Low income Kit Cabins:
This year I finally got around to making the small ultra low home, ultra inexpensive and first kit cabin that we can pre-assemble and ship to a remote location. This will be the smallest kit we offer. IT is always a battle to keep down the cost of construction per sq ft on smaller projects. As with the other kit homes these are ultra low waste and ultra lightweight.
This simple kit offers many options! It was designed as ultra low income housing, a quality structure that would last for generations. Not insulated, but secure, and can be transported and built in remote locations and on hills. This same design can be adapted to use a beautiful ceiling with 2” or more Styrofoam insulation, insulated walls with interior finishes that is suitable for affordable housing for a foreign market with different expectations and budget. They can also be utilized for storage buildings, garages, workshops. They are 20 ft long and up to 24 ft wide but can be made longer. They are simply one of the fastest and least expensive structures you can build.
Building your home:
The roof structure is made from bamboo triangles which can be precut ready for onsite assembly. Everything can be assembled inside the floor area. The roof structure is assembled on the floor and lifted onto the side walls and bolted down. The end walls can be precut with a final height adjustment if needed on site to accommodate actual roof height. Walls can be mostly sided on the ground before lifting into place. The roof zinc, screws on using an extension ladder and a simple “scaffold” that holds the ladder and the roofing square and level to the bottom of the building. This scaffold is easy to build on site and is screwed onto the inside to hold it in place during use.
The tools needed are few. A 3/8” drill, 4” grinder with metal blades, 8 ft ladder and an 20 ft extension ladder, and some simple common hand tools like pliers, squares and tape measures etc. An extra long 3/8 or 5/16 drill bit is required for the 3/8” bolts.
We designed a foundation that is super light, supper strong and super fast. The footiings are at soil surface or just below with the welded 4X4” carriola posts penetrating about 18” into a concrete encasement. The posts are pinned into the footing reinforcement. This means that even on a slab floor, the slab has no bearing requirements and can be a thin as needed.
Each site has different requirements to get it ready for the foundation and building depending on slope and whether it will be a slab or framed floor. Framed floors cost more than a slab, once the site is readied. The cost to ready the site for a slab may be prohibitive compared to floor framing. This cabin took 2 people 14 days to build including digging the post holes, placing the posts in concrete, to finalizing the roof with walls and windows and doors in place. A basic shell. This for many people is all they need. With some more time and money, you can frame in a bathroom, and supports floor a second story loft, significantly expanding the floor area and reducing the cost per sq ft of the structure even more. The time to clear and partially level the site was not included as it is site specific.
This structure can be finished off with sheetrock to make bathrooms, a second bedroom and kitchen area with electrical and plumbing in the stud walls. This house has no insulation in the roof. A light or white covered roof will be essential especially in hot areas. As will ventilation. The tops of the end walls can easily be left open and screened without affecting security. We installed skylights in the roof, just below the peak for very little time and money. One advantage of a steep roof is that it is much quieter in the down pouring rain.
These structures can be modified to fit your needs:
Within the parameters of the essential elements that make up these kits, they can be modified in many ways to fit your individual needs. Size of the structure, window and door locations, finish of floors, walls, ceilings. Floor plans are flexible, as are locations of windows, doors, skylights, screened ventilation areas, patio areas, etc.
These roof designs can be modified to allow the building to be extended beyond the 20 ft length to cover a patio area with not much more cost or labor. And these buildings can be upgraded to a different roof framing design that would allow for installation of plywood, OSB, or tongue and groove siding with 2” of Styrofoam insulation before the zinc roofing is installed. This offers the opportunity to turn this style of building into a middle class rental or house.
The height of the outside walls can be raised to allow for a larger loft area with more headroom.
For very little extra, the houses can be widened from 16 ft up to 24 ft. This allows for a larger loft area bringing the total sq footage to up to with the loft covering half of the floor area. This allows for these cabins to have footprints of 20X16-320 sq ft 20X20= 400 sq ft with patio areas in 5 ft deep by the width of the building with little waste. So patio areas can be 16/20 ft X 5 ft or 10 ft deep with a bamboo roof covering equal to the rest of the house. This also allows for flexibility in making the inside space larger and more flexibility in interior design while maintain a very low cost per sq ft.
Advantages of using Bambu in this design and in many roof designs:
Unlike carriolas which are not very pretty, bamboo is stronger, lighter, and far more beautiful. It’s beautiful when left exposed, whereas carriolas are not!
If you cover the carriolas from below, you will have an extremely difficult time of insulating it with Styrofoam and the problems of future sagging of the ceiling covering. Sheetrock needs a ventilation space or moisture from condensation, over the span of years will cause sagging. Bamboo easily supports a solid sheathing on the top to which Styrofoam boards and zinc roofing are easily fastened. Styrofoam is a fraction of the cost per R Value than the cost of that roll out foam or bubble wrap insulation.
Treated wood; Still not a beautiful as bamboo culms, and in 20 ft lengths is cost prohibitive here in Panama. Carriolas and treated lumber have their place in construction and we use them as needed. They are good for creating flatter surfaces for membranes than bamboo alone can due to its changing dimensions and natural occurring bends.
I was asked the question at a presentation about why we do not use all bamboo. Bambu could be used for the entire structure, but it has some issues that either will take more time and require some acceptance of dimensional downfalls. It is not strength, bamboo is more than strong enough! But it is not square, does not have a flat surface and evenly dimensioned. So there is a place that suits other building materials better. All bamboo, like all sheetrock makes for a boring house. It is the contrasting mixed use of materials that makes houses not only more appealing, but better suited to hanging pictures, mounting doors and windows, covering electrical and plumbing, and insulating walls.
Siding, ceiling, and flooring sheathing options:
The cheapest covering for roof or siding is zinc roof. A pre-painted zinc roof can be used for siding and looks quite nice. I would do all the exterior siding in this in the future and change the color for the walls to compliment the roof color. The doors and window openings can be framed in ½ or 1/3 round bamboo culms and screws to cover the foam sealant. This is the least expensive option.
More expensive is Plycem sidings, sealed plywood, or OSB board. These will take longer and the material costs more, but depending on your budget and the market you are building for this may be appropriate. This also works well as a ceiling covering above the bamboo roof framing with Styrofoam and zinc roofing on top. All of these can be used a a flooring option, but all except plycem will require treatment and sealing before installation. Plycem is probably the best choice. All can be sealed, and painted and varnished for a final inexpensive finish. Plycem can be tiled. Again depends on your personal tatstes, final market, and budget.
For exterior patios we can recommend either Plydecking which looks like 2X6 wood and is quite durable.
Inside wall finishes:
All the above options work for interior finishes. So does sheetrock. I like sheetrock on vertical surfaces. You can insulate the walls if desired and if you will have an AC load it would be a good idea! For bathroom and kitchen I recommend plycem. It is waterproof, fire proof, and you can tile it, mud and paint it, etc. PVC would be an ultra cheap, cleanable, waterproof finish for bathroom (and other) walls, and they make a PVC flooring that is quite nice and easy to install.
Advantages to building with our kits:
These are kits, so while everything is not precut exactly, the bamboo roof framing will be completely pre cut awaiting assembly and installation. The exterior peak walls are precut a bit long so they can be adjusted to length on site depending on the actual measured peak height. This is easily laid out and drawn on the floor so it can easily be trimmed and assembled and installed. Also the windows and doors can be cut in and placed where you want them, not at a pre determined location or size. Again in a few minutes with a grinder and metal blade you can easy customize your house to fit your personal needs.
For interior walls we provide the stock material as this leaves you some ability to make simple changes to meet your desires. These are all simple rectangular mostly stud walls, one with a door.
Ultra Low Waste Designs:
These kit houses are inexpensive because we save on labor, not on materials. In fact the materials are expensive in comparison to block houses. Including the treated bamboo, so why would you want to buy expensive building materials, pay to ship them to your site, pay to cut them into smaller pieces, and then pay to transport and dispose of the waste?
These kit houses are designed around the building materials. Floors have minimum cutting to offset the seams but use whole sheets with little to ½ sheet waste. The roofs are designed to minimize waste for bamboo, ceiling, insulation materials and zinc. The wall height are a multiple of a full width, or one and one-half width of a sheet of plycem, or zinc siding. They are 20 ft long which is the floor and exactly five 4ft wide sheets of floor sheathing. Even with sheetrock, waste disposal can be managed by burying the plycem and gypsum waste below your septic tank, or elsewhere. The small amount of carrila and zinc roofing or siding can be recycled. Using 97percent of the building products with fewer custom cutting and installation labor is what makes these kit buildings so cost effective.
We are continuing to update our material lists as we move forward. Our first 1450 sq ft house had a file of receipts from hardware stores that was 2” thick. That’s a lot of trips to the hardware store. The second 1450 sq ft house, all these receipts were consolidated into a single list. Needless to say we spent a lot less time at the hardware store and more time building a house. Labor went down by 25% on this house! In Boquete, the hardware store is min 15 minutes away, plus waiting in line to order, pay, and receive the materials, a simple nut costing $.25 could take an hour costing $8 with SS benefits plus gas and wear and tear on a vehicle! The second house had a final of about ¾” of receipts. House 3 was a much bigger 1850 sq ft house and we used the same list for the previous houses with some addition of some easy major components. It was built at a cost that was less than the two preceding houses which were at least 20% smaller. This is what allows us to prefabricate and ship these kits to remote locations. With time it will only get perfected.
While it will take building a few of these kits to get to a list that is “perfect”, these kits are already very close now. The savings in labor and time on this is not to be underestimated. These are some of the advantages of our kit designs.
Cost per sq ft:
Normally the smaller the building envelope, the more it costs per sq ft. And these kits are no exception, but the differences in percentages of increases to build small is significantly diminished in these kit homes due to the above parameters.
Other economic considerations:
Time: If you are building this for your self or to rent or sell, the time it takes to finish the project costs money. It is either lost rental income, or cost of renting a house while waiting. This can be from, in Panama, $600-$1600 per month and up depending on where you are renting or the amount you will charge for rent. This can be a significant amount and when subtracted from the total cost of building. Not to mention the wasted time you spent not living in your house.
Cost of capital: While presently bank return rates are very low, in Panama you can get much better returns on long term savings. This makes cost of capital while waiting for a house to be constructed a factor as well.
The ultra cheap homes are not about energy efficiency as they do not include insulation. They are for shelter only and compete with the alternatives. However insulated homes with roof and exterior wall insulation will have significant savings. Compared to block walls, these walls even uninsulated have little thermal mass and will be cooler as the sun shines on them. These radiate heat to the inside for 4-6 hours after the sun stops shining! In cheap shelters these heat gains are mitigated by using white or very light roof colors, and using open screened natural ventilation openings at the peaks of the roofs on both end walls. With open ends above, hot air will rise and leave the building. A few fans will keep you cool.
There are two different ways to frame the roofs,. For the inexpensive models we use a triangle structure and for sheathed and insulated roofs we use a rafter structure similar to our other.
In higher end houses, installation of 2” or more of Styrofoam on the roof is possible and very inexpensive compared to the 3/8” roll out foam or bubble-wrap insulations. But again this is only easily done on this type of bamboo with Plywood or OSB roof structure. The insulation value is probably 10 time that of the bubble wrap. Using fiberglass in the walls will insulate the walls. It is also easier to cut and place Styrofoam in these walls than it is into a carriola framed roof. Even if you do not get every square inch, 90-95% is a lot. Especially if you are running AC with the costs of electricity in Panama (one of the highest in the world).
With the installation of LED lighting, you will not only save money but reduce the heat gain into the home.
These roofs are much quieter than uninsulated roofs. While the steep angle of these roofs reduces the noise of heavy rain significantly, with Styrofoam insulation it will be very quiet.
Natural light has been one consistent theme in our houses that people love. In our other more expensive kit homes we use indirect lighting either in a cupola or roof overhang. In these inexpensive homes we use a few SMALL skylights. It only takes a small area to provide a lot of light, especially if it is direct light. Keeping the areas small is crucial to limiting heat gain.