The ideal construction method, from hot-tubs to homes!

• super strong thin-shell concrete/foam sandwich
• minimal materials, labor, maintenance - oxide color coat never needs painting
• super-insulation sealed in concrete ~ no more rodents in insulation
• no vapor barriers, dewpoint condensation, rotting boards, air infiltration
• no tedious fitting of siding, calking, trim work
• No need to conform to flat and square surfaces ~ Frees up your creativity.

Pole-Stucco-Foam-Plaster Construction

Wood poles are ideal for building sturdy structures. They are readily available for the taking in rural areas. Here in the Pacific Northwest, people welcome having the small spindly trees thinned out of their woods. These tall, straight poles are the best, with few branches to trim off and strong close-grained growth. Unlike cut lumber, poles do not warp with seasoning, are stronger than dimensional lumber because the grain is continuous, and knots, checks and twists do not weaken the members --- every pole is #1 select! Exposed poles are aesthetically pleasing, with a natural smoothness and roundness that softens the lines of a building and weathers gracefully.

Then why don't we see more pole buildings? Because with traditional building techniques they are very time-consuming to work with. To custom-fit every wall-board that touches the pole and make a tight weather seal as well can be a real headache! Here is one answer to that dilemma that has many additional advantages: Build a sturdy framework --- walls and ceiling, with poles; stretch stucco wire mesh or chicken wire over the framework then a layer of foam insulation, then another layer of wire; stucco the outside of the walls and plaster the inside of the walls and ceiling, leaving the poles exposed to view; add roofing, windows and doors, and you have a beautiful, tight, well-insulated and maintenance-free dwelling reminiscent of old-world half-timber or fachwerk buildings, at a cost comparable to, or less than, conventional construction.

The rigidity and durability of such a structure is excellent. The stucco shell referred to here is closer to the hard ferrocement used in boat construction than the softer stucco one sometimes sees in need of repair on old buildings. "Ferrocement" refers to a composite building material that combines the high tensile strength of iron (L. Ferrum) with the high compressive strength of concrete. Ferrocement boat hulls have several layers of steel mesh and reinforcing bar to resist cracking from the severe stress and strain they are subjected to. These boat hulls are made thin (usually 1/2 to 1" thick) so they are actually quite flexible. Ferrocement diving boards have even been made! The ferrocement (stucco) skin for a house does not need as much steel in it, since it doesn't need to be so strong and it is made considerably more rigid by the foam backing and the stucco or plaster behind that. The pole framework not only keeps it all rigid, but acts as expansion-joint as well, and it is easiest to analyze the pole structure to satisfy the building department. Therefore a single layer of 1" chicken wire or stucco wire (heavier gauge hexagonal mesh) is sufficient to insure a solid, crack-free wall.

Poles

The house pictured here was framed with poles between 2" and 6" in diameter. For vertical wall framing don't be overly concerned about sizing poles for strength. One 6" diameter fir pole, with a compressive strength of 40 tons or more, might be able to hold up your whole structure! For rafters and joists, however, a 6" diameter pole (crossectional area 28in²) is not as stiff as a 2x10 (cross sectional area only 14 in² but is stiffer than a 6x6" cut beam (crossectional area 30in²). Thin, deep beams offer a decided structural advantage---it is therefore cheaper and easier to use dimensional lumber for floor joists. Aesthetics is another matter --- you may feel more at home with massive beams holding up the floor above you and enjoy hefting them around during construction. I have seen pole-frame buildings that would be considered quite under-built by today's building department, yet the rafters are as straight and true as they were seventy years ago. But, of course, in most areas of the U.S. today, the building department has the final say on that matter.

If you prefer to peel your poles by hand then cut them when the sap is flowing best, in late spring and summer. They will peel many times easier than ones cut in the fall and winter, and you will end up with a smoother pole, free from nicks and cuts from peeling. Peel them within a couple of days after cutting, as the sap quickly becomes glue. If you want to use poles that are already dead (slash left over from logging or trees that naturally select themselves out in dense growth) saturate them underwater for a month or more, otherwise you may never get past the peeling.

There is a quicker solution, however. A high pressure washer will peel these poles and also make quick work of Fall/Winter-harvested poles too, and the surface wood is denser (more lignin in the winter wood).

If you want the surface to be light and even colored and free of mottled dark spots, season the poles in the sun with air spaces in the stack, rather than in the shade, or treat them immediately with an anti-fungal agent such as Woodlife; or build the framework while the poles are still green and let them season while they're up. A super-sharp broad hatchet (with one side flat) is real handy for trimming branches off close and peeling loose-barked poles.

The poles can be exposed on the outside or the inside of the walls with enough cross-bracing to afford a sturdy structure. If desired, some of the cross-bracing may be removed as the stuccoing is done, since the ferrocement shell is an extremely rigid diaphragm. The stiff sandwich wall sections can easily span between pole framing members as far apart as 6 feet. If the pole is twisted, it can usually be lined-up flat along the plane of the wall, which makes it easier to get the wire tight against the foam. If you purposely want to build with crooked poles, for the freeform frivolity of it (as In photo #3), You can build up layers of thin insulation to follow the curves. White beadboard insulation is the most flexible, although lowest in R value/inch. If available in your area, and if you can afford it, foam-in-place Urethane foam is the most appropriate insulation for irregularly-curved surfaces. Regularly-curved saddle surfaces, however, such as the hyperbolic paraboloids shown in the photograph of the model, can be built with evenly-spaced straight poles and crisscrossed layers of wire, insulation, and roofing to form a very sturdy, gracefully-curved ceiling-roof for a building. Fabric can be woven to form the web under the insulation. However, foam can be a killer in fires, so I feel best about shielding the foam from the fire's heat with a layer of stucco or plaster. A lot of water, chemically bonded in plaster and cement, must be boiled off before the fire can heat up the foam.

Where an exposed pole rests on the floor or foundation, taper it as shown in the drawing to prevent water from saturating the end grain of the post and eventually rotting it out. The countersunk pole-pad design pictured here provides the best long-term rot protection. Where the stucco-insulation is continued to below ground-level, no additional anchoring is necessary for wind, earthquake protection. Continuing the Insulation two or three feet below the ground level and providing a vapor barrier under the crawl-space allows an excellent sub-floor heat circulating system, with cold-air grates under the windows and a hole in the floor at the heater to provide even air circulation and warm, draft-free floors.

Always treat the exposed poles, especially the end grain, with a clear preservative. (End grain absorbs moisture about ten times as fast and will be the first site of rot.) For a final sealer coat, I have found the Use of one of the metal protecting oils, such as LPS-3, works great and gives a warm, aged glow to the wood.

An electric chainsaw and broad hatchet are quick and handy for rustic joints. For precision cuts, make a log vice, as pictured, to hold both ends of the pole securely in alignment. This allows you to carve the end accurately with an adz, hatchet, or chisel, without the pole moving out of position, and to measure more precisely the angle of cut on a curved pole. The pole is clamped down firmly without cutting into the log, with a truck leaf spring hinged at one end and held in adjustable position by a notched steel bar. (see diagram)

SCREEN

Next, stucco wire is stretched and stapled firmly and tight to the inside of the wall poles, and 1" chicken wire is attached likewise to the top of the ceiling poles. Then rigid foam is attached tight against the wire. It can be made more solid and weather-tight by gluing the joints with polyurethane foam from a can. A second layer of stucco or chicken wire is stretched tight on the inside of the walls and held taught and even at the corners by sheetrock edging or 1/4" steel rod. (see diagram) Nailers for shakes or metal roofing or plywood for composition shingles are nailed to the ceiling rafter poles through the foam. The final step before stuccoing or plastering is to make sure the screen is no further from the foam than 1/4", except right next to the poles. This is important so that the layer of stucco or plaster does not get so thick that it sloughs off as you are applying it. If you do a good job with the wiring, you will only need to apply two coats of stucco and one of plaster. Nails with a rough shank and large head (ring-shank or hot dipped galvanized poked straight into the foam (so that the heads don't protrude at an angle) will usually pull the screen in tight. 1 1/2" to 2 1/2" staples for a pneumatic gun will also work well. If you find loose and floppy places in the wire crimp it in several places with a twist of the pliers to help it lay down flatter with fewer nails. (see diagram) Problem spots may need 3" staples made with stiff wire inserted at an angle. Fine welding wire is straight and easiest to bend into a hairpin shape. When you apply the stucco, you will see why it was important to get the screen stretched uniformly tight. Don't worry that the screen is too tight against the foam. The stucco will work its way in behind it surprisingly well, unless the screen is imbedded in the foam, a condition you want to avoid.

If you have horizontal or diagonal poles exposed to the rain, add a strip of screen to shingle the stucco over the top of the pole. (see diagram) Expanded metal plaster lath or hardware cloth is much easier to use for this than hexagonal mesh.

Stucco

You are now ready to apply the stucco. If the poles have been oiled / cleanup will be easy. The stucco described here is harder and more durable, moisture-impervious and frost-resistant than what you usually see on stuccoed houses. The finished shell is thinner and similar to ferro-cement used on boat hulls, but with less reinforcing wire. If you haven't worked much with concrete before, check a couple of books out at the library. An excellent general introduction is The Practical Handbook of Concrete and Masonry, by Richard Day, 1964, Fawcett. If you also read a book on stucco and plaster and on ferrocement boat building, you should be well prepared, except for learning how to lift mud off your hauk without spilling it and placing it deftly on the wall or ceiling. The technique is like flipping a sloppy pancake with both the spatula and the pan. First you cut a piece of mortar away from the main pile and then launch the trowel up by pushing it , with the hauk held in the other hand, at the same time turning your trowel-wrist to bring the trowel under the selected blob of mortar. (see diagram 3) Like juggling, it takes practice... or ask around ... there may be a retired plasterer who'd love to demonstrate his art. You can always resort to working in pairs--one serving a portion onto the trowel of the other, who smears it on the screen... then you will see why plasterers are a jolly lot!

So let's mix a batch of mud. Any old cement or mortar mixer will do. Throw in about 3 parts masonry sand to 1 part Portland cement type I, and 1/2 part lime or 1/4 part fireclay (for easier handling), enough water to make a stiff mixture, and a small amount of liquid dishwashing detergent or air entraining agent. The latter is available from your concrete dealer--add enough to get 6% air entrainment, or about a teaspoon of detergent per 15 gallons of mud. The detergent is an anionic surfactant, which allows a more thorough wetting with less water and adds air bubbles, which make a stiff batch much more plastic and workable, thus increasing its strength (the less water, the stronger the stucco, which is one reason why commercial stuccoing is sometimes soft and crumbly). Type IA Portland cement already contains an air entraining agent.

The entrapped air also increases greatly the stucco's resistance to freezing damage. The lime or fireclay can be eliminated where maximum strength is desired. This makes it a more difficult to apply, but the air entraining agent helps make up for the loss of plasticity. One to 1 1/2 inch long hemp fibers or horse hair are traditionally used in stucco to aid in application and prevent cracking. I have not found fibers necessary In this kind of stucco and would omit this ingredient where maximum waterproofing is called for.

Apply a coat about 1/2" thick onto the screen. As long as the wire is not imbedded in the foam, the stucco will squeeze in behind it and form an integral bond. Cover the wire completely so you will not have to do a third coat. Just as the surface begins to set, brush it with a whisk broom to provide a rough surface for the finish coat to bond to. Brushing too soon makes the surface too rough and lumpy, with little pieces that can break off and show in the color coat. Timing will come easily after a little practice. Traditionally stucco was applied in three coats: a scratch coat, which was grooved with a comb to receive a brown coat, where surface irregularities were smoothed out with a long rod and darby, in preparation for the finish coat. This also lessened final cracking where wood lath was used. The use of foam backing, wire screen, air entrainment, and a thinner coat of stronger stucco virtually eliminates the problem of cracking and roughness. (unless you are trying for plasterboard smoothness)

The stucco must be cured by keeping it wet constantly for at least 7, preferably 9 or 10 days. The importance of this simple step cannot be overemphasized, as the process of crystallization that gives cement its strength is disturbed by allowing dry spots to develop, however briefly. Spray it constantly with a mist, or keep damp blankets or polyethylene sheeting hanging over it and spray underneath frequently.

The finish coat can be applied as soon as the base coat is cured hard enough to resist cracking (8 hours). The two coats can then be cured together. The finish coat is usually mixed with white sand, white Portland cement, lime and air-entraining agent in similar proportions to the base coat, a little richer (2 1/2 sand to 1 cement), along with an oxide color. Many colors are available and can be mixed to create in-between shades. These Ingredients are more expensive that gray cement and sand, but the color coat also replaces several paint coats and is applied only 1/8" to 1/4" thick, so much less is needed.

Plaster

The inside walls may be first stuccoed where there is rough traffic, then covered with a thin layer of plaster. This makes a very hard and durable wall, and less plaster is needed for the finish coat. Otherwise, inside walls and ceiling can be rough trowel-finished in one coat of perlited gypsum plaster. This is a ready-to-mix, easy-to-apply plaster with an insulating light-weight expanded rock aggregate. Unlike some other plasters, and there are many to choose from, it cures without cracking in thick applications, but try for a 1/2" thick coat. The same oxide colors can be mixed into the plaster, eliminating the need for paint. Make sure on both stucco and plaster color that proportions are kept the same from batch to batch and that it dries the color you want. Masking tape can be used on the logs to simplify cleanup, although once you get good at it, you shouldn't need much cleanup. Plaster cures upon drying and should not be wetted down, but you should dampen a stucco base-coat before applying either finish coat.

Any kind of roof can be applied over the foam: nailers and shakes (use felt paper too), plywood and composition shingles, corrugated metal, tile, etc. Do this, of course, before any plaster work, to prevent staining from rain. Electric wires can be laid in grooves in the foam, unless local codes require conduit. Conduit laid-out inside the foam, with frequent junction boxes, has advantages for future changes in wiring, since new wires can be strung or old ones replaced without disturbing the wall surfaces. Plumbing can be set in likewise and it will be fully insulated.