Adobe Madre Building SystemConstruction Overview

Adobe Building Systems, LLC

Presentation by Lisa Schroder

August 2010

What is Adobe?

ADOBE – An air dried brick

made from a puddle earth

cast mix in a mould and

which contains a mixture of

clay, sand, and sometimes

silt. Sometimes contains

straw or a stabilizer.

Also known as mud-brick.

History of Adobe BuildingStructural remnants of earthen walls provide evidence that humans have been building with earthen materials for more than 10,000 years. Still today, earthen homes provide shelter for more than 50 percent of the world's population. Due to their longevity and ease of use, adobe bricks rank as the world’s most popular earth building material.

The ancient city of Arg-e-Bam in Iran is made entirely of mud bricks, clay, straw and the trunks of palm trees.

Overview of PresentationThe lay-up of adobe bricks is the easiest, most forgiving way to achieve a solid masonry wall system. Motivated by this fact, this presentation focuses on the construction of adobe walls which includes our patented reinforcement and scaffolding systems. We will discuss how to make and lay adobe bricks, how to install lintels and arches, conduits and pipes, doors and windows, top plates and bond-beams.

Our Adobe Product

Our methods of building will produce a premium product that will:

• Meet and often exceed inspection standards.

• Have structural integrity and aesthetic appeal.

• Are sustainable due to the efficient use of natural resources

• And have minimal effort for long-term maintenance.

Ideal Building Material

1. Ease of extraction from the earth 2. Minimal manufacturing costs3. Ease of construction4. Long duration of high-performance

use. 5. Biodegradable6. Non-toxic7. Affordable.

Adobe bricks come closer than any other building material in meeting these standards.

As well as…Energy Efficient

Adobe homes have good

thermal dynamics and

thermal mass. This is a

measure of how much

energy or heat the material

can retain. When the brick

heats up, it can hold a large

amount of heat and then

release it slowly.

Thermal Insulation

• For earth walls the thermal resisitance, R, may be taken as 2.04 times the wall thickness in meters plus 0.12. The units are in m2 deg C/W.

• The thermal performance of earth walls is greatly improved by the effect of thermal mass due to an effect known as “thermal lag”. The thermal lag for earth walls is of the order of 7-10 hours for a 280mm thick wall. The wall thickness is generally required to satisfy without additional insulation.

Strength Requirements• The building department in

New Zealand allow adobe bricks to be as low as 190 PSI (1.3 MPa). However, such a brick would be so weak that it would be difficult to handle without breakage and would certainly not last as long as a brick with a higher PSI (or MPa). The use of about 5-7% cement increases the strength by three-fold, creating a brick with a 580 PSI (4 MPa).

Design StrengthsCompressive Strength (flexural, direct compression or bearing)

fe = 0.5

Maximum total nominal shear stress fn = 0.09

Shear strength of earth for wind loading and for seismic load with elastic response

fes = 0.08

Shear strength of earth for limited ductile (µ = 2.0) seismic loading

fes = 0.0

Shear strength of steel reinforced earth fes = 0.35

Tensile/flexural bond strength feb = 0.02

Flexural tensile strength (modulus of rupture) fet = 0.1

Strengths (MPa) to be used for design or standard grade earth wall construction.This guide can be found in New Zealand Earth Building Standards

www.standards.co.nz

Adobe Brick Testing

• At various points in the brick-making process, bricks must be strength-tested with a compression test or “crush test”. This is to ensure that the engineered mix design has been met and that the bricks are generally uniform in strength. Other tests include an erosion test, absorption test, and modulus of rupture test.

Tests for adobe constructionCompression or flexural tensile strength

fe > 1.3 MPa or > 1.9 MPa for special grade (compression)

fet > 0.25 MPa or > 2.1 for special grade (flexural tensile)

Wet/dry appraisal Pass

Durability Required to provide for a building life of not less than 50 years.

Shrinkage of cement stabilized mortar

≤ 1.0%

Whole Brick drop Test Pass

Materials for Adobe

• For workability and durability the most desirable adobe mixture consists of about 70% sand, 23.5% clay, 6.5% cement and just enough water to achieve the proper consistency. The sand and aggregate provide strength, whereas the clay acts as a binder and plastic medium to “glue” the other ingredients together. The cement fills smaller voids, which “chink,” or lock the matrix together.

Typical Particle Distribution

Alternative Stabilizers

• Lime • Bitumen

Other natural alternatives include: • Pozzolanas (a natural or artificial material

containing silica and/or alumina)• Volcanic ashes• Pulverized-fuel ash• Rice husk ash• or even some types of manure.

Simple Jar Test

• Use a jar with a flat bottom and a capacity of at least one-quart (one liter). Fill the jar half-full of soil and then fill with water. Shake the jar vigorously for 30 seconds and allow the cloudy water to sit completely still for at least 12 hours. Shake vigorously again, this time for one minute and allow mixture to rest again in an undisturbed, still place for at least 24 hours.

Water

Clay

Silt

Sand

Unsuitable Soils for Adobe

• Organic matter of a type prone to rot or breakdown within the wall;

• Those that contain soluble salts to an extent which will impair the strength or durability of a wall;

• Those containing aggregate large enough to impair the strength or homogeneous structural performance of the wall. Such soils may be suitable if screened.

• Some soils dry to form an earth building material with a surface containing fine cracks. The cracks are generally short with a random orientation. The surface layer will continue to flake off, particularly if there are changes in moisture content.

• Soils which fail the wet/dry appraisal test.

Adobe Brick Production

• Mix the adobe mud in a regular concrete mixer

• Wheelbarrow it to the molds• Tip the adobe mixture into the

molds• Pack and level off flat with a

concrete rake• Lift the molds off right away and

“leap-frog” the molds forward• Continue

A team of 3 workers can produce 600 bricks a day. An average size home would use around 5,000 bricks.

Our Unique Brick Types

Half U-Brick Double U-Brick Channel Brick Standard Brick

Scaffold-Service O-Brick U-Scaffold Brick U-Brick

Bricks in Construction

The Vertical Column• Individual adobe bricks are laid into the wall based on the design requirements of the structure.

In other words, the brick pattern is determined by the following that are already in place:• Vertical Reinforcing• Electrical Conduits• Plumbing Pipes• Spare Sleeves• Standard-Bricks are most often used though you could use an “O-Brick” or “U-Brick” and fill the

void with adobe mortar as you lay the brick into the wall.

Footings for AdobeThe footings are part of the foundation system which serves as a rigid collar on which the structure sits. It must be rigid and unified so that the structure above will not settle, nor allow the walls to spread or separate.

Ground Level

Floor Level

4” Concrete SlabUnderslab (DPC)1” Sand Blinding1” Polystyrene4” Compacted HardfillCut ground level cleared of top soil down to firm undisturbed ground

½” starer rods at 2’6” centers fold into slab

Footing for Round Structure

Footing on Sloping Ground

Even Courses to Sills

Timber Floor System

Concrete Bond-Beam

Concrete Bricks 9”Adobe ground level

2’ deep footing for Two storey building

Concrete brickShown hatched

Starter rods at 36”c. extendInto 1st 2 coursesOf adobe wallWherever mainWall rods not Present

Adobe Wall Construction

The primary aim of the bricklayer is to create a wall that is level. By laying uniform bed joins and by keeping the top of the bricks parallel to the string-line, the wall will be level.

Adobe Brick Buttresses

All house walls over a

certain length must have

intersecting walls or

buttresses to add

structural integrity.

Buttresses, also called piers,

are actually short walls that

intersect the main house

walls.

Adobe Wall Reinforcement

Typical cross-section showing anchor rods folded over timber top plate

1-3/8” sand/cement join

Durable timber plate spans fromintersecting wall to intersecting wall. Fixed with wall reinforcing rods folded 10” over plate with five 2” galvanized staples.

Rod for timber lintel hooks under lintel in predrilled holes. Use 2” staples to temporarily affix rod to lintel.

Anchor Rods

Typical Cross-Section showing anchor rods grouted into 3 courses of adobe bricks and folded over top plate every 30”.

Durable timber plate for fixing roof. Use suitable damp-proofing under. Fix with 1/2“ galvanized bolts poured into concrete beam.

11-1/4" wide concrete beam to required depth with required steel

Wherever main wall rods not present ½” rods @ 30" c. grouted into 3 courses of adobe brick wall. Fold 10" over top plate with 5-2" galvanized staples.

Horizontal Reinforcement

• If your engineer has required horizontal mesh, it is normally placed at every fifth course (i.e. over the 5th, 10th, 15th, etc) before the mortar is placed for the next course.

668 galvanized mesh strips or Geogrid (fabric) every 5 courses (where required by engineer) biased towards inside of wall (allow 2-3/4” cover from outside of building)

Kabul, Afghanistan USAID project

What about Cracks?• Cracks can occur on any masonry

surface, including adobe walls. Yet, if care is taken, a home can be built that has no cracks. In addition, if adobe walls do crack, they are usually minor and do not require any structural repair.

The major causes of cracks are:• An inadequate foundation system.

Your engineer should establish that your building site’s ground is firm enough.

• Laying bricks before they are sufficiently cured.

• Inadequate mortar joins.• Inadequately cured the mortar

(probably due to failure to keep the walls damp).

• Failure to strategically place control joints.

Control Joints

Control joints are

planned vertical wall

separations. They

basically divide a wall

into separate panels,

similar to what happens

naturally after shrinkage

cracks occur.

2-1/3" (60mm) DIA CORE FOR SCAFFOLD PIPE

4¾" (120mm)

11¼" (280mm)

11¼" (280mm)

"SCAFFOLD-STANDARD" "U-SCAFFOLD"

11¼" (280mm)

11¼" (280mm)

4¾" (120mm)

2-1/3" (60mm) DIA CORE FOR SCAFFOLD PIPE

CORE 4½" (115mm) DIA.

Scaffold SystemTo ensure the safety of the scaffolding, adhere to the following requirements:• A 1⅞” (48mm) scaffolding pipe

must be placed directly in the corners and then every 4’ (1200mm) on centers.

• A minimum of 6 adobe brick courses must be laid over the scaffold pipe locations.

Lintels for Adobe Building• Lintels are the beams over windows

and doors. They can be made from timber, concrete, or when reinforced, even the adobe bricks themselves. The purpose of the lintel is to support the load above, be it bricks, roof, or a second story. In addition to the adobe bricks, the lintels have an important aesthetic impact on the structure.

Construction of Timber Lintels

Two 4-3/4” x 4-3/4” timber lintels. Use 2 coats damp-proofer at all contacts with masonry.

Drip groove

Rod for timber lintel hooks under lintel in predrilled holes. Use 2” staples to temporarily affix rod to lintel. Sand/cement mortar join over lintel.

Concrete Lintels

8” wide x 5-1/4” tall concrete bond-beam with reinforcing at floor level. Veneer bricks cover bond-beam.

Rod ties concrete lintel to concrete beam. Use at 4’ centers max starting at center of lintel.

Timber joinery shown – can be aluminum or PVC.

Adobe Brick ArchesIncorporating adobe arches into your design is a great way to achieve structural integrity in your openings, as well as creating a beautiful and inviting entry.

This enchanting design element has been built over the centuries and remains one of the strongest geometrical shapes used in construction.

Construction of Adobe Arches

Cross-section for a reinforced adobe arch

Adobe Channel Bricks

Rebate all lintels and arches by 5/8” to provide weather seal

Rod ties arch to top plate or concrete beam. Use at 36”c. max. starting at center of arch.

Adobe Arch Considerations

• The joinery tends to cost more than for square openings.

• Formwork must be built for each different size of window.

• Formwork should be left in place until two or more courses are laid up above the arch to ensure even compression. • Properly built arches will not collapse, while anything else can be disastrous.

Joinery for Adobe • The joinery can be made from

wood, aluminum, or PVC. It is important to note that the type of joinery one selects will affect the overall cost of the building. Custom-made joinery is the best option because it can be made to suit the brick increments. If custom-made joinery is not available, prefabricated joinery is also acceptable. The widths of the openings or the height of the lintels can be adjusted by chopping bricks to fit the required size of the joinery.

Installation of Joinery

The joinery may be fixed with one of the following:

• 5¼” (135mm) expanding shaft nylon anchors

• 6” (150mm) galvanized bullet-head (jolt-head) nails.

• 4” (100mm) screw fixed into gringo blocks.

Sills always even Courses from FL

Fix the joinery firmly into every 4th course of adobe bricks. Vertical Rough

Opening = Odd number of courses + ¾” (20mm) mortar join

Window and Door Sills

• Sills are a very crucial part of the wall system because the glass sheds rainwater quickly and it accumulates on the wall below the sills more so than any other part of the building.

Sturdy sill tile protrudes past wall

Concrete sill beams required for all 2 story windows or single story windows when earthquake risk is high

Bond-Beam for Adobe Structures

Bond beams do the following:• Lock the top of the wall

together in event of an earthquake or severe winds.

• Assist in supporting lateral loads between adjacent transverse structural walls.

• Provide anchorage of floor and roof members.

• Tie the adobe walls together.

Types of Bond-Beams

There are two types of bond-beams for the top of the wall:

• Timber plates • Reinforced concrete.

Timber Top Plate

Sand and cement mortar is packed between the last course of bricks and the top plate once the plates are level.

Rebar is shown folded over and stapled in place.

Concrete Bond-Beam

11-1/4” wide concrete beam to required depth with required steel.

Timber boxing in place for concrete bond beam at mid-story level.

Multi-Storey Adobe Structures

• Concrete bond-beams can be slurry washed or plastered to suit the color of the main wall.

Cross-section showing a timber floor system at mid-floor level

Boundary joists bolted to bond-beam at 2’c.and affixed with ½” x ½” washer and nut.

8” wide x 5-1/2” tall concrete bond-beam with 2 rods at mid-floor level. Veneer bricks cover bond-beam.

½” galvanized bolts poured into bond beam.

Adobe Plaster and Design Elements

Application of Adobe Plaster

• Wait at least 4 weeks after the last bricks are laid before starting your base coat to allow any wall shrinkage to occur.

• Always start at the bottom of your reach and work upwards.

• Always apply coatings in fair weather followed by several days of fair weather with temperatures remaining above 40°F (4.5°C).

Summary of Adobe Construction

• The humble adobe brick has been in constant use for over 10,000 years. It is the only building material that is not a fad. Suitable to any architectural style, it can be engineered to suit even a wet climate and earthquake prone region.

• Using local materials for construction is an environmentally-friendly way to build.

• A green solution for today’s construction.