What a building day looks like

Most of a day goes to moving and mixing. You dig and sift clay soil, measure it out in buckets with sand, wet it, and tread it on a tarp until it is one stiff, even dough, then work in straw. Building is the shorter part: pressing handfuls onto the wall, or laying bricks, bales or bags, and checking the face with a level as you go. Earth goes up in layers that have to stiffen before they can carry the next one, so a wall rises about a foot at a time with days in between. The work is easy to share, which is why so much of it happens at work parties: four people on a tarp make far more than four times what one person can.

Many pairs of hands pressed into wet gray clay mud — Many hands in wet clay

Codes and permits come before a real building

A garden bench needs no one's sign-off. A building does: anything you plan to sleep in, heat or wire needs a permit and has to meet your local building code, whatever it is made of.
The model residential code used across most of the US has optional appendices for these methods. In the 2021 edition they are Appendix AS (straw bale), AU (cob) and AR (light straw-clay); the 2024 edition renumbers them BJ, BK and BI. An appendix only applies where your city, county or state has adopted it, so ask the building department which edition and which appendices are in force.
Where no appendix is adopted, an earthen or straw wall goes through as an "alternative material", which normally means paying an engineer to stamp the plans.
The cob appendix shows how tight the limits are: one story, walls no taller than 20 feet, and only in the three lowest seismic design categories unless an engineer designs the building.
New Mexico has its own statewide earthen building code covering adobe, and several other states have adopted the straw bale appendix. Rules differ enough that a plan approved in one county can be refused in the next.
Small sheds are often exempt from a permit. The model code exempts one-story detached accessory structures up to 200 square feet, fences up to 7 feet and retaining walls up to 4 feet, but many places set lower limits, and zoning setbacks and wildfire rules still apply. Exempt from a permit does not mean exempt from the code.
An outdoor oven is a fire appliance. Ask the fire department or zoning office how far it must sit from buildings and property lines, and check burn bans before you light it.

The codes, free to read

Tall ochre earthen-walled houses with gray tile roofs in a mountain village

Six ways to build with earth and straw

Same clay, different ways to stack it

CobClay soil, sand and straw trodden into a stiff dough and pressed onto the wall by hand, with no forms and no bricks. It suits curves, benches and ovens, and it is the slowest way to build.

Start here

Tread one bucket of clay soil and two of sand together on the tarp, work in straw until the mix holds a shape, and press it into a few fist-sized loaves. Let them dry and see whether they crack or crumble.

AdobeThe same mud, shaped in a wooden form and dried in the sun into bricks, then laid in mud mortar. You can make bricks for weeks and build in a few days.

Start here

Screw four scrap boards into an open frame about 10 by 14 inches and 4 inches deep. Fill it with stiff mud, lift the frame off, and dry the brick in the sun, turning it onto its edge after a few days.

Adobe in Action

Straw BaleBales stacked like giant bricks and plastered on both sides. The walls go up fast and insulate very well, but the straw has to stay dry from the field to the finished plaster.

Start here

Buy two bales from a feed store, read the middle of each with a moisture meter, then practice turning one into two half bales with twine. Download the code appendix and read the moisture and foundation sections before stacking anything.

California Straw Building Association

EarthbagDamp soil tamped into woven bags and laid in courses with barbed wire between them. It tolerates poor soil that will not make good cob.

Start here

Fill ten bags with damp soil, lay them in a row on a gravel-filled trench, tamp them flat, and run two strands of barbed wire along the top before the next course. Three courses make a garden bench base.

CalEarth

Clay PlasterSifted clay, fine sand and chopped straw troweled onto a wall. It works indoors over existing walls too, so it is the one method you can try without building anything.

Start here

Sift clay soil and sand through a fine screen, mix three or four small batches with different amounts of sand, and trowel each onto a scrap board. The one that dries hard without cracking or dusting is your recipe.

Lime PlasterLime and sand, used as the weather coat outdoors and in wet rooms. It is harder and more rain-resistant than clay, and it is caustic, so it comes with its own safety gear.

Start here

Put on goggles and gloves, then mix one part hydrated lime to three parts sand by volume with just enough water to make a stiff paste. Trowel it thin onto a dampened sample board and mist it twice a day for a week.

Open a card to see its first step. Straw Bale, Earthbag and Lime Plaster each add their own gear to the buckets, and you can switch them back out from the kit.

Reading your soil and getting the mix right

Use subsoil, the lighter-colored layer under the dark topsoil. Topsoil is full of roots and organic matter that rot inside a wall.
Jar test: fill a straight-sided jar a third full of sifted soil, top it up with water, shake hard and set it down. Mark the sand after one minute, the silt after two hours and the clay after two days, then compare the heights.
Feel test: wet a pinch and rub it. Clay is sticky and smears shiny, silt feels like flour, sand is gritty. Roll a pencil-thick worm and bend it around your finger. If it bends without breaking there is plenty of clay.
Clay is the glue and sand is the structure. Too much clay and the wall cracks as it dries; too little and it crumbles. Builders who test their soil look for roughly 10 to 25 percent clay with mostly coarse sand, and add sand or clay to get there.
No test replaces test bricks. Make several with different amounts of added sand, dry them fully, and keep the recipe of the one that does not crack, does not dust when rubbed, and survives a drop from waist height.
Before every batch, check the wet mix: a ball dropped from waist height should hold together and flatten slightly. If it splats it is too wet, and if it shatters it is too dry or too sandy.

Close view of a rough hand-applied mud wall with straw and wood chips showing in the surface — Clay, sand and straw in a wall

Sun-dried mud bricks stacked on edge in rows, with one lying flat on top

How to get started

Tick each one off as the wall goes up

What you can build in your first month

A row of test bricks

Five or six small bricks with different amounts of sand, labeled and dried, so you know which mix your soil wants.

A plaster sample board

Three clay plaster recipes troweled side by side onto one board, the fastest way to learn the trowel.

A cob garden bench

A stone or broken-concrete base one course high with a cob seat sculpted on top, small enough to finish in two or three weekends.

A low garden wall

A few feet of cob or adobe on a stone base, kept below sitting height, with a cap of flat stones to shed rain.

What trips beginners up

It is slower than it looks. One person mixing by foot makes a few wheelbarrow loads a day, and a thick wall needs weeks of dry weather before it can be plastered.
The season sets the schedule. Earth has to dry before the first hard frost, so in most of the country building stops in early fall.
A full-size house is years of weekends plus permits, a roof, wiring and plumbing. The walls are a small share of the cost and work of a building.
Skipping test bricks. Soil changes from one side of a yard to the other, and a recipe from a book or video is a starting point for tests, not a result.
Building on the ground. Earth and straw walls fail from the bottom, where water splashes and wicks up, so the base and the cap matter more than the wall between them.
Using hay or damp straw. Hay has seed heads and leaves that rot and feed mice. Straw is the dry hollow stalk left after grain harvest.
Plastering too soon or too thick. Plaster over a wall that is still wet traps the moisture, and a single thick coat cracks. Thin coats on a dry, dampened wall hold.

An ochre earthen wall with visible layer lines, hairline cracks and one small barred window — Layer lines and cracks in an earth wall

Safety: lime, dust, weight and water

Start with small projects that are not shelter. Earth walls are very heavy and plain ones do badly in earthquakes, which is why the codes limit them. Keep a first wall low, and never build anything a person could be under or beside if it fell without engineering and a permit.
Lime burns. Wet hydrated lime is strongly alkaline and causes serious eye damage and skin burns that you may not feel at first. Wear sealed goggles, waterproof gloves, long sleeves and long pants every time you open the bag, and keep a hose or a jug of clean water within reach.
If lime gets in an eye, rinse with clean water for at least 20 minutes, holding the lids open, and get medical help right away. Wash it off skin immediately and change out of any clothes it has soaked.
Do not start with quicklime. Slaking it gives off enough heat to boil water and spit. Buy lime that is already hydrated.
Dry clay, sand and stone dust contain crystalline silica, which scars the lungs for good. Wear an N95 respirator when sifting, pouring or sweeping dry material, dampen piles before you move them, and mix outdoors.
Straw dust and moldy bales irritate lungs too. Shake out and chop straw outdoors with a respirator on, and send back any bale that smells musty or shows gray or black patches.
Lift less than you think you can. A bucket of wet cob or a filled earthbag is far heavier than it looks, and a straw bale is awkward even when it is light. Half-fill buckets, fill bags in place on the wall, bend your knees, and carry bales in pairs.
Water is what destroys these walls. Raise them on a base of stone, concrete or gravel bags so splashing rain cannot reach the earth, slope the ground away, and give every wall a cap or a roof overhang wide enough to keep rain off its face.
Finish with clay or lime plaster, which let a wall dry out. Natural builders avoid cement stucco and waterproof paint over earth and straw because they hold moisture inside.
Contact 811 before any digging, including a shallow trench or a clay pit. The service is free, most states want two or three business days of notice, and it marks utility-owned lines only, not private ones such as a line to a shed.
Earth ovens: build on a stable masonry base well away from fences and buildings, dry the oven completely before the first small fire, and never leave a fire in it unattended.

Official guidance, free

Where to learn

This is a hobby learned on site. Regional natural building groups, straw bale associations and earthbag and adobe schools run workshops from spring to fall and post volunteer work parties, where a day of mixing buys a day of teaching. Between builds, the code appendices for cob and straw bale are worth reading even for a garden wall, because their foundation, moisture and plaster rules are the collected lessons of failed walls. Online adobe and earthbag courses cover design and theory, and a printed handbook gives you recipes and details to keep by the tarp.

Schools and free reading

Close view of rectangular straw bales stacked tight, seen end-on — Straw bales, stacked

Why the kit looks the way it does

The first two lines are not Amazon purchases: a workshop or work party, and the wall itself (clay soil, sand, straw and stone), which you dig or buy locally. The essential lines cover one day at the tarp: goggles, gloves and respirators, then the tarp, shovel, buckets and screen that turn soil into a mix, and a trowel to finish it. The recommended lines save your back and keep walls straight. Cob, adobe and clay plaster need nothing more. Straw bale, earthbag and lime plaster each add a few items of their own, so pick one above and its gear joins the kit. A roof, windows and doors are a different budget and belong to a permitted building, not a first project.

Fill the buckets

The first two lines are not things you buy online: a day on a real build, and the clay, sand, straw and stone you dig or collect locally. The essential and recommended tools start in the kit. Gear for Straw Bale, Earthbag and Lime Plaster joins once you pick that method, above or from the add-ons in the kit. Compare the options, then set your picks and check out from the kit. Clicking a card selects it there.

Hands-on natural building workshop

essential · Training

How wet a mix should be and how hard to work it into the wall are things you learn by feel, standing next to someone who has done it. A day on a real build also shows you the foundation and roof details before you pour money into your own.

Not sold on Amazon · find it locally

Not sold on Amazon. Look for a course taught on a real building site that has you mixing and building for most of each day. Volunteer work parties, where you trade a day of labor for instruction, are often free. Paid courses run from a weekend plaster class to a cob course of a week or more, and tuition varies widely by school, length and country. Check the school's current listing for the price and what it covers, such as meals and camping, before you book.

Clay soil, sand, straw and foundation stone

essential · Building materials

These are the wall itself. Clay soil binds, sharp sand stops it cracking, straw holds it together, and stone or broken concrete lifts it off the wet ground.

Not sold on Amazon · find it locally

Not sold on Amazon. Clay subsoil is often free from your own yard or a neighbor's excavation. Buy coarse, angular sand (sold as concrete sand) by the half yard from a landscape supplier, and straw by the bale from a feed store, checking that it is straw and not hay, and that it is dry and has no musty smell. Stone, broken concrete and gravel for the base come from the same landscape yard or a demolition pile. Prices vary a lot by region, so phone around.

Sealed safety goggles

essential · Safety gear

Lime can blind, and a flick of wet plaster or a gust of dry clay finds the gap around ordinary safety glasses. Goggles that seal to your face close that gap.

budget

Safety 91252-8002S Safety Goggle, 1-Pack, Clear

4.3(144)

$11.13

Natural Building

What a building day looks like

Codes and permits come before a real building

Six ways to build with earth and straw

Reading your soil and getting the mix right

How to get started

What trips beginners up

Safety: lime, dust, weight and water

Where to learn

Why the kit looks the way it does

Fill the buckets

Hands-on natural building workshop

Clay soil, sand, straw and foundation stone

Sealed safety goggles

Waterproof long-cuff gloves

N95 dust respirators

Heavy-duty mixing tarp

Round-point digging shovel

5-gallon buckets

Soil sifting screen

Steel plastering trowel

Wheelbarrow

4-foot level

Mortar mixing hoe

Pump sprayer

Natural building handbook

Bale moisture meter

Polypropylene baling twine

Polypropylene sandbags

4-point barbed wire

Hand tamper

Hydrated lime

Plaster hawk