A Building Code for bearing and retaining walls made from earth rammed tires.
In Earthship Volume I, we presented a method of building living modules from discarded automobile tires rammed with earth. Over the thirty years of research &?development, we have come to the determination that this method far exceeds any other known building technique with regard to thermal, structural, environmental and availability aspects.
The Earthship Volumes are aimed at making this concept physically available to owner builders. If the methods put forth in these books are followed, the result is a very “substantial living module.” However, if the concept is used but not executed competently with appropriate respect for and understanding the nature of the material, an unsafe building can be the result. This is true of any building technique. This is why we have building inspectors. These building inspectors have a code (the Uniform Building Code - UBC) to follow. This code provides criteria for an inspector to relate to in determining whether a particular building technique is being executed safely or not. The purpose of this building code for bearing and retaining walls made from earth-rammed tires is to provide that same kind of criteria for an inspector to relate to in determining whether a tire building is being executed safely or not. Any building technique can be executed in a competent manner or an incompetent manner. Tire bearing walls and peripheral details are no exception. This code is aimed at both the inspector and the builders as a clear simple presentation of tire construction standards (“Do’s and Don’ts)?that must be followed to insure a successful, safe, comfortable building. It is our hope that various states will adopt this code as they move into the era of the use of automobile tire casings for the construction of buildings here in the beginning of the 21st century.
The walls are really the only aspect of a tire building that is significantly unconventional. The roof and floors use conventional materials and are covered by the existing Uniform Building Code. Therefore a thorough presentation of the standards for bearing and retaining walls made from automobile tire casings rammed with earth will be used as a guide to those whose job it is to inspect tire buildings for structural integrity, safety and quality.
1. TIRE SIZES USED IN BEARING AND RETAINING WALLS
Automobile tires come in sizes called 13, 14, 15 and 16. These sizes relate to the radius of the tire in inches, #13 tires being the smallest tires used in a bearing or a retaining wall and #16 tires being the largest. These sizes will be specified in different parts of the structure as such.
2. TIRE WALL AS FOUNDATION
In that a tire wall is already wider than its required foundation, it becomes a monolith which is both wall and foundation (see EARTHSHIP VOL. 1 pp. 65-66).
A. The first course of tires of any tire wall must be leveled and dug into undisturbed soil free of organic surface matter such as plants, tree roots or other biodegradable substances.
B. The first course of tires must be as large in diameter or larger in diameter than any other tire in the wall. No tire may appear in a wall that is larger in diameter than the tires on the ground course of that wall.
C. Tire walls over six courses high must have a ground course of tires #15 or larger exclusively.
B. Joints between tires on any given course must be aligned with the central area of all tires on courses above and below. No joint between tires on any given course may align with any joint on the courses above or below.
C. Half tire techniques as outlined in article 4 must be used to maintain running bond coursing.
4. HALF TIRE TECHNIQUES
A. CONCRETE HALF TIRES
Concrete half tires must use a mix of 3 parts cement-4 parts sand-5 parts gravel with engineering fibers. All tires adjacent to concrete half blocks must be porcupined (see EARTHSHIP VOL III pp. 2-4) with 16d nails to lock concrete to tires. In that concrete half tires are the most substantial half tire method, they will be specified in some situations by the architect. All two story tire wall applications will use concrete half tires.
B. RAMMED EARTH HALF TIRES
Rammed earth half tires are made by cutting a tire in half and leaving tabs on the sides to screw into the adjacent tire. This half tire is then pounded like a regular tire. Rammed earth half tires can be used only in tire walls five courses high or less and never at the end of a wall.
5. BEARING WALLS
A. Bearing walls built from earth rammed automobile tire casings must follow articles 1 through 4 of this code.
B. All bearing walls built from earth rammed automobile tire casings must have a continuous bond beam of wood or concrete as described in EARTHSHIP VOL I pp. 101-103 or EARTHSHIP VOL III pp. 6-9.
C. All bearing walls eight courses or higher for their entire length built from earth rammed automobile tire casings must have a continuous bond beam that connects to a continuous bond beam on adjacent non bearing tire walls.
6. RETAINING WALLS
A. All retaining walls built from earth rammed automobile tires must follow articles 1 through 4 of this code.
B. All retaining walls built from earth rammed automobile tire casings must be stepped back or lean into the earth they are retaining.
C. Specifications and construction drawings certified by a licensed architect or engineer must appear in the stamped construction drawings for the permitted building for all retaining walls built from earth rammed automobile tire casings.
7. FREE STANDING WALLS
DEFINITION - Any wall not tied into the roof structure of a building.
A. All free standing walls built from earth rammed automobile tire casings must follow articles 1 through 4 of this code.
B. All free standing walls over 2 courses high built from earth rammed automobile tire casings must have continuous arcs built into the design of the wall. These walls cannot be straight for any distance.
C. Free standing walls built of earth rammed automobile tire casings cannot be over 5 courses high unless designed by an architect and certified specifications and construction drawings are provided for that wall.
8. PLATES AND BOND BEAMS
A. All tire walls that are an integral part of the roofed building shall have a continuous wood or concrete bond beam. This bond beam shall be anchored to the tire wall with 1/2" anchor bolts set in concrete every other tire or 1/2" rebar driven down through three courses of tires and bent over the top of the wood plate or set in the concrete bond beam.
B. Wood bond beam plates shall be no less than four inches thick and twelve inches wide. Wood bond beam plates can be made up of (2) 2 x 12 's with 6 mil plastic between the rammed earth tire wall and the wood bond beam plate. The bottom bond beam plate must be treated lumber. Joints in the lower layer of lumber shall never be closer than 2'-0" away from joints in the upper layer of lumber. Upper and lower layers of lumber shall be laminated with (6) 16d nails per running foot.
C. Concrete bond beams shall be a minimum of 8"deep x 8"wide and have two pieces of 1/2" rebar continuous.
9. OPENINGS IN WALLS
A. All openings in walls made of earth rammed automobile tires shall have concrete half blocks on either side of the opening.
B. The wood or concrete bond beam spanning the opening shall be increased in thickness by a minimum of 8". This additional thickness shall extend on either side of the opening a minimum of 2'-4" and shall set on and be anchored to a concrete bearing block equivalent in thickness to the tire coursing height.
10. TWO STORY
A. All two story earth rammed tire structures shall be designed by a licensed architect or engineer.
B. A continuous 9" deep x 2'-0" wide concrete bond beam must occur at each floor level.
C. All tires on the first level must be #15 or larger.
D. All tires on the second level must be #14 or smaller.
E. All blocking must be concrete.
F. All void packing on the first floor level walls must be concrete.
G. All earth rammed tire work must follow articles 1 through 4 of this code.
11. LENGTH OF WALLS
A. There is no limit to the length of earth rammed tire walls, since rammed earth tire walls are not made of a rigid material that is sensitive to expansion/ contraction cracks.
12. HEIGHT OF WALLS
A. The maximum height for a straight earth rammed tire wall which is an integral part of a structure with a roof or floor load is 10 feet. At this point a wood or concrete bond beam must be installed as per article 8 of this code.
B. The maximum height for a circular earth rammed tire wall which is an integral part of a structure with a roof or floor load is 12 feet. At this point a wood or concrete bond beam must be installed as per article 8 of this code.
C. The maximum height for a free standing earth rammed tire wall that is not a curved or a battered retaining wall or otherwise structurally integrated into a building is 6 feet.
D. There is no maximum height for a battered retaining wall constructed from earth rammed tires. All battered retaining walls must be engineered by a licensed architect or engineer.
13. LOADING OF WALLS
A. Loading on earth rammed tire walls must be distributed loading only from joists, beams or rafters setting on a continuous wood or concrete bond beam as per article 8 of this code.
B. No point or collected loading is possible on earth rammed tire walls unless special engineering is provided by a licensed engineer or architect.
C. The limits of the evenly distributed load an earth rammed tire wall can accept are determined by the bearing capacity of the soil that the earth rammed tire wall is setting on. In cases where an earth rammed tire wall is setting on rock or a concrete foundation which is wider than the tire wall itself and more than typical roof or second story loading is desired, the bearing capacity of the tire wall will be determined by a licensed architect or engineer.
14. FILL OF WALLS
A. Earth rammed tires walls can be filled or rammed with any type of earth, clay, sand or rock fill.
B. All tire casings must be packed tight to 90% compaction with a 6# to 9# sledge hammer. Soft spongy tire packing is not acceptable.
15. VOID FILLING
A. All voids between tires in earth rammed tire walls must be packed solid with mud in a four coat procedure described in Earthship Volume I pages 174-175 unless specific conditions require this packing to be done with concrete as per article 10 of this code.
16. EARTH CLIFFS
A. All Earth cliffs shall be 12" minimum from an earth rammed tire wall.
B. All earth cliffs shall be approved as a result of site and soil inspection by a licensed architect or engineer.
A. All joints and connections in earth rammed tire walls must must be designed and assembled in such a way so that no voids occur within the earth rammed tire wall. These voids must be filled with concrete or 90% compacted earth contained in a double layer of metal lath or a rubber tire casing.
B. All joints and connections in earth rammed tire walls must employ over lapped tires and joining methods so as not to result in stacked joints occurring over each other.
The regulations for earth rammed tire construction put forth in this code are a guideline relating to structure only and are subject to evolution, refinement, and addendum.
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