Tiny House Framing: Steel, wood, or SIP’s?
Lets look at the types of tiny house framing to determine which best fits your needs, design, and skill level.
Steel frames are 25 times stronger than wood, they are 30% lighter, and you don’t need to add hurricane brackets or other structural enhancements. They are rust and pest proof. So why would anyone use anything else?
Metal is more expensive than wood. There are only a few companies in the country that make steel framing. Here is a link to Volstrukt. If you bring the trailer to them they will fabricate and assemble the frame for you in in a matter of days. You need to have your framing plan firm to the smallest detail because these are difficult to change. They can also fabricate the beams necessary and ship them to you for assembly. You can, with a little extra time, fabricate your own metal framing.
Depending on your level of construction abilities, or lack of abilities, you can now order your tiny house on a trailer, framed and dried in with insulation and windows installed. This can really be a time saver and get you a superior product to begin with.
As a TV installer I really disliked steel studs. It’s way harder to bolt things to your walls. You can’t just wrench in a bolt and expect it to hold like you can with a wood stud. If you know exactly where your TV is going to go you can add a wood insert into the metal stud before closing the wall for the bolt to grab. This would need to be done with anything needing a firm anchor like cabinets as well.
If you have building skills you can buy steel studs in the same standard lengths as wood studs and assemble it yourself. Here is a great video of a couple who used steel framing for their tiny home:
Wood: Framing with wood is easier and the methods are well known. Lumber can be easily obtained. However, framing methods need to be adjusted to take into account the movement and bouncing of a Tiny House On Wheels. Nailed joints will loosen when the structure is moved. I recommend screws even tho that will take a lot more time and effort. In addition, wood beams are not necessarily straight. If you are buying your lumber you can carefully inspect each piece, but if the lumber store is dropping off a pallet, you can be sure that some of the wood will be twisted or curved.
You will need to install simpson strongtie hurricane brackets and other metal corner supports to account for the high wind and shaking encountered during a move.
Here is the simpson strongtie High Wind-Resistant Construction Application Guide.
SIPs (Structural Insulated Panels): I cannot express strongly enough my dislike of this building method. These are delivered, pre-made, to your design specifications. They can be assembled very fast. Tunnels thru the foam filling are created for plumbing, electrical, and other infrastructure installation. However, I guarantee you will not have thought of everything and end up tunneling thru hardened foam for hours, popping holes everywhere, trying to get wires where they need to go.
If a contractor tells me they are using SIPs I immediately triple my cost estimate and mentally prepare for some hard work days. Additionally, if an area of a SIPs panel gets damaged by water or other condition you may need to replace the entire panel.
RV companies use SIPs because they can engineer and mass produce entire walls for instant construction. SIP’s are very strong, and have great insulating qualities but are very heavy. They’re just not right for the DIY crowd.