Tiny House Weight Debate

February 26, 2013 § 21 Comments

How do you calculate the weight of your tiny house and how do you know if your trailer can handle it?  There are several ways these things can be determined, it all depends on your situation, as does everything… Here is my logic and some of the tools I used to get there.

lifting-weights-to-lose-weight

The first thing to decide would be if you already have a trailer you’re going to build on, if so then you have to decide how much it can carry and design within this.  I am not going to go through the details of how to find out how much your trailer can already carry because Andrew already did a stellar job of demystifying that over at Tiny r(E)volutions HERE.   So, if you already have a trailer, figure out how much you can load it with and design your house using the basic principles below.  Note:  If you buy plans from Tumbleweed or the like they generally come with a gross build-out weight to them, that is handy to use so long as you know you’re going to use those plans with no/minor modifications, if however you are going to change some materials around (say you want granite counters instead of plastic laminate counters) you can use some basic calculations with the tools below and add that to their weight to verify that you’re in the right range still.  

What if you design your own tiny house, how can you guesstimate your weight so you know how much your trailer will have to hold so you can buy the correct trailer?  You COULD find a similar-ish Tumbleweed and err on the side of caution guessing a little heavy but that isn’t really a solid method and I don’t suggest it…  For those of you who have followed my project you know that I pretty much had the house designed before I got the trailer and that the trailer I found needed to be modified to hold the weight I wanted it to… Because I had these known modifications I was able to more accurately plan my axles, both the location and the maximum weight.  I ended up buying a duel 5600 pound (each) capacity axle flat-bet goose-neck trailer, but initially I was planning on a concrete floor (6000 # in itself) so I ended up installing a third axle just to be safe.   If you are going to go this way and customize your trailer be sure to calculate in the weight of your trailer, mine is just shy of 3000 pounds for all the steel.  If you add 6000 for the concrete and 3000 for the trailer (it is home made and a little beefier than a trailer shop would make a trailer, so it is heavier than most) it brings you to 9000 pounds before you even add the house!  So two 5600# axles would only leave me 1600 pounds for the rest of the house in that example, hence I welded on a third axle allowing me to go up to 16,800# total, allowing me 7,800 for the rest of the building materials.    Now, through the design process I have since nixed the concrete in favor of much lighter weight tiles so my trailer is overkill, that was a calculated decision though.

Through the planning phase you will most likely be doing a sketchup model or somehow actually drawing plans, tiny houses are small enough that you can pretty easily take a volume or square foot count of materials fairly painlessly, you have to do this to buy your materials anyway.  Once you have those calculations you can apply weights to things and get a pretty decent idea of where you’ll stand.

I have collected a list of common building materials that you can use.  I like to add a contingency onto the end weight to account for things that are harder to pin down, like the  faucets, hardware, furniture etc., I suggest about a 20% contingency, that may seem high but it’s better to be over than under!   If you make a material list and add things up and it’s too heavy you can start to massage your finishes to make things work out better.  This is a pretty important part of the process so spend some time on it.  I keep saying that this project is weird for me because there are three main design factors that went into my project and the least important is aesthetics (weird for someone with a design background).  The MOST important has been weight and number two is cost since I set a pretty tight budget.  THEN I get to worry about looks :).

Common Material Weights:

Wood Stud, 2×4 (pine):      1.31#/linear foot

Wood Stud 2×6:    2.05#/linear foot

Metal Studs:  1#/linear foot

SIPs Panels, 6″:   3.47#/square foot

Insulation, rigid – 1″:  1.5#/square foot

Insulation, batt 1″: .04#/square foot

Insulation, spray-in 1″:  .5#/square foot

OSB Sheathing, 3/8″:  1.22#/square foot

OSB Sheathing, 1/2″:  1.63#/square foot

OSB Sheathing, 5/8″:  2.03#/square foot

Plywood, 3/8″:  1.08#/square foot

Plywood, 1/2″:  1.44#/square foot

Plywood, 5/8″:  1.8#/square foot

Gypsum (drywall), 1/4″: 1.1#/square foot

Gypsum (drywall), 3/8″:  1.65#/square foot

Gypsum (drywall), 1/2″:  2.2#/square foot

Gypsum (drywall), 5/8″:  2.75#/square foot

Metal Roofing: 2.5#/square foot

Asphalt Roofing: 2#/square foot

TPO Roofing:  .7#/square foot

Carpet: .3-.7#/square foot

Porcelain tile: 4.5#/square foot

Hardwood Floor (birch), 1/2″: 2.4#/square foot

Hardwood Floor (oak), 1/2″: 2.05#/square foot

Hardwood Floor (poplar), 1/2″: 1.45#/square foot

Wood Planks (pine), 1/2″: 1.46#/square foot

Cement, 1″: 12#/square foot

Granite, 1/4″: 3.6#/square foot

Hardie Board Siding, 1/2″: 3#/square foot

Linoleum: .75#/square foot

For a more comprehensive list click HERE.

For a more comprehensive list of various woods click HERE (a board foot is equal to a 1′x1′x1″ section of wood, you can do simple math from there to get to your thickness/width).

You’ll notice some of these are assembly weights, if that is the make-up of your wall skip adding up the individuals and just use that weight per /square foot of wall.

In addition to your building material weights you will need to account for your appliances, the best way to do that is, if you order them on amazon there is an exact weight.  If not you can certainly get an idea on how much a stove similar to the one you’re getting will weigh, again, lean to the cautious side and round up… If you are going to have a water tank on board or a water heater use it’s ‘when full’ weight (water weighs 8.34# per gallon).

Once you have all of that added up figure out your contingency, I use 20% to account for the faucets, the furniture and all those little pieces that it wouldn’t be efficient to add up…  Then you have your weight or at least a healthy stab at it to get you started!

Hopefully that is a semi helpful bit of info!  Anyone else?  How did you determine this?  Did you figure it out beforehand or just build?

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§ 21 Responses to Tiny House Weight Debate

  • Great information this will be very helpful in my build

  • April says:

    This is amazingly helpful. Since I am building on a 30ft trailer and planning tip-outs, weight is one of my big concerns. Thank you!

  • Great resource you’ve got here, Macy! I’ve been considering sheetrock for my interior walls and now that I see that it’s not much heavier than ply, I’m even more inclined to go that route. I know you did this as well- any tips for how to avoid cracking in a moving house?

    • Macy M says:

      Hi Ethan! There are no real good tips or tricks on that but the great thing is that drywall is easily fixed. If you can build a house you can definitely patch drywall if needed! That being said, I had planned to use 1/4″ drywall but whimped out and beefed it up to 3/8″ in the end. After dry-walling, in hind-site, I would not have any reservations about going to 1/4″ next time. I know others have used drywall, Carrie and Shane with Clothesline did 1/2″ drywall and used some sort of special caulking detail I believe in between the sheets rather than taping and mudding. They have moved their house a couple times and had zero issues, I’m not sure if this is attributed to their edge detail or that it just wasn’t an issue, they may have some good comments to share though!

  • caseyfriday says:

    Or you can take the approach Jessica and I did – just buy a MONSTER trailer with two 7,000 lb axles! That beast will carry anything!

    I actually thought about weighing every single piece of wood, screws, windows, etc before I started. That thought didn’t last long. :)

  • […] This site seems to be a good start on estimating your weight issue. […]

  • […] Tiny House Weight Debate at MiniMotives […]

  • Tom Swinburn says:

    I’m figuring on determining a finished weight for my tiny house before hunting for a trailer. I want to go as light as possible and still make it rigid and strong. I’d like to be able to tow it with my half ton pick-up, which pretty much limits me to around 5000# total. Fir studs, light but not as strong as pine. Hurricane straps for strength and rigidity. 1/4 inch sheetrock inside and no cabinet doors, just dowels for holding back cans, etc. The outside finish is where I’m having trouble. Metal roof for sure, but I really like the horizontal cedar, stained very lightly. I also want to go 102″ wide, the legal limit here. I’m THINKING about using 1X4 cedar, split with a thin saw blade for the narrowest possible kerf. Question? Will that make the exterior too thin to withstand wind, blown around objects and the like? It’ll end up being shy of 3/8 ” if I go that route.

    • Macy M says:

      I’m not all that familiar specifically with cedar, 3/8″ is not too thin for like a hardie-board, it may be pushing it a little for raw lumber though. Come to think of it, some of my pieces of siding are just as thin and they do just fine and traveled well (I am more worried about them flying off on the road than something flying at them!). Wondering though, since you are SO light on weight have you considered using metal studs instead of wood? You could see some weight savings there and they would be strong! Not positive but it seems worth looking into! You can definitely get away with 24″ o.c. studs too either way rather than the standard 16″ o.c. Are you documenting your house build at all? I would love to follow along!

      • Tom Swinburn says:

        I’ve already figured on 2 foot stud spacing. I haven’t even started yet, as I want a complete picture in my mind. Still need to verify weight and get a trailer. MANY used ones around here. Following along on some of the threads I keep seeing new ideas, wonderful ideas. Yours though is the first I’ve been able to get weights of materials, the kind of info I MUST have. I gave metal studs (structural) a thought, but though lighter you need to encapsulate your wiring in conduit of some sort. Kind of kills the savings although it beats termites. When I get started I’ll document and share, for sure. People in this group are FANTASTIC about sharing the exact kinds of things one needs to know. I appreciate that beyond words. The more the tiny house movement grows the better off we, as a country and the world at large will be.

        • Macy M says:

          Ah yes, I can see that about running conduit! I think it’s still worth it in a cold climate ESPECIALLY if you’re using spray in insulation because the insulation can really get in there, there is a lot less thermal bridging! But I have no idea where you are. That is one of the things, the openness of the TH community, that I loved the most, I am always here and happy to help however I can! I couldn’t agree with you more about it being best for everyone, be sure to keep in touch and let me know when you kick off! :)

    • MiniModernMansionProject says:

      Thank you bareearthpottery! This is a very thorough sheet!! I’m planning out a a 26′x12′er (wide load!) so I really need to watch my weight so I can still pull with a C-class license.

  • MiniModernMansionProject says:

    Has anyone tried TPO roofing for their tiny house? It’s certainly the best option in terns of weight savings – is there any reason this wouldn’t work as well as shingles or metal?

    • Macy M says:

      I used it, works great.

    • TPO or a similar product would also help eliminate leaks. Try to design with few roof penetrations though. As far as wiring with metal studs you might be able to install plastic bushings for the wire to pass through, and cable clamps to tighten down and secure the wiring where required.
      Btw, my wife and I remodeled and lived in a 15′x30′ building for over 6 years. It’s become a rental now but maybe someday we’ll be back. It was an enjoyable experience and all it lacked was some square footage. I’m envious of you guys doing the tiny homes on trailers and wish all good luck! Hmmm, I’ve got an old 20′ trailer frame up in the pasture! Just saying (and dreaming).

  • Night*sky says:

    I’ve got a vintage travel trailer I plan to restore and live in full-time, and because the entry door is on the back I have been looking at tiny house plans for ideas. It seems many if not most TH have a majority of the weight in the front, kitchen, bathroom and loft. Since I will be very mobile I need to try and figure out how to build and space heavy items to come up with the proper 9-15% tongue weight. Other than checking tongue weight as I build, any suggestions?

    • Macy M says:

      My method was to make the list of all the heaviest items in the house and put those over the axles. I have noticed the same trend of front loaded trailers, sometimes those are accounted for with special made trailers but not usually. Unfortunately I don’t have much of a better process than checking as you go but I found it to be pretty spot on to take all the heavy stuff and put it over the trailers axles, wish I was more help!

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