Monday, September 16, 2013
I will have to build the front door, I just can not find a 6 foot 2 inch tall 24 inch wide door out there except for paying a carpenter to make it for me. I don't want to spend $1500 on a custom door, so I will be building it myself. Windows, I have discovered are available. 17" wide by 24" tall double hung windows are available commercially, they are aluminum frame, but only $50 each. I still may just make my own windows, and I will have to make the ones for the loft as nobody makes a 18"X18" diamond window that opens.
My Construction is going to be simple. 2X2 walls, 2X4 for the loft floor, and 2X4 for the roof (because I am going to bird mouth the ends and do traditional roof construction) 1/4" plywood for all exterior surfaces and interior wall finish. with 1/2 for the loft floor and the main floor. Vynal siding or Cedar siding is possible as they both are close to the same weight. I dont trust either to deliver any structual stability to the microhome, so the 1/4" plywood sheathing will still be installed.
I feel better with 16" spacing on studs for 2X2 studs, I may try 20" on the roof and loft to save a little weight by cutting out 2 2X4's from the construction. The loft will add strength to the whole building. I am still very worried about weight, so I really need to calculate things out exactly, then compare to the real world. Let's start with the weight of a 2X4...
So, let's assume the 2x4 is eight feet long. A 2x4's actual dimensions are 1.5" x 3.5", so its volume is 1.5 x 3.5 x 96 = 504 cubic inches. Divide that by 12 to get 0.2917 cubic feet The nearby link shows the weight densities of common lumber. Let's assume it's made of pine, which is pretty common. If we use the high end of the range, pine has a weight density of 34 pounds per cubic foot, so 0.2917 x 34 = 9.9167 pound = 158.7 ounces, more or less, depending on the type of pine and the corresponding density. So my calculations are a bit more conservative than the estimates I made. 1 Linear foot of 2X4 is 1.25 pounds, so 1 linear foot of 2X2 is .65 pounds. That is a little lighter and makes me feel better. for the framing. It is actually surprising how heavy wood really is and how even a tiny house can weigh a TON in short order even when using smaller lumber for framing. Let's try and get a better calculation for the plywood. This one is easier as the APA has a specification that the manufacturers are supposed to follow.. 3 pounds per square foot per inch of thickness.. So if we calculate that out, .75 pounds per square foot of 1/4 inch and 1.5 pounds per square foot for 1/2 inch This is darn close to my guessimates. I found that 2 inch foam board is about .3 pounds per square foot, and Cedar lap siding is .5 pounds per square foot.
We can now run some real weight calculations, and things get heavy fast. the wall framing will weigh about 40 pounds, the sheathing on the outside and the paneling on the inside of the walls will weigh 330 pounds. The insulation for those walls will weigh 62 pounds. The trailer frame is 350 pounds, and the floor plus insulation is 77 pounds. The Loft being built from 2X4 and covered in 1/2 ply will weigh a whopping 208 pounds. The last bit is the roof, and this will be heavy. 3 feet 4 inches to the peak from the loft floor. with 3" of insulation and 1/4 sheathing on the outside and inside as paneling. PLUS the tar felt and metal roofing. Each rafter will be 4 foot 8 inches to give us the 12/12 pitch that we need for the headroom inside. using 2X4's we have 25 of the boards at 4.67 long and 1.5 pounds per foot. Gives us 370 pounds for the roof. So we are already at over 1400 pounds and we have not added anything inside. like flooring, siding outside, windows, trim, electrical, furniture, etc... I can easily see it hitting 2000 pounds without much effort. and this is going for light weight and nothing inside it. My other concern is that I have the BULK of the weight in the entire trailer above the 6 foot level making the Center of gravity dangerously high for the wheel width, just by guessing I place the CG at the 7 foot mark above the deck on a trailer with a 6 foot wide tire stance.
This means that my PopUp trailer find will NOT be a good candidate for the microhome project. It will make a fantastic Large Teardrop camper though so that will be my project for that frame. I need a trailer that can hold 3000 pounds, preferably 3500 pounds. and I still have no idea how I am going to get the center of gravity to a location that does not make me afraid for my life. A CG that high will mean a trailer tip over If I ever had to swerve. I am starting to wonder if ANY of the microhome designers out there ever put any engineering into CG and towing safety.. I am also starting to wonder about safety of 2X2 construction with well over 700 pounds of just the building on the walls. add another 500 pounds for 2 people and gear in the loft and you now have a 1200 pound LIVE load on the 2X2 walls. I am certian that 2X4 and 2X6 will easily handle it, but that will drastically increase the weight to the world of 4500 pounds finished.
I do know that this will slow down my build process, but having real information instead of trudging ahead on a guess and a golly is a good thing. I still need to get more weight and design information going, but Instead I am changing to building a teardrop camper for the spring to get some construction experience with the trailer I already have. I am not abandoning the microhome project, but I am seeing a feasibility problem creeping in that will exceed my limits. I need to be able to tow it with my Jeep and at what I see is becoming a 4000-4500 pound project is beyond the towing ability of my current vehicle. At that point you might as well build a larger microhome because the needed jump up in tow vehicle and trailer size will allow you to build a much larger microhome that will be far easier to live/camp in. Even just increasing the size to 7.5 feet wide and 16 feet long will give a drastic space increase.
Friday, September 13, 2013
Again using the 5X9.5 above... 60 inches by 114 inches with studs at every 18 inches aprox. end walls will need 5 studs plus 3 for top and bottom plate. Side walls need 10 studs plus 3 for top and bottom. Figure them at 6'4" tall or 76" so let's calculate the amount of inches of boards just for the lower framing. 76" X 30 vertical studs + 76" X 15 horizontal studs (overestimate a bit) I get a total of 3420 total inches of 2X4 or 285 linear feet. Multiply that by 1.5 and we get 427.5 pounds of JUST the wall framing add another 160 pounds for the loft floor and the roof framing. we have a total of 590 pounds of wood just for the framing add in another 20 pounds of screws and 10 pounds of glue to assemble it all. 620 pounds and we just got started.
Let's look at the floor, roof and sheathing. 1/2" ply will be good for the roof, 3/4 for the floor, and 1/4 for walls. Plywood is 3 pounds per square foot per inch of thickness, so 1/2 ply is 1.5lb and 3/4 is 2.25 with 1/4 at .75 round that to .8 we have 108 pounds in just the floor 3/4 115 lb for the roof and 146 pounds for the wall outside. 989 pounds for just a box with a loft and floor. not including any siding, no interior wall covering, no interior walls, no insulation, no wiring, no windows, no doors. BUT you can safely fudge that to see that the complete place will weigh near 1400 pounds if you went for very light materials. And this is for the ungodly small 4' 4" interior width. Here is some perspective on that size, a very very small cubicle in an office is 6' wide by 6' deep you have just enough room to move your chair to get to your desk.
The harbor freight trailer is rated at only 1500 pounds, so it's straight out unusable, we can not use it just because of weight capacity, and honestly it's too small anyways. Time to find a junker camper to get the frame from, I'm thinking a popup camper that is rotted out. The smallest I recommend is a 6.5 foot wide by at least 10 feet long those typically are rated for around 3500 pounds (old ones) so that will work for our mobile micro home. I need to find a trashed popup camper or other camper that I can salvage the frame from....
NOTE :The weight calculations are not needed if you are building on the ground as a permanent building, only a trailer really needs this unless you are thinking of using the cement block piers that have for making decks, then you need to understand the structure weight so you can calculate out how many piers you will need. This can be used in some communities to get past zoning laws as the building is not considered permanent if it is only sitting on the ground.
Next we explore the safety and load capacity of 2"X2" lumber that they make most travel trailers and RV's out of... as well as lighter materials for siding...
Sunday, September 8, 2013
Most of the Microhomes you see online are built on very large trailers and they have a high weight that requires a F-350- F550 truck to pull them. If you were to build your microhome on land as a cottage, this is not a concern to you, so you can completely ignore this restriction. My ultimate goal is to build a permanent microhome on a plot of land as a "cottage" but right now I dont own any land outside of the stamp sized plot here in the city that my house takes up more than 80% of. So my first attempt is going to be a small camper that looks like a nice tiny cottage that my Jeep Grand Cherokee can pull. It will NOT be spacious, as I am looking at using a 8' by 4' harbor freight trailer as the base. But I have some plans for squeezing some extra room out of that platform. And if I am able to find a better low cost platform, such as the Northern tool 5' by 8' I may investigate that.
I am looking at conserving space and making it light. So walls will be 2"X2" lumber similar to RV construction but using foam board for higher insulation and lower weight. Bathroom facilities in this design will be a portable toilet only. Space is going to be extremely limited, I am looking at a max of 43 Sq feet of living space with a tight sleeping loft that will have a useable 4' by 7' sleeping space but with sloping walls that peak at around 3'5" The largest space that needs to be "wasted" is the bathroom area at nearly 9 square feet. Building very small for my first attempt forces me to be hyper sensitive to space concerns and space waste Most people will sneeze at 9 sq feet, but I am losing almost 20% of living space over it. I am not going to build in any water plumbing as it is a waste of space and resources for something so small. I will be building in technology that will make the place feel like a home. Networking, Wireless, and even a "whole house" automation system that will run off of the 12 volt power that it will be wired for.
Electrically, the whole place will be 12volt based. All lighting will be LED and 12 volt. I will wire in one 120V outlet in the "kitchen area" that will only be live when on shore power at a campground. I am also going to install my solar power/charging system in this camper to test viability and real world performance. I am going to aim for 200 watts of solar with about 600AH of battery storage. Total normal daily draw should be less than 800 Watt hours considering that most of it will be wasted running the network and automation equipment 24 hours a day with the largest draw being the TV or the whole house audio for a few hours at a time. Wall outlets in the loft and main floor will be standard Car power outlets to allow phone chargers, etc to be used. I am tossing around the idea of building in a 2 amp USB charge station to reduce clutter and the need for chargers. I will use a marine fuse panel using standard car ATO fuses with a voltmeter, battery health meter, and master shutoff switch in the bathroom area.
I have not figured out heating, I will be using Polyisocyanurate foam board for insulation as it has the highest insulation value and has reflective film on the facing. two layers of this in the walls will give me a Wall R insulation value of 13.2 and a ceiling of nearly double that. Plus the reflective facings will decrease the amount of heat loss/ heat gain from outside. A portable small electric heater when on shore power will provide more heat than the place will ever need. I want the place to look like a cottage, so it will be sided with cedar (or pine) shake and all windows and the door will have to be custom made. I will probably use standard asphalt shingles to reduce noise in the loft while sleeping and it will actually add another 2-3 R value to roof insulation. main floor ceiling height will be at 6' 2" I need the rest of the vertical space in the loft. Entry will look grand as that will be open to the peak for access to the loft with a simple ladder that is stored on the wall by the door. Lastly to make it look even more "cottage like" I am going to embellish the entry end with a 1 foot wide "porch" with a matching roof overhang and a pair of Corner posts. This will be purely decoration but act as a step for the entrance and finish the look. This will overhang the end of the trailer by 1 foot I may put a short railing up as well to further add to the illusion. The entry door will swing outward to save space inside the camper, yes this is not ideal but every camper made has this design to save precious space.My biggest challenge is to keep the whole thing light. I need to come in under 1000 pounds so I have cargo capacity to put camping gear and bedding inside to use it as a camper. The trailer I am looking to use as a base is rated at 1700 pounds. So saving weight will be high priority. Luckily 2X2 lumber is less than a pound per linear foot. I still need to decide if I do a small table and 2 chairs for the main floor or build in a bench that slides out to add sleeping for a 3rd person.
Wednesday, September 4, 2013
Work has consumed all of my summer. I was hoping to start building a "microhome"/ "camper" on a smaller trailer this summer but I spent most of it in an airplane and airport and in other cities other than my own.
I hope to pick back up where I left off soon, until then, here is a very cool finnish microhome I missed earlier this year
I hope to pick back up where I left off soon, until then, here is a very cool finnish microhome I missed earlier this year