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Minimum Standards Document - Organization of American States

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Minimum Standards Document - Organization of American States

    Minimum Building Standards and Environmental Guidelines

    for Housing

    Safer Housing and Retrofit Program

    St. Lucia National Research and Development Foundation

    This document was originally prepared in May 1997

    and substantially updated in May 2003

    Table of Contents

    Page

    Minimum Building Standards..................................................................................................... ii

    Introduction ............................................................................................................................ ii

    Preface ................................................................................................................................... ii

    Hurricanes ...............................................................................................................................4

    How are they formed? .........................................................................................................4

    How do they affect/destroy buildings? .................................................................................5 Basic Minimum Standards and Quality Control Tips for Builders, Artisans and Homeowners .7

    Building Shape ....................................................................................................................7

    Foundations .........................................................................................................................8

    Concrete ............................................................................................................................ 11

    Floors ................................................................................................................................ 12

    Exterior Wall Framing and Cladding ................................................................................. 16 Roofs ................................................................................................................................. 20

    Nails .................................................................................................................................. 25

    Porches .............................................................................................................................. 26

    Shutters, Doors and Windows ............................................................................................ 26 Good and Poor Building Practices in the HRHIP ............................................................... 30 Building Design and Construction ..................................................................................... 34 Building Maintenance ....................................................................................................... 35

    New Construction Methods for Low-Income Housing ....................................................... 36 Users Guide for Hurricane Straps and Other Framing Anchors .............................................. 39 Hurricane Straps ................................................................................................................ 39

    Securing the Load Path ...................................................................................................... 42

    Health and Safety .................................................................................................................. 43

    Relationship between the Minimum Standards Guide and the Building Guidelines ................ 47 Building Code ................................................................................................................... 47

    Building Guidelines ........................................................................................................... 47

    ReferencesMinimum Building Standards ........................................................................... 48 Environmental Guidelines for Housing...................................................................................... 49 1.0 Background ................................................................................................................. 49

    2.0 Introduction ................................................................................................................. 49

    3.0 The Location and Placement of Houses ....................................................................... 50 4.0 Site Preparation ........................................................................................................... 54

    5.0 Drainage ...................................................................................................................... 56

    6.0 Waste Disposal ............................................................................................................ 59

    7.0 Concluding Remarks ................................................................................................... 62 ReferencesEnvironmental Siting Guidelines ...................................................................... 63 Minimum Standards Checklist for use by Builders .................................................................... 65 Easy Guide Checklist ................................................................................................................ 67

    i

    Minimum Building Standards

    Introduction

    Providing comfortable and safe shelter for the family is perhaps the single most important aspiration of heads of household anywhere in the world. In St. Lucia, a safe home must be able to stand up to tropical storm winds, rains and hurricanes, which all too often visit the region. When a house suffers damage, family members‘ lives are disrupted, belongings are lost, and sacrifices need to be made to reconstruct and replace what was lost.

    Low and modest income families are particularly vulnerable to the effects of natural hazards. The bulk of these families‘ financial worth is tied up in their house belongings. Their houses are likely to be constructed without due regard to building standards and quality of materials; they may be located in hazardous areas and are unlikely to be insured.

    Each year tens of thousands of people die and billions of dollars of property damages result from disasters related to natural hazards. The risks from natural hazards change and increase as the Caribbean region grows and develops. Economic losses from these disasters will continue to increase and economic development will be retarded, unless serious attention is paid to mitigating the effects of these hazards.

    Preface

    This document has been compiled to provide guidelines to local builders and agencies in St. Lucia involved in safer housing/retrofitting work, so as to ensure that such work is carried out in the most effective manner. This document highlights the basic minimum standards for retrofitting and quality control tips for both new and existing wooden houses. Its purpose is to inform homeowners of the proper design and construction of safe housing and to serve as a reference for builders, artisans and inspectors. Inspectors play an important role, as frequent and informed inspections are necessary to ensure that structures are being built correctly and safely.

    This document is not intended to be a detailed construction manual, but presents a summary of the recommendations of the writers‘ experience, observations and research over the years. It is intended to be used as a reference/guide for artisans, builders and homeowners in St. Lucia. Specific solutions are not offered, but the document details a number of options that the homeowner can use in building a home. St. Lucia has developed a national Building Code and the accompanying Building Guidelines for Small Structures. The guidelines in this document are not intended to replace any National Code or Housing Manual in existence, but recommends, in some cases, techniques that may be stronger than the ones required in the code.

    Acknowledgements

    Under the USAID-sponsored Caribbean Disaster Mitigation Project (CDMP, 1993-99), the Organization of American States helped the St. Lucia national Research and Development Foundation (NRDF) with the establishment of a Hurricane Resistant Home Improvement Program. After seven years of operation, a thorough review was called for to update the procedures and revitalize the program. Principal funding for this review project was provided by the World Bank and the Government of the Netherlands, through the Bank-Netherlands Partnership Program. The World Bank established a cooperation agreement with the Organization of American States (OAS) for the implementation of this project. The Government of Brazil provided the OAS with seed funding as counterpart to the Word Bank funds.

    Arnaud Guinard of the Latin America and the Caribbean Regional Group of the World Bank served as project manager for this activity and provided significant guidance throughout its implementation.

    ii

    Assistance was also provided by Alcira Kreimer and Margaret Arnold of the World Bank's Disaster Management Facility. The support of Orsalia Kalantzopolous, Caroline Anstey and Tova Solo is also appreciated.

    Jan Vermeiren of the Unit for Sustainable Development and the Environment of the OAS provided oversight through field visits to St. Lucia and review of the documentation. Steven Stichter served as the project manager for this activity and was responsible for the review and editing of the final documents. Authors

    The Minimum Building Standards section of this document was prepared by George Dujon and Fillian

    Nicholas. The writers have both been involved in the building field in St. Lucia for the past 30 years. Mr. Dujon has a Degree in Technical/Vocational Education. He is a member of the Institute of Carpenters and has also obtained the City and Guilds of London Institute Advanced Craft Certificate. Mr. Dujon has been a Carpentry and Joinery Lecturer at the Morne Fortune Technical college, presently known as the Division of Technical Education and Management Studies, Building Department of the Sir Arthur Lewis Community College for the last 22 years. He has been associated with the Retrofitting Project from its inception in 1994.

    Mr. Nicholas holds a Bachelor‘s Degree in Construction Engineering and Management and a diploma in Design and Drafting Technology. Mr. Nicholas has been involved in the building field for the past 32 years. He has been a lecturer at the Morne Fortune Technical college, presently known as the Division of Technical Education and Management Studies, Building Department of the Sir Arthur Lewis Community College for the last 18 years, lecturing in the areas of Architectural Drafting, Building Construction and Surveying, and has involved in the design construction of private and public buildings in St. Lucia. The Environmental Siting section of this document was prepared by Peter Norville. Peter Norville is a Registered Professional Engineer based in St. Lucia. He has over twenty years of experience in the areas of soil and water engineering, environmental engineering, agricultural engineering, environmental planning and management, rural development and project management. He has held several professional and managerial positions within the St. Lucia Public Service. He has also worked with the Organisation of Eastern Caribbean States. Mr. Norville currently operates as a Consultant Engineer, practicing in St. Lucia and in several other Eastern Caribbean States. Mr. Norville wishes to express his thanks to the following persons who provided assistance during the writing of this document: Mr. Bryan Walcott (NRDF), Ms. Joan Cools (NRDF), Mr. Roland Charles (NRDF), Mr. George Dujon (Sir Arthur Lewis Community College), Mr. Wenn Gabriel (Ministry of Health) and Mr. Joseph Medard (Ministry of Health).

    Steven Stichter compiled and edited this manuscript. Steven Stichter is a natural hazards specialist within the Caribbean division of the Unit for Sustainable Development and the Environment of the Organization of American States in Washington DC. He has served as project manager for a range of programs, which all have had the aim of reducing the vulnerability of the Caribbean. These include the Caribbean Disaster Mitigation Project (CDMP), the Post-Georges Disaster Mitigation (PGDM) project in Antigua & Barbuda and St. Kitts & Nevis and the Coastal Infrastructure Design, Construction and Maintenance (CDCM) training program.

    George Blankson undertook a technical review of this document. Mr. Blankson is the Director of Construction Engineering Programme of the University of Technology (UTECH), in Jamaica. Use of these materials: This document was developed with funding through the World Bank and

    copyright for it remains with this institution. The materials developed under this project, including this document, are intended for wide use and distribution. To support wide use, this document may be extracted or reproduced, as part of safer housing initiatives, provided that appropriate acknowledgement of the source document and copyright holder is retained.

    iii

    Hurricanes

    Before one can seriously appreciate and be committed to the importance of safer housing construction or retrofitting, one needs first to understand hurricanes and how their destructive wind forces affect or destroy buildings and homes, especially those built of timber.

    How are they formed?

    The word Hurricane comes from the Spanish word ‗hucan‘, which originates from the arrival of the

    Spaniards to the Caribbean. It comes from the Taino word ‗Juracan‘ that means ‗Evil Spirit‘, according to the Indians who lived in the Antilles at the time.

    A hurricane can be described as a low-pressure area into which the hot and humid tropical air enters and tends to rise. This process acts as the motive force of the storm. The rotation of the earth causes the wind to turn in a counter clockwise, spiral path. A hurricane has several distinctive structural features, shown in Figure 1.

    Eye: In the Northern Hemisphere,

    hurricane winds spiral counter

    clockwise around an eye, which is

    a low pressure area in which wind

    speeds are only 10 to 20 m.p.h.

    The area in the eye is

    characterized by a marked

    reduction in wind speed, a ceasing

    of heavy rain, and a partial

    clearing of the sky. In the most

    spectacular cases, the wind speed

    drops to nearly calm over an

    appreciable area, and all clouds

    disappear. The eye is usually

    circular in shape, the size of which

    can vary 10 100 miles in diameter. Figure 1 Structure of a Hurricane

    Wall Cloud: Surrounding the eye

    of the hurricane is the so-called wall cloud. In the best-developed cases, this cloud structure completely encircles the eye and extends from the earth‘s surface to above 50,000 feet. The strongest wind speeds are usually found in the wall cloud, normally in the upper right quadrant, because the forward movement of the storm is added to the wind speeds in the storm. It is in this area that the pressure gradient is strongest and the rainfall is heaviest.

    Storms are classified by the U.S. National Hurricane Centre using the Saffir/Simpson Scale, which is based on wind velocity and barometric pressure. The scale establishes five categories, of which Category 1 is a minimal hurricane and Category 5 the worst case. See the table below.

Category Wind speed (m.p.h.) Barometric pressure (in.) Storm surge height

    1 74 - 95 4 - 5 ft. above normal greater than 28.94‖

    2 96 - 110 6 - 8 ft above normal 28.50 - 28.91‖

    3 111 - 130 9 - 12 ft above normal 27.91 - 28.47‖

    4 131 - 155 13 - 18 ft above normal 27.17 - 27.88‖

    5 Greater than 155 greater than 18ft less than 27.17‖

    Minimum Building Standards and Environmental Guidelines for Housing 4

How do they affect/destroy buildings?

    As the eye of a hurricane approaches a site, the winds increase gradually to a peak before the eye passes over the site. On the backside of the eye, winds increase again to another, lower peak. The winds on the backside blow in an opposite direction to those on the forward side as a result of the circular wind pattern in the hurricane. Since buildings may be subject to winds from several different directions as the storm approaches and passes, buildings must be designed to resist wind from all directions. Wind damage is caused by the wrenching and bending forces imposed by gusting winds and the rapid increase in wind force as the wind speed increases. Wind force increases with the square of the wind speed, which means that when the wind speed doubles, the force of the wind on the structure increases four times.

    Wind striking a building produces pressure, which pushes against the building on the windward side, and suction, which pulls the leeward side of the building and the roof (Figure 2). If no air leaves the building, then the pressure inside pushes against the walls and the roof.

     Figure 2 Figure 3

    Failure may occur when the external pressure and suction on the wall combine to push and pull the building off its foundation. Overturning can occur particularly if the structure is lightweight and its weight is insufficient to resist the tendency of the building to be blown over (Figure 3).

    Wind penetrating an opening on the windward side of a building during a hurricane will increase the pressure on the internal surfaces. This pressure, in combination with the external suction, may be sufficient to cause the roof to be blown off and the walls to explode (Figure 4).

     Figure 4 Figure 5

    During a hurricane an opening may suddenly occur on the windward side of the building. The internal pressure that builds up as a result may be relieved by providing a corresponding opening on the leeward side (Figure 5).

    Minimum Building Standards and Environmental Guidelines for Housing 5

    Another mode of failure occurs when then windward side of the house collapses under the pressure of the wind (Figure 6).

    If the building is not securely tied to its foundation and the walls cannot resist the push/pull forces they are subjected to, the structure tends to collapse, starting at the roof, with the building leaning in the direction of the wind (Figure 7).

     Figure 6 Figure 7

    All modes of failure can be avoided or mitigated by providing adequate bracing, clamping and anchoring of framing components in timber construction, and by the use of good quality concrete and concrete elements with adequate steel reinforcement, particularly in foundations.

Minimum Building Standards and Environmental Guidelines for Housing 6

    Basic Minimum Standards and Quality Control Tips for Builders,

    Artisans and Homeowners

    The following areas will be given attention in this document since they are the areas that cause the most concern during a storm or hurricane. They are:

    ; Building Shape ; Porches

    ; Foundations ; Shutters, Doors and Windows

    ; Framing (external walls and cladding) ; Connections between all components

    ; Roofs ; Location

    ; Floors

    Building Shape

    It is reasonable to say that low-income house owners typically pay much more attention to size than design when building their homes. The shape of the house, however, is an important factor to be considered when thinking of resistance to high winds. The shape should be as simple as possible, preferably rectangular or square. Avoid ‗T‘ or ‗L‘ shaped houses; because they channel the wind into the junction between the two wings, they are especially vulnerable to high winds. The increase in wind pressure in the junction may lead to failure of the structure. When building rectangular houses, the length to width ratio should be 3:1 or less.

    Figure 8 shows four building configurations, in order of increasing vulnerability to wind forces. The L-shaped houses are particularly vulnerable to hurricane-force winds at the interior corner where the winds develop higher forces.

    Safest Least shape safe shape

     Figure 8

    RecommendationsBuilding Shape

    ; Ensure that the house is rectangular or square in shape. Avoid irregular shaped houses (i.e. L-

    or T-shaped). If the need for extensions or additions to an existing house requires such shapes, it

    is safer to separate the two units by a corridor or walkway, which is itself a separate, self-

    supporting structure.

    Minimum Building Standards and Environmental Guidelines for Housing 7

Foundations

    The foundation anchors the house and transfers the weight of the structure to the ground. The practice of simply laying a structure on large stones, loose concrete blocks or wooden pillars is not recommended. A safer practice is the use of concrete columns or concrete block walls, reinforced with ?‖ mild steel bars.

    The use of mild steel is encouraged since it is easier to bend than is high tensile steel. These bars must be continuous and project beyond the foundation by at least 12" to 14" (300mm to 350mm) to facilitate the securing of the structure to the foundation (Figure 9).

     Figure 9 Concrete Columns for Wooden Houses

    The footing of the foundation should be on firm soil, 2‘-0‖ (600mm) wide Height Minimum

    by 10‖-12‖ deep (200mm – 300mm) with 6‖ or 8‖ concrete blocks (Figure (up to) Column Width

    10). When concrete columns are used, column that are up to 3 ft above 3 ft 9‖ x 9‖

    ground should be a minimum of 9‖x9‖. The length of column below 4 ft 10‖ x 10‖

    ground should be roughly equivalent to the length of column above ground. 5 ft 11‖ x 11‖ (etc)

    With every increase of 1 ft in the height of the columns, the width should

    be increased by 1 inch in each dimension.

    When wood posts are used instead of a concrete block or column foundation, the posts should be treated with preservative and then buried in concrete four to eight feet (4'-0" to 8'-0") into the ground. The posts should have a minimum dimension of six by six inches (6" x 6") (Figure 11). The minimum diameter for round posts should be eight inches (8"). The hole in which the post is placed should be larger than the post itself to accommodate the backfill. Existing houses that do not meet the above recommendation should be improved by building proper pillars and securing the structure to them.

    Existing houses with wooden pillars can be strengthened by excavating around the pillar, casting them in the ground with quality strength concrete (Figure 12) and bracing the pillars to provide lateral support to resist wind action (Figure 13). It is important that very strong pillars be used. Green heart, Capeche, Glory Cedar, Coconut trunks or Balata are a few examples of appropriate choices for pillars. For all types of pillars, the depth of pillar below ground should be similar to its height above ground to the underside of the floor.

    Minimum Building Standards and Environmental Guidelines for Housing 8

     Figure 10 Strip Footing for Wooden Houses

Notes:

    1. Minimum size of posts: 6‖x6‖ or 8‖ diameter when round.

    2. Backfill: well-compacted materials that will provide drainage.

    3. Soil cement is made by mixing 5 parts each of crushed rock and

    sand and 1 part of cement plus water. All particles larger than one

    inch and all organic matter should be removed from the earth.

    4. Steel bars in the concrete pier should be covered with at least 3‖

    of concrete.

    Figure 11

    Minimum Building Standards and Environmental Guidelines for Housing 9

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