straw bale building training for european professionals: load bearing

UNIT 3Load bearing

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UNIT 3 LOAD BEARING Training Page

U3 Learning Outcomes 5

U3 Session 1: Design and Planning 5 hours 6

U3 Info Sheet: Drawing Basics 8

U3 Info Sheet: Drawing for Exercises 10

U3 Session 2: Construction 18 hours 13

U3 Info Sheet: Preparing Bales (Overview) 14

U3 Info Sheet: Notching Bales (Overview) 15

U3 Session 3: Tools 2 hours 16

U3 Info Sheet: Tools on Building Site (Overview) 17

Partner STEP (Straw Bale Training for European Professionals) 19

Credits & Imprint 20

IND

EX

S1 – Design & Planning Session Plan

S1

U3 - Load-bearing

Objectives:- Have the ability to read and understand architectural

plans and construction drawings- Know different structural options- Know the dis-/advantages of every solution

Kind of skills:- Make a building schedule- To organize and do the work within the schedule- To make a cutting list- Calculate the building costs

Method:- Lecture/Talk- Explanations- Practice

Trainer:

Location:

Classroom

Duration:

21 hours

Equipment:

Over-head projectorFlip chart

Th

eo

ry - Basics of architectural plans and construction drawings

- Different structural options, characteristics and bale requirements

- Advantages and disadvantages of different techniques

- How to prepare a building schedule- How to make a cutting list- Calculate the building costs (material, labour,

etc)

Documents :

Info sheets: I1 Drawing basicsI2 Drawings for E1 & E2

Text sheets:X1 Straw bale and legislationX2 Advantages and disadvantagesof load-bearingX3 Characteristics of different optionsX4 Organisation of building site and scheduleX5 Design basics

Exercise sheets:E1 Make a building scheduleE2 Cutting listE3 Calculating material and costsE4 Drawing construction details

Evaluation:

Multiple choice

Pra

cti

cal

- Study and develop a case-study comparing the results with other trainees.

Organisation :

Prepare a case study for every group of trainees (2-3 persons), study it in order to be able tocompare it with the results of the participants.

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S1 – Design and planning Info sheet

I1

U3 - Load-bearing

Info sheet 1 – Drawing basics (understanding architectural plans)

Architectural drawings are a way of representing three dimensional shapes in twodimensions. When drawn accurately and to scale they can be used for a variety of purposes;from calculating quantities of materials needed to helping workers to construct the building tothe right size and shape with doors and windows in the correct positions.

Plan view:The plan view is the most basic drawing and is a “top-down” view of all or part of the building.Various information is shown in plans. A floor plan is typically used to show layouts of rooms,stairs, doors and windows and can be visualized as what you’d see if you looked down aftercutting through the building at about eye level (1500mm above finished floor level), witheverything above the cut removed. Typically a separate floor plan is included for each floor inthe building. Other plans may show specific parts of the building, e.g. sole plate plan, baleplans, wall plate plan.

Elevations:


U3 I1 – Drawing basics

Elevations are views of the front, back and sides of the building. Elevations are used to convey an impression of how the building will look from outside but are also used to show positions and dimensions of doors and windows, roof pitch and sometimes detail such as external finishes etc.

Sections: Sections are used to show additional information. A section is, a bit like a plan view, a slice through the building. Sections are generally a vertical slice through the building and are typically used to show detail on the roof construction, room heights, foundations etc. A “cross-section” is a section through the shorter axis of a building, whereas a “long section” is a section along the longer axis. Sometimes several sections will be needed, especially where different parts of the building are different heights, have different roof construction/pitch etc. Large scale sections are often used to provide construction detail on specific parts of the building.

Conventions and good practice: It is good practice to include scale bars on scaled drawings so that any distortions in scale (when printing, photocopying, converting between digital file types, etc) can be easily identified. The scale bars should be checked before measuring off drawings. Where sections are included they are normally marked on the plans and elevations with a line and arrows. The line shows where the building is “sliced”, the arrows point in the direction of view. Each section is typically allocated a letter, and this letter appears by the arrows at each end of the section line.

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S1 – Design & Planning Info sheet

I2

U3 - Load-bearing

Info sheet 2 - Drawings for exercises 1-3

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U3 I2 – Drawings for exercises

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S2 – Construction Session Plan

S2

U3 – Load Bearing

Objectives:- Know different structural options for load-bearing

construction and their characteristics and bale requirements

- Know how to fix the bales, to stabilize the system and allthe different techniques

- Know different options for compressing the bales - Know details for how to connect with other building

elements; foundations, corners, windows, doors, roof, etc.

- Know how to prepare different surfaces for plastering

Kind of skills:- To build with load-bearing straw bales- To use different compression and fixing techniques- To organize and do the work within the schedule- To execute good connection details- To maintain integrity of the insulation- To prepare different surfaces for plastering

Method:- Practice load-bearing construction

Trainer:

Location:

Workshop or building-site and classroom

Duration:

35 hours

Equipment:

Over-head projector BalesStructure of model to work onTools

Th

eo

ry

- Different structural options for load-bearing, their characteristics and bale requirements.

- Fixing the bales, and different techniques.- Compressing bales using different methods.- Advantages and disadvantages of load-bearing

construction.- Details of connections: foundation, corners,

windows and doors, roof, etc.- Preparing different surfaces for plastering.

Documents:

Info sheets: I1 Preparing balesI2 Splitting balesI3 Notching balesI4 Compressing balesI5 Levelling & stuffing bales

Text sheets:X1 Load-bearing (Best building practice)

Exercises:E1 Bad practice

Evaluation:

Multiple choice

Pra

cti

ce

- Study and develop a case-study comparing the results with other trainees.

Organisation:

Prepare load-bearing build, prepare structure to demonstrate different construction details.Order bales, prepare tools for measuring, cutting, adjusting bales, fixing, compressing.Order all the material needed for preparing for plastering.

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S2 – Construction Info sheet

I1

U3 - Load-bearing

Info sheet 1 - Preparing & dressing bales

It is good practice to inspect and dress bales before use; checking the bale has been keptdry and is free from seed heads etc. Bales tend to bulge up in the middle of the end faceand drop away towards the corners.

“Dressing” the bale involvesflattening off the ends to allow balesto meet more snugly. Straw can beslid under the strings, moving strawfrom the high points in the centre tothe lower parts at the sides andcorners.

Left; bale to be dressed and jointbetween undressed bales.

Right; “dressed” bale and jointbetween dressed bales.

Dressing bales gives a much better junction between bales, improving thermalperformance and minimizing work later (reduces need to stuff gaps etc). Dressing balescan be most easily done by a pair of people working together as shown below.

The bale can be held in place by the twopeople pushing against it from opposite sideswith one lower leg each.

Both hands should be made like gardenclaws; palms held flat, fingers splayed slightlyapart and angled down and back towardsthem.

Both ends of the bale should be dressed before the bales are laid or worked further (e.g.split, notched etc).

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I2

U3 - Load-bearing

Info sheet 2 - Splitting bales using a baling needle

Making bales of a particular size is a key element of working with bales. Bale plans shouldgenerally aim to work to whole bale sizes where possible but there are frequently times whenpart bales are required. Also it is important to stagger joints between courses of bales so halfbales are required every other course where a straw wall meets an opening.

The baling needle is a simple tool forinserting new strings into a bale. It is along, thin rod with two holes drilledthrough the tip and a handle at the otherend.

The point where the bale is to be split should be measured and marked, for example bypushing a pencil, screw-driver or similar into the bale (see point marked “m” below). In thediagrams the original baling twine has been shown in red. For clarity the strings for one ofthe new part bales are shown in blue, the other in orange.

Two new strings should be measured foreach part bale to be made. Here we’llassume that the bale will be split into twonew part bales so four strings will beneeded.

The strings should be measured so theyare long enough to go around all foursides of the new part bale and haveenough additional string left to do theknots needed to tie them off.

For the bale on the left the two new strings would each need to be (a + b) x 2 plus an extra450mm / 18”. For the bale on the right the new strings would need to be (a + c) x 2 plus anextra 450mm / 18”.

One string for each part bale is insertedthrough the holes of the baling needle. It isvery important that the strings do notcross inside the bale as if this happens thetwo bales will be fastened together.

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I3

U3 - Load-bearing

Info sheet 3 - Notching bales

Where a straw bale wall meets a post (for example at window and door openings, at junctions with other materials etc) bales will need to be notched. This improvesair-tightness and minimizes draughts and also helps make the wall rigid.

There are two sizes of notch that may be required. Wheretwo bales will meet at the post, one on each side, eachbale should be “half-notched”. In other words, the depth ofthe notch in each bale should be equivalent to half thediameter of the post (for a 100mm / 4” post this wouldmean a 50mm deep notch). This typically occurs beneatha window.

Beside windows and doors, the post will be entirelyrecessed into the straw with a “full notch” – 100mm deepnotch for a 100mm / 4” post.

The process is very simple. For a 50mm notch a piece of 100x50mm / 4x2” timber is laidacross the centre of the bale where the notch is to go. An old saw is used to cut the strawusing the timber as a guide. After the first few strokes to mark the cut, the timber should beremoved and the saw angled slightly outwards as it will naturally tend angle inwards,resulting in a “V”-shaped cut if unchecked. Once one side of the cut is done, the wood shouldbe replaced before removing the saw blade so the timber can again be used as a guide for acut the other side. The depth and size of the cut should be checked using the guide timber.When the notch is the right depth and shape, the timber should sit snugly inside it with thetop of the timber flush with the surface of the bale.

For a full notch, the process is identical butusing a 100x100m / 4x4” guide timber. Careshould be taken to avoid the strings eitherbeing accidentally cut or slipping into thenotch.

Notching can be carried out much quickerand more accurately using machines suchas alligator or shark saws.

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I4

U3 - Load-bearing

Info sheet 4 - Compressing bales

Why compression is important

Whilst it is possible to simply stack straw bales to make a structure, an uncompressed strawbale wall will remain wobbly and vulnerable. Loads being added (e.g. heavy furniture beingput into an upstairs room) could compress the straw over time. This can lead to a variety ofproblems such as;

- cracks in plaster and render- deformation and/or damage to door and window openings making them difficult or

impossible to open- differential settlement between settling straw and uncompressible elements such as

timber stud walls etc.

By compressing the straw it becomes much more rigid, robust and predictable. Compressionshould generally be done before plastering / rendering, fitting doors and windows, internalwalls etc. The exception to this is the base (slip) coat which can be applied beforecompression if necessary. Applying compression also allows more accurate leveling of thewall to provide a flatter surface for plastering and rendering.

Requirements for compression

Straw is capable of carrying large loads but the surface of a bale has a low resistance toconcentrated loads. Something is needed to spread compression forces over a section ofwall.

This can be done by using a permanent part of the building (for example by squeezing thestraw between two permanent and rigid elements such as a sole plate beneath and a wallplate above.

Alternatively something temporary can be used and then removed when compression hasbeen achieved and held (for example a flat steel plate the same width as the wall).

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I5

U3 – Load-bearing

Info sheet 5 – Leveling, strimming & stuffing

Levelling:

Levelling walls makes the surface flatter ready for plastering. It is most easily carried outworking in pairs with one person on either side of the wall. One person uses a persuader toknock back any areas that protrude too far. The person on the other side should braceadjacent bales by leaning against them. Communication is important!

The wall should be regularlychecked for plumb using a longspirit level, or better still, a spiritlevel taped to a longer straighttimber. The sides of the sole andwall plates are also useful startingpoints for checking against.

Levelling can take place before compression but it’s often easier to level more accuratelyafter compression as the bales are less mobile and tend to hold their position better.

Stuffing:

It is good practice to fill any voids and cavities before plastering. If deep holes are filledwith plaster it will form a “cold bridge” as the plaster conducts heat better than theinsulating straw and will impair how the insulation functions. Deep pockets of plaster willalso dry out much slower than areas of wall with thinner plaster, making cracking morelikely. Very deep holes should be filled with a twist of long straw.

A handful of long straw should betaken, folded double and thentwisted into a plug which can thenbe inserted into the cavity.

The twist should be pushed intothe wall so that the “head” isrecessed below the surface toavoid it being pulled out whenstrimming.

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S3 – Tools and the Building Site Session Plan

S3

U3 – Load Bearing

Objectives:- To know the tools and machines used on the straw bale

building site- To know specific problems of straw bale building site

organization- To know how to solve any technical problem conveniently

Kind of skills:- To handle tools and machines which are used in straw bale

construction

Method:- Demonstration, explanation, practice

Trainer:

Location:

Workshop or building-site

Duration :

4 hours

Equipment:

Tools

Th

eo

ry

- Specific problems of straw bale building site organization

Documents :

Info sheets: I1 Tools

Text sheets:X1 Building site

Evaluation :

Multiple choicePra

cti

ce

- Trying the tools, visiting building site

Organisation:

Looking for an appropriate building-site in the surroundings or preparing different tools and material forthe demonstration

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S3 – Tools and the Building Site Info sheet

I1

U3 - Load-bearing

Info sheet 1 - Specialist tools

Tape measure: Used for measuring bales

Pencil / screw-driver or similar: Useful formarking the point where a bale will be split.

Handsaw: Used for notching bales in the absence ofpower tools.

Hatchet: Used for initial pointing of hazel stubs andpins.

Retractable (Stanley) knife: Used for cutting balingtwine and sharpening hazel stubs and pins.

Baling needles: Baling needles are used forinserting new strings through straw bales, usuallywhen splitting or resizing bales.

Gap filler: Gap fillers or “stuff sticks” are simple toolsfor pushing straw into hard-to-reach places (such asinto fixing-post notches)

Persuader: A persuader is a specialhammer with a large surface area whichis used to adjust the position of strawbales in the wall when leveling.

Drawknife: A tool used with ashavehorse for sharpening hazel stubsand pins.

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PART

NER

THE PARTNERS OF THE LEONARDO PARTNERSHIP STEPThese 9 partners signed a memorandum of understanding with the aim to promote and improve training opportunities in Straw Bale building all across Europe.

FASBA - GERMNAYFachverband Strohballenbau Deutschland e.V., Artilleriestrasse 6 in 27283 Verden, DE

PARTICIPANTS: Sissy Hein, Dittmar Hecken, Burkard Rüger, Heinz Michael Fischer,

Dirk Scharmer

www.fasba.de

ASBN - AUSTRIAAustrian Straw Bale Network, Baierdorf 6 in 3720 Ravelsbach, AU

PARTICIPANTS: Herbert Gruber, Erwin Schwarzmüller, Helmuth Santler, Gerhard Scherbaum

http://www.baubiologie.at/wp/strohballenbau/asbn-netzwerk/

SBN - NETHERLANDSStrobouw Nederland, Pauwenkamp 45 in 3607 GC Maarsen, NL

PARTICIPANTS: Wouter Klijn, Sissy Verspeek, Florian van Roekel, Piotr Bronicki

http://www.strobouw.nl

ARTUR - SLOVAKIAArchtektura pre Trvalo Udrzatelny Rozvoj, 90301 Hruby Sur 237, SK

PARTICIPANTS: Zuzana Kierulfova, Marian Ontkoc, Peter Coch, Boris Hochel,

http://ozartur.sk

RFCP LES COMPAILLONS - FRANCE Reseau Francais de la Construction en Paille, SCM le Jeune, 28 avenue Léon Blum,

31500 Toulouse FR

PARTICIPANTS: Isabelle Melchior, Noé Solsona, Dirk Eberhard, Manas Melliwa, Cedric Hamelin

http://www.compaillons.eu / http://rfcp.fr

RCP - SPAINRed de Construccion con Paja, Doctor Fajames 44 in 03204 Elche, ES

PARTICIPANTS: Valentina, Maini, Alejandro Lopez, Maren Thermes

http://www.casasdepaja.org

STRAWBUILD – UNITED KINGDOMSedum Cottage, Owen Street, Pennar in SA 72 6SL Pembroke Dock, UK

PARTICIPANTS: Bee Rowan, Michael Howlett, David Semenysin, Chris Hawker, Kuba Wihan

http://www.strawbuild.org

COMPALHA - PORTUGALAssociacao para a bioconstrucao com fardos de palha e materiais naturais em Portugal,

Rua Abade Faria 40 3D in 2725-476 Mem Martins, PT

Participants: Catarina Pinto, Joao Barbosa Sequeira, Luisa Alves de Paiva

http://compalha.pt

MAGYAR SZALMAÉPITOK EGYESÜLETE - HUNGARY Joka u. 14 in 5650 Mezoberény, HU

Participants: Titusz Igaz, Gabriella Revesz, Gabor Szücs

http://www.szalmaepitok.hu

STEP – Straw Bale Training for European Professionals

UNIT 3 – Load bearing

Editors UNIT 3: Michael Howlett, Bee Rowan (Strawbuild)

Coordination: Sissy Hein (FASBA), Dirk Eberhard (RFCP)

Authors Session Plans: Leonardo Partner (see p. 23)

Design: Herbert Gruber (Layout), Michael Howlett (Drawings, Logos),

Isabelle Melchior, Alejandro Lopez (Templates)

Photos: Herbert Gruber, Bee Rowan, Barbara Jones, Werner Schmidt