Going Green - The Tiny House Project - Trailer Design CRITICAL IMPORTANCE (Part One)

My current job, it is not mentally demanding and it allows me time to think through problems and find different solutions.  This often means that a design I figured out the day before goes in the filing cabinet and a new modified design or a entire new design is born to solve the same problem.

SEGWAY, case in point, just got off my shift, but during my shift I mentally calculated my Minimum Critical Build Height requirement.  This excludes trailer bed height, and thickness of the floors and ceiling.  My critical required minimum build height is 10' 5", and can squeeze to 10' 2.5" but I will be making energy efficiency trade offs that I would prefer to avoid

The Problem - A Tiny Home on wheels requires a trailer, the size, dimensions and load characteristics of the trailer greatly effect the end design of the Tiny Home.  The end result is the Tiny Home is often designed to fit the trailer and not the trailer designed to fit the Tiny Home.  To get the MAXIMUM design space we need to design the trailer to FIT OUR NEEDS and not fitting our Tiny Home design to the trailer specification.

PROs - It maybe cheaper to construct the trailer than to buy a custom trailer or even a stock trailer.  The trailer construction will be designed to fit the needs of Tiny House Design.  The trailer will be design so it can be reusable.  By reusable, I mean it will be a simple process to jack the Tiny Home up and drop the trailer and then the Tiny Home could be lowered and leveled on to blocks.  So in theory you could design a Tiny Shed and attach to the trailer and move it, then attach a Tiny Green House and move it and the then attach your Tiny Home and move it.  One Trailer serving all you Tiny Homestead moving needs.

Since I actually plan on doing a storage shed and Tool Shop/Work Shop shed and I also want to do a Tiny Greenhouse and external vegetable garden boxes it makes sense to design one trailer to move all these objects.  So if I move from one plot of land to another I will only need one trail.  Moving day will require multiple trailer trips, but then again, most moving days do anyways.

It may also prove to be a major cost savings if we do this our selves.

CONs - We will have to go through the hassle of registering the trailer with the MTO and make sure it complies with ALL HTA codes.  We will also need to source and purchase all the parts and we will need to design and build the frame and all the mechanics for raising and lowering the Tiny Home and designing the connection and securing points.

MAXIMUM Tiny Dimensions

Since the Tiny Home we are design is meant to moved on the road without special permits, we have to comply with the HTA,  I am designing for Ontario, but the HTA none-special load restriction are uniform with all regions in Canada, and I believe the USA as well.

Load Restriction  Ontario HTA Section 109

There are weight, length, width and height restrictions that are all addressed under the HTA, the ones that are critical us are WIDTH and HEIGHT.  Weight is also important, but as long as your Tiny Home is within the weight restrictions of the trailer frame and axle limits we are fine in that department, I seriously doubt anyone's Tiny Home will exceed 65000 Kg (a special HTA weight limit)

1. Maximum Length - 23 meters or 75.4 feet (includes towing vehicle 19 feet)
2. Maximum Width - 2.6 meters or 8.5 feet
3. Maximum Height - 4.15 meters or  13 feet 7.25 inches

The Length Limit here is the combined length of the trailer, the trailer's tail overhang load and the length of the towing vehicle and the length of the trailer tongue and the length of the towing connection points.  A Ford F-250, F-350 and F-450 all have the same vehicle length 19 feet.  So we really don't need to worry about the length limit here

The Width Limit is not something to screw around with.  The width limit includes wheel axle assemble, the load on the trailer, the trailer frame, the trailer wheel fenders.  If you exceed this 8.5 foot limit you may be in for a world of inconvenience.  Getting special permits in Ontario is easy enough, providing you don't exceed other special over size limits, but if you want to go to another Province or to the USA, you will need special permits in each State or Province.

The Height Limit is another one not to screw around with.  If you get caught with an over height load the police can remove the plates and tags of the trailer right on the spot.

For the Tiny Home Design, it is the width and height that are critical design limitations, every inch is worth its a mile and the lose of a single inch in width can make or break a kitchen design.  Trust me on that one, going from walls with 2 by 4 studs to walls with 2 by 6 studs will cost you 4 inches in internal width, that lose of four inches was enough to completely trash my initial kitchen design. The difference in R value for a my 2x4 walls design is R=23.5 the 2 by 6 wall has a R=33.5.  So there are trade offs to be consider, loose 4 inches but get a 40% improvement in wall's ability to resist heat transfer.  The recommend R-Value for Southern Ontario is 28, so it is worth considering.  While Tiny Homes are NOT subject to building codes if they are on a trailer, you still may want to consider getting as close to or exceeding the building codes them if you can.

As for Height, it is best to limit your design to 13' 6" and this from the ground to the tippy top of Tiny Home WHILE it is on the trailer.  The critical trailer design characteristic here is your trailer bed height.  The lower slung the trailer the better.  Many off the shelf trailer designs have beds that start at 20 inches and go as height 30 inches.  That is a lot of lost height and can make or break you bedroom and storage loft areas.  So anything we can do reclaim from the trailer bed height is living space we can add to our Tiny Home. 

• A trailer bed with a 30" high bed is an 18.5% lose in living space
• A trailer bed with a 20" high bed is a 12.4% lose in living
• A trailer bed with a 12" high bed is a 7.5% lose in living 

The lowest deck height I could find in a trailer were those that are used to transport cars, from my limited search the lowest was 18"  I think this will be very best we can do in the design, but further research is required, but I think with specialty design for tiny homes I can get it down to 16", that and possible cost saving, the trailer designed to fit our needs and some other added design benefits, I believe it worth while to invest further research time into this area.

On a related note, just got the final design for the Kitchen and Bathroom completed.  I don't want to boast, but it is pretty awesome and fully functional.  Counter top space galore and plenty of room to move around in,... for one person.  Only one Chef allow in my Kitchen at a time,... and it be me!!!

Related Articles

1) December 3rd, 2015 -  The Tiny Home Project
2) December 5th, 2015 - The Tiny Home Project - The General Plan
3) December 7th, 2015 - The Tiny Home Project - Minimum Requires For Going Off Grid