Glossary of
Straw Bale Construction Terms

A

B

Bale

The brick-like product results from the harvest and compression of straw by a baler. Typical strawbale construction bales are 2 or 3-string. The strings can be metal or nylon baling twine, which comes in various colors to indicate strength. Bales are stacked lego-like (only without the snap in feature!) to form the insulative wall-systems in strawbale structures.

Bale Orientation

Straw bale orientation refers to the specific arrangement or direction in which straw bales are positioned within a wall structure, typically aligned “flat,” “on-edge,” or “on-end.”

Baler

A mechanical device that shapes cut straw into large “bricks.” These bricks are the ‘bales’ used in the insulative wall systems for straw bale homes.

Barge Rafter

The end rafter in a gable roof that supports the edge of the roof sheathing.

Beam

A horizontal structural element that supports loads from above.

Bird Block

A block installed between rafters to allow ventilation and prevent birds from entering.

Birds Mouth

A notch cut into a rafter to fit securely on the top plate of a wall.

Box Beam

A beam constructed from two vertical webs and horizontal flanges creating a hollow, rectangular section.

C

Casing

A trim piece used to provide a transition between different surfaces or materials, such as plaster to wood. It is often installed around openings or the ends/edge of a wall.  Also referred to as J-Channel and Stucco Stop

Code

Building Codes, or often referred to in the shortened name of ‘Code’ is the standard to which a structure is built and evaluated as safe for occupancy. The International Residential Building Code (IRC) includes an appendix specific to strawbale construction. See 2021 Appendix AS here.

Collar Tie

A horizontal member connecting two opposing rafters to prevent them from spreading.

Conventional Construction

Typical framed (‘stick-built’) construction.

Cripple Stud

A short stud placed above or below a door or window opening.

D

Diamond Lath

Metal used as a backing to support plaster over wood and straw bales. It helps ensure the plaster adheres properly and provides structural reinforcement. Often used to shape curves near windows, doors, or niches or to assist plaster adherence. Often used to shape curves near windows, doors, or niches or to assist plaster adherence. Also known as ‘expanded metal,’ ‘plaster,’ or ‘blood’ lath, the unfinished edges of the metal sheets produce razor-sharp edges. 

Door Rough Opening

The framed opening in a wall where a door will be installed.

E

Expanded Metal Lath

Metal used as a backing to support plaster over wood and straw bales. It helps ensure the plaster adheres properly and provides structural reinforcement. Often used to shape curves near windows, doors, or niches or to assist plaster adherence. Often used to shape curves near windows, doors, or niches or to assist plaster adherence. Also known as ‘diamond,’ ‘plaster,’ or ‘blood’ lath, the unfinished edges of the metal sheets produce razor-sharp edges. 

F

Fascia

A horizontal board attached to the ends of rafters or trusses at the eaves.

Finished Grade

The final grade comes up to about 8″ below the bottom of the plaster and slopes away from the building.

Fire Resistance

Straw bale structures are actually very fire resistant. The American Society for Testing and Materials (ASTM) testing has shown that straw bale structures have a 2 hour fire rating, far more than the standard 20 minute burn rating of traditional drywall construction. 

See the report entitled ASTM E 119-05a Fire Tests of Building Construction and Materials: 2-HR Fire Resistance Test of a Non-Loadbearing Wheat Straw Bale Wall (Project No. 3098054A).

Flakes

Pieces of the bale are created by the plunger on the baling machine as the straw is picked up in the field. When you cut open a bale, it falls into several smaller, compact pieces. Each of these sections is a flake, and they are ideal for stuffing in between bales as you build or for stuffing small areas where a tied bale is not required.

Fly Rafter

The end rafter in a gable roof that supports the edge of the roof sheathing.

Framing Terms

Watch this short video to view a walk-thru of Straw Bale Construction Framing Terms on a small cabin. 

Foundation

Lowest load-bearing part of the straw bale building. Often a monolithic slab on grade. ‘Slab’ refers to the concrete surface itself.

Framing

The process of constructing the structural framework of a building, typically involving the assembly of wood or metal studs, joists, and beams to form the skeleton of the structure.

G

Grade

The level of the ground around a building.

H

Hay

Grass contains nutrients that are cut and dried for typical use of livestock feed. Hay is not used for straw bale construction. As the saying goes, “Hay is for horses, not for straw bale houses.”-unknown

Header

A horizontal beam over a door or window opening that distributes weight.

Hurricane Clip

Metal connectors that secure the roof structure to the walls, providing resistance to uplift forces.

I

J

J-Channel

A trim piece used to provide a transition between different surfaces or materials, such as plaster to wood. It is often installed around openings or the ends/edge of a wall.  Also referred to as Casing and Stucco Stop.

Joist

A horizontal structural member used to support floors or ceilings, typically running between beams or walls.

K

King Stud

The full-length vertical framing member on either side of a door or window opening that supports the header.

L

Lath

Metal used as a backing to support plaster over wood and straw bales. It helps ensure the plaster adheres properly and provides structural reinforcement. Often used to shape curves near windows, doors, or niches or to assist plaster adherence.

Lookout

Horizontal members that support roof overhangs.

M

Mesh

Welded wire or netting used to reinforce the exterior and interior plaster layers, improving their strength and durability while helping the plaster adhere to the straw bales.

N

Niche

A decorative and/or functional recess into a straw bale wall. Often one of the most noted aesthetics of finished strawbale walls.

O

On Edge

A straw bale-oriented “on-edge” means arranging straw bales vertically with the narrow edge facing upwards and downwards.

Oriented Strand Board (OSB)

Oriented strand board (OSB) is a type of engineered wood made from layers of compressed wood strands arranged in specific orientations and bonded with adhesives. It’s commonly used for sheathing, flooring, and roofing due to its strength and affordability.

Outrigger

Horizontal members that support roof overhangs.

P

Post

A vertical support member that carries weight from above to a foundation or other support structure below.

Q

R

Rafter

Sloped beams that support the roof.

Rafter Tail

The portion of a rafter that extends beyond the wall to form the eaves.

Ridge

The horizontal line at the top of a roof where two sloping sides meet.

Ridge Beam

A structural beam that supports the upper ends of rafters at the ridge.

Ridge Board

A non-structural board at the ridge of a roof where rafters are attached.

Roof Sheathing

The boards or panels that form the surface to which roofing materials are applied.

S

Scarifier

Plastic scratch tool for roughing up a plaster layer to improve keying, or connection, between the layers.

Sill

The bottom part of a window frame or a horizontal member at the bottom of a wall opening.

Slab

A large, flat, concrete surface used as a foundation.

Straw

The stalks of grain crops, such as rice, wheat, oats, barley and so on, that are a by-product of agricultural grain production. It is the stalks only that are baled and used for installation in straw bale home construction. 

Structural Insulated Panels (SIP)

An assembly of a rigid skin (typically OSB) to provide strong resistance and strength while the inner core of insulation (typically foam). Imagine an ice cream sandwich…

Stucco Stop

A trim piece used to provide a transition between different surfaces or materials, such as plaster to wood. It is often installed around openings or the ends/edge of a wall.  Also referred to as Casing and J-Channel

Stud

A vertical framing member in a wall that provides support for the wall’s structure and to which other elements like drywall or sheathing are attached.

T

Toe-up

Exterior toe-ups are what are referred to in conventional construction as the ‘sill’ or ‘sole plate’. Toe-ups get the posts up off of the ground. They are made from pressure-treated lumber due to being in contact with the slab. Exterior toe-ups are used together with interior toe-ups to provide an elevated surface to set wall system straw bales on top of in construction. They also provide a means to attach the bottom portion of the wire mesh, if used.

Top Plate

The uppermost horizontal framing member on top of the wall studs.

Trimmer Stud

A vertical framing member that supports the header above a door or window opening.

Truth Window

A common feature in straw bale houses, where in the finished wall a view port is created to reveal the ‘truth’ behind the wall finish and see the insulative straw material. The portal is often framed creatively, covered with glass, and sometimes operable.

U

Underlayment

A protective layer installed between the roof sheathing and the roofing material.

V

W

Window Seat

Often a favorite feature of a strawbale home, where the thick walls (due to the size of the bales whether on edge or flat) creates plane beneath window openings. This wide plane is often reinforced or finished to provide a seating area to soak up the views or sunlight! 

Welded Wire Mesh

Often used in straw bale wall systems as a layer exterior to the straw bale but interior of the plaster skin. If used for shear in a structural capacity, it is likely 2″ by 2″ 14 gauge galvanized wire mesh.

X

Y

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Glossary of Straw Bale Construction Terms

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