Window/sliding door fragility on tiny house trailer builds?

I'm getting my toes wet on tiny house-style building by first making a bunkie on top of a 6x12 utility trailer on my off-grid property.
The goal is to tow it to a new place on the property 2-3X a year.

It will be conventionally framed 2x4 lumber construction. Do I need to be careful, i.e. go beyond what is typical for stick-built construction on a fixed foundation, for windows and doors? Especially the 5' sliding double patio door I want to put in the back?
While I won't be towing this at highway speeds, it will unavoidably bump around when being pulled down my forest dirt/gravel road.

Are large-ish windows and the patio door a bad idea altogether in this case? Do I need special bracing of the framing studs to avoid it being jiggled out of square? Special materials (e.g. tempered or laminated glass, acrylic instead of glass) to avoid heartache and glass framents later on? Or does conventional framing of the wall and conventional windows/doors provide the right mix of rigidity and flexibility to be OK as long as I don't do anything silly?

This project will be an uninsulated, summer use only bunkie, with single pane (or 2nd hand double pane) windows quite OK. But I guess the question applies too to fancier, insulated, double- or triple-pane higher-grade windows too.

Thanks for any advice!

Maybe.

In typical construction, the plywood or osb provides the shear (keeps it square).  We run it solid across the doorway and window holes and then cut it out with a sawzall or router.  That way we have C-shaped pieces that wrap the windows and stay perfectly square.  That will work with 1/2 sheet if you have about 2 foot around each window to the roof/floor/corner.  I would use 3/4 if you have around a foot.  If your patio door goes edge to edge, find a welder to weld a rectangular frame out of strap iron that you use to keep that wall square.  

Things like "patio doors" where the glass was/is intended to go down to the floor where it could get kicked etc is built out of thicker, more fracture-resistant glass than a regular window at waist height or higher would be. When vehicle glass breaks, it shatters into all those little bits to be safe for the occupants, and our motor home was required to have the same, so salvaging windows at a wreckers and looking for used motor home windows might be an approach for the small ones, or windows from an old industrial building that wanted security might also be a source. A typical patio window should be fine, but they're *heavy* so make sure you're not ending up with too heavy a build for the trailer shock absorbers - consider beefing them up a little before you start?

Alternatively, if this is just for summer use, look at how they used to install "storm windows" in old houses, and follow that design. When you want to move the house, just remove the windows if you're hitting a rough spot on the planned route.

Martin, last year I transported a load of windows in the bed of my pickup truck.  About fifty miles.  No cushioning or wrapping of the windows at all. I live on a farm and the roads sometimes look like the moon.  They were bumped around plenty.  None broke.  

Thanks for the replies, so far. In particular the creative ideas and the reminder on the structural role of sheathing and how its presence (or absence) around the sliding door and/or windows may have an impact, and ways to get around that. I had been toying with getting a few metal support elements welded on for extra rigidity, and this makes me think in a different way about where they might go. For instance, around the sliding patio door rather than in the corners or where there's a bit of a jut-out.

Alden, thanks, I am reassured by your experience transporting windows without special protection; that alleviates my concern on breaking them by vibration, though that still leaves the potential shear issue.

Jay, interesting idea re wreckers and storm windows. Not overly worried regarding the weight, given the trailer has 2x3500 lb axles.

I guess I'd say two of the most important things I've ever learned about building a structure is, one, overdo the foundation, and try to put as much quality into the infrastructure as possible.  

If the thought comes to you, "That'll be good enough for 10 years, it won't be hard to replace," rethink it.   I've never found myself with extra time to replace basic infrastructure, yet it happens for various reasons, often builder error, so it's a real pain when it has to happen, and cuts into all the other projects that are ongoing and on the list.  The stuff is always more expensive, we're always up against weather deadlines, and trying to limp through a winter with things going wrong is no fun, and not really a sign of being a quality off-the-grid person.

So, yes:

- double-paned windows have more structure, and if one pane should crack the other will keep moisture out, especially if the building will be abandoned for periods of time.
- protection on all the wiring in the walls, because mice are just relentless experts at getting into walls
- sliding glass doors often use rubber flaps around the bottom to block the weather and seal the door, but mice chew right through that and get inside between where the door slides and the solid pane sits.
- quality insulation in floors, ceilings, all walls, because a structure in a frozen environment undergoes a lot of stress
- Roof strong enough to handle snow-load.  Even if you don't get snow, a limb or a tree falling on it will do less damage when the roof is constructed for snow-load.
- protection of all propane hoses, they get chewed as well
- Rodent-proof screens on windows
- 30-year roofing
- All pipe and wiring openings through the floor sealed to keep mice and rats from chewing the opening bigger and getting inside.
- No plastic vents to the outside - rodents chew right through them
- Gas heaters need vents to the outside because of toxic carbon dioxide (to humans and pets.)  Even vent-free heaters need lots of air circulation because they are relying on "perfect" combustion, which won't always be perfect.  
- propane tanks need to be external, never inside, so they need a location that is vented and won't be near a crack in the wall where it can get inside anyway


If you have a quality building it will always be a pleasure to use and will only need regular maintenance, not endless repair/replacement issues.  If it works well you might even want to use it in the winter, because just leaving a building like that abandoned for winter months, any number of things could happen to it while you're not looking.

If during construction two boards or pieces of siding don't quite come together, there's a gap, and you think, well, just cover it with trim....perfect mouse opening.  If a gap can't be avoided, there are expanding gap fillers that harden like stone.  That's the only type of expanding filler I've ever found that they can't chew through.  Steel wool rusts, so it's not reliable in the long run.

And hopefully when you move it you won't be in a hurry.  Easy does it.

Cristo Balete wrote:- 30-year roofing

Only 30? I'd go for 50 at least! There's a *lot* of embodied energy in most roofing systems, and much of it doesn't recycle all that well. And I also find that many things that "claim" they're 30 year, don't actually last that long (there are exceptions). Also, roofs tend to be expensive and hazardous to replace compared to a window for example.

I know, we live in an "instant" society, so contemplating 30 years is beyond what many of us are programmed to do, but there are houses in England that are over 300 years old and still in use. Let's work at "resetting" our brains in terms of building for not just ourselves, but for the next generation as well. Even if you're circumstances "out-grow" a tiny house, if the roof is sound it can likely be re-purposed or sold or even just given away to someone in need.