Complete Loft Conversion Book E-Book

Julian Owen

• Herausgeber: Crowood
• Kategorie: Lebensstil
• Sprache: Englisch
• Veröffentlichungsjahr: 2013

Beschreibung

Loft conversions are one of the most popular types of home alteration and, as this book shows, they can be an enormously useful and stylish addition to a house. If you have not been involved in a building project before, The Complete Loft Conversion Book guides you through the entire process with chapters arranged so that they follow the sequence of events in a real project.Shows how to identify whether your roof space is suitable for conversion and how designers work out ways to make the best use of available space.Using three-dimensional sketches and colour photographs of actual projects, the author illustrates the options for fitting in a staircase and indicates how to estimate the headroom that will be available. Considers the requirements of the local authority planners and building control officers, and provides tips on how to make applications and approvals run smoothly. Presents highly detailed drawings and photographs showing the conversion process. Provides advice on how to avoid cowboy builders and track down the ideal company, how to draw up a fair contract and how to deal with the legal issues that may arise. Supplies checklists and specifications to help monitor progress and ensure that the work is completed to a good standard. A practical, informative book which guides the reader through the entire building project following the sequence of events for a real project. Brimming with useful advice, it contains information not found in other publications. Aimed at all those considering having a loft conversion, those who have made the decision to convert but are still carrying out research and those just about to have work started. Superbly illustrated with 303 colour photographs and highly detailed drawings. Julian Owen MBE is a chartered architect with over twenty years' experience.

Leseprobe

THECOMPLETE LOFT CONVERSION BOOK

Planning, Managing and Completing Your Conversion

Julian Owen

Copyright

First published in 2009 by The Crowood Press Ltd Ramsbury, Marlborough Wiltshire SN8 2HR

www.crowood.com

This e-book edition first published in 2013

© Julian Owen 2009

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publishers.

British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library.

ISBN 978 1 84797 580 5

Disclaimer The author and publisher do not accept responsibility, in any manner whatsoever, for any error, or omission, nor any loss, damage, injury, adverse outcome or liability of any kind incurred as a result of the use of any of the information contained in this book, or reliance upon it. Readers are advised to seek specific professional advice relating to their particular property, project and circumstances before embarking on any building or installation work.

Diagrams by Keith Field and Julian Owen.

Photographs by Julian Owen unless otherwise stated.

Front cover photographs by The Loft Company (top left), Julian Owen Associates Architects (bottom left) and Telebeam.

Frontispiece image courtesy The Velux Company Ltd.

Dedication

For Paul, Zoe, Judy, Nick, James, Derek and Sue at Julian Owen Associates Architects

Acknowledgements

I would like to thank Richard Owen for his comments and advice and Sue Mercer for her invaluable help with administrative matters.

Thanks are also due to the following firms for providing photographs as illustrations for the book:

Absolute Lofts

Attic Designs Ltd

Room Maker Loft Conversions

Telebeam

The Loft Company

Julian Owen Associates Architects

The Velux Company Ltd

Contents

Title Page

Copyright

Dedication

Acknowledgements

1 Introduction

2 Assessing a Loft for Suitability for Conversion

3 Setting Up a Project

4 Designing a Loft Conversion

5 Preparing and Submitting Applications to the Local Authority

6 The Detailed Construction of Loft Conversions

7 Getting the Loft Conversion Built

8 Two Examples of Successful Loft Conversion

Glossary

Recommended Reading

Index

CHAPTER 1

Introduction

Loft conversions are usually one of the first options considered when looking at ways of increasing the floor area of a house. The weather protection and floor are apparently already in place and it may be possible to stand up in the loft and look around at what seems to be a large potential bedroom. Up to 30 per cent of the floor area of the whole house may be gained, only needing a floor and staircase to make it complete. It is usually cheaper than adding an extension, as well as being relatively quick and less disruptive. But as you might expect having picked up this book, it is not quite so simple.

Lofts are a modern invention and are generally used for storage.The Velux Company Ltd

The loft space is believed to have first appeared in the fifteenth century and developed in parallel with the chimney. Until chimneys were invented, a large open roof was needed to disperse the smoke from internal fires. Once the smoke was being piped directly to the outside through a chimney, it was logical to reduce the space that needed to be heated by introducing a ceiling, creating a separate space above – and so the first attics were created. Soon these spaces were made use of and even small buildings were able to have two storeys. The ceilings were supported by the main trusses, which were also carrying the roof and consisted of planks of wood on thin wooden joists. Plaster ceilings followed later, supported on thin strips of wood (‘laths’). As living standards improved, the two-storey house became the commonest form of dwelling, even for the less well-off, and the roofspace was mostly used for storage.

All these roofs were built up from timber on site and often improvised by the carpenter as he built it, but just after the Second World War, when timber for building was scarce, the Timber Development Association produced a range of standard roof truss designs to use as little timber as possible as efficiently as possible (known as a TDA truss). By the mid 1960s the fink truss, or trussed rafter, began to be widely used. This is a development of the TDA truss, which uses the minimum amount of timber reasonably possible to span the house from one side to the other. A trussed rafter is prefabricated off-site in a factory. Most importantly, it uses small sections of wood that interrupt the roofspace and is designed to be just strong enough to support the ceiling of the room below and roof. These two characteristics make it more difficult to convert than a traditional roof and the problem is made worse by the introduction of shallow pitch roofs, made possible by the introduction of the concrete interlocking tile.

A successful loft conversion is an asset to any house.The Velux Company Ltd

Many people start by using a loft for storage with access provided via a simple ladder. Improvements begin with the addition of a chipboard floor, followed by a better ladder, a roof light and a plasterboard ceiling fixed to the underside of the rafters. Eventually a new room is created. Although relatively cheap and easy to do, this approach will leave a room that is cold, that has condensation problems in winter and that may be a fire risk. When a house with such a room is offered for sale, potential purchasers are likely to raise questions and ask for proof that it has received Building Regulations approval. If it turns out not to have been approved, the house may be unsaleable.

Good Reasons for Converting a Loft

There is a large existing roofspace with plenty of space to stand up in.There is limited space around the house to add an extension.Other people in the area with similar house designs have already done it.You would like a slightly unusual space with lots of natural daylight.The cost of moving to get more space is more than the cost of a loft conversion.There is a lot of space on the ground floor compared to the first floor, or the building is a bungalow.Planning restrictions limit the addition of a normal extension or are difficult and complex to negotiate.The space is needed quickly.

When to Consider not Converting a Loft

You can hardly stand up in the highest part of the loft.You have assumed that it is a quick, easy way to increase the value of the house before selling.You have assumed that it will be very cheap because it will need minimal building work to create a bedroom. It is easier to add a two-storey extension.You will end up with far too many bedrooms relative to the other rooms in the house. You need the loft for storage and there is nowhere else to put it.

A conversion that is well designed and constructed will increase the value of your home, provide an interesting, unconventional space to live in but also change the character of the house as you move around it. If it is not well designed and constructed, a property can be blighted and dogged with maintenance problems for the rest of its useful life. A badly converted loft can even endanger the health and safety of the occupants. The purpose of this and the following chapters is to assist anyone who is considering a loft conversion to make the decision and then, if the work is to go ahead, to explain the crucial issues that should be dealt with as the project proceeds.

There is no doubt that some lofts naturally lend themselves to being converted. The following issues are dealt with in detail in separate chapters later on, but often it is quite easy to identify whether a roofspace will be straightforward to turn into a room or whether it is probably best left well alone.

HOW TO DECIDE WHETHER TO CONVERT A LOFT

Is it Worth It?

The main reason for considering a conversion is usually that more space is needed for an expanding family. Another reason is that the existing house is not selling for the amount hoped for by the owners and it may be a way to make more money. Some people consider making use of the loft as a temporary stop gap to cover a time when a bigger house is needed but is too expensive at that point in their lives. Whatever the objective, the financial implications should be examined at a very early stage – certainly before starting to follow up the idea with enthusiasm. The danger at this point is that a simple loft conversion may be cheap to build, but some house plans will benefit more than others from the addition of an extra floor level.

You will get contradictory advice from estate agents on this subject. A favourite phrase is something like ‘it will certainly add value to the property’, along with ‘it would help the property to sell more quickly’. Both these statements are unhelpful, because the crucial question is: ‘How much will the conversion cost compared to the extra value that is added?’ The answer will vary depending on the type of property, its location and the suitability of the loft for conversion, factors that are explored in more detail further on in this book. But it is possible to look at a typical situation and see how cost-effective a loft conversion is likely to be.

First of all, in terms of cost per square metre, a typical loft conversion is usually cheaper than adding the same floor area with an extension or a conservatory. However, it is not always as cost-effective, since it may not add as much to the value of the house as these alternatives. A loft conversion tends to add between 10 and 20 per cent to the value of the house. For example, converting the loft of a three-bedroom semi-detached house worth £180,000 would increase its value by between £18,000 and £36,000. If the cost of converting the loft to add an extra bedroom is between £30,000 and £40,000 there is a clear possibility that the project will not make money. This is especially likely if the existing structure does not make the building work easy to carry out or a high standard of fittings and finishes is required. So anyone undertaking a loft conversion to generate a profit needs to investigate the costs and the ultimate sale price in some detail before committing to the project. Generally speaking, most roads have a ‘ceiling’ price, which represents the maximum possible price a house there will sell for, regardless of its size or quality. If you own a three-bedroom house in a street of mainly four-bedroom properties it will probably add significant value if you upgrade yours to a similar size. By comparison, if all the houses have three bedrooms and a loft conversion will increase yours to five bedrooms, it will generate less of an increase in value.

An extra bedroom can add value to a home. The Loft Company

From the point of view of a family who needs the space but either cannot afford to move or does not wish to, the figures should be looked at in a different way. Moving house is not cheap and trading up from three to four bedrooms could easily cost £30,000–£40,000. Once expenses such as estate agent’s fees, solicitor’s fees, stamp duty and other general costs are added into the equation, the final cost of acquiring extra space by moving house could be between £40,000 and £50,000 – in other words well above the cost of a typical loft conversion. If the family are happy to live in the house for at least a few years after it is completed, it is an entirely sensible financial decision to convert, even though all the money spent will probably not be recovered.

What are the Other Options?

Even if a loft is a good candidate for a conversion, there may be other, better ways of increasing the number of rooms in the house, or improving the design. The alternatives and their relative benefits and disadvantages should be at least briefly considered. An extension to the ground and/or first floors is probably the best way to increase the floor area of a house. If the extra space is not for a bedroom, but for extra living space such as a children’s room or a study, it is definitely a better option to build a ground floor extension, which is far more flexible in use than a loft space. However, many houses do not have sufficient space on their plot to allow an extension to be built at ground level, while planning restrictions often prevent them from being added on the first floor because they will overlook or overshadow a neighbour’s house or garden. If you simply want an extra bedroom on the first floor, you would still incur the hefty expense of constructing an unwanted ground-floor room to support it. In terms of adding value to the house, an extension will typically add around 10–15 per cent to the sale price of your home. This is significantly less than the cost of building such an extension, which is why in most cases extensions should not be added to generate a profit.

In an area where there is no space for an extension, such as near a city centre, another option is to excavate under the house, either from scratch or by enlarging an existing basement with low headroom. This is a very expensive undertaking and will only pay for itself where land values are very high and there is no other option, so a loft conversion, however difficult it may be, is likely to be a better option.

The most common reason for a loft conversion is because more bedrooms are needed. The Loft Company

Too Many Bedrooms

The distribution of rooms around the house is another important consideration. If a house has a large number of bedrooms compared to limited ground-floor space, adding what is effectively a further bedroom in the form of a loft may be a bad idea. This situation typically occurs where there is an integral garage built into the body of the house, which restricts the amount of space available on the ground floor. Unless one of the first-floor rooms can be released to become something other than a bedroom, such as a family living room or study, adding a loft conversion will leave the house with a disproportionate number of bedrooms compared to general living space. This problem is made worse if the number of bedrooms is increased to more than five or if there are not enough bathrooms. A house that just about runs effectively with three bedrooms and one bathroom may become unworkable if the family expands into a fourth bedroom without adding at least an en suite. Living in such a house with all the bedrooms in use will feel cramped and the property will be less easy to sell when the family finally decide to move on.

You and Your Family

How the family adapt to and use the new space should be carefully considered. If the extra floor is being added to a two-storey house, the addition of a third level may bring benefits or disadvantages. Any parents of young children know that they require a lot of looking after even when they are supposed to be asleep, not so easy to do if the adults are trying to sleep a flight of stairs away. Older people, or anyone who expects to grow old in the house over time, should realize that the effort needed to circulate between three levels instead of two is significantly more tiring for weaker muscles. Sometimes the staircases up to the loft are so limited in size that they are not suitable for a stair lift to be fitted.

What will your family use a loft conversion for? The Velux Company Ltd

In an ordinary house, the space in the loft is a vital storage area. Lack of storage space is a common complaint heard from owners of modern houses. Rather than disposing of their unwanted possessions, many families are used to sticking them in the loft to be dealt with later, or kept in case they become useful again. If the loft is to become a bedroom, the contents will have to be removed or stored somewhere else in the house.

Is the Loft Suitable?

Assessing the suitability of the loft is dealt with in the next chapter, but even a quick look can give you a strong hint as to how difficult the venture is likely to be. Some roofs naturally lend themselves to conversion and others make it an uphill battle. The less building work that is necessary the better. This doesn’t mean that a difficult conversion should always be avoided, but it may sway the balance in favour of moving or extending instead. Some loft spaces almost seem to cry out to be converted and others promise little return for a lot of effort. Because it is sometimes quite difficult to judge how much space will be created from the drawings used to plan the work, one of the major mistakes people make is to spend a great deal of time and money to create a relatively small room that hardly has space to walk around a single bed without knocking your head on the ceiling.

Some lofts are more suitable for conversion than others.The Loft Company

If a house is particularly suitable for a loft conversion, it will reduce the disruption to the family living in it during construction and the building work itself will be relatively quick. This contrasts with the construction of an extension, which can interfere far more with the running of the household and usually is a longer and more complex process, particularly if a planning application is necessary.

It takes a good imagination to visualize a dark, dirty storage area as a new living space. The Velux Company Ltd

As well as the space available within the roof structure, the condition and standard of the construction are important. As long as it is all basically sound, it will not be a problem, but if there are existing problems, such as rot in the timbers, defective roof slates or undersized rafters, these will have to be put right to make the project worthwhile. Of course if the condition is so bad that major remedial work is required anyway, it may be well worth spending a bit more money converting the loft at the same time.

Planning and Building Regulations

In the UK planning approval from the local authority is sometimes necessary to alter the external appearance of a roof. Whether or not permission is necessary depends on a number of factors. In rare cases alterations to the interior of a loft may also need consent from the planning authority. If a building is deemed to have historic value it will be listed to protect it from unacceptable alterations and this may prevent any kind of building alteration. Another example is if there are bats roosting in the roof void. Bats are a protected species and disturbing them without permission is a criminal offence.

The Building Regulations have some very specific requirements that cover aspects of the design and construction such as fire escape, fire spread, headroom, heat loss and structure. There is very limited scope to deviate from the standards set so if there is something about the construction of the existing loft space that makes it impossible or, more likely, very difficult to satisfy the regulations, the project may have to be abandoned. The classic ‘killer’ problem is the inability to achieve sufficient headroom, particularly over the staircase. Even if it is possible for most people to stand up without bumping their head, if the requirement for 2m at the head of the stairs is not met, the plans are unlikely to get the approval of the building control officer.

For full details of the likely effects of planning and Building Regulations requirements, seeChapter 5 on local authorities.

How Will it Look?

Assuming that all the practical aspects have been dealt with successfully and it appears to be a viable project, a final aspect to consider is how a new room-in-the-roof will look and how it will relate to the existing building and its neighbours. Even if you are not concerned at all with the appearance yourself, a poor-looking conversion can wipe thousands of pounds off the value of a house, despite satisfying all of the functional requirements such as the Building Regulations and providing adequate space. In its simplest form, a loft can be made usable with the only change visible outside being some windows that follow the line of the roof. Once extra features such as dormer windows are added, the character of the house will be affected. Sometimes the only way to get the desired space involves ruining the appearance of the building.

If in doubt the best thing to do is to consult an architect to get the opinion of a trained designer as to whether the end result will be acceptable. It may be that a professional can suggest a way of rearranging the design to make it more pleasing to look at. Ultimately, whether or not to proceed with alterations that damage the appearance of a home is up to its owners, but they may lose out in the long run if they get it wrong.

It may be worth investing in an architect to produce a considered three-dimensional design if the final appearance is important.Julian Owen Associates Architects

STEP BY STEP

Any significant home alteration project can seem daunting to a family when it is first contemplated. However, like any project, the best way to approach it is to break it down into a series of steps or stages that have to be completed. The serious commitment doesn’t have to be entered into until an instruction is given to a building company to carry out the work. Up until this point, although there may be some expenses, these are relatively minor compared to the actual construction cost. If the project does not live up to early expectations, or proves to be generating a lot more aggravation that planned, it can be halted and the whole thing put down to experience. What is more likely is that as you progress through the process, you will gain confidence and enthusiasm for the transformation that is about to occur in your standard of living. Unless there is an urgent reason for the project to be completed quickly, it is very important to take the time to go through each stage properly. Too much impatience may lead to problems later on if there is not enough advance planning.

Step 1: Make your Own Appraisal

Most people can at least make a basic check on the feasibility of a conversion. Using a book such as this, it is possible to make a fairly considered appraisal and avoid paying out for professional advice for a project that could never be viable.

Step 2: Talk to the Experts

There are many building companies that will carry out loft conversions. Some are only interested in straightforward, easy work that they can carry out quickly before moving on to the next, others relish a challenge. They will usually come and look at your house for free and make some comments on the viability of a conversion. It is not reasonable to expect them to provide a detailed design without being paid, but they should be able to explain how it would be done in principle and describe the problems that will have to be solved. If your house has particular architectural quality, or you are unhappy with commissioning a builder right at the start you can consult an architect, who may charge for the time but will offer impartial advice and may be able to offer some more creative solutions.

With smaller houses, there is a limited combination of room layouts that are possible and a professional with experience should be able to tell straight away whether or not it is a good idea to proceed. At the end of this stage you should have a clear idea of what is possible and a shortlist of firms that you are considering using.

Step 3: Commission a Design

This is the point where you will have to commit to paying out some money. There are two ways of employing a designer. You can engage the builder right at the beginning, who will in turn pay the designer as part of his total costs, or you can pay your own designer and use the resulting drawings to get competitive prices for the work. The design process and the relative benefits of the two approaches are discussed in Chapter 4.

Step 4: Get Planning Approval (if Required)

If a project requires planning approval or a related permission such as listed building consent, work must not start until it is in place. Even apparently straightforward applications have been known to hit unexpected snags in the approval process so it is not sufficient just to assume everything will be fine until you have the signed permission in your hand. From the date that the application is submitted to receiving that approval can take eight weeks or longer, so it can delay the start of a project. Fortunately, most loft conversion projects do not need formal permission from the council.

Step 5: Get Building Regulations Approval

All loft conversions need approval under the Building Regulations. It is possible to get the work approved by the building control officer as it is actually being built but the more sensible option is to have detailed construction drawings prepared and submit them for approval before the building work starts. The building contractor may deal with this process, but it is your responsibility to ensure that the regulations are complied with, and you are entitled to see all the paperwork. The regulations are mostly for your benefit, to ensure safety both during construction and once the new spaces are occupied.

Step 6: Agree a Price

If you have used a builder from the very beginning, before the design was prepared, you will probably have a good idea of the cost. However, most contracts allow for some adjustment to the price once the detailed construction has been finalized and even during construction. If you have used an architect to prepare plans and used them to invite competitive tenders, you will have fixed a price before agreeing to the work proceeding. Either way, you should have a proper written contract that does not allow the contractor to add to his charges without very good reason. If the only price stated is an estimate, or the likely cost is not absolutely clear, do not instruct building work. Just as important is a proper programme of work with a fixed completion date.

Step 7: Start Building

A typical conversion can take between five and eight weeks. There will be some disruption, particularly when the staircase is built, but at least it will be less fuss and quicker than an extension.

Step 8: Completion

A completion date should be agreed between the builder and the client before the work starts. It usually triggers the final large payment to the builder so it is important to walk round and check that everything has been done, to an acceptable standard. Most builders are anxious to get on with the next project and occasionally the final few tasks are rushed or forgotten. Once payment has been received, it is much harder to get any outstanding issues dealt with. 

When the going gets tough it helps to focus on the end result – a useful and attractive addition to your home.The Velux Company Ltd

Common Pitfalls when Converting a Loft

Going over budget This is the biggest risk of any building project. Advance planning and a proper contract with the builder are the best ways to reduce the chances of it happening to your project. Starting before planning permission is in place This occasionally happens, either through the ignorance of the building team or a desire to cut corners. It is almost always spotted by neighbours. Any competent builder knows the rules and will build in the time and cost needed if they quote for a design and build service. If work is well underway and the expected planning permission is not granted and the local authority either refuse to allow the work as proposed or at all, you will be left with a major problem. Poor design and construction Doing the conversion too cheaply will probably cost more in the long run when it has to be upgraded later. The local authority building control approvals process protects you from poor building work to some extent, but this is a safety net imposing only minimum standards. It is essential to use a professional team. Failure to appreciate the impact on the house A classic example of this problem is when on completion you find that the staircase has filled most of the new loft space created and drastically reduced the space on the floor below. Avoid this by ensuring that the designer is experienced in this type of work and can visualize three-dimensional space. Two-dimensional plans can be deceptive and sometimes three-dimensional drawings such as perspectives or card models can give a better idea of how the rooms will look. Realizing too late that the loft does not comply with Building Regulations Some roofspaces cannot accommodate a conversion to a habitable room without major rebuilding work. Very occasionally the plan of the existing house makes adequate fire escape impractical. Basic checks early on in the process can usually establish this. Staircase too steep and too tight to get furniture up The tightest possible staircase allowed by the regulations will easily allow a person to use it and a lot of modern furniture is designed to be carried through a house and up typical staircases, possibly in parts that are assembled in the room. The same is not true of older furniture, especially if it was made for up-market homes. Creating an ‘unlivable’ loft This is one of the commonest mistakes, often seen by surveyors who are valuing a property for sale. It is where the loft has been gradually converted over a period of time, with floorboards, plasterboard linings, a window and then a better ladder all being eventually fitted. This sort of room is not considered ‘habitable’ by a purchaser’s solicitor or an estate agent and will not get Building Regulations approval for use as a bedroom. The only solution is to rip out most of the work and do it all again properly.

CHAPTER 2

Assessing a Loft for Suitability for Conversion

Before getting too far into the process of converting a loft or incurring the cost of hiring professionals the suitability of your roof should be assessed. For many, the best way of doing this may be to contact a builder or architect and ask them to take a look at it. However, it does no harm to do your own research first. Some aspects of the roof design and construction, such as the headroom available, may prevent a loft conversion from being carried out at all unless the roof is rebuilt. Other limitations, such as the structure of the roof, may not prevent a conversion, just make it more expensive. Provided that they can get into the loft safely, most people are able to check the key elements themselves. The detailed design work that will be needed is covered in later chapters, but at this early stage it is possible to visualize how a finished conversion might look and identify the area of the existing construction that will have to be altered.

The key questions to ask when considering a loft conversion:

Is there enough headroom?Where will the staircase go?Where will windows go?Is the roof structure in the way?Are there any services to be altered, for example electrical wiring, water tank? How easily can it be insulated?What will happen to all the junk currently stored in the loft?

HEADROOM

The first, basic test for the feasibility of a loft conversion is to go up into the roof and try to stand up without bumping your head. If you can’t, conversion is unlikely to be cost-effective because you will have to put on a new roof or lower the ceiling of the floor below to get enough space. This may seem an obvious point to check, but some lofts can be inaccessible because there is no loft hatch. Also the infirm or disabled are not able to climb up a ladder easily, or if the house is being inspected by a potential buyer access may not be immediately available. Roofs look higher than they actually are if only seen through a loft hatch whilst standing on the landing.

This loft has sufficient headroom, but will need some structural alterations to carry out a conversion.Attic Designs Ltd

Assuming that it is possible to stand up comfortably, the next question is, ‘How much space is there above your head?’ If your head is tucked into the space under the ridge of the roof, with little space around it, a conversion is going to be difficult. Even if you have reasonable clearance, the finished conversion will need a stronger floor, raising the floor level, and the roof must be insulated, which usually means that the insulation will be deeper than the existing rafters. The result is that the space that you stand in before the conversion will shrink once the work is complete. There are ways to add more space, such as adding dormer windows, but if the roof is too low in the first place, they will not necessarily help unless they involve extensive alterations to the roof.

What to look for in a loft.

The minimum height that you need from the top of the existing ceiling joists to the underside of the ridge (the highest point of the roof) is about 2.3m. In most cases this will allow just enough width to move around in the narrow corridor of full height space under the ridge and should allow some dormer designs to extend the volume of the room. If the height is less than this, some roofs may still be convertible, but it will depend on the design and construction of the alteration work. Because the Building Regulations require that there is at least 2m clear headroom over most of the top of the new staircase, if the clear height under the ridge would be less than this once the work is complete, the roof is not suitable for conversion into a habitable room and a new roof structure would be the only way to create sufficient space.

How to Estimate a Roof Pitch

If you want to work out the approximate pitch of your roof, there is a simple method using the ‘3:4:5’ relationship between the sides of a 90-degree triangle that you may have learned at school: that is, if one of the angles of a triangle is 90 degrees, then the ratio of the length of the sides is 3:4:5. If this is too complicated, the following chart will help make a more approximate estimate. If you measure 1m from the point where the rafter meets the ceiling joist and then measure the height of the underside of the rafter at this point, the table indicates the approximate roof pitch. If you want a more precise measurement, you can use an angle finder. There is an electronic version of this tool, which is quite expensive, but the more old-fashioned manual version cost only a few pounds, is quick to use and may be worth investing in if you are going to construct a roof or need to measure the angle of a lot of rafters.

Chart for Estimating Effect of Roof Pitch and Span on Headroom

Chart for estimating effect of roof pitch and span on headroom. These dimensions are very approximate. Some roofs are built with slightly different pitches to each side. The diagrams show the internal line of the existing roof, so the headroom shown here will be reduced by the new floor and linings under the rafters. Dimensions are in millimetres except where otherwise stated.

How to estimate a roof pitch.

The chart on pages 18–19 shows the relationship between the pitch of the roof, the span and how much loft space is available. It shows that to be sure of getting a workable loft conversion with a 30-degree roof pitch the span must be around 8m or 9m. With a 40-degree pitch, it is just possible to create a room when the span is around 6m. It can be seen from this table that where the roof is on the borderline of being convertible, it is essential that accurate measurements are taken when making an assessment of its potential. Sometimes the difference between success and failure is decided by a matter of a few centimetres. An added complication with older houses is that the pitches on different sides of the roof can vary by several degrees – something that is not immediately noticeable, even to the experts, unless an angle finder is used to check each pitch. Very old houses are also often not built square in plan as well. These inaccuracies in the construction are usually irrelevant unless the loft conversion is very short on headroom, in which case they should be checked to make sure that the headroom at one end of the building is the same as at the other. This is why some smaller loft conversions can take more time to survey and design than larger roofs with plenty of headroom.

If the headroom is not sufficient, it may still be possible to create a loft conversion, although relatively elaborate solutions are required. One is to replace the roof completely and either make the roof pitch steeper or build up the main walls of the house. Apart from the significant extra cost, planning approval will be needed to do this, which may not be granted if your house is one of a row of identical properties. The alternative is to lower the ceiling of the rooms below. To do this there must be sufficient headroom in these spaces and structural work will probably be required to prevent the rafters of the roof from pushing out the tops of the walls. It may be possible to form a mezzanine level to avoid the roof height becoming oppressively low.

Plenty of headroom is essential for a successful loft conversion.Room Maker Loft Conversions

STAIRCASE ACCESS

Assuming that there is adequate headroom, the next issue is the location of the staircase. For a house with two storeys or more, this should ideally be directly over the existing staircase. Unfortunately, in many houses, the staircase is sited at the edge of the house under the eaves, where the roof is at its lowest and so a dormer window is usually needed to allow the extra headroom. If it is not possible to position the new stair over the existing one, space will probably be lost from one or two of the existing bedrooms. In the worst cases a whole bedroom can be lost in which case clearly the new loft space has to be significantly bigger to make the project worthwhile. When trying to work out the staircase locations that are possible, it can be helpful to start by identifying whereabouts the top step can go in the loft. Because there should be 2m headroom at this point, the number of possible locations is fairly limited in all but the largest roofspaces.

There must be sufficient headroom at the top of the stairs.Attic Designs Ltd

If the house already has two floors, the Building Regulations require that there should be a safe escape route in the event of a fire. This can be achieved by creating a route from the loft room to the front or back door that is completely fire protected for 30 minutes, or a similar route to the first-floor landing with windows that can be climbed through.

Sometimes it is necessary to cut through the existing structure to create a window at the right height.Attic Designs Ltd

WINDOWS, VIEWS AND DAYLIGHT

The new rooms to be created must have daylight, ventilation and ideally a view out. Roof windows that follow the line of the roof are the simplest and cheapest solution. Dormer roofs are also a well-used method, with the added benefit that they also add extra space with headroom. Sometimes where a main wall of the house extends up to form a side of the loft space, usually in the form of a gable, it offers an easy way of creating a conventional window. When making an initial assessment of the loft, likely locations for the windows should be considered. If possible they should allow a view but not significantly overlook a neighbour’s garden. If they have to go on the front-facing roof of the house, they may need planning approval. Sometimes, to position a roof at the right height and location, it is necessary to cut through a significant element of the structure, such as a purlin (one of the horizontal beams that supports the rafters). It is usually possible to do this, but you will require some extra structural supports, such as steel beams, to compensate for the missing sections.

SERVICES

Many lofts have water tanks of some kind in them, especially in houses that have older heating systems. If there is no space for them once the conversion has been completed it will be necessary to fit a new system. Some boilers work on mains pressure, without using a water tank, which means that there is a good chance of getting hot water up to a bathroom or WC in the roofspace. Systems that rely on a large water tank providing a ‘head’ of water cannot provide enough pressure to supply water to fittings that are at the same level or above. In the former case, it may just be possible to get taps to a washbasin to work, but a shower will never have sufficient pressure unless you introduce a pump system, such as a power shower. 

Water tanks often have to be moved as part of a loft conversion.Julian Owen Associates Architects

INSULATION

Modern standards insist that any habitable room in a house is insulated to reduce heat loss – but with rising energy costs it is an important part of the building work regardless of the rules and regulations. Consequently, a new layer of insulation is needed immediately below the roof covering. The line of the new ceiling will be lower than the underside of the existing rafters because they are unlikely to be deep enough to accommodate the thickness of insulation that is needed. This means that the overall headroom of the space may reduce by anything from 50mm to 100mm.

How well insulated is your loft? The pigeons know, because a badly insulated loft provides the perfect warm roost in winter. Much of the heat energy paid for by the house owner escapes to the outside.Julian Owen Associates Architects

If a loft has been used only for storage, it may not have any insulation in the roofspace at all, especially if it is an older property. It is more likely that it will have some insulation laid directly above the ceiling below, between the ceiling joists. The latest Building Regulations require that an extra layer of insulation is laid over the top of the ceiling joists as well. Apart from insulating against heat loss, the insulation can also reduce noise transmission between floors, so it does some good to leave it where it is rather than lower the height of the new floor. It is unlikely to be thin enough to be reused to insulate between the rafters.

STORAGE

Most unconverted lofts are a handy place for storage. There is little enough space in modern houses and it is easier to put items up there than get rid of it. However, there are also things, such as suitcases, books and memorabilia, that are not needed in everyday life but the family do not want to lose. In some cases, the amount of such clutter can be considerable. Even after a major de-cluttering process, which is time-consuming and is best started as soon as the decision to convert is made, there is likely to be a need for a sizeable amount of extra storage space. This can be dealt with by incorporating new cupboards in the house as part of the project, or building a new shed in the garden or by hiring long-term storage space elsewhere. 

Most lofts are full of junk that needs to be thrown out or stored elsewhere.Julian Owen Associates Architects

Some Definitions

Typical terms for parts of a roof.

Section showing some typical components of a roof.

Barge board This board follows line of tiles at the gable end of roof to conceal the joint between roof and wall.

Ceiling joists These span between wallplates on top of the walls at either side of roof. They carry the weight of ceiling and insulation only, and if there is extra load such as a water tank, extra support is provided. They also tie the feet of the rafters together to stop them from moving outwards and pushing over the tops of the walls. They are often too slender for the distance that they span, so a binder spanning between cross walls provides intermediate support.

Common rafters The main structural element of the roof, spanning between ridge and wallplate, supporting battens for the roof. They are birdsmouthed over wallplate.

Dormer A way of increasing headroom in a roof and also forms a vertical window.

Eaves The section of roof that overhangs the top of the external wall.

Fascia board Board that is fixed to the end of the rafters, supporting the gutter and the last row of tiles.

Gable end The triangular end of a double-pitched roof.

Hip roof An extra slope to the roof in place of a gable end.

Purlin This provides intermediate structural support to the rafters when they are too thin to span distance on their own. They are supported off walls. If a purlin is cut before it is properly supported a roof could collapse.

Ridge The top of the roof, where rafters meet.

Soffit board Closes off the gap between the fascia and the top of the external wall.

Valley Where two roof pitches meet and form a drainage channel, usually made with glass fibre or lead flashing.

Wallplate Typically 100 × 50mm in size, this softwood section supports the rafters and ceiling joists. It is bedded on mortar on top of the external wall. Modern wallplates are fixed to the wall with steel straps, with the rafters and ceiling joists nailed to them.

Two of the most basic structural components of the roof are the rafters, which follow the slope of the roof, and the purlin, a horizontal beam that the rafters rest upon.Julian Owen Associates Architects

TYPES OF ROOF

Although the pitch and construction are also important, some roof shapes are easier to convert than others. Assuming that there is at least one part of the roof that is high enough for someone to stand up in, the arrangement and shape of the roof will partly determine how easy it can be converted.

Gable Roof

This is one of the simplest forms to construct and, in terms of shape, is one of the easiest to convert. The triangular walls at the end allow the possibility of ordinary windows and there is a long section of continuous usable space. Dormer roofs can be added easily, although there are often purlins in the way that will need to be cut to allow this.

Hipped Roof

Along with gable roofs, hipped roofs are the most common type of shape in the UK, particularly in the suburbs. They are slightly more difficult to convert than a gable, because the extra sloping roofs reduce the space available and also reduce the option for locating a staircase. For a standard three- or four-bedroom detached house, it is likely that this type of roof will require a dormer or other roof alteration to allow the staircase sufficient headroom. Because the roof structure all leans into the centre of the building, any purlins have to be supported off internal walls with props, which makes the roof structure slightly harder to alter.

Monopitch roof.

Monopitch Roof

Monopitch roofs are often found over single-storey ancillary rooms and spaces such as utility rooms at the side or back of the main building on traditional houses. If a monopitch roof spans across a whole house, the end at the top of the roof can be disproportionately high relative to the other side, which is at eaves level. To avoid this problem, some modern roof designs tend to reduce the pitch and span of a monopitch, but this leaves little or no space for a conversion. If the monopitch does have a steep enough pitch and is over a ground floor only, it may be possible to get to it from the first floor. Staircase access is tricky to this type of roofspace unless the void is unusually large.

Mansard roof.

Mansard Roof

Mansard roofs are usually created at construction specifically to allow the roofspace to be used. If it has not been made use of, it is a prime candidate for conversion. If an existing roof is too low to be converted and a new roof has to be built, a mansard is a good way to increase the height and volume of the roofspace whilst keeping the ridge relatively low.

Butterfly and Four-Pitch Roofs with Parapets

Butterfly roof.