How to Build an Earth-Sheltered Home

Where Do I Start?

Where to begin really depends on how much you already know or don't know about these types of homes. If the concept is fairly new to you but the idea intrigues you, it is best to start at the beginning. Gain a working knowledge of What an earth sheltered home actually is and whether or not one is right for you!
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What are Earth Sheltered Homes?

earth sheltered home in new zealand
While not commonplace place here in the US, earth sheltered homes have been utilized around the world for thousands of years. As the name implies, these houses are built either partially or entirely underground. Their rather unconventional structures provide superior insulation, energy efficiency and protection from the elements. Earth-sheltered homes make a lot of sense in regions where extreme climate conditions are present. The earth is a great thermal insulator that can protect residents from intense heat or cold. While the first such living places were rather primitive, today's earth-sheltered homes are a far cry from the stereotypic caveman abodes. These homes can now be built with the same modern luxury amenities as any above ground build. Recently, an upturn in consumer awareness has caused an increased interest in these intriguing alternative dwellings. We'll discuss the benefits, challenges and building methods of these unique alternative homes.

Types of Earth-Sheltered Homes

There are two basic types of earth-sheltered homes; under-ground and bermed. Underground, as the name implies, are built primarily below ground level. Bremed, (or banked earth) homes are partially covered, oftentimes built into existing slopes. Depending on the topography of the construction site, building methods will vary.  
earth sheltered bermed home built into hillside

Bermed Home Building Methods

Bermed homes can be built on flat flat ground with soil mounted around them. Yet, a more advantageous way is to take advantage of the natural terrain and build the home into a preexisting, natural slope. This is a more cost effective method that requires less soil excavation. It also helps your home blend in with the natural beauty of the area. One or more sides of a bermed home are left uncovered to allow for natural light to shine through. Keeping the front and rear of the home uncovered also allows for cross ventilation.
underground earth-sheltered hoime

Underground Home Building Methods

Unlike bermed designs, an underground home's roof and outer walls are all completely covered. This allows for maximum insulation and energy efficiency. These homes also offer superior sound proofing, privacy and protection from high winds. But subterranean homes tend to have more issues with water leakage than other types of homes. Steel reinforced concrete is typically best suited for underground construction. insulated concrete forms (ICFs) are commonly used for these types of structures. High efficiency drainage systems are also a must.  Where to build is also an important consideration. Flat land with high water tables is certainly not the ideal location. a hillside with a reasonably steep slope is ideal. Although less common, underground homes can sometimes be built into a solid stone hill or mountainside. Referred to as cave constructed homes, this type of venture is more risky and expensive than a typical underground home. This is due to extensive blasting and increased safety precautions. 

What to Consider Before Building an Earth-Sheltered Home

Building an earth-sheltered home starts with a lot of pre qualifying and planning. Determining if your area is suitable for an earth-sheltered home is the first step. Getting approval from your local zoning board, securing financing and selecting a qualified buyer are also issues to address before ever breaking ground.

Environmental Conditions

Addressing three key environmental factors should be part of your preliminary investigation. Topography, soil type, and groundwater levels help to determine your project's feasibility. We have outlined these topics as a means to open a preliminary discussion to help you start your journey.

Topography

The topography of an area determines the difficulty in which an earth-sheltered home can be built. The higher the slope of the landscape, the easier it is to surround a home with soil. Higher slopes are also more cost effective because less soil needs to be excavated. Flat ground presents the most difficult and costly construction challenges. Another important consideration is which direction the slope faces. The preferred direction is typically determined by geographic location and climate. In regions with long, cold winters, south facing slopes allow for direct sun exposure; providing natural heat and light. In warmer climates, a northern slope may be more desirable for keeping your home cooler in the summer months.

Soil Type 

When building any type of subterranean home, the kind of soil at the construction site is very important. Soils that contain some sand or gravel have better weight bearing qualities and also provide better drainage. This helps keep moisture away and limits below ground structural damage. Conversely, soils with large concentrations of clay raise considerable concerns for below ground structures. Rather than allow water to filter through it, clay absorbs water and expands. As it does so, this expansion can cause cracks in foundations and below ground walls. As it dries, clay shrinks and can create gaps, causing your foundation to settle deeper into this space. Excavating soil on the construction site and mixing in gravel to increase permeability may help with water drainage. We recommend enlisting the assistance of a soil engineer to evaluate the suitability for this type of project.

Groundwater Level

Groundwater levels higher than your lowest finished floor can cause severe leakage problems. As the snow melts and the rain falls in late winter and early spring, the ground saturates and water levels fluctuate significantly. A safe, conservative plan calls for building down no closer than 10' from groundwater levels consistent with the rainiest times of the year. The topography of your particular area is also a major factor. Groundwater levels are highest under hills and lowest under valleys. Your proximity to a lake, river or stream impacts levels in your area.

Zoning Codes for Earth Sheltered Homes

All standard and earth-sheltered homes are subject to the same zoning codes. While it is absolutely possible for alternative homes to meet these guidelines, the process of getting your plans approved will usually be a bit trickier than a standard house. Underground homes utilize different building methods to attain the same safety and structural requirements. While your earth-sheltered home's design may be quite sound, the burden of proof falls on the prospective builder to convince the zoning board. Codes are written to facilitate conventional homes and state specific ways these standards are to be achieved. There are typically provisions made for alternative building methods that meet the intent of the code. That said, the burden of proof is on the builder to substantiate their unique alternative designs that fulfill all requirements. The most important aspects of code deal with homeowner safety. It also must be shown that ground-water levels will not be problematic for an underground dwelling. To make this process smoother, seek out a builder with a proven track record of construction of earth-sheltered homes.

Initial Cost vs Long Term Energy Savings

One potential drawback of building an earth-sheltered home is the initial cost to build one. Estimates can range up to twenty percent higher than the cost of a standard house. But, long term energy savings of up to 80% can offset this additional expense. You can also factor in less outside upkeep expenses like replacing roofs and shingles.

Securing Financing

In addition to the added initial expense, securing financing for an earth-sheltered home may be a difficult obstacle. Many lenders  may decline your application due to no comparable housing in your market. Possible foreclosure is also viewed as a risky outcome if the finance company feels reselling your home may be difficult.

Insuring an Earth-Sheltered Home

Earth-sheltered homes provide extra protection against high winds, hailstorms, wildfires and most natural disasters.  For this reason, many insurance companies offer lower rates for subterranean homes.

Earth-Sheltered Home Pros

  • Energy Efficiency
  • Protection from Natural Disasters
  • Home security and privacy
  • Less maintenance 
  • Homes blend with natural environment

Earth-Sheltered Home Cons

  • Higher initial Cost
  • May be more difficult to finance
  • Zoning code approval can be challenging
  • Might not be suitable for every area
  • More prone to water leakage

Selecting a Qualified Builder

So, after considering all the benefits and potential drawbacks, you have decided an earth-sheltered home is right for you. Your next important decision is choosing an experienced, qualified builder. A company that also understands your specific needs and can confidently help you navigate through the process. Remember, at this point, there is no such thing as a foolish question. Take your time evaluating builder's recommendations and quotes. You may find several architects that can meet your design requirements. But cost, quality and company experience may vary greatly. Be sure to utilize every information source available while vetting your prospective builders. This includes Google reviews, Yelp, Better Business Bureau and customer references. Building your earth-sheltered home is too big of a decision to make without doing your due diligence. Let your search begin!
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