You can always resort to working in pairs one serving a portion onto the trowel of by v7166R


									            Pole-Stucco-Foam-Plaster Construction
                         Written by Larry Dobson for Mother Earth News
               Now greatly expanded with graphics, photos and detailed explanations!

         A superior construction method for hot-tubs or 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, dew-point 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.

     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 ---
almost 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 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, nor does it need to be so thick and strong on
its own, since 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

     The house pictured above 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 much
                                                           easier than ones cut in the fall and winter, and
                                                           you will end up with a smoother pole, free
                                                           from nicks and cuts. A specially-designed tool
                            (above) will greatly facilitate peeling the bark without cutting into the
                            wood. The blade is curved in cross-section in proportion to the curvature of
                            the pole, and the edge is also concave as pictured to glide smoothly under
                            the curved bark. The outer corners of the peeler are smoothly rounded to
                            facilitate slipping under the bark without cutting it into thin strips or
                            digging into the wood. Sharpen the edge to where it feels sharp but doesn’t
                            cut the skin. This tool is worth its weight in gold!
                            Another tool that can save much labor removing the stubs of branches flush
                            with the pole surface is
                            pictured here. Coupled
                            with the smooth peeler
                            tool, the pole can be
                            finished without further
                            need of sanding or
                            disturbing the naturally
                            perfect surface.
     Peel poles 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 acetic acid. I haven’t tried acetic acid, but hear it works, and it
isn’t toxic like some synthetic products – it’s just concentrated vinegar. Slow dried poles have the
fewest cracks, and often a rustic mottled surface patina, which is the easiest to produce, if you like that
look. Ideally, suspend a tarp over the stacked poles to keep them dry and shaded, and allow plenty of
air circulation between the poles and tarp.
      Or you can build the framework while the poles are still green and let them season while they're
up. For most applications this works fine, but if the poles for the door & window frames are twisty or
knotty they can warp out of alignment while drying and require re-planing.
     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 (photo left), 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 (Right), 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 to
                                prevent water from saturating the end grain of the post and eventually
                                rotting it out. The countersunk pole-pad design, pictured left and below,
                                provides the best long-term rot protection. To greatly increase rot-and-
                                insect resistance, torch a thin layer of charred wood on the bottom .
                                     Where the stucco-insulation is extended well below ground level
                                with backfill, no additional anchoring is necessary for wind or
                                earthquake protection (although your building department may have
                                different ideas…). 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.
     You may treat the exposed poles, especially exposed 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. All sealant/preservatives wear out eventually, and the wood will weather.
This will not reduce the life of your building significantly,
since wet areas where rot can set in are the most common
cause of deterioration. If you choose not to use any
sealants on the poles, do seal the cracks where they could
leak into the wall or floor with a super-long-life
penetrating sealant/calk.
     An electric chainsaw and broad hatchet are quick and
handy for rustic joints. For precision cuts, make a log
vice to hold both ends of the pole securely in alignment
(pictured on right). 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 into a V-notch without cutting into the log, with a
truck leaf spring hinged at one end and held in adjustable
position by a notched steel bar.

     Door and window frames
     For elegantly clean lines and simplicity of construction, cut grooves in the poles for door jams and
window frames, as pictured below. You can build a cutting jig of welded angle-iron. Bed-frame angle
iron is light-weight and highly tempered for stiffness.
     Next, hexagonal woven 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. The stucco wire is
sturdier than chicken wire for walls exposed to rough abuse. A fence-puller or nail-studded stiff board
and come-along is a great help in tightening the wire mesh. 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. The screen can also be
stretched around the foam and inserted between poles, as pictured here, to expose the poles both inside
and outside. In this case, poles should be well seasoned and shrinkage cracks calked in the heat of
summer to prevent air infiltration.
Nailers for shakes or metal roofing or plywood for composition shingles are nailed or screwed 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.
     A hooked tool (pictured right) works well to twist-
tighten areas of screen that are too loose. 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. If you are using only a couple of
inches of soft foam-board, you can stick the wire all the
way through and pull the wire mesh in on both sides.
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 into 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. Expanded metal plaster lath or hardware cloth is much easier to use for
this than hexagonal mesh.

    You are now ready to apply the stucco. If the poles have been oiled, cleanup will be easy.
Otherwise you can use masking tape, but that is more work. 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 Portland Cement Association’s Portland Cement Plaster (Stucco)
Manual or 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. 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 (by
volume) masonry sand to 1 part Portland cement type I, and 1/2 part lime or 1/4 part fireclay, pozalon
or fly-ash (for easier handling), enough water to make a stiff mixture, and a small amount of liquid
dishwashing detergent or air entraining agent. The consistency should be almost as stiff as room-
temperature creamy peanutbutter, so that a trowel-full only slumps slightly when placed on a surface.
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 weakens
the surface tension of the water, allowing more thorough wetting with less water, 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. With longer
mixing, detergent also adds air bubbles that reduce the chance of damage from freezing water. Type
IA Portland cement already contains an air-entraining agent.
     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. Pozzalon, flyash
and other additives can also be added to increase strength or save on cement. 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.
                                                                  You can mix small batches quickly in a
                                                             5-gallon plastic bucket with a sturdy drill and
                                                             a large paddle mixer. To prevent the bucket
                                                             from spinning out of control, make a simple
                                                             stand with bungy-cord hold-downs as
                                                             pictured here. This jig will accommodate
                                                             both tall and short buckets.
                                                                    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 detergent in similar proportions to the base coat, a
little richer (2 ½ to 3 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. Most oxide colors will not fade over time. A proper color coat never needs painting!
You can also imbed stones, gravel, memorabilia and leaves into the color coat, (as pictured above).
Remove the leaves or branches after the stucco is well set (2 hrs or more) to reveal beautiful “fossil”-
like impressions.

     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.
     Enjoy your building project, and send pictures and comments! I welcome suggestions to improve
these plans. I am available as a consultant if you would like further assistance in design and advice.

    Larry Dobson, , 360-579-1763, 7118 Fiske Rd., Clinton, WA 98236

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