Goss's Roofing Ready Reckoner E-Book

C. N. Mindham

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 169

Veröffentlichungsjahr: 2016

Beschreibung

Goss’s Roofing Ready Reckoner provides cutting angle and lengths for traditional ‘cut’ roofs and design tables for timber sizing, based on BS5268 ‘Structural use of timber’ and now including a comparison of timber sizes using Eurocode 5 ‘Design of Timber Structures’. Additional information is provided on wall plate and gable strapping, wind bracing, truss clips and other roofing metalwork, plus information on tools, equipment and health and safety matters. Detailed drawings for tiling, slating and other roof coverings are included, with fixing requirements revised to BS 5534:2014. Information on lead substitutes and roofing putties is also provided. Design of warm and cold roofs is fully covered, including ventilation and insulation requirements. The fifth edition also includes new chapters on engineered timber roofing components, solar panel fixing and outbuilding roofs.

Leseprobe

GOSS'S ROOFING READY RECKONER

FROM TIMBERWORK TO TILES INCLUDING METRIC CUTTING AND SIZING TABLES FOR TIMBER ROOF MEMBERS

Fifth edition

C. N. Mindham

This edition first published 2016

© 1948, 1987, 2001, 2008 the estate of Ralph Goss, Blackwell Publishing and Chris N. Mindham © 2016 by Chris N. Mindham

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Library of Congress Cataloging-in-Publication Data

Names: Mindham, C. N. (Chris N.), author. | Goss, Ralph. Roofing ready reckoner. Title: Goss's roofing ready reckoner : from timberwork to tiles. Other titles: Roofing ready reckoner Description: 5th edition / C.N. Mindham. | Oxford, United Kingdom : John Wiley & Sons, Inc., 2016. | Includes bibliographical references and index. Identifiers: LCCN 2015044551 (print) | LCCN 2015045710 (ebook) | ISBN 9781119077640 (pbk.) | ISBN 9781119077664 (pdf) | ISBN 9781119077657 (epub) Subjects: LCSH: Roofs–Handbooks, manuals, etc. | Carpentry–Mathematics–Handbooks, manuals, etc. | Roofing–Handbooks, manuals, etc. | Engineering mathematics–Formulae–Handbooks, manuals, etc. Classification: LCC TH2401 .G67 2016 (print) | LCC TH2401 (ebook) | DDC 694/.2–dc23 LC record available at http://lccn.loc.gov/2015044551

A catalogue record for this book is available from the British Library.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

Cover illustration by kind permission of Kier Living Ltd.

CONTENTS

1 Introduction and Acknowledgements

ACKNOWLEDGEMENTS

2 Roofing terminology

3 Calculating the size of timber members

STRENGTH AND SECTION SIZE CALCULATIONS

HOW DO WE CALCULATE THE LOADING ON THE ROOF?

TIMBER MEMBER SIZING DESIGN: AN EXAMPLE

COST CONSIDERATION

4 Calculating the length and cutting angles of timber members: data tables 5°–75°

THE PITCH

USING THE TABLES TO CUT A COMMON RAFTER

HIP JACK RAFTERS

HIP RAFTERS

VALLEY JACK RAFTERS

THE RIDGE

PURLINS

5 Wall Plates – Strapping and Gable Strapping

6 Wind bracing and openings for dormers and roof windows

OPENINGS FOR DORMERS AND ROOF WINDOWS

7 Roofing metalwork and fixings

NAILS, BOLTS AND SCREWS

8 Engineered timber roofing components and prefabricated roofs

TRUSSED RAFTERS

SPANDREL PANELS

CRANE-ON ROOF ASSEMBLIES – TRUSSED RAFTERS

CRANE-ON ROOFS – STRUCTURAL PANELS

CRANE-ON ROOF ASSEMBLIES – STRUCTURAL INSULATED PANELS

ATTIC TO ROOM-IN-THE-ROOF CONVERSION

9 Roof coverings – underlay, battens and tiles

UNDERLAY

BATTENS

INSULATION AND VENTILATION

CHOOSING THE ROOF COVERING

BUILDING REGULATIONS – THERMAL PERFORMANCE

10 Roof coverings – building detail drawings

THE NEW BS 5534:2014

MANUFACTURER'S SPECIFICATION

HIPS, RIDGES, VERGES AND VALLEYS – TRADITIONAL AND NEW METHODS OF CONSTRUCTION

ROOFING PUTTIES

NATURAL SLATES

CONCRETE INTERLOCKING TILES

PLAIN AND PEG TILES

ASPHALT SHINGLES

METAL TILES

LEAD SUBSTITUTES

11 Solar panels

PLANNING AND ROOF SUITABILITY

ROOF CONSTRUCTION

FIXING THE PANELS

POSSIBLE IMPROVED FIXING

VARIATIONS ON PANEL DESIGN

12 Sheds and outbuildings

PERMITTED DEVELOPMENT

TYPES OF PERMITTED BUILDING

DESIGN

THE STRUCTURE

THE MONO-PITCH ROOF

THE DUAL-PITCH ROOF

ROOF COVERINGS

MAKE YOUR NEW BUILDING SAVE MONEY!

13 Tools and equipment

OBTAINING INFORMATION FROM THE DRAWING

TO CUT THE ROOF

SETTING UP THE ROOF STRUCTURE

ROOF COVERINGS

14 HEALTH & SAFETY CONSIDERATIONS

ACCESS TO THE ROOF

BASIC PRINCIPLES

RESTORATION AND RENOVATION OF EXISTING ROOF STRUCTURES

NEWLY CONSTRUCTED ROOFS

THE ROOF COVERING

CONCLUSION

Bibliography

Index

EULA

List of Illustrations

Chapter 2

Figure 2.1

Illustration of terms used in chapter.

Figure 2.2

Illustration of terms used in chapter.

Figure 2.3

Attic or room-in the-roof truss.

Figure 2.4

Illustration of terms used in chapter.

Chapter 3

Figure 3.1

Dimensions of a roof in a worked example.

Figure 3.2

Span tables for ceiling joists. The above table is reprinted from Guild to Building Control by Anthony Gwynne with the permission of Wiley Blackwell.

Figure 3.3

Span tables for ceiling binders. The above table is reprinted from Guild to Building Control by Anthony Gwynne with the permission of Wiley Blackwell.

Figure 3.4

Span tables for purlins. The above table is reprinted from Guild to Building Control by Anthony Gwynne with the permission of Wiley Blackwell.

Figure 3.5

Span tables for common rafters. The above table is reprinted from Guild to Building Control by Anthony Gwynne with the permission of Wiley Blackwell.

Figure 3.6

Timber member size comparison between design standards and between timber strength classes.

Chapter 4

Figure 4.1

Cut Roof Valley construction.

Figure 4.2

Cut Roof Hip construction.

Figure 4.3

Roof Pitch Angle.

Figure 4.4

Run and Rise of Rafter.

Figure 4.5

Rafter Length, Overhang, and Birdsmouth.

Figure 4.6

Hip and Valley Jack Rafters.

Figure 4.7

Hip and Ridge connection.

Figure 4.8

Abutment of Hip and Intersection of Purlins.

Chapter 5

Figure 5.1

Wall plate and Gable Wall strapping.

Chapter 6

Figure 6.1

Bracing required for typical trussed rafter roof.

Figure 6.2a

Trimmed opening for dormer. Reproduced from C. N. Mindham (2006)

Roof Construction and Loft Conversion

, 4th edn. Blackwell, UK.

Figure 6.2b

Trimming construction rules. Reproduced from C. N. Mindham (2006)

Roof Construction and Loft Conversion

, 4th edn. Blackwell, UK.

Figure 6.3

Some typical roof window installations. Reproduced from C. N. Mindham (2006)

Roof Construction and Loft Conversion

, 4th edn. Blackwell, UK, p. 216.

Chapter 7

Figure 7.1

Some items of roofing metalwork. Illustration taken from Simpson Strongtie, Cat. Connections for Masonry and Timber Construction C-UK 14, p 145.

Chapter 8

Figure 8.1

Trussed rafter quality standards label.

Figure 8.2

Typical prefabricated spandrel panel.

Figure 8.3

Engineered timber composite ‘I’ beam and construction details.

Figure 8.4

Construction of a structural, insulated roof panel. With permission of Kingspan Insulation Ltd. Figure 4 from the Kingspan TEK Specification Manual (9th Issue, Feb 2014).

Figure 8.5

Metal reinforcement fitting for ‘I’ beam used as attic floor joist.

Chapter 9

Figure 9.1

Underlay detailing.

Figure 9.2

Minimum horizontal laps for unsupported and fully supported (shown in brackets) underlay.

Figure 9.3

Specification of multilayer insulation in warm and cold roofs. SF60 Superfoil.

Figure 9.4

Cold and warm roof voids.

Figure 9.5

Designs for cold and warm roofs with (a) traditional non-permeable.

Figure 9.5

(b) vapour-permeable underlay. (c) Designs for mono pitch cold roof and attic warm roof with permeable underlay.

Figure 9.6

Typical construction for a vapour-permeable underlay in a cold roof with insulation at ceiling level (unventilated loft). Easy Verge Trim by Permavent.

Figure 9.7

Typical construction for a vapour-impermeable underlay in a cold roof with insulation at ceiling level.

Figure 9.8

(a) Typical ventilated ridge: trussed rafter roof. (b) Alternative ridge fixing: traditional cut roof.

Figure 9.9

Minimum pitch for slates, tiles and shingles for roofs with normal exposure.

Figure 9.10

Approximate roof covering weights in kg/m

2

.

Chapter 10

Figure 10.1a

Slate roof. Eaves and verge.

Figure 10.1b

Slate roof. Hip detail.

Figure 10.2a

Single interlocking tile. Barge verge and eaves detail.

Figure 10.2b

Single interlocking tile. Side abutment gutter detail.

Figure 10.3a

Plain tile. Valley detail.

Figure 10.3b

Plain tile. Sprocket eaves detail.

Figure 10.4a

Redland Rapid HIP System.

Figure 10.4b

Marley Eternit Universal Ridge Fast Dry Ridge System.

Figure 10.4c

Permavent Easy Verge Trim.

Figure 10.5

Asphalt shingle roofing details.

Figure 10.6

Metal tiles – typical details.

Chapter 11

Figure 11.1

Proposed improved fixing to trussed rafters.

Figure 11.2

Proposed alternative fixing bracket for use with solar panels.

Chapter 12

Figure 12.1

Permitted building cross-section size limitation.

Figure 12.2

Stability effect of rafter tie.

Figure 12.3

Typical outbuilding roof construction.

Guide

Cover

Table of Contents

Chapter

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1Introduction and Acknowledgements

The aim of this book, when first published in 1948, was to provide quick reference tables for the length and angles of cut for timber members in a traditional cut roof construction. Today, when many houses use trussed rafters for their roof construction, there is still a need for some parts of those roofs to be built using traditional methods, especially with the ever-increasing use of attic roof structures. The renovation of older roofs, extensions and conversions all require knowledge of roofing from wall plate to ridge, and the correct detailing of the roof covering materials themselves.

Relaxation in planning controls has allowed a wide range of smaller buildings to be constructed without planning permission. These include sheds, garages, garden office buildings and workshops. New information on the limitations of building profile and construction is included in this edition, together with some helpful drawings.

This book assumes that a basic architectural design of the roof to be constructed is already completed, that is, the span, pitch, length and any additional supporting walls. Guidance is given on how to calculate the size of individual roof member timbers, the cutting length, the angles and the compound cuts. The tables shown are based on BS5268 ‘Structural use of timber’ and a comparison of timber sizes using Euro code 5 ‘Design of Timber Structures’ is shown as both design documents are currently acceptable by building control regulations. The book now also includes all aspects to be considered when choosing the roof covering, including the suitability of the tiles or slates for the pitch and exposure of the roof concerned, the choice of a ‘warm’ or ‘cold’ roof, the considerations to be given to the correct insulation, and the possibilities and avoidance of condensation within the roof space by dealing correctly with ventilation.

Solar panels, now frequently fitted to both new and existing roofs, impose different loads on roof structures and these have been addressed in a new chapter.

Finally, Health and Safety matters are addressed, including the ‘Working at Heights Regulations’, loading the roof structure with the roof coverings, lifting components, and the correct use of preservative-treated timber.

Acknowledgements

My thanks are due to all the manufacturers who have allowed me to use their product illustrations. I am particularly indebted to Robinson Manufacturing Ltd, for the help they have given on engineering timber components, and especially for help on spandrel panels. Thanks are also due to Kier Living Ltd for access to their construction site for photography for the cover of this book.

The Trussed Rafter Association helped with solar panel fixing research, and Anthony Gwynne kindly contributed with his overview of the building regulation requirements with regards to thermal performance.

2Roofing terminology

The main terminology used for roofing is listed below (see Figures 2.1–2.4).

Wall plate The ‘foundation’ of the roof, usually 50 × 100 mm wide, must be bedded solid, level and straight on the top of the wall, or nailed to the timber-framed panel and strapped in place to prevent movement from the structure.

Purlin The member carrying part load of the long common rafters, traditionally placed at rightangles to the rafter but now more commonly fixed vertically.

Pitch The angle made by the slope of the roof with the horizontal. This may be stated in degrees on the drawing, it may have to be measured by protractor from the drawing, or it may have to be calculated by measurement if the new work is to match an existing roof.

Ridge The timber at the top of the roof where the rafters meet, giving a longitudinal tie to the roof structure, commonly 38 mm thick, and of a depth equal to the top cut on the rafter plus approximately 38 mm. This depth will depend on the pitch of the roof and the tile batten thickness.

Common rafter The timber running from the ridge, down over the purlin if fitted, over the wall plate, and to the back of the fascia.

Jack rafter The timber running from the hip rafter down over the purlin if fitted, over the wall plate, and to the back of the fascia.

Figure 2.1 Illustration of terms used in chapter.

Figure 2.2 Illustration of terms used in chapter.

Valley jack rafter The timber running from the ridge, down over the purlin, down to the valley board or rafter.

Trussed rafter A prefabricated framework incorporating rafter, ceiling joist (or tie), and strengthening webs forming a fully triangulated structural element.

Ceiling joist or tie Timber supporting the ceiling of the building, but often importantly ‘tying’ the feet of the common and jack rafters together thus triangulating and stabilising the roof.

Wind bracing Usually 25 mm × 100 mm timber nailed to the underside of rafters and trussed rafters running at approximately 45. to them, to triangulate and stabilise the roof in its vertical plane.

Attic or room-in-the-roof truss or trussed rafter This popular truss shape allows the use of steeper pitch roof voids for habitable accommodation. There are no set minimums for dimensions H and W, but 2.3 m and 1.2.1.5 m are practical recommended minimums unless the room is to be restricted to storage only (see Fig. 2.3)

Longitudinal bracing Usually 25 mm × 100 mm timber nailed to the underside of rafters and trussed rafters both at the ridge position on a trussed rafter roof, and at ceiling joist level on all roofs, to maintain accurate spacing and stiffening of the members to which it is fixed (Fig. 2.4).

Hip or hip rafter This is a substantial timber member running from the corner of the roof at wall plate level to the end of the ridge. In some designs the hip may stop lower down the roof, producing a small gable at high level (Fig. 2.4).

Figure 2.3 Attic or room-in the-roof truss.

Birds mouth The cut in rafters at the fixing point to the wall plate and/or the purlin (where purlins are fixed vertically); this should leave at least 0.7 × the depth of the rafter to give the strength necessary for the rafter to continue to provide an overhang to the roof. If a common rafter is fitted as part of a trussed rafter roofing system, then the 0.7 × the depth of the rafter must be the same as the depth of the rafter on the trussed rafter component. (Fig. 2.4)

Fascia Board fixed to the rafter feet, supporting both gutter and soffit (Fig. 2.4).

Soffit Timber board or sheet material used to close off the overhang between the back of the fascia and the wall. This soffit may have a roof ventilation system built into it (Fig. 2.4).

Figure 2.4 Illustration of terms used in chapter.

3Calculating the size of timber members

Knowing the overall dimensions of the roof, that is, the span over the wall plates, pitch of the rafters, length between the gables or hips, any internal supporting walls and the specification of the roof covering, the following data will help to design the size and strength specification of the individual roof members themselves.

Roof structure design must satisfy the requirements of the building regulations for the individual countries of the UK. Currently (at the time of writing this edition), the building regulations can be satisfied by designing either with the British Standard BS 5268-2 2002 ‘Code of Practice for Structural Timber Design. Permissible stress design materials and workmanship’ or BSEN 1995-1-1 ‘Eurocode 5 Design of timber structures’. Common rules and rules for building, the UK National Annex to EC5 and Published Document PD6693-1 ‘Recommendations for the design of timber structures to Eurocode 5’, as above. Clearly, at some time in the future the building regulations will be amended to allow only the EC5 design standards. A limbo situation exists in the timber design industry at present, with some trussed rafters being designed on BS5268-2 and some on EC5. For individual timber roofing members, Trada have two sets of span tables available, one on each of the design methods above. These cover rafters, purlins, ceiling joists and ceiling binders, plus floor joists and trimmers as well as flat roof joists. Designs based on either of these design documents should satisfy local building control. The Trada Technology Ltd documents are:-

SPAN TABLES for solid timber members in floors, ceilings and roofs of dwellings, 2nd edition.

Eurocode 5 SPAN TABLES for solid timber members in floors, ceilings and roofs for dwellings.

The first document is based on BS5268-2 and the second on EC5 (see Bibliography for full contact details to obtain the publications). The term ‘solid timber’ describes natural sawn timber from logs, and not engineered timber components such as Ply Box beams, or ‘I’ beams.

A brief word on timber size design considerations. The loads to be supported by the roof structure are made up of a number of elements:

The roof covering: tiles, slates, etc.

The self weight of the structure: timber, felt, battens, insulation, and ceiling if an attic structure, plus water tanks as necessary.

Snow load.

Wind load.