Heritage advice - alterations and additions

Points to keep in mind when performing alterations and additions on a heritage home:

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This advisory information is intended to assist you in making the most of your existing house when planning alterations and additions. It should be read in conjunction with the relevant planning controls for your area.

It is probably the heritage character of the property that attracted you to your house in the first place, so it makes good sense to preserve this character in the interests of future resale. Poorly planned or designed alterations and additions will adversely affect the property's street appeal and value – avoid making unsympathetic changes to what the passerby sees. If changes must be made, at least try to conserve the
outward appearance and proportion of your house.

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When planning renovations it is a good idea to look at other houses in a similar style to yours for inspiration. Look at how varying rooflines, projecting gables and lower roofed verandahs, for example, have been used to reduce their bulk and add interest in the details. The Toowoomba House book has examples and addresses of many of the styles of homes typical in Toowoomba and region up to World War II.

The philosophy guiding the design of alterations and additions to existing houses can be broadly categorised as - either replicative, complementary or interpretive. Each of these design approaches is discussed below.

Before starting it is critical to understand the special characteristics that make your building or place, unique, as this can influence the design approach. We use the term "cultural heritage significance" to describe those special characteristics or values. They can include aesthetic values as well as historic, scientific, social or spiritual values.

Design approach

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A. Replicative

Replicating exactly the materials, form, details and ornamentation of the original house requires a great deal of effort and can be expensive. While this approach is usually acceptable, it is not recommended as it can cause confusion between what is original and what is new.

B. Complimentary

This is a design approach in which new work complements the original house rather than replicating it exactly. This approach relies particularly on the design details discussed in this brochure, such as similar building proportions, scale and overall form.

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This approach also relies on the use of similar materials and colours to the original building. This is generally a successful approach as it can provide a cost-effective design with minimum impact on the original building.

C. Interpretive

Although this approach can be successful in combining older buildings with very modern designs, it is also the most difficult of the three design approaches. It is only recommended if a professional architect or designer experienced in heritage design is engaged. Each case will have its own particular problems and solutions, so this approach is outside the scope of this brochure.

Design elements

To ensure the heritage character and significance of your property is maintained, certain design elements and details need to be considered when planning alterations and additions. Any drawings prepared need to document carefully the existing form and detail of the building. New work can then be considered in relation to the existing structure. The more detailed the drawings, the easier it is to assess the impact any change will have on the original house.

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Earlier alterations or additions may need to be changed to be more sympathetic with the original character of a house.

Building form / shape, bulk & scale

The overall form/shape, scale and bulk of your new additions are some of the most critical elements in designing successful additions in heritage and character areas. It is important that new work reflects the character and scale of the original house. Typically, pre-World War II homes in Toowoomba and the surrounding region are smallscale cottages or modest houses. Additions need to be carefully planned so that this character is not lost.

The following diagrams show some simple examples of how this might be achieved. Though the general principles in these diagrams apply universally it is important to look at the specific features of each individual place when planning new work.

Roofs should be simple hipped, gable or small scale skillion, pitched to match the original building. It is often a good approach to design a sympathetic roof form first and then plan within that, rather than planning your extension and then sorting out how to put a sympathetic roof over it. Elements 

such as projecting side gables and lower verandah type roofs help reduce the bulk of large additions. The placement of openings is another design element that can be used to reduce the mass of large expanses of wall. This can be in the form of doors & windows or open decks or verandahs.

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Flat roofs are usually not acceptable unless they are an original feature of the house.

Traditional building form

Because most old houses are small to modest in size they tend to have walls and roofs of a particular scale. It is important that this scale be retained when planning additions.Avoid reshaping the whole roof to cover the additions as this usually results in an unsympathetic change in the scale of the house relative to its neighbours and streetscape. A better approach is to leave the original roof form and volume intact and express the new work separately, such as in a wing addition or linked pavilion as discussed below.

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Pavilion additions

If the form of your house is clearly defined making it difficult to extend, pavilion style additions are recommended. This form is the most appropriate where large additions are planned. It can be achieved by introducing a link between the pavilion and the original house or by attaching the pavilion directly. To minimise the impact on the street view of the house the pavilion addition should be located behind the original house.

The pavilion concept can be incorporated cleverly into the floor plan to create separate areas within the house – for example the new pavilion could contain only children's bedrooms and play areas, or perhaps only a parent's retreat or a kitchen family room.

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Lean-to additions

Extending your house at the back in the form of a lean-to or skillion is probably the most familiar and economical type of small addition. As a guide if they are no more than 3 metres deep and set behind the original house, the impact on the street facade is minimal. The form, shape and size of the original house usually remain clearly visible and are not dominated by the smaller lean-to addition. However, large or conspicuous lean-to additions are generally not recommended.

It is important that the scale and roof pitch of the new work be compatible with the original character of the building. For example, the roof pitch should ideally match the pitch of any verandah roofs. If there is an existing verandah it may be possible to extend it along the side of the building to create additional space. A long extension with a minimal roof pitch is generally not recommended.

Wing additions

If space allows on your site and there is a preference for using existing roof shapes in the design, wing additions can be considered. These additions can take the form of a new wing or an extension of an existing wing. These are most successful where the new addition is similar in proportion, size and bulk to the original house. In planning wing additions it is important that the new wing does not dominate the scale and form of the existing house. The roof form and pitch should match the original.

Be careful not to create long side facades that are not in proportion to the scale of the original building. Projecting bays or side wings and sections of lower roofs can be added to prevent this occurring.

Recommended addition forms

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The most successful approach for large extensions is to use a combination of the pavilion, wing and lean-to building forms. Clever placement of the built elements should help to ensure that the scale and bulk of new work do not overshadow the original house. Furthermore this approach can help keep the distinction between the original house and new work clear.

To ensure new work is compatible with old, the height of new walls, roof ridge heights and gutter lines should be the same or lower than those of the existing house. Most roof styles have an eaves or roof overhang. It is important to maintain this feature in any alterations or additions.

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Window and door placement in walls

It is important that you consider the relationship of wall area to the area of window and door openings.

Large areas of glass are generally inappropriate and should be broken into groups of traditionally sized or proportioned windows. The most acceptable types of windows are those that match those of the original building such as double-hung and casement windows.

It is important that you take your neighbours into consideration. Place windows so that they do not look directly into theirs. If this is unavoidable, try to provide privacy in the form of planting or lightweight screening. Consider, also, their right to daylight and sunlight when planning the bulk form of your additions.

Window sill and window head heights should also be consistent with the existing house. Most old windows are protected by window hoods. These are a practical way of blending new and old windows to complement each other.

Materials, surface finishes and building elements

Wall cladding, gutters, roofing and ventilators should complement the existing house. Whilst it is desirable that these elements be similar to the original house, they need not necessarily be exact replicas. It also makes good sense for future historic research to make some distinction between the original buildings and the new additions.

For example, the size of weatherboard or chamferboard on walls is more important than matching an exact prole, since the horizontal lines of the boards will be visible from some distance, but the profile could only be compared if examined in detail. It is preferable that any sheet material, such as custom orb prole steel, be laid so that the dominant lines run horizontally rather than vertically.

Box gutters are an acceptable element if a particular type of design requires their use. Note that they must be correctly designed and maintained to ensure their adequate performance.

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Decorative elements

Your house may have a number of decorative elements such as ornate bargeboards, decorative gable ends and balustrading, finials etc. Consider carefully the use of these elements in the design of your additions, as an attempt to replicate them exactly can often detract from the character of the existing house. It is sometimes preferable to use certain elements from the original house but to simplify or modernise them.

Two-storey attic additions

Unless your house is unusually large, creating an attic room will not result in much extra space. Whilst there may seem to be an enormous volume up there under the roof, not much of it is of a habitable height.

To use this space in most houses, it will be necessary to punch a dormer window or two through the roof or install one or more operable skylights for light and ventilation. Dormers and skylights were seldom used on our older houses and on most styles they were never used at all. If you must choose this option, however, dormers and skylights should face to the rear and not be seen from the street.

The typical iron roof is a fairly efficient solar collector and the space below such roofs becomes extremely hot in summer. If creating a new attic room insulate above the ceiling to protect the inside of the house from this heat and also ventilate the attic space so the hot air can escape.

Most old timber houses have light weight framing and were not designed to carry 2-storey floor loads to today's standards. There will usually be added structural costs to make this form of addition comply.

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Second storey additions to an existing house

The alternative to extending into the roof space is to plan for a second storey addition. Again, this form of addition was rarely if ever used on older houses in Toowoomba and the surrounding region. Adding a second storey alters the scale of a building dramatically and is not usually recommended. The scale, bulk and form of the extension need to be carefully considered to minimise the impact of the addition on the streetscape.

Rear two-storey additions

Rear two-storey additions are not usually recommended because of styles, their visual prominence in the streetscape and lack of compatibility with existing house 

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Basement additions

An alternative to adding a second storey in the roof of a house is to build in underneath. Raising houses is not usually recommended as this can upset existing streetscape patterns consisting of other low set houses.

Building in underneath may occasionally be suitable where the land slopes steeply to the rear of the block and the outside walls are set behind a row of timber stumps (see illustration) This gives the illusion that the house is still single storey, and helps to maintain the original form, scale and bulk of the building while minimising any impact on the streetscape.

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Streetscape and siting

When designing your additions consider the streetscape and how the changes you plan to make will impact on the street and nearby buildings. The aim is to ensure your extension does not dominate your neighbours' houses.

The general rule to follow is to minimize the visibility of any new work from the street. Note that even additions at the rear of a building can often be seen from the street. This particularly applies where you have a wide allotment or large side boundary setbacks to either your home or adjacent buildings.

Careful consideration needs to be given to additions or alterations to homes on lots with more than one street frontage, such as corner lots. Special attention should be paid to the form, bulk and scale of additions to ensure they complement those of the existing house when viewed from all street frontages.

Our libraries have a number of excellent reference books with information on house styles, history and details. These can be valuable tools for planning alterations and additions that are sympathetic to the character of your house.illustration19ato19c

 

Last Updated: Sunday, 02 July 2017 13:44