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Are Tiny Homes built from Sheds a Good Idea?

At least every other day, I see an ad for a tiny home or office that companies or individuals built from what used to be backyard “sheds”.  Now, don’t get me wrong, I am all for repurposing buildings and materials, when they are done the right way!  (In fact, I even repurposed a large metal workshop building into a 2 bed/1.5 bath “condo” for my parents.  This one is on a concrete slab and for all intents and purposes, could have been built that way as a home). What are the advantages, and what are the cautions, of making a home from a shed?  (Many great points adapted from Living in a Shed: 9 Things (2023) You Must Know):

The advantages to living in a tiny home are many, for example:

• Up-front cost is cheaper than a house
• Smaller utility bill
• Less square footage to clean
• Less impact on the environment
• Privacy
• Portability
• Customization
• Ability to live in nature or “off-grid” more easily

However, “sheds” are only a subset of tiny homes, specifically, tiny homes that started out as prefab backyard buildings.  Let’s take a look at what could go wrong from making one of these into a habitation.

First of all, when considering whether to build out a shed as a home, you should check into local building codes.  If you live within city limits, there are likely laws about what type of buildings can be built or placed on your property to become “habitations”.  Plopping a shed down and running electricity to it for your teenager to live in could be a big problem whenever it’s noticed by the building inspectors!  Moving it to the middle of a few acres in the country doesn’t normally pose these legal issues, but again, it’s best to check with your local building inspector!   If it’s illegal to live in a shed, it may be legal to live in an ADU-an Accessory Dwelling Unit.  For example, ADU’s in California are required to be at least the size of an efficiency unit (at least 150 sq. ft. livable space plus a bathroom), they must contain a kitchen, a bathroom, they must be built on a permanent foundation, and must be able to turn on/off the ADU utilities without entering the primary unit.  (ADU vs Finished Shed Comparison)

Construction: This is the largest area of caution we see.  Within this topic, we need to highlight: 

• Off-gassing of toxic compounds from interior building materials.  If the building was never meant for habitation (even as a chicken coop!), then it may contain building materials that are rated for “outdoor use only” which may give off dangerous pesticides/weatherization chemicals.
• Inferior flooring and framing techniques:  We’ve seen them: sheds built to hold push lawnmowers and Christmas decorations may not hold up to daily living over a number of years.  Holes or loose joints that develop inevitably allow pests to come in (they want to be cool/warm/fed too!).  
• Inferior foundation: Setting a shed on a few cinder blocks is typically not sufficient for daily living and if the floor begins to sag, all kinds of structural issues (including leaks and mold) can ensue. 
• Poor insulation:  Typically, storage sheds only need to keep the paint from freezing, not keep a person comfortable, so insulation may not be optimal.  This includes roof and floor insulation–yes, if your shed is not mounted to a slab foundation, it needs to be insulated!
• Improper sealing (which can cause moisture infiltration and mold growth): If siding is applied over the frame without an air or vapor barrier, it’s easy for moisture to condense inside the walls if they are heated for a living space, or similarly cooled during a hot summer.  These steps in normal construction are what inspectors look for, for the safety of the homeowner and longevity of the building.
• Addition of water and sewage facilities warrants several considerations:
  • Where is your water source and how will you deal with sewage?  Sewage service is probably the biggest hurdle to overcome, as there are 3 options which may or may not be permitted in your locale: connection to the city’s sewer system, installing a septic tank, or installing a composting toilet. 
  • Plumbing in sinks, toilets, showers and drains also is done by code for a reason–leaks can cause serious mold and hygiene issues.  It’s not a good idea to buy that shed if these appliances are added without proper spacing and materials by someone who knows plumbing code.
• Addition of power to the shed:  Sometimes power service to a shed (50-100 amp service) is not what you would get for a normal home (200 amp service).  Like the plumbing, wiring the shed for power should be done by someone who knows electrical code, so that it’s wired safely!
• Addition of HVAC to the shed: Sticking a “window unit” AC or space heater in the side of the shed may keep you cool or warm if it’s the right size, but without proper ventilation, you could build up CO2 and mold very quickly.  CO2 is the product of insufficient ventilation, and face it, a shed is just a small, closed room unless proper ventilation is planned and built-in!  The mold can result from simply living in that closed room, because along with CO2, every human exudes water vapor through their lungs and skin.  If there are 2 people living there, the air quality will be even worse.

So far, it may sound like a major “NO” to use sheds as homes, but that’s just not true.  If you’re allowed to use one in your locale, you can safely do so by starting from scratch (buying a bare-bones model) or buying one from a builder that knows good home construction.  Then you can make sure that the construction, outfitting and customization will work for years to come without causing health issues.  Let’s face it, home ownership is expensive, but saving on a tiny home just to live uncomfortably from lack of weatherization or get sick from mold is definitely not worth the savings.  Therefore, planning is essential!

How do older homes compare to newer homes?

According to Realtor.com, older homes are those that are not built with modern building materials like high-performance concrete; typically they were constructed before the 1970's.  

Many older homes can be purchased at a discount because they have not been “updated”.  These updates of course include aesthetics like granite or marble counter tops, as well as necessary systems like modern electrical wiring, HVAC and plumbing.  Aside from the normal aspects that buyers of older homes will want to renovate, what are the hidden pros and cons that come with older homes?

Arguably, construction and maintenance of the roof and foundation of older homes may have the most to do with the condition it is in today.  

Older roofs can be much more durable, as well–here are the lifespans of typical roofs according to their materials (“composite” means the fiberglass-and-asphalt shingles which are on 80% of US homes today):

Not included is the asbestos shingle, which is estimated to last 30-50 years. (nowenvironmental.com)  Although this is a reasonably durable material, due to its health problems (fibers exposed to the air can be breathed in, causing disease), asbestos tiles are no longer sold for repairs, so an asbestos roof would likely need replacement. (rooforia.com)

In addition to the longer lifespan of older roofing materials, there is the underlayment–what the roof is attached to.  Before plywood and oriented strand board (OSB) were available, sturdy “two-by” boards such as 2x6 or 2x8’s were used over rafters to provide the base for applying a roof.  These were much more durable during severe weather, and more durable in terms of rot and deterioration. Of course, they are not used in most modern homes because of cost; homeowners would rather invest more money in something they can see!

Older homes also typically had the benefit of larger roof overhangs.  Prominent overhangs do several things that increase the longevity of the house: they deflect sunlight and UV damage from the windows and walls, and protect the same areas from rain and water intrusion.  Skimpy overhangs in modern construction do not do either!

Foundations of older homes (before concrete slabs were widely used) could be good or bad, depending on the method of construction and materials.  Here are some foundation materials commonly used (inspectapedia.com):

• Wood, beams set on grade or on flat stone set on or close to ground level (older, very susceptible to rot and damage)

• Stone, natural found on site or brought to the building site (older, susceptible to movement and settling)

• Brick, less commonly used below grade, more often used from grade-level up, set on stone below grade. (older, susceptible to movement and settling)

• "Cinder blocks" or concrete blocks (from early 1900’s, persistent through today for smaller homes)

• Poured concrete (poured concrete footings as early as 1912; wisconsinhistory.org)

• Pre-fabricated concrete foundation sections assembled onsite (since early 1900’s)

• Wood, treated lumber, treated plywood on treated wood or on concrete studs (also used today for smaller homes)

Obviously, the quality and maintenance of the foundation determines the condition of the home.  It didn’t take an earthquake to start a home into deterioration; one groundhog can make a burrow that will damage a pier and cause the house to lean and crack, allowing water intrusion.

Subfloors: A floor with particle board or even higher-quality plywood as subflooring under carpeting won't feel as sturdy as one that's made from multiple layers of solid boards laid diagonally, an old technique that's now prohibitively expensive. (washingtonpost.com)

Construction materials:  Even the wood of “stick built” homes has changed.   The change has to do with the loss of “old-growth” forests in the US, where trees were between 100 and 500 years old.  By 1940, old growth lumber was not available for construction anymore, and lumber came from younger trees.  Today's building lumber is made from trees that are between 12 and 20 years old. These trees have fewer growth rings per inch than old-growth trees. Older trees have more dense wood, which is also more rot-resistant.  (WisconsinHistory.org) 

Old-growth lumber may not be available anymore but naturally insect-resistant trees, provided they are sustainably harvested, are significantly more ecological and healthy than pressure-treated lumber.  Western Red Cedar and Redwood have unique compounds within the cells of the heartwood that protect against insect and water damage. They usually only require topical treatments for coloring or sealing. (thinkwood.com)

Before the 1920’s, “2x4” wood studs were actually 2” by 4” in dimension.  After that time, dimensions varied and ended up at 1-½” x 3-½” as the standard since 1964.  Even though you may think wood is old-fashioned, flammable, inferior to steel or concrete, or too pricey to use it for interior design such as timber-style construction, architects are using it in new ways for safety, strength and design.  “Mass Timber” is a new style of design in which wood is used for large commercial and residential buildings.  It’s appropriate since wood has many biophilic benefits that can contribute to the health and well-being of building occupants. (thinkwood.com)  New methods of laminating wood such as cross-lamination, nail-lamination, dowel-lamination and glue lamination, makes it strong and able to span long distances, as steel girders and concrete do.  The laminating adhesives and fire-retardant treatments of such products are the main concerns for use of these products, however if they follow industry-standard manufacturing practices such as ANSI A190.1 (Product Standard for Structural Glued Laminated Timber) then it should be naturally low in VOC emissions such as formaldehyde. (anthonyforest.com)

Construction methods:  Kit vs. Pre-fab vs. on-site 

Although “kit” homes were originated in the UK in the late 1800’s and became popular in the US in the early 1900’s, they were very different from the pre-fab homes of today.  Kit homes, like pre-fab homes today, were offered to make housing more accessible.  One Sears catalog assured that “anyone with rudimentary skills could have their home built in 90 days.” (thecraftsmanblog.com)  Many kit homes from the early 1900’s are still standing today and demand a premium in the housing market, a testament to the quality of materials and design in these homes.

However, the quality of pre-fab homes today do not resemble that of kit homes because they are built off-site and transported in large pieces to the building site, then assembled.  "They don't build them like they used to--and a lot of that comes in economics, labor versus material costs. Historians have documented, beginning in the 19th century, labor costs going up and up, and material costs going down and down. Now, we're in a time when bringing someone on site to do the work is the expensive part, not the material." –Bill Dupont, an architect who works for the National Trust for Historic Preservation in Washington (washingtonpost.com)

Another victim to rising labor costs has been plaster and lath.  Although mold can grow on painted or dirty plaster under the right conditions, plaster does not support microbial growth because it is non-porous and lime-based or clay.  The wood (lath) behind it, however, most certainly can harbor mold.  (lookmold.com)  In contrast, the drywall core of gypsum does not support microbial growth, but the outer paper facings do.  Which is better?  According to eSub, a construction software company, plaster is by nature a more durable finish than drywall, even high-level drywall finishes. In addition, plaster outperforms drywall in a number of key areas, including insulation, soundproofing, and fireproofing (instead of lath, modern plaster is set over a type of wallboard called blue board, which is similar to sheetrock at first glance, but it is specially formulated to handle high amounts of moisture in wet plaster, so it bonds tightly with the plaster.)  Blue board is highly water and mold resistant. Therefore, in an older home with plaster and lath walls, it may be a good choice to repair the plaster and replace it in kind with new blue board and plaster (if you can find and afford the skilled craftsman to do so!). 

Many older homes were “custom” homes, because they were hand-built by the owners.  This can be good, or not so good, depending on the design experience of the builder.  Today, “custom” homes demand a premium price, because unique plans, changes from pre-made plans and changes on site cost more money.  

Whether your style is traditional or modern, the marriage of durable materials, good design and good construction is timeless!  Make sure that any home you purchase or build has these characteristics and it can last for generations to come.