Which material to use for your tiny house frame?
Timber, Steel or Sip panels
Lets take a look at the three most popular ways to build a tiny house and some of the pros and cons of each
Timber frame construction has been around for thousands of years and is a trusted and reliable way to build a home. This also applies to tiny homes with many people choosing to build their frame with timber.
Lets take a look at some of the pros and cons of timber frame construction.
1-Renewable resource - Plantation timber can be grown so its not a finite material being extracted from the earth making it a long term solution. It also can be recycled easier than other materials.
2-Easy to work with- The timber being used for tiny houses is usually a sort of pine framing which is soft ,easy to cut and nail/screw together. This makes the build process easier especially if any changes need to be done whilst building and also renovations in the future.
3- Less labour- As mentioned above timber is easy to work with which reduces labour time compared to building a steel frame house. You can nail and glue wall linings compared to steel which requires screwing everything. Even screwing into timber is easier than steel. The only method requiring less labour than timber is SIP panels.
4- Thermal properties- Timber does not transfer heat like steel which makes it attractive for insulation purposes as well as to stop moisture problems from condensation inside your wall cavities. Timber can also absorb small amounts of moisture inside wall cavities and then let it evaporate later, which can help with moisture/mold issues.
5- Readily available - Timber is usually available at your local hardware store and can be purchased easily, this may be very important if you live somewhere rural and cannot access other materials like steel frame or sips.
6- Price- Timber is generally an affordable material being cheaper than steel and sip panels for the materials themselves.
7- Flexibility - Timber can be used to build many different shapes and designs and is time tested as a suitable material for building.
1-Weight- Timber is the heaviest material available amongst to three we are discussing. Although we use a pine which is a lot lighter than many other denser timbers it still has a considerable weight to it which means it will reduce the size of your tiny house if your working with weight restrictions.
2-Termites- Termites can eat your timber frame away causing considerable damage.
Although as tiny houses are on trailers with exposed steel members the mud tracks of termites will be easily seen which help to discover them quickly.
3-Availability- has been a recent problem in Australia with our 2020 bush fires and covid causing other problems that hardware stores just didnt have the stock needed for alot of builders. Hopefully this problem doesnt last long.
Steel frame construction for residential houses has been in Australia for over 50 years and the first documented use of cold form steel framing was in 1925 in Virginia USA. There has been many variations of steel framing dating all the way back to the 1800s but the type we use today somewhat replicates timber and is cold formed.
Even though it has been around a while it was not a very popular way of building as it cost up to six times more than using timber. So it never took off until recent times where steel has made a comeback and is replacing timber in a lot of buildings.
Lets take a look at some of the pros and cons of using steel for tiny houses.
1-Weight- The absolute best reason to use steel for tiny houses is the weight. It is said to be 30-50% lighter than using timber. This helps to keep your overall weight of your home down as most tiny houses are working on weight restrictions.
2-Strength- Steel is also very strong and can be used to create many different shapes when building. It is said to be stronger than timber although stronger doesn't necessarily mean it will last longer and timber is strong enough for the intended purposes so for tiny houses that is not a big reason to use it.
3-Bracing- Steel frames can have braces put in the wall frames creating very strong lateral strength and avoiding the need for brace ply that is needed with timber frames.
4-Pre fab- Steel framing is usually prefabricated by a company and then sent to site in wall frames for you to erect on your tiny house trailer. This takes out a step in your build allowing you to build more houses faster if you are a business.
1-Thermal bridging- Steel is very good conductor of heat meaning that it can get really hot or really cold when used as a building product. This can create multiple problems for your building not just the temperature of the house. A way to avoid this is to insulate the external of the frame with insulation boards but that makes your wall frames heavier and thicker which defeats the purpose of using steel for a tiny house.
2-Moisture problems/mold - As steel frames can transfer heat really well condensation can occur on the frame and it ‘sweats’ this can then create moisture to accumulate inside your wall cavity which can lead to corrosion and mold. This problem is particularly bad with tiny houses for a couple of reasons.
A- The subfloor (being the trailer) is also steel and gets cold at night and then transfers into the wall frame if no methods are in place to diffuse thermal transfer.
B- the walls can transfer heat through screws from the exterior siding or just through the siding itself and again create the frame to sweat.
3- Cost - Steel typically cost more to build a tiny house for two reasons.
A- The cost of the materials itself
B- The added labour costs as its harder to work with compared to timber.
4- Creaking - I have heard reports of the frames creaking as the temperature changes throughout the day.
5- Corrosion- Possibility of corrosion if near coastal areas.
Metal structural insulated panels also called SIPS are a new way to build houses but are not that uncommon and have been used to build coolrooms for many years.
There is also timber Sips available to build with but i use the metal variation.
Basically its a sandwich of a thin metal skin then a type of insulation inside (usually foam) then another metal skin on outside. They can come in many different colours and thicknesses and also face profiles to be more decorative. You can choose to line the panels with your typical lining or keep the panel exposed or maybe a mixture of both.
Lets take a look at the pros and cons
1-Cost- building with SIP panels is by far the cheapest option compared to steel and timber and thats mostly because the build method is alot quicker and requires less labour. Its also possible to not line the internal and external walls which would save you even more.
2-Weight- Sip panels are also lightweight and very good for tiny house construction
3- Insulation- SIP panels are very well insulated with no air pockets or missed pockets like you will find when using batts.
4- Minimal thermal bridging- There is minimal thermal bridging from the outside of the wall as the steel skin doesnt go inside the wall its only a thin layer on the outside of wall. This also applies if your screwing into the wall, The screw penetrates into the foam which will diffuse the thermal bridging very well.
5- No moisture / mold issues- As the is no wall cavity and the walls do no allow vapour to pass through there is no issues with moisture/mold in the wall system. Mechanical ventilation will be needed in some circumstances to help keep the right humidity inside the house.
6- DIY friendly- Building with sip panels requires less skill and time to build a tiny house than any other method so its very good for beginners wanting to build there house.
1- Not eviromentally friendly- Sip panles are made of steel and a type of foam so neither product is very good on the enviroment and will take a long time to break down in land fill
2- The feel- If your not lining the interal walls leaving the metal skin exposed, the feeling of being inside a metal box isnt the best so its important to bring in lots of warm elements to offset it like natural timbers and soft furnishings. The walls should also be painted to take off the metal shine look, when done correctly you wont be able to tell its metal
3-Cant put services in the wall cavity- This is the biggest challenge when building with these panels.I really do not like exposed conduit with electrical wires inside and exposed plumbing pipes so i must be creative with how i run everything so that it looks great in the end without to much hassle. Some manufactures do have channels for the servies in the walls but with tiny houses i find its possible to avoid that as its time consuming.
4- Not as easy to repair- As i dont use internal wall lining any damage to the panels can be harder to fix compared to typical wall lining. Some of my electrical wires are also very hard to access compared to when i build with timber or steel if i ever need to access them.
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