Build a small and sturdy residence in the woods. Plan on moving to the property somewhere in a 5 year time frame as we are both still working 90 miles away. Do the construction ourselves for multiple reasons - keeping the cost down, having a hobby we both could enjoy, sense of accomplishment, etc. I wanted something which would be long lasting and low maintenance since there's no such thing as maintenance free! :( I'm in my 50s and have 3 herniated disks in my back. My wife is 5'3" and afraid of heights. I needed something we could work with that was light weight but I also wanted something strong and durable. We ruled out a 2 story structure and eventually even eliminated the prospect of a sleeping loft. (No one my age wants to wake up and climb down a ladder in the dark of night to pee!) When we were planning our Little House in the woods, I wanted to do so without a mortgage. This meant buying materials as we went. We didn't have a budgeted amount to spend monthly or a good estimate of what the building would cost. We just wanted to take whatever we had left over that month and add to the project as we went. It might take 3 months, it might take 2 years to get it dried in. We had to plan for something that would withstand the weather while under construction. After researching the matter for quite some time, I came to the conclusion that we had 2 choices - concrete & steel. Concrete cinder blocks would be something we could use. I could buy a handful at a time but the weight of the blocks in addition to the weight of the concrete it would take to put it together put this on the "NO" list. Steel, on the other hand, was light weight and went together like a stick house. (I really don't like the look of concrete block houses.) It would also weather well if the project got delayed or suspended for a while. Steel it was!
Steel v Wood
Advantages of Steel:
1. Stronger than wood - The same steel dimensional member (2x4 or 2x6) is typically 5x stronger than it's wood counterpart. Wood studs in a wall can typically withstand about 500 lbs of pull before they separate. A typical steel stud would withstand 2500 lbs of pull before it starts to fail. Steel is measured in gauge or thickness. By offering the same component (2x4) in varying strengths, this allows you have longer spans without using multiple members. If you have a floor or ceiling opening that's 30' to span, with wood you would need need to go to a larger dimension, say a 4x12 or 4x14. With Steel you could still use a 2x configuration (2x12 or 2x14) and just dial up the strength. Typical structural steel is 18 gauge but it is also offered in 16, 14 & 12 gauge. You can also nest components for additional strength by putting a stud inside of a track and creating a single width beam. We used 18 gauge steel for almost all of our house. The exception was on the roof. We had a large overhang and I wanted to make sure it was secure enough to walk out on top of. Here I used 16 gauge.
2. Lighter than wood - Steel is much lighter for the same strength component and often for the stronger component. Kim and I were loading and unloading all of our own materials. We were climbing ladders and installing 18' ceiling joists. We could not have managed this without a lot more wear and tear on our bodies without steel. I would think that a lighter and stronger component would be very desirable in a mobile Tiny House.
3. Weatherable - We couldn't afford all of the materials and time needed to get the house dried in in a short period. We needed something that could sit out in the rain, for months or years at a time if needed, without warping or rotting. This meant steel. Galvanized and weatherproof, this would work. There's a custom home builder here in North Texas that builds with steel. I noticed a steel frame in one of their neighborhoods several years back. They built it for demo purposes to show people the skeleton of the house. It had been there for several years when I noticed it yet there was no weather damage. They could have sheathed the house and put a roof on it as it sat.
4. Consistant Pricing - Steel is priced by length and by weight (gauge). Much like wire, the smaller the gauge, the thicker (stronger) the metal. Your pricing will be by the component and length. it doesn't get more expensive as it gets longer, like wood. Try ordering a bunch of perfect 20' wood 2x4s and compare the price per foot to 8' components. The reason is simple. A tree that yields a perfect 20' 2x4 is much rarer than one that is suitable for smaller lengths. Steel is delivered to fabricators in large rolls. They feed it off of the roll and into a machine that rolls and forms the shape desired. This means you can design and order the components for a project at the exact dimensions you need instead of 2'-4' increments, knowing you will need to cut off the ends and throw them away. If you want the wall height in your Tiny Home to be 10'7", you can order the studs in that exact length and only get charged for that length - no waste. If yo were building out of wood, you would have to order 12' components and cut them to length, wasting the other 1'5".
5. Durability - There's something very comforting about building a house in the forrest made out of a material that's water, insect and fire resistant. We hope that by building out of avery durable materials, our Tiny House will be here for 100 years or more.
6. Straight & Consistent - If you've ever built with wood, you either have to go to the lumber yard and hand pick each component or you have to order more than you need because you know that you get boards that are warped or arched or have knots and weak spots in them. Steel is straight and consistent, pretty much all of the time! You get straighter walls with a lot less effort.
7. Environmentally Friendly - Steel is 100% recyclable and very long lasting. You can order the components at the exact length you need, reducing waste as well as labor and resources to cut them to fit. You can also take all of the scrap that you did end up with to a metal recycler and sell it. It will be melted down and used in the next project that comes down the road. Steel typically lasts longer than today's wood components. Wood construction material is made from soft woods that are harvested from fast growing trees. It would be cost prohibitive to frame a house out of oak or hickory for this very reason yet you can build with steel and use a component that is rot/insect/fire resistant, stronger than Oak and a fraction of the cost. Our scrap steel from our house project is still out at the property in a Walmart tote. I kept waiting to see if we would fill it up before we took it to the recycler. We haven't filled it up yet - maybe when we build the decks and the storage building. :)
Advantages of Wood v Steel
Wood is not without advantages. It's cheaper than steel in short components. When buying in typical 8' lengths or less, wood is cost effective. That gap closes though as the boards get longer. You also have to look at how many components you have to use to get the strength you need in a wall roof or floor. If you have to order 4x or 6x wood components to make a span, you can often buy the same strength 2x in a thicker steel component. You also need to look at permanence. To have wood last, you often need to use pressure treated components. These still have a limited life span but last much longer than untreated wood. They are also much more expensive than untreated wood so you should consider this cost when estimating. Consider how often will the building have to be repaired or torn down. Steel will typically last 3-4 times as long as wood, depending on the environment. Wood is easier to attach other wood components. You just nail them together. Things like small trim boards and narrow strips of wood are easier to attach to a wood backing than to steel though typically if I have these components, I use an adhesive like Liquid Nails. Wood is a better insulator than steel. You will get some transfer of heat and cold through steel components. This is a bigger concern for bigger houses as they are MUCH more expensive to heat and cool. If your typical heating cost on a Tiny House is $30-$40/mo, a couple of % increase in heating cost is not that big a deal. If you have a large house and your heating bill is $500-$600/mo, it's a bigger factor.
Attaching Steel to Steel
Primarily by self-tapping screws. I have a clamp that I use to secure the 2 pieces together for at least the 1st screw. Most of the time I can release the clamp and set additional screws after that. Most specs require 2-3 screws per intersection just like you would use 2-3 nails on a wood counterpart. They sell these at the drywall supply shops.
Attaching Sheetrock to Steel
There are self-drilling drywall screws just like screws made for wood. Drywall suppliers and some home improvement stores.
Attaching Wood to Steel
I either use self-tapping screws or I drive steel pins with an air gun. If it's only a couple, I use the screws. If I have a lot to do, like siding a wall with OSB, I fire up the compressor and use the air gun.
We did find an option for "nailing" boards to steel but it meant buying a tool that we would not typically have bought. That being a siding nailer. Specific nail guns are compatible with steel pin coils (just like nails, except sharper and hardened to penetrate steel) and are used with a compressor just like a regular nail gun. You do need lots of pressure so make sure your compressor will deliver 120-150 lbs. Other than that, you load the nail coils and fire away. The steel pins that are used are less forgiving than nails. If you do not have your components properly aligned, you will likely have to use a cut-off and cut the pin out. They have an incredible holding strength. We went with a Max (SuperSider CN465-S) gun as it was more readily available at the time we were ready to purchase. Aerosmith also makes a gun as well as their line of pins. Here's a brochure on the subject:
We bought a Dry Cut Metal Saw at Northern Tool for cutting the studs and track. Many people use a high-speed cut-off saw with an abrasive disk but I found this to be very crude. It uses brut force to burrow through the steel with a thick, rough disk. Lots of sparks. Metal is literally melted through. Ends are rough and VERY hot after a cut. The Dry Cut Saw we bought was made for this and uses a carbide steel blade at a low RPM with high torque. Just pull the saw down and let it work through the steel. Very little sparking. You get a VERY clean cut that's just warm after the cut. It's a dream! I find it cuts better when you sandwich 2 pieces of steel together. They tend to support each other when it gets to the loose lip or flange of the member. The blades are more expensive for the Metal Saw but they last a long time. I think we went through 2 building our house. The abrasive disks on a regular cut-off wear out quickly. You can also use this saw to cut just about any metal including rebar, fence posts, any steel up to about 2" thick. We also got a small cut-off saw (uses thin 4" blades) from Harbor Freight for trimming and splicing. I found the metal too thick to effectively use tin snips though I didn't buy any electric ones. When we were installing our steel roof, we used a circular saw with a plywood blade turned backwards. It cut like a champ. This is a thinner steel (25 gauge) than the structural steel (18 gauge) we used on the framing.
Here's a list of sites that will help when working with steel:
Steel Construction Guide (my favorite illustrated guide for construction)
Aerosmith Fastening (steel pins that are used like nails)
Great Air Gun by Max
Builder's Guide to Steel
Insulation Supply Company (my supplier here in North Texas)