Excerpt from our Digital Tiny House Workshop
Weight calculations in a tiny house may not be the most exciting topic for you, but they are incredibly important nonetheless. If you don't pay attention to how the weight of your moveable tiny house will be affected by your design, you leave yourself open to a long list of problems, not the least of which is the total failure and destruction of your home. Okay, I imagine I have your attention now! I'm not trying to scare you just for the sake of scaring you. I'm trying to make clear that the importance of accurate weight calculations cannot be overstated.
Many people go straight to the obvious way of knowing their house's weight: they weigh it! Sure, you can drive the home to a weigh station and have the numbers pour out of the scales, but that is really only good for confirming your earlier estimates or checking to see how the addition of furniture or personal items has impacted your overall weight. After all, you've already built the house at that point. If you learn that the weight is close to 20,000 pounds and you've built it on a trailer rated to 14,000 pounds, you've got a serious problem. What's more, it may be too late to remedy that situation.
So how do you go about calculating the accurate weight of your home in advance of the build? The good news is that there are several good options available. You can take the literal approach of counting every piece of wood, metal, and glass that goes into your house and creating a weight list. The numbers for those items can be found on websites like HomeDepot.com that list unit weights for almost every item they sell. The challenge here is that the weight listed may be for a full-length wall stud at 8'-0", and you may only need to use 7'-6" of it.
You'll have to adjust each number to the amount actually used if you want a completely accurate weight calculation. Of course, you can always estimate things and round up to the closest full foot or another unit of measurement. This is what Gabriella did in the lead-up to our tiny house build, and her accuracy was amazing. When we finally had the chance to see what hOMe looked like on the scales, we discovered that Gabriella's number was within a few pounds of the actual weight. Nicely done, babe!
Another option is to use engineering tables and/or the building code. There are specific tables and lists within the code and books like "Basic Engineering Calculations for Contractors" that address common building materials' weight. For example, you can search for the weight per square foot of a wall assembly built with 2x6 studs: 16" on center, with 1/2" subsiding (sheathing), 1/2" interior wall paneling, and 3/4" exterior pine lap siding. This eliminates the need to count every stick and nail but also gives you a well-researched number to work with during your weight calculations. It's a faster way of generating an accurate weight for your home, assuming you can find assemblies that match your design and construction plans.
As a reminder from the recent blog post "How to Tow a Tiny House: TinyHouseBuild.com Digital Workshop," it's important to know the weight of your house, but it's equally important to know the weight distribution of the build. The side-to-side weight distribution is paramount to safe towing practices. We've all seen the sign on the highway of the truck tipping over on a tight curve, right? That could be you if you don't pay attention to the way you distribute weight around your moveable tiny house.
I'll give you a quick example. Imagine how your house might become dangerously weighted if you designed it in a way that placed all of your kitchen cabinetry, appliances, clothes storage, and solar batteries on one side of the house and the open space of the "great room" on the other. Can you see how the risk of roll-over would be huge in this scenario as opposed to having the home balanced from one side to the other?
The same attention to weight is true, although perhaps less obvious, regarding front-to-back distribution on the trailer. You want to lock in the ratio as close to 60:40 as possible. This means that 60 percent of the weight should be in front of a line drawn in the center of the axles, towards the towing vehicle, and the remaining 40 percent behind that line. This will reduce the amount of sway your trailer produces, thus making the house easier and safer to tow.
Too much sway can cause you to lose control of the trailer and can ultimately lead to it flipping over at speed. This is obviously bad for so many reasons, from the safety of others around you, to the well-being of your home, to your own personal safety.
So yes, weight calculations in a tiny house may not be sexy, but the results are what you're after, not necessarily an exciting evening with your construction plans. Think of it this way. If you do your calculations well, towing your moveable tiny house will be boring, as it should be. If you don't take the time to do the calculations well (or at all), then towing your home could move from boring to exciting to deadly in a heartbeat. I prefer the boredom of calculating weights myself.
Stay tuned for more from the TinyHouseBuild.com Digital Workshop Series, or click HERE to purchase the entire 54-episode tiny house workshop, covering everything from tools to codes to construction details, creating a tiny house lifestyle and everything (truly!) in between. Each purchase comes with over $300 in FREE bonuses (including our hOMe Digital Total Plans Package).
FREE Episode: IMPORTANCE OF WEIGHT CALCULATIONS IN A TINY HOUSE
by Andrew Morrison