RFadobepressblockrpt

Smart Shelter Reports

Pressed Block Adobe Construction

(Nov 20, 2001)

(rev: 26 Aug, 2004)

Smart Shelter Network

"...healthy living spaces for the people and environment of Western Colorado"

POB 981, Paonia, Colo 81428 <gd@smartshelter.com>

www.smartshelter.com

Adobe-Pressed Block

20 nov, 2001

Note: The following information summarizes conclusions and building owner performance reports from the two hundred plus case studies conducted by Smart Shelter in the past six years. Opinions vary from builder to builder. Those stated here represent a broad consensus based on actual building performance in this region. Your experience with these materials may or may not be the same.

Background:

Pressed block adobe is considered to be a significant technique in the construction of high integrity natural buildings in this region. Many of its practitioners utilize it as a general exterior and interior wall system in all applications. Smart Shelter has identified a "Regional Hybrid Signature Architecture" as a composite of the case studies on natural structures in Western Colorado. This hybrid design system utilizes pressed block for interior partitions only. Hybrid architecture incorporates a wide range of building ingredients including pressed block along with strawbale, timber frame, etc. and places them strategically in the building according to individual wall performance needs, cost, attainability, labor intensive character, environmental impact, etc.

Hybrid design is explained in the video course Natural Homes #101 (available on the website www.smartshelter.com). Planned, but not yet available at the time of this publication, will be an additional summary report on hybrid signature architecture. To fully understand where this and other materials fit in sophisticated natural building design, one or both of those references should be reviewed completely before integrating what follows here.

Overview

Buildings made of earth are considered sustainable and natural because the material is locally available, does not involve harvesting of forestry products, is nontoxic and moldable into a variety of shapes. Traditional adobe architecture involves forming blocks, turning them several times to dry, transporting them and mortaring them into place. Traditional blocks weigh about 30 pounds each. The work is labor intensive, and expensive if labor is paid.

Pneumatic presses have been developed which press a mixture of moistened soil, sand (and often straw) into a uniform, cubic building block (called "pressed block adobe"...Mark and Diane Schevene call theirs "Presto Block") under very high pressure (28,000 psi) which can be laid immediately on the previous course without mortar by wetting the existing block surface to form a slurry, onto which the new block is bedded . This process is much faster and less energy intensive than traditional adobe construction.

The walls are built continuously and cure as a monolithic structure requiring no mortar.

Traditional adobe advocates maintain that the pressed blocks are not as stable as traditionally formed and cured ones. No case study evidence is known to the Network here to indicate this as a problem. This would obviously depend on soil content and manufacture.

Precident

The landmark structures built with pressed block to date include the Leroux Creek Inn, the Willett residence and a series of homes by Dave Rosenbaum. These employ insulated exterior block walls with one exception.

The Leroux Creek Inn (Bed and Breakfast) is several miles up Leroux Creek road west of Hotchkiss. Built by Tom Leach. It is a two story structure with double wall block and 4" insulation fill space on the bottom story and 2x6" insulated frame wall on the top...a decision he regrets...the bottom story is of significantly superior comfort and appeal. This is a beautifully executed lodge, since sold, but accessible to the public by arrangement.

The Willett residence near Crawford was designed and built by Mark and Dianne Schevene (Paonia). It is single story with double wall insulated block exteriors and received an award from Natural Homes Magazine in 2001....beautifully executed.

Dave Rosenbaum (Olathe) has built several block homes in the area and has a self-built block press. His first personal residence was single wall exteriors and the subsequent owner had to add insulation. His second was double wall.

Though built of traditional mortared adobe bricks, the John McWilliams residence (Government Springs Road, Montrose) was one of the first successes with spray foam exterior application over single wall exteriors and is reported to be successful.

Design

Common and widespread misunderstanding persists concerning the insulation qualities of soil-based walls. We live in a climate zone with extremes of heat and cold...necessitating a highly insulated exterior wall system. Adobe is a very poor insulating medium, even in thick walls. Extensive and consistent poor performance in single wall uninsulated earth structures here have echoed the technical calculations which indicate that extensive insulation is necessary for these systems. Adobe construction in this area is not recommended for exterior walls without added insulation.

There are several ways to achieve the necessary insulation. However, as mentioned above, hybrid architecture and case study evidence consistently indicate the higher R-value materials such as strawbale are better choices for exterior partitions, especially on the north, east and west exposures. (see Natural Homes #101 and the smart shelter report on hybrid design).

Regional pressed block designers and builders will argue with this recommendation and they have, indeed, produced some excellent homes with pressed block and natural adobe exterior walls. This, however, is accomplished at significant expense and at reduced wall R-values.

There is another consideration to be used here which cannot be evaluated in hybrid design....the tastes and resonances of the owner. There are definitely people who are more comfortable with adobe than straw (and vice versa). This especially becomes observable after many case studies and watching hundreds of people on home tours.

The materials match for an individual's personality can only be made individually. The only way to prepare yourself to make that choice is to spend significant time in a number of different homes. The criterion presented here and the advice of pressed block designers and builders (who appear at the end of this report) should be taken into consideration first and understood thoroughly as preparation to making that decision. However, the final say should come from a subjective affinity for the medium...whatever it is. If you decide to use a soil medium like pressed block on exterior walls, be prepared to do extensive insulation work and incorporate that into your design. Also expect that system to cost significantly more than equivalent bale walls(probably 20-60% more). Note, however, that the cost of exterior walls typically constitutes 7-15% of the total price of a home...making a reasonable increase in per-foot wall cost not such a huge impact in the overall budget.

Insulation systems for exterior block walls involve either the creation of a wall cavity or by application to the exterior of the wall.

A cavity system involves building two complete walls with a space (typically 4-6") between them which is then filled with a pourable insulation such as vermiculite. These are obviously quite expensive and time consuming systems and eat up a lot of floor space.

Exterior insulation systems typically involve either sheathing the outside of the wall with rigid foam insulation ("blue board) or spray applied foam insulation (isocyanate or isonene). Both systems require a minimum 2" application and should optimally be 4" thick in this climate. Both require coating with cement-based or synthetic stucco. Foam boards and spray biodegrade in sunlight and are not suitable for exterior finish. Adobe/natural clay stuccos have a very high failure rate here and are not recommended because of constant maintenance requirements.

Viable exterior wall systems have been made with single course pressed block and 2" of spray foam with cement based stucco. The walls are structural and adequate for loading (see engineering discussion below), eliminating the need for an additional structural frame, although there are limits and considerations.

Sizes of pressed blocks vary with the particular machine used to produce them. A ball park standard is about 4" tall, 6" wide and 10"-12" long. Prior to finalizing design, a decision is made regarding block walls and a press is located to be used to ascertain block size so that adequate partition thickness information is available. Not doing this thoroughly can end up in significant loss of interior room space, especially if multiple course wall thicknesses prove necessary.

Consultation with any of the competent and experienced block designers and builders listed in this report is strongly advised as early in the design phase as possible, if you or a designer inexperienced with pressed block are doing the drawings. $50-100 for a couple of hours early in the game can save thousands of dollars of mistakes later. They will most likely try to talk you into a complete home of block walls, contrary to the hybrid formula, but that's a consideration only you can effectively resolve. If the home is to utilize block exteriors, you should seriously consider having someone like the Schevenes design it for you. Each of these media have idiosyncrasies that require extensive considerations to successfully utilize.

Signature Hybrid Design restricts the use of pressed blocks to interior partitions only. There are several reasons for this. The typical alternative in conventional construction is a 2x4 frame wall with 1/2" drywall textured and painted on both sides. It's difficult to degrade this partition system adequately, but we'll try.

First of all, the United States enjoys the world's highest incidence of death due to building fire of any country in the world...because of stick frame construction such as this. It is the equivalent of building a wooden chimney every 16" around your sleeping space and hoping. The dimensional wood framing lumber is unsustainably harvested from vanishing forests, pesticide sprayed before it crosses state lines and transported hundreds of miles to be used. The drywall and finishing compound are laced with fungicides and solvents, which your family will be breathing for years along with the paint out gassing. Sound transmission through frame walls is terrible. This is, by the way, the building system used to build Hollywood movie sets. It should be kept there.

By contrast, interior block walls are sound proof, fire proof, bullet proof (beyond 4" thick",constructed of local site materials, completely owner buildable, have no waste and will last infinitely longer(4-600 years) than frame construction, provide highly effective solar massing and are easily modified in remodels...just chip away what you don't want and make more blocks.

Finishes for pressed block walls can be as simple as wire brushing and oiling or painting the surface, which produces a rustic, pleasant effect. The blocks will flake dust if left uncoated. They can be plastered to a sculpturally smooth, flat surface with clay/soil based plasters if something more elegant is desired (finish details are explained below)

The largest single advantage of pressed block (and other earth based) interior partitions is their contribution to passive solar heat storage mass on the interior of hybrid structures. (Massing is explained in Natural Homes #101...it's the "sun energy storage battery" effect of heavy interior materials which makes passive solar design work). In comparison to frame walls, the soil based partitions provide an infinitely superior massing addition to the building interior. This is an absolutely crucial ingredient in solar design and the single most important reason for using massive interior materials extensively. This coupled with the advantages of block over frame partitions mentioned above make pressed block the obvious choice in hybrid design by far. Their effectiveness in stabilizing interior temperatures produces a livability and comfort unattainable by any other system. This huge storage mass enables cooling through passive nighttime ventilation in summer typically effective enough to eliminate the need for cooling systems or air conditioning all together (given adequate exterior wall and roof insulation.

The feelings of substantiality and quality put homes built with these walls well into a quality class of their own.

Mass Positioning in solar design is a science in itself and too involved to discuss effectively here. However, the plasticity and formability of pressed block makes the fabrication of trombe walls, bancos, massing knee walls , etc. in proper proximity to south-facing windows easy. No massing design is ever 100% effective on first design. Of particular value is the fact that if, after a year or two, it becomes obvious that less mass is needed here or more there, with block systems, those changes are as easy as digging in one place and adding block in another to "tune" the passive structure.

Curvilinear and dome structures are comparatively easy to execute...impossible with frame systems. Mosaics and imbedded inclusions (such as bottles) are often used. A few domes and curved archways have been beautifully executed...best to consult or hire an experienced technician like Russ Harvey (contact below) to help. These are dangerous undertakings if not properly pursued. Art always completes expertise in a building form and seals the livability of a home. Block systems, especially in conjunction with cob(separate report) are sculptural media, enabling creation of fire places, nichos, archways, statues, furniture, pedestals and the like. They are easily carved and changed. Their surfaces can be polished and plastered to elegant patinas.

Disposal of waste or demolition building materials is often a design/sustainability criterion which is overlooked. 40% of our landfills are demolished stick-frame building materials. 30% of all the materials imported to conventional building sites leave the site as waste. The beauty of pressed block in this regard is that you only make what you need where you need it and when its life is over, it returns to the dirt from which it came.

Warnings regarding using pressed block include the fact that they are water soluble and will deteriorate in rain,flooding or wet conditions. Structural walls must be stabilized or protected from moisture with over coatings which are moisture proof. These stuccos must be maintained. There are reports of entire unprotected walls "melting" in rain storms. Research is needed into stabilizing techniques for these blocks. Some code jurisdictions may require stabilized blocks for construction.

Just as in strawbale construction, even in interior applications, flooding can occur from burst water heaters, overflowing sinks, etc. It is prudent design to extend the concrete grade beam or foundation supporting block walls a couple of inches above the finished floor to create a water-stop curb.

Plumbing & Utility Raceways require planning. Design vent stacks, etc into adjacent frame walls, or create box raceways in block walls. Pressurized water pipes in block walls should be double sleeved with a drain out of the wall.

Electrical outlet boxes are carved into blocks and anchored with drywall screws directly into the blocks. Wiring is cut into groves in a block course, routed to boxes and another course of block applied over them. No conduit should be required. Blocks are non combustable...but that depends on the whims of the inspector.

Hangings such as pictures can be made with nails or drywall screws angled down. It's a good idea to pre drill for screws or nails to prevent spawling.

Engineering

Technical engineering for pressed block walls is beyond the scope of this report and needs to be addressed by a competent Civil Engineer. Civil Engineers are licensed professionals in the State of Colorado. Smart Shelter tracks engineers supporting natural building..some are listed on our website (www.smartshelter.com) under "service providers" or "business members". More extensive referrals are available to Network members on request.

Structural walls bearing roof and floor loads are consistently built in this area and to date there have been no known structural failures recorded with the Network. As a masonry media, pressed block will not withstand the loads of concrete block or similar units. Strength of actual block will depend on the soil mixture, curing and assembly. If engineering is a criterion, actual block tests will probably be necessary. Supporting members such as archways, lentils, door headers, etc. will bear extensive loads because of the mass of this media. Extreme care must be taken to insure their adequacy and bearing support.

Foundation design is critical for exterior walls because of soil conditions in this area (expansive and often saturated near agricultural area) and the weight of these walls. Interior partitions should be underlain by strip footers...typically 8-10" reinforced concrete the width of the block wall. Note: the foundation design on the Leroux Creek Bed And Breakfast is a reinforced slab without footer on a 12" bed of compacted gravel...a permafrost building technique designed for areas where excavation is impossible. Engineered by Ted Hermans-Mesa Engineering, Montrose.

Fabrication

Not all site soils are suitable for pressed blocks. Regionally, soils from the Mancos Shale deposits (commonly called "the adobes") typically provide good soil base for blocks when mixed with the right proportion of sand and straw. This is a bentonite clay, found in extensive deposits in the area, expands with moisture, can have high salt content, typically needs at least 50/50 mixture with sand, but dries hard and solid. The "Adobes" form the flanks of the foothill area on the east side of the Uncompahgre/Grand Valleys.

Red/tan soils from the Dakota and Morrison formations (on the west side of the valleys) are typically not known to be good basis for blocks...though some have been used successfully. These are often referred to as the "Mesa Soils" and are preferred for agriculture, but have lower clay content for building.

It is not untypical (especially west of the Gunnison and Uncompahgre Rivers) to encounter sites with both soils/bedding deposits. Soil conditions can vary radically within a few feet on a site.

Top-soils containing too much organic matter and jeopardize the stability of blocks...which will cause block failure. As a rule of thumb, remove the top foot of top soil, look for a change in color and watch for roots and debris. Dig down until the soil is clean.

Soil Tests can be done through a soil lab (listed below). Not much useful seems to have come out of the ones done with the attention of the Network. Of particular concern is salt content, which can undermine block stability.

The "mayonnaise jar" test is favored by some builders to determine adequate clay content...which is the "glue" which holds adobe together. Soil is placed in a jar, which is filled with water and shaken thoroughly. The soil will settle out in layers, sand on the bottom, silt in the middle and clay on top. Organics will float. 13-15% clay is deemed optimal.

A "block test" will give a quick idea of soil usability. Make a wooden form about 2" wide and 12" long . Fill it with wet soil mixture, let it dry and check for shrinkage/cracking. Adjust soil to clay mixture until shrinkage is not more than 10%...about an inch in the length of the block. Sand prevents shrinkage and cracking. Typically try about a 50/50 mix in mancos shale "adobe". Mesa soils may have adequate sand as they are or require very little "tuning"

Jerry Hobgood (hybrid bale/adobe solar builder...Grand Junction) had the most pragmatic and appealing approach to date...make a ball...let it harden...drop it on the ground. If it breaks, adjust the mixture and test again.

Chopped straw added to block binds the block together. This is not used in exterior walls, because the straw will wick moisture. Chopped tumble weeks are like iron and form the hardest organic, natural binder available regionally. A lawn mower with leaf bag is a good week chopper...quick and fine.

Moisture content in the blocks is critical. Too much and they will not compress (muddy globs) Too little and they will crumble. Add just enough to allow the soil to congeal under pressure.

Block Pressing Machines come in three varieties: a non-motorized hand press, a medium sized shovel fed motorized pneumatic press , and a large front-loader fed hopper press with conveyor.

One farmer near Delta reports having built a small home in New Mexico using the hand press model, which consists of a chamber which is shoveled full of moist soil and a lever to compress the block. The home was built in a summer "one block at a time."

The Schevenes use the medium sized pneumatic press (Rosenbaum too), which can be loaded onto a pick up truck, is fed with a shovel and produces blocks quickly.

Stucker (listing below) operates a large hopper press fed by a back hoe and delivers the blocks onto a roller conveyor.

Some machines apparently exist which end press the blocks. There are reports of this process not working. Blocks are apparently best when made in a machine which presses them from above.

Select one first. So much depends on the block press...the size of the block, the thickness of the wall, the soil /moisture mix, size of the crew needed, cost of the project. Early in your project design, interview the block providers, get their input and design help (don't expect them to provide extensive input for free), have some test sample blocks made with the machine and your soil and decide who you're going to use.

Get costs, arrangements and labor agreements in writing and specifically detailed.

Ways they Work: If you buy a hand press, have no time limit and work by yourself things will be predictable.

If you have no experience, consider hiring someone like the Schevenes or Stucker to provide the machine and operate it....you provide the labor and soil. You need a bit of their input for design, etc...or they may design the whole project for you.

Sometimes regional equipment rental houses have block machines. Be sure you know what you're doing before running these. The pneumatic presses are dangerous if you get a hand or finger caught.

A typical operation is to have two people mixing and feeding soil, two running the machine and two stacking block.....six person crew. This is heavy work and once you start, it's difficult and counterproductive to stop a lot. A typical house can stand in a few days.

Your options are: buy a hand press(maybe $500-1,000 new), buy a pneumatic press ($2,000-15,000 used/new), rent a pneumatic press, contract with a press owner for operation/supervision, or just have them do the whole thing.

Stored Blocks don't seem to work very well. Many projects have made up the blocks and stacked them to dry before placing them into the walls. The blocks cure unevenly and often crumble, making the wall assembly process a problem.

The technique seems to work best when the blocks are pressed as they are stacked onto a slurry surface, raising the wall continuously and allowing it to cure as a monolithic unit. Typically half the wall is assembled and let cure to prevent crushing the blocks below with too much overburden. Blocks are set in their own mud. A wet paint brush is used to wet the surface of the blocks to a "slurry" consistency. The new block is applied to the wet surface without mortar.

Finishes as mentioned above can vary from simple to quite elaborate. Rosenbaum's first home had no interior plaster. The blocks were wire brushed to clean and smooth them. They were then painted with standard latex house paint. The walls were quite attractive. (Note: Sherwin Williams "Health Spec" and Glidden "Spread 2000") are the only two paints which consistently pass Chemical Sensitivity standards for nontoxic outgassing...recommend you use them...watch out for the color additives...that's where the toxins are. Straight linseed oil (down to a mixture of 50/50 paint thinner) can be used to seal the block (which will flake dust if not sealed). However, this produces a very dark brown finish, often too dark for most rooms.

Mud soil plasters of the same material and mix as the block work well if you want a smooth wall and are willing to do the work. Colored plasters are made by adding colored soil, colorants, paints, etc. This is a matter of experimentation. Some hardener (cement) is often added to stiffen up the surface.

Exotic finishes are done by adding mica flakes or chopped straw for sparkle, lime/gypsum plasters and even the pastel french swirl (faux) plasters with hand rubbed bees waxed finishes. Smart Shelter indexes several regional plaster professionals. Their ingredients are a trade mark and techniques are usually well guarded...but they can produce exquisite interiors...and have.

Publication Notes/update (26 august, 2004)...site experience in pressed blocks made with a vertical press resulted in irregular heights in the blocks, which prevented their "wet stacking" straight out of the press and consequent curing as a monolithic unit in place. Instead, the blocks were stacked and dried, assembled with adobe mortaring, resulting in loss of about 5% due to cracking and a lot of extra labor in mortar assembly. Recommendation is to use a horizontal press resulting in uniform height if the blocks are to be assembled wet and straight off the press, which is the time effective manner. At any rate, the walls were very satisfactory and massing performance in the hybrid structure was good.

A resource encountered after the initial publication of this report tells of building an entire 1200 sq ft home for himself in a summer using a hand operated leverage press which was a steel box, loaded from the top and pressed with a lever to produce one block at a time. He loved the project...like much that's good in natural building...do it as a part of your lifestyle...a little every day...not in a hurry and with no time agenda and before you know it, one day you'll look up and there will be your home.

Service Providers dealing in pressed block adobe:

John Burritt (970) 835-8689 (Hotchkiss)- contractor and experienced adobe builder

Russ Harvey (970) 325-0635 (Ridgway)- experienced adobe craftsman

Marc and Diane Shevene (Alive Designs) (970) 527-6460 (paonia) -experienced design and construction in pressed block adobe. Have a block machine available for their operation on your site or your rental. Can provide for purchase of machines ($16,000 range)(note...26aug04...marc and diane have relocated due to illness and are no longer in this area)

Dan Stucker (970) 872-4714 (Hotchkiss) block maker with large, hopper fed machine to make custom bricks on site or elsewhere. (note-26 aug 04

Dan has sold his machine and is out of the business)

Dave Rosenbaum (970) 323-6347 (Olathe)- adobe builder-works with Dean McHenry-has produced several pressed block homes in the Uncompahgre valley including his own.

Dean McHenry (970) 323-6702 (Olathe) -same as above-built his own pressed block machine

Marty Watts (970) 856-7187 (Cedaredge) <watts@gj.net> -adobe contractor, solar design 4 buildings to date (2000), consulting, adobe floors, plaster, rumford fireplaces designer/builder, some nontoxic building experience.

Jim Hallack (970) ??????? (Bayfield)- re: Bruce Glenn- does pressed block adobe construction .

Hotchkiss Rental (970) 872-2626 (Hotchkiss) 3505 Hwy 92- reportedly has pressed block machine for rental.

____ Williamson (??????) (Moab)- reported to have pressed block machine. Contact indicated they may be a big motel owner.

Earth Block Inc. (970) 731-2569 (Pagosa Springs) POB 3605, 81147- earth block builder has tour available and information kit. reportedly built homes in area.

Mike Folkert (970) 874-4634 (Delta) information and history on pressed block buildings in area

Soils Testing

Root & Norton Labs (970) 249-5366 (Montrose) 576Spring Creek Mesa (re: Steve Boyle 249-8731- owner builder who used them to test soil). only provide agricultural tests. salt content, etc.

CSU Extension (check your area phone directory)

Tri-River Extension (970) ___ ____ (Grand Junction -Curtis Smith)

Pressed Block adobe building owners

These are owners or builders of homes using pressed block techniques in the area.

Rolland Holzwarth (970) 249-0397 (Montrose)

Tom Leach/ Leroux Creek Inn (970) 872-4746- (Hotchkiss)double wall building by Dan Stucker

Steve Boyle/ Missy Rogers (970) 249-8731 (Montrose)-remodel using Stucker's blocks

John and Connie Willit (970) ___ ____(Crawford) double wall adobe by Schevene's

Jeff Hahn (970) 323-8640 (Olathe) bought Dave Rosenbaum's adobe home, found single wall uninsulated adobe to be lacking in R value for exterior walls

Susan Billings/ Duncan Ferguson (970) ___ ____ (Norwood) adobe home ???pressed block

Ken Peterson (970) ___ ____ (Colona) adobe home

Todd and Stewart Chappell (970) ___ ____ (Montrose) adobe home by Rosenbaum/McHenry

Tina and Byron McNew (970) ___ ____ (Montrose) adobe home across from new City Market -since sold and moved ???pressed block

Paradis (last name) (970) ___ ____ (Montrose) adob