Reprinted 1988
Photosetting by: Arrow Stationers, P.O. Box 6207O, Nairobi,
Kenya.
Cover design by Pål-Anders Stensson, FAO/SIDA Rural Structures
Programme
The copyright in this book is vested in the Food and Agriculture Organization of the United Nations. The book may not be reproduced, in whole or in part, by any method or process, without written permission from the copyright holder. Applications for such permission, with a statement of the purpose and extent of the reproduction desired, should be addressed to the Director, Publications Division, Food and Agriculture Organization of the United Nations, Via delle Terme di Caracalla, 00100 Rome, Italy.
(c) FAO, 1986
A growing awareness of the need for better farm structures has in recent years occurred in many developing countries. So far, farm buildings and structures have, in many countries, been built either, on a traditional basis without much improvement, or in an inadequate and often too expensive way, guided by people without appropriate knowledge of the special technical, biological and economic problems involved. Therefore in 1979, the FAO/SIDA Cooperative Programme: Rural Structures in East and South East Africa was established, with the objective to provide assistance to member countries in the development of functional, low-cost rural structures using a maximum of locally available building materials and skills.
To achieve its objective two regional six-months courses on farm structures were conducted by the Programme in Nairobi to cater for the immediate requirements of Farm Building Specialists. Since then many universities, colleges and institutes have come up with plans or activities aimed to expand the teaching in farm buildings. It seems logical to include this subject within the department of Agricultural Engineering because of the agricultural knowledge required, however, clear links with the Extension Service are also needed to spread understanding and skills to artisans and farmers.
Farm buildings and structures are now important parts of an integrated rural development, for instance, about two thirds of the food grain produced in Africa is kept on the farm; this makes it particularly important to develop methods and structures for effective storage, especially for the new high yielding grain varieties which are more susceptible to pests than the traditional types.
Improved management and breeding programmes to increase animal production have created a need for more appropriate animal housing. To improve the standards of living for the rural population, it is necessary to provide durable, comfortable and healthy homes, with clean water, sanitation facilities and community infrastructure.
To improve the assistance given to the rural population, the subject of farm buildings needs to be included at all levels of agricultural education. Farm Building Specialists need to have a thorough knowledge of farming systems, crops, domestic animals, climatological considerations, and a genuine understanding of rural life and the farmer's social and economic situation. They should also be familiar with the whole range of building materials and types of construction, from traditional indigenous to industrially produced, as applied to farm structures. They must be able to select appropriate installations and equipment required for farm buildings. This knowledge will enable them to produce, in cooperation with the farmer, specifications for functional building designs that provide good environment and durable construction, thus contributing to an efficient and economically sound farm operation. To interpret and explain the drawings and technical documentation to farmers, as well as supervise the construction works is another important task for the Farm Buildings Specialist. They should, however, be aware of when there is a need to consult specialists in related fields.
The book is a first attempt to compile a comprehensive text on Farm Structures for Tropical Climates with emphasis on structures for small to medium scale farms and, to some extent, village scale agriculture infrastructure. We hope it will contribute to the improvement of teaching on the subject of farm buildings at all levels in tropical developing countries and to assist professionals already active in Farm Building Extension.
While the book is primarily intended for use in Teaching Farm Structures in Agricultural courses at Universities and Colleges, it is also our hope that resources will be made available to produce textbooks derived from this material, suitable for other school levels. Parts of the bac kground material used come from East and South-East Africa, but the book can be used in the whole of tropical Africa as well as Latin America and Southern Asia, the building traditions may vary but the materials available will be similar.
Comments concerning this book and its contents will be appreciated and will be considered for future revised editions. Comments should be sent to:
Agricultural Engineering Service, ACSE
Food and Agriculture Organization of the United Nations,
Via delle Terme di Caracalla,
00100 Rome, Italy.
This textbook is based on the material and documentation produced by the FAO/ SIDA Rural Structures Programme and the lecturers involved in two six months intensive training courses conducted by the Programme in the period 1981 to 1983.
We wish to thank the following persons who produced hand-outs for the training courses:
Mr. E. Agevi; Mr. L. Bengtsson; Dr. O. Bodholt; Mr. T.S. Buteyo; Mr. A. Caro-Griffenstein; Mr. R.R. Caukwell; Mr. T.S. Chana; Mr. H.J.S. Crees; Ms. Z. Devji; Mr. M. Eshani; Ms. R. Gatabaki; Mr. D. Hanjari; Mr. K. Haugum; Mr. G.L. Hunt; Mr. Z.Y. Ismail; Mr. S. Lund; Mr. J. Kateregga; Ms. Kiugu; Mr. E. Luitjens; Mr. K.N. Mbugua; Dr. E. Meffert; Mr. E. Nissen-Petersen; Dr. G.K. Nganga; Mr. C.A. Rannfelt; Mr. O.J. Sode; Dr. D. Swift; Mr. B. Wouters.
A first draft of the book was produced between October 1983 and January 1984 in Nairobi by Mr. Lennart Bengtsson, FAO/SIDA Rural Structures Programmer Mr. Paul Douglass, Silsoe College, England, Mr. Graham Redding, Department of Agriculture in Victoria, Australia.
The draft was sent, for proof reading and comments on the technical content, to the lecturers in farm buildings at; the University of Zambia; The National Resources Development College in Lusaka Zambia, Sokoine University of Agriculture in Morogoro Tanzania; Egerton College in Kenya; Bunda College in Malawi and to AGSE, FAO Headquarters. We would like to thank the persons involved at these institutions for their advice and many useful suggestions.
Guided by these comments, the technical content of the draft was thoroughly revised and edited into a final manuscript by Professor James H. Whitaker, University of Connecticut, USA and Mr. Lennart Bengtsson, assisted by Mr. Magutu (Chapter 6); Mr. J. Enzmann (Chapter 12); Mr. M.L.A. Bascombe (Chapter 4) and Mr. M.P. Douglass (Chapter 9). The illustrations for the book have been inked by messrs. S. Muli; Y. Ebrahim and J. Chaundry, students at the Faculty of Architecture, University of Nairobi.
It would not have been possible to prepare this book without access to the FAO/ SIDA Library. Some of the books which have been included in the lists for further reading at the end of each chapter will all together form a comprehensive reference library for an agricultural engineering department.
Permission to adapt or use information and illustrations from the work of other authors and publishers is acknowledged with thanks and detailed where they occur in the book.
We are grateful to the ILO Project-Skill Development for Self Reliance-for placing their word processing facilities at our disposal, and Ms. Hanne Moll who did most of the word processing. Gratitude is also due to Mrs. A. Whitaker for her assistance with proof reading of the edited manuscript, and to all staff at the Regional Office of the Rural Structures Programme in Nairobi.
We would like to record our special thanks to:
Mr. Carl A. Rannfelt, Senior Agricultural Engineer, AGSE, FAO Headquarters in Rome, who came up with the idea of making this textbook and who during the production has given us valuable assistance, support and encouragement.
Mr. Ove J. Sode, the former Regional Coordinator of the FAO/ SIDA Rural Structures Programme, now working with AGSE, FAO Headquarters, who has given us great support in making the outline of the book.
Mr. Goran Bruhn, Training Officer in the Rural Structures Programme who has done the final work on the book including the supervision of the photosetting as well as the printing.
Most of the funds for the preparation and printing of this manuscript were made available from the Swedish International Development Agency through FAO/SIDA Cooperative Programme: Rural Structures in East and South-East Africa. Additional funds has come from the FAO Regular Programme.
H. Thorshaug, Regional Coordinator,
FAO/SIDA Rural Structures Programme, Nairobi.
Drawings are essential for planning buildings, for completing the engineering design, for estimating the quantities of materials and relative costs and finally to communicate to the builder all of the information that the designer has developed.
Although it is expected that a course in drafting will already have been completed by the reader, those phases of drawing which are essential in building design, costing and construction are reviewed in this chapter.
Drawing Equipment
Because building drawings include many details, they should be large enough to be accurately executed and easily read. The standard formats from the A-series should be used for all drawings for a building. However, several detail drawings may be put on one sheet. The A-series include the following sizes:
A0 841 x 1189mm
A1 594 x 841 mm
A2 420 x 594mm
A3 297 x 420mm
A4 210 x 297mm
If the building plans tend to be very long, one of the following alternative sizes may be useful:
A10 594x 1189mm
A20 420 x 1189mm
A21 420 x 841 mm
A31 297 x 841mm
A32 297 x 594mm
If possible, only one format should be used for all drawings in a project or alternatively all drawings should have the same height. The formats A0, A 10 and A20 are difficult to handle and should therefore be avoided. One should instead try to use a smaller scale or divide the figure into more drawings.
Obviously a good drawing board, large enough to hold the size paper selected, is essential. One of the following sizes should be suitable:
A0 920 x 1270mm
A1 650 x 920mm
While a sheet of hardboard or blockboard may be used as a drawing board, it is advisable to install a hardwood edge such as ebony. It may be necessary to saw longitudinal grooves 75 to 100mm apart in the back of the board to prevent warping. The board may be placed on a table or on trestles as shown in Figure 1.1. The board should be covered with thick white paper or special plastic to make a smooth surface.
Drawing table with T-square.
Figure 1.2 Borders for various drawing formats.
Drawing Office Practices
Simple freehand sketches are convenient forerunners to final working frequently used for preliminary studies or to illustrate an explanation during a discussion. They are also the logical way for the building designer to convey his ideas to the draftsman. They may be used for developing plans by testing a number of alternative designs or for evolving detail drawings of complex building elements. They are particularly useful in recording details and dimensions from existing structures or prefabricated units.
A soft pencil, eraser, inexpensive paper and a clipboard complete the sketcher's equipment. Principal lines are sketched lightly using a number of short strokes. Once the joining points have been established and lines are satisfactorily straight, they may be darkened as needed to give emphasis and easy reading. Although they are not given a scale and need be in only approximate proportion, all measurements should be clearly shown with dimension lines and legible figures and symbols.
Just as with final drawings, plan (top) and section (front + side) views are simplest to sketch and dimension. However, isometric sketches are useful in presenting a more pictorial view of a structure.
When a final design has been chosen, it is drawn with instruments on tracing paper so that prints may be readily made. A 70/75g paper is usually sufficient. However, if many prints are to be made a heavier paper should be used.
Plastic tracing film is a new material which is more durable for handling and storage and has the advantage that ink can be removed with a moist eraser. It is however much more expensive than tracing paper and requires the use of special lead and drawing pens, since its surface is much harder.
Whatever paper is chosen, it is best to use drafting tape to affix it to the table as the low adhesion allows easy removal without damage.
Drawings should always have borders and title boxes as shown in Figures 1.2 and 1.3. The wide border on one side allows several drawings to be bound together. The title box provides identification of the drawing, the designer, the draftsman and a date. The revision table above the box keeps an accurate record of all revisions.
Prints of the originals will be folded to A4 if stored in folders or binders. The title box should be visible on the folded print and it should be possible to unfold the print without taking it out of the binder. The drawing originals should never be folded!
Before starting to draw, one should estimate how large the figure will be and center it on the page. A worthwhile aid to include is a small figure identifying the location of a detail drawing, in relation to the master plan.
If text is to be written on the drawing, it will normally be placed on the right or the bottom part of the drawing. The text is used to explain symbols, methods of notation and abbreviations used in the drawing. It is also possible to give directions about materials, designs, surface treatments, assembly locations, etc.
Capital letters of a straight upright type are used on building drawings:
Clear lettering can be produced as easily and as swiftly as scratchy letters, by using the correct technique. Form each character by using a sequence of separate, simple strokes for the lines and bows. Use the least possible pressure and hold the pen upright and at 45° angle to the line of writing.
Suggested heights for the letters are: 3mm for text in the figures, measurements and descriptive text; 5 and 7mm for headings and for drawings which are going to be reduced.
Lettering will normally run from left to right on the sheet and be parallel to the bottom edge. When it becomes necessary for lettering to run vertically, it should always run from the bottom upwards. (This applies also to strings of dimensions).
Horizontal guidelines are essential unless the draftsman is very experienced and skillful. They may be drawn lightly in pencil for subsequent erasure when the lettering is in ink or may take the form of a closely gridded sheet laid underneath the tracing paper.
Letters and words are spaced by eye rather than by measuring. If the proportion, form and spacing of the letters is properly executed, the result will be legible and pleasing to the eye.
The thickness of lines should be chosen so that the figures on the drawing are easy to read. The outer contour of the building and the walls between rooms should be thicker than equipment, fittings and measurements. The major outline will then be noted first and the details later.
The view should be chosen so that a minimum of hidden contours need be shown. Concealed contours and those in front of the cut are shown with broken or dotted lines, but should be included only when necessary to aid in the interpretation of the drawing.
It requires practice to draw lines of even thickness and blackness with lead. It is imperative to use a pencil with a sharp point. By rotating the pencil while drawing, the point will stay sharp longer. All lines should be drawn with the help of a ruler, except when sketching or drawing a perspective.
Dimensions are a very important part of the drawing and must be unequivocal and complete. No measurements should have to be calculated by the one who is using the drawing. Duplicate dimensions should be avoided since one may be forgotten if a change is made.
Dimensions should be easy to read and placed where the reader will expect to find them. They should appear 1 mm above the line and be placed so that they can be read either from the bottom or the right edge of the drawing. Dimensions should appear outside the figure if it does not make interpretation difficult. Related dimensions should be placed together, preferably in the same string. Dimensions may be given in a chain (See Figure 1.5a) or from a common point (Figure 1.5c), the latter being used mainly when surveying existing buildings.
Contour lines on maps, site plans and master plans are drawn as unbroken lines to show the levels after the site work has been completed. The levels, as they were before the building activities started, are drawn with broken lines. Contour lines are not shown within structures. See Figure 1.6.
Figure 1.3 Titlebox with revision table.
Figure 1.4 Lettering on building drawings.
Sometimes outer walls and room-dividing walls are shaded with a pencil for emphasis. Alternatively, thicker lines may be used. Elevations are more attractive if shadows are shown under the roof, in windows, doors, etc. In addition, the use of hatching to show the texture of the surfaces of the face-work will provide a better impression of how the finished building will appear.
A wide range of transfer symbols is available including symbols used for hatching, lettering, furniture, electrical equipment, water equipment, vegetation, etc. It is also possible to make symbols and copy them on self-adhesive transfer plastic in a photo-copy machine. However, dry transfer symbols may not adhere permanently and thus be lost. See Figure 1.8.
Conventions of various kinds are used to give a graphical indication of different materials. Where hatching is used, it should be kept simple. Some conventions in common use are given in Figure 1.9. If other conventions are used their meanings should be explained on the drawing. However, different materials are generally more clearly indicated by a proper annotation and this also allows the specification of qualities, etc.
Hatching and shading, especially if done with a pencil, are often done on the back of the drawing in order to avoid blackening and to make it easier to make any revisions on the drawing.
Figure 1.5 Techniques for giving dimensions.
Note that the lines indicating the limits of the dimension do not touch the figure.
Prints of the original drawings are always used to present the project to the client, government authorities, manufacturers, building contractors, etc. In practically all cases, one of the following processes will be used:
Electro-static copying, used in most modern photocopying machines, has the advantage that the original may be on opaque paper. But most machines have a maximum size of A4 and even very expensive machines will not go beyond the A3-size.
The diazo or dyeline process relies upon ultra-violet light passing through a translucent original and activating diazonium salts carried on the copy paper. The image thus formed is developed by the action of ammonia vapour or a liquid develper. Most machines in this field will take paper up to 1200mm wide and, if supplied in roll form, virtually unlimited length. Paper is also available in standard Aformats.
Where no machines are available copies can be made by exposing the sensitized paper overlaid with the translucent original to sunlight for a few minutes and then developing the copy with ammonia.
Prints are available in three colours: black for architectural drawings, blue for design drawings and red for installation drawings.
Diazo copying requires high contrast between lines and bac kground. If for some reason lines drawn in lead are not sealed or the bac kground has been blackened by loose graphite, the copy will come out blurred, or with a dark background.
When drawings are submitted for printing, they should be rolled with the side carrying the text outwards, otherwise they may make a roll inside the printing machine and be destroyed.
Due to shrinking or the method of copying, prints are seldom absolutely to scale. Accordingly, one should never obtain dimensions by measuring on a construction drawing, with a scale on the print!
Diazo process originals can also be duplicated on plastic tracing film giving copies with brown lines which can themselves be copied on paper. Such copies may be used where, for example, a basic plan view is to be converted into various installation drawings etc.
Original drawings should be stored unfolded either hanging or lying on shelves or in drawers. A simple hanger can be made from a piece of cardboard with two clothes pegs glued to the surface as shown in Figure 1.10.
The drawings should be stored in a cool, dry and dark room. It is well to note that a large stack of drawings can be very heavy and put a considerable load on shelves, drawers and hanger rails. Dust can be a problem in the dry season and if shelves are used, measures for control of termite and insect attacks may be necessary.
Copies can be stored in the same way as originals or, in addition, folded in binders or rolled. They should be stored in darkness to avoid fading.
As the number of copies and originals increase in the drawing office through self-production or by obtaining from other sources, it is useful to have an indexing system.
Figure 1.6 Drawing contour lines.
A building project normally requires several types of drawings which will be discussed in sequence in this section. In small- and medium-sized projects, two or three drawings may be combined into one, whereas in large projects each title listed may require several drawings. One should not include so much information on one drawing, that interpretation becomes difficult.
Figure 1.7 Architectural symbols.
Figure 1.8 Symbols for installations in buildings.
Figure 1.9 Symbols for materials.
Figure 1.10 Simple cardboard hanger for drawings
Site Plan
Scale 1:1000, 1:500, or 1:200
The location of the building in relation to its surroundings, including:
Plan of External Service Runs
Scale 1:500, or 1:200
The layout of external service runs including:
External service runs are often included in the site plan or the foundation plan.
Foundation Plan
Scale 1:200, 1:100 or 1:50
Plan View
Scale 1:200, 1:100 or 1:50
Section Scale 1:100 or 1:50
Elevation
Scale 1:200, 1:100 or 1:50
Details
Scale 1:20, 1:10, 1:5, 1:2 or 1:1
The information that a builder needs to know for each element of the building he is to construct may be classified as follows:
What has to be installed or erected, including information about its nature and physical dimensions.
Where it is to be placed, demanding graphic and dimensional information regarding its location.
How it is to be placed or fixed in relation to adjacent elements.
The designer must include all details necessary for the builder to complete all elements of the building. When standard practice, general specifications or building codes are not followed, it is particularly important to include complete detail drawings, annotations and specifications.
Where prefabricated elements are used, for example windows, a specification rather than a detail drawing is adequate. This allows the builder to chose the least expensive alternative that meets the specification.
Where machinery and equipment require special foundations, supports, openings and cavities, the required detail drawings will, in most cases, be supplied by the manufacturer.
Often there is no need to produce detail drawings specifically for each project. An established drawing office will have detail drawings covering the most frequent requirements which may be affixed to current projects.
Plan of Electrical Installations
Scale 1:200, 1:100 or 1:50
Plan of Water and Sanitary Installations
Scale 1:200, 1:100 or 1:50
List of Drawings
Where there are several drawings for a building project loss or omission of a single drawings may be avoided by listing all of them on an A4 paper. Information on latest revisions will ensure that all drawings are up to date.
Technical Specifications
The technical specifications should set out quality standards for materials and workmanship in respect to building elements that have been described in the drawings. Where general specifications are available they are commonly referred to and only divergencies are specified in the technical specifications.
However, in drawings for small- and medium-sized farm building projects, one tends to include much of the information normally given in the specifications, directly on the drawings.
As a basic rule, information should only be given once, either in the specifications, or on the drawing. Otherwise there is a risk that one place will be forgotten in a revision and thus cause confusion.
Functional and Management Instructions
Frequently information has to be transferred to the person using a structure to enable him to utilise it in the most efficient way or the way intended by the designer. In, a pig house, for example, different types of pens are intended for pigs of certain age intervals. Alleys and door swings may have been designed to facilitate handling of pigs during transfer between pens. In a grain store the walls may have been designed to resist the pressure from grains stored in bulk to a specified depth.
Bill of Quantities
The bill of quantities contains a list of all building materials required and is necessary to make a detailed cost estimate and a delivery plan. It can not be produced however, until the detailed working drawings and specifications have been completed.
Cost Estimate
The client will require a cost estimate to determine whether the building should be constructed or not. He needs to know whether the proposed design is within his financial means and/or whether the returns of the intended use of the building will justify the investment.
Time Schedule
A simple progress chart as shown in figure 1.11 will considerably facilitate the planning of the building operations and subsequent activities.
The farmer may obtain information on when he and any farm labourers will be involved in construction operations, when animals and feed should be delivered, when a breeding programme should be started or the latest starting date for the construction of a grain store to be completed before harvest. All this is the type of information needed to enable the returns of the investment to be collected as early as possible. A contractor will require a more detailed chart for the actual construction operations to promote an economical use of labour, materials and equipment.
Specifications, bill of quantities, cost estimating and time scheduling will be further dealt with in Chapter 6.
