Latest Cabin / Retreat Shelter Building

Dear CPT Rawles,

This letter is provided as a reply to your reader who wrote in about “Building Cabins on a Shoestring Budget”. 

There are two viewpoints to this reply, one from the vantage point of an architect with a couple dozen years of real world design and construction experience as though one of my clients was cabin builder whom I was trying to advise, solely for a cost effective, build – as-you-go, off grid home solution.

The second vantage point is that of a fellow prepper, former Army National Guard Infantry Lieutenant, and in my present role as an Architectural Consultant to Hardened Structures LLC, as though the cabin builder were a client to Hardened Structures.

First, congrats on the land acquisition. This is a great blessing. Be so very thankful for three teen boys who hopefully can share the workload. This will be a key to your accomplishing realistic goals. Next, pray, and be super safe with power tools. I have had three architect bosses over my first dozen career years that were missing a finger or part of a hand from a table saw or something. In my very first self-constructed project, the electrician cut his own kneecap off with a Skilsaw.  

Starting as the first viewpoint as an architect.  Before getting to my answer, I need to disclose that I receive no compensation from any of the brands, products or web sites listed (except in my role as an architectural design consultant to Hardened Structures LLC.).  

Homebuilding can also be stressful on some family relationships, so expect good days and not so good days, but others have gone your way before and came out okay.

Mr. Rawles is correct about the shed arranged as spoke on a wheel concept with shed structures. I have also considered this concept for the same reasons of affordability to getting the first structures up and expanding as budget allows. Depending on the shed structures selected, an octagon or hexagon gazebo kit could provide the central space which the shed “spokes” radiate out from. This is a valid “build as you go” plan. But just please be aware, the chief drawback with the spokes design is the amount of wall area per square foot of living area. Five sheds at 14’x40’ is 540 lineal feet of walls needed to be built to enclose 2,700 SF. Conversely a 52 foot square structure would achieve the same 2,700 SF of living area, with only 208 lineal feet of wall to construct. So a square in plan is our best bet to achieve the most square feet for the least cost. So, on the build as you can afford plan, I’d steer a family towards each unit being a 20’x20’or even 24’x24’ “garage kit” but replace the standard roof trusses with “room in attic trusses” in particular Gambrel style because of the high amount of bonus living space which can be gained in a second story under a roof you would have to build anyway.

I like Gambrel so much that I’ll throw out my favorite type of shed if that’s the route you choose (but not an endorsement of this particular brand, just the style.)

Another consideration which people often fail to account for in the early stages of being an owner-builder is all the other skilled trades not related to the shell of the house: electrical, plumbing, and heating.  For this reason it is not an invalid starting point to build out and around and over a functional used trailer home, which comes readymade with plumbing electrical and a heating system. On Craigslist, a trailer still in towing condition can be found for $3,000-$9,000. Even if the interior finishes of the trailer need a complete rehab, this often falls within the skill set of the do-it-yourselfer, flooring, paint, cabinets, even replacing the lighting or plumbing fixtures is a plug and play, unlike actually setting up an actual hot and cold water, or electrical service within a new home. Most likely the roof on the old trailer is worn out, so a pole barn structure over the existing roof is a very common sight on homesteads with an older trailer.
Windows should be replaced if they are single pane, with dual pane type.

Some important considerations regarding cold climates:
Research has shown that continuous insulation is far more effective than cavity insulation. People like to think going to a 2×6 wall with R21 is far superior to a 2×4 wall with R13, however both walls have studs at 16” on center which transmit cold straight through the wall to the inside drywall. This is called a “Heat Sink” and is highly undesirable. So it is actually superior to save the money on 2x6s by building with 2×4 with  R11 (or R13HD) then sheath the home entirely with 1” of “Polyiso” type rigid foam board with a value of R6 per inch. R11 plus R6 only equals 17, but in the real world the R17 wall is a warmer home with less energy costs than the R21 2×6 wall. If you live in a seismic zone then either wall will require wood OSB sheathing directly against the studs, and the polyiso goes over the OSB.

Next, research has shown that after about R40 ceiling insulation is not a good cost investment, but foundation perimeter insulation in a cold climate is a highly beneficial upgrade that many builders totally overlook.  2” thick polyiso board installed against the concrete foundation wall from top to bottom after the forms are stripped off and before backfill will keep the cold out around the perimeter of the house.  I cannot stress enough how beneficial this is. Think of it this way, cold air is much less dense than cold ground, it takes far more energy to heat the ground than the air, so don’t waste your heating with concrete touching freezing ground.

A dilemma to struggle with for the economically constrained “retreat shelter” is also wood frame construction versus anything else.

Up till this point, we have been discussing Wood frame construction, since is the most commonly known method for the novice American builder to work with. However, this method is among the least secure from ballistic impact and fires.

Many other alternative construction methods are possible, but your first hurdle to cross is the local building and zoning department regulations. Depending on your location, this can range from onerous to nonexistent, but please be advised these authorities have the power to fine you  daily until you tear down what you built that violates their regulations.

Among the nontraditional home construction methods, Straw bale construction is an incredibly easy construction method.  In my past as an architecture instructor, I once led a design build class where the final exam was teams of students to build outhouses. Straw bale won the day when evaluated by a jury of local contractors and architects. The students who attempted this project had never built anything before. Construction by used wood pallets with foam insulation inserted in the pallet cavity by another group of our students was a very interesting design concept I think bears some mention as a fast and economical construction method.  There are YouTube videos of pallet-built sheds.

Other alternative construction methods include rammed earth, adobe, cob, sand bag/earth bag, or earth tube. Many of these methods are very cheap from a material standpoint, yet incredibly labor intensive.  

I am also going to mention two additional alternative construction methods later as part of second viewpoint of this reply, that of the e- infantry, Hardened Structures LLC representative.

As we transition now to this second part of the reply, we would be asking questions of what your goals are in your retreat shelter, namely:

What are your potential threat scenarios?

What are the human and material assets you are seeking to protect?
What is your budget?

Do you plan to mount an active defense or do you plan to take shelter in a safe room or shelter of some type and allow the danger to pass before reemerging? Or some combination of both?

If sheltering, how long do you plan to stay sheltered?

If mounting an active defense is your team specifically trained in this role or are you seeking training?

What equipment do you have for this role?

If mounting an active defense what consideration have you given to your existing topographic surroundings?

What are any special needs your group has?

As we go through these and other questions, we would be able to develop an outline of solutions for your specific group, given your own known threats. Also we would be asking if you have concerns for threats not mentioned. For example: What are the known weather disasters to your region? Have you considered the possibility of EMP caused by solar flares or terrorist activity, or a regional nuclear incident, or a localized chemical accident or attack?

The goal is to provide a solution with no Achilles Heel, but every client and every situation differs as to how this is achieved.

Since we are aware that your budget plan is to self construct, it may be that Hardened Structures role is that of an advising or design and security planning consultant and as source for specific products for your needs. However, for most clients, we would be performing those services plus managing the actual construction of your shelter. Often this is as your construction manager overseeing the efforts of local architects and contractors.

Depending on many factors, budget, timelines, threat analysis, site constraints, etc, Shelters for clients can be modular units constructed of steel and delivered ready to install on your site, or built from structurally engineered reinforced concrete build on site or other solutions. They may include EMP protection, provisions for extended durations, actively filter the air from contaminants, maintain communication with the outside world, handle human waste safely, and even provide a home like environment where inhabitants and relax, have entrainment and even exercise. Some clients choose a hardened retreat shelter built to withstand the complete loss of the home while protecting the human and material assets in the shelter.

If in this particular case you asserted the need to protect the home itself from some level of ballistic threat, but were on a tight budget, there are two affordable, do-it-yourself construction methods come to mind which may be of interest.

These two methods are Dry stacked masonry load bearing walls, and non load bearing rock gabions wall infill with a post and beam supporting frame.

Dry stacked masonry walls were developed as a result of a 1970s US Dept of Agriculture rural housing initiative for improving housing of persons living on Indian reservations. Instead of skilled labor with  mortar joints between every course of block, the block walls are stacked without mortar, totally dry and a special fiberglass fiber reinforced “surface bonding mortar” is trowel or sprayer applied to both exterior and interior face of the wall.

The dry stacked walls are only about 70% the load carrying strength of wet set block walls, but for one or two story residential construction it is strong enough.  Hollow block must be filled with a solid material to have effectiveness against ballistic threats and there are requirements for reinforcing steel which also requires filled block..  A “dry pack” of one part sand to one part cement to one part fine gravel with post install watering may be the easiest method of filling block cores for the novice owner builder. This would be done after the surface bonding mortar has cured. I would recommend 12” block over 8” or 10” if a budget will allow. There are “U” blocks for window and door headers, but I have seen many 100 year surviving masonry buildings with timber lintels in Chicago. Either an exterior insulation and stucco finish or an interior insulation system is possible. There are merits to each.

Another method of construction which I have been developing myself is to use a “pole barn” frame and roof structure with a Rock Gabion infill wall system. Gabions are used in combat theater defenses, albeit in a less elegant manner.

This construction method, however, is a derivation of how a Gabion fence is constructed and is more economical than a concrete wall. The poles of the pole barn not only provide the support for the roof, but the lateral support for the rock gabion wall, so that the gabion thickness can be kept at about 12”-18”. Crushed rock and concrete are about 11 0lbs per cubic foot, and concrete is about $200 per cubic yard.  4” crushed stone is only about $9 per ton or less than $20 per cubic yard.

Wire gabions filled with stone are attractive to many people, and allow a place for vines to grow, if that’s the look you desire, or another school of thought is that the wires themselves are a weak link to a persistent person with wire cutters, and they should be covered over in shotcrete.  If covering the wire with a cement, one may wish to opt for stainless and not just galvanized wire mesh, and cover with a minimum of 1” of shotcrete or layers of stucco. This is because the covering of shotcrete traps moisture with leads to corrosion, but how many years to failure is a variable, houses with stucco over chicken wire last in San Diego a hundred years, in Chicago, perhaps 30 years.

An 18” thick wall of 2” to 4” crushed rock gabion will defeat nearly all commonly available small arms, with the possible exception of .50 BMG. Added benefit of the Gabion system include, self healing from ballistic attack; any rock damaged by incoming rounds is crushed down by the weight of the stone above. Minor breaks in wire can be field repaired. Gabions provide a high level of thermal mass, which though not the same as insulation, is beneficial, but a topic for another post.

The roof itself must be addressed and there are several tiers of upgrade from conventional shingles. A metal roof is a low cost fire resistant upgrade. Tile roofs, clay or concrete are even more so. Actually building the underlying structure of hollow core concrete panel or “Spancrete” is a more expensive upgrade but of some ballistic protection. A “flat” roof (actually low slope) of corrugated metal panel with a topping of concrete, then insulation, then any of many rubber or PVC roofing membranes is a common commercial roof structure not beyond the skill of  most owner builders with proper instructions on  temporary shoring. This method could allow either direct run off of water, or drains, or even incorporate a concrete block parapet wall, which can be of tactical value.
For the very budget conscious, but defense minded, one could envision how this pole barn and gabion structure could be the basis for enclosing one or more used mobile home trailers as mentioned earlier to create a “dirt cheap” homestead retreat starting point, (see also the short book Dirt-Cheap Survival Retreat by M.D. Creekmore) but there is a much larger topic of “defense in place”, and one is advised to investigate foreseeable threats and how to respond to them.

While this is only a primer on these topics, a wealth of information is available with online research or by seeking out consulting advice.
I sincerely hope the best for all your readers and welcome any questions on the built environment and active or passive defense. – Douglas Clark

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