2. Hands on for Rammed Earth and Traditional Adobe
May 24/25, 2014 (Sat./Sun.)
Bosque, New Mexico
General Plan ~This class is held near Bosque, New Mexico, 8 miles south of Belen at the SWSA Field Station. It repeats the Adobe portion of the previous weekend, but replaces Pressed Earth Block with Rammed Earth. Students roll up their sleeves to mix mud and lay adobe, but also set up forms to ram a wall section. Learn to build arches and walls to Code. Get the heft of the materials and an idea of how many blocks you can lay per day as well as how many cubic feet of wall you could ram a day. If you have a building site, bring a sample of your earth for an evaluation- we’ll test it and amend it if necessary.
Weather is likely to be warm, but mornings and evenings are still cool. On Saturday, students participate in setting up forms and ramming a wall section. On Sunday early, the forms are removed to view the results and we move on to Traditional Adobe.
At the site ~ You will be asked to sign a waiver on arrival. Conditions at the Field Station are rustic in a countryside setting. Conditions can be windy and dusty. Bring your hat, gloves, polarized sunglasses and protective footwear. Light jacket suggested for early mornings. Camera advised for shots of equipment, attachment assemblies, etc. Coffee & fruit juices each morning with cold drinks for warm afternoons. Shade, chairs, tools, materials on hand. Maps to class and local info provided once you register, along with pre-class reading assignments.
Saturday, May 24 ~
8:00- 12:45pm Soils and Earth Mixes for Rammed Earth Construction
Rammed Earth today is not the quieter, meditative experience that Adobe can be. Before about 1940, Rammed Earth was hand tamped, but these days, it’s done with power tools, sturdy forms and various attachments. Typical on site are tampers, air compressors and tractors to raise walls 24” thick. Safety is a greater concern with Rammed Earth. If you feel at home around hydraulics and heavier equipment, you will probably love rammed earth. A “qualified” soil is essential- to be maintained through the ramming process. Like Pressed Earth Block, Rammed Earth has an “optimum” moisture content to be properly compacted. Your soil must meet Code for Compression and Modulus of Rupture. We demonstrate what does/doesn’t work using soils on site and samples you have volunteered. We’ll spend the morning setting up a rammed earth wall section, and study the equipment below. In the afternoon, we’ll ram our section.
Forms, fillers, corners, attachments and ties: Forming systems are available throughout the USA and Internationally. Most feature special plywood and steel frames. Forms come in many sizes, with 2x4 feet as most common. Dimensions for rammed earth tend to be in whole foot sizes. Job-built fillers are used to fill miscellaneous spaces. Inside corners come in different sizes to allow cross bracing and matching of forms from side to side. Students set up the forms for our section and learn that it’s actually fairly simple, BUT safety is #1, as forms are heavy and can pinch fingers and toes.
Air Compressors use a big automotive engine to pump air. You’re looking for a 185 CFM compressor to run two tampers at once on a typical job. The air compressor puts out air- and noise. We’ll fire it up to tamp our wall section. Various companies make them, such as Ingersoll-Rand or Grimmer-Schmidt. They are a common rent item. Most are trailer mounted with lights.
Tampers and air hoses Tampers with a 4” diameter foot are heavy, but lighter ones, with 2 ½” diameter feet, tamp just as well. Rented tampers are often faulty (test them at yard), so this is one tool you are better off owning yourself. Hoses are relatively cheap, so have a few of your own 50’ lengths, as the rented ones can fail.
(take your breaks as you need them)
Other Equipment: Skip loaders (Bobcats and some tractors) place “lifts” of qualified soil into the forms. They can mix soils and stabilizers (blending in Portland cement). Larger jobs use soil blender-mixers and conveyors to feed material to the forms. Rounded corners can be achieved via sawn inserts (we’ll do one). Colored soils can be rammed in lifts to achieve a Painted Desert effect (we’ll try it). To stabilize, you must meet an ASTM standard as with pressed block. You’ll receive a hard copy of the ASTM procedure in your handout package.
12:45- 2:00 pm Lunch Break
2:00- 5:30 pm Ramming a Wall Section.
Using precaution and safety, those students most interested can take turns on the tamper. It’s a dusty job, with bits of dirt and rock rooster-tailing into the air, but some love it. Hats, goggles and gloves mandatory. Please- no sandals or bare toes! An interesting fact is that it takes about the same amount of time to ram a 24” wide wall as an 18” wide one. This efficiency is why rammed earth is often preferred over Adobe or Pressed Earth Block for super wide walls.
Before we begin our wall section, we’ll try to have the following bases covered:
Electrical circuits- UF cable is not allowed in RE. All circuits must be in pipe. Students will set up a pipe circuit and plug boxes within the void of the forming before ramming takes place. As we ram the section, see how to ram around electrical components and to later remove the forming safely, without affecting the cosmetic appearance of the wall.
Nichos- Nicho plugs can be shaped and set into the forming, then removed later; forming the desired nicho shape (we’ll try one). The code is quite specific about different types of nichos.
Plumbing- The class reviews NM Rammed Earth code specifics about how rammed earth walls can accept pipe. For example, vent pipe is typically rammed into the wall.
(take your breaks as you need them)
Once our section is rammed, we’ll leave the forms on until the next morning. Removal of forms is a stepped procedure, where caution, safety and appearance are important. Once forms are removed, the wall will be misted at intervals to properly cure the work.
Tool cleanup at 5:20pm - Class ends for day at 5:30pm
Sunday, May 25 ~
8:30- 12:45pm Traditional Adobe, different sizes of Adobe and Making and Laying Sun-cured Adobes the Traditional Way.
Qualified Soils for Adobe – Adobe was the first to become encoded, a process that began after 1910 when the Dept. of Agriculture first issued practical homesteading manuals. In the Southwest, a sort of empirical code has existed for generations, derived from Spanish and Native American traditions. Today, as with pressed earth block, Adobe makers must use a qualified soil, then maintain that standard through the production process. Traditional adobe is sun-dried, whether it contains a stabilizer or not. Your block will have to meet code for compression and modulus of rupture. We demonstrate what works and doesn’t using soils on site and samples students have transported to class. Traditional Adobe is a fully saturated, stiff mud when it goes into the form. The form is lifted and the block dries. After several sunny days, it’s turned on edge to dry faster. Adobe is labor intensive, but green- no furnaces of natural gas are needed to cure the product. Soil preparation is essential for quality. After going over forms, we’ll cast the following adobes:
The Holey Adobe and Form Manufacture: Holey adobes feature a hole in their centers, or with a half-hole at one end. They allow Lego-block type connections for uplift anchors, or to run conduit or vent pipe depending on code and wall design.
Forms range from those that make one block at a time to longer ladder forms that make 8 or 10 adobes per casting. Wood and Metal ones present in the sizes below:
The Vault and Dome Adobe: Smaller adobes of about 7x2x10” in size. Lightweight and easily custom-shaped using a hand adz. Can be tossed to the mason. Used in several areas worldwide in vaults and domes, as in Mexico and Egypt. Sometimes fired in a kiln as in Sonora, Mexico.
The Standard New Mexico Adobe: The standard 32-pound adobe from New Mexico, also used in Southern Colorado and SE Arizona. It measures 10x4x14”.
The “improved” New Mexico Adobe: It measures 10x4x16” and has the advantage of a better corner overlap for a stronger corner.
(take your breaks as you need them)
The Arizona/California Adobes: One of the more successful adobes worldwide, the 8x4x16” adobe is easy to handle. It can be used to create a 16” wall by alternating the coursing, while also accommodating code-required rebar and concrete in seismic zones. Its big brother, the 12x4x16” adobe is popular for 12” interior walls, and 16” exterior walls, but masons don’t prefer it - each block weighs 50 pounds. Both of these block sizes are fired in Sonora, Mexico (adobe quemado) into a ceramic adobe, common in SE Arizona.
The Mission Adobe: A monster adobe that was swung onto the wall by two people, like a sack of flour or cement. One size, used at Guadalupe church in Santa Fe (1790s), measures 10x4x20”. A California cousin measured 12x4x24”. We’ll cast a Mission block, and then reuse the mud on some horno adobes.
The Horno Adobe: A smaller, typically trapezoid-shaped adobe used in building the Adobe cooking oven or horno, used to bake bread and meat. Students wanting to put up horno adobes can do so on the SWSA horno during the afternoon session. Horno adobes should not contain any substance that could outgas under the frequent firings.
12:45- 2:00 pm Lunch Break
2:00- 5:15 pm Laying Traditional Adobe – (take your breaks as you need them)
Leads, lines and laying block- As with pressed earth block, students set up Speedleads and mason lines to lay adobes on a stem set up by SWSA. They practice stacking and cutting Adobes and code overlaps. The project is to build an adobe wall, and then turn a corner while keeping courses level, plumb and attractively finished. SWSA instructors show you tools and tricks of the trade, such as adobe files, shovels vs. trowels and how roughbucks are set in the wall for windows and doors.
How many adobes per day? You should be able to get an idea of how many adobes you can lay in a reasonable time period. For example, along stretches of wall with few windows, turns or complications, you can easily lay one adobe a minute. Corners will slow you down, as will the installation of an electrical circuit, or the roughbuck for a window.
Arches- Students learn to construct a 3-foot Roman arch using traditional adobes. The instructor first builds the arch, step by step, with student help. He then drops the form. It’s now the students’ turn to build one as the Instructor coaches. Trimming adobes to fit the arch is demonstrated. Arches are important in open floor plans, for aesthetic effects and to save money vs. doors between some living spaces.
Electrical and Plumbing- Traditional adobe uses a thick mud joint that can accept in-wall reinforcement, electrical circuitry and some plumbing. We’ll run a stretch of wall with boxes, using both pipe and UF cable. On another course, we’ll lay in-wall reinforcement.
Tool cleanup at 5:00pm - Class ends at 5:15pm
Cost: $323 single/ $516 for two registering together
Class Capacity: 15
Students receive: Earthbuilders Encyclopedia CD, Copy of NM Earthen Materials Code, various hard copy handouts and a set of working drawings for an Adobe/CEB home.
Teaching Methods: Hands-on, Show and Tell, Q&A.