dining room is the most configurable area of the house. The large table and futon fold against the wall to provide a large, open area for a yoga session or slumber party. The energy-efficient chest-style refrigerator, located to the right of the futon, provides extra lounging space. The Seiki 39” TV / Monitor is mounted on an extending arm, functioning as a TV when against the wall and a computer monitor when extended towards the futon.

Most tiny houses sacrifice bathroom space for extra living and cooking space. While that seems to make sense at first, when you consider that showering, shaving, dressing, and using the toilet are activities that are best performed in the comfort of your own private space, I realized I wanted a generously-sized bathroom. I can use the extra room as a clothes closet, and do laundry in the shower pan.

That just about summarizes the design of the tiny hacker house. The next post will detail the electrical system!

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