Contents
INTRODUCTION
GENERAL APPEARANCE
DORMER ADDITIONS
SINGLE STORY SIDE ADDITIONS
TWO STORY SIDE ADDITIONS
SINGLE STORY REAR ADDITIONS
TWO STORY REAR ADDITIONS
GARAGES
CONCLUSION

 INTRODUCTION

The design of a good home addition requires considerable skill and it is strongly recommended that you employ an architect or other professional representative with design qualifications and experience.

In recent years many people have thought of extending their home to meet changing family needs rather than accepting the expense and disruption of moving to another larger house. This posting offers guidance and basic principles for the design of a home addition.  It is not meant as a set of rigid rules as each planning application will be considered on its own merits, but by following some basic guidelines you are much more likely to achieve a good design that satisfies your requirements without degrading the appearance of your home.  The objective is to both improve your living environment and enhance the value of your property and the neighborhood.

Additions which greatly alters the shape of a house is not recommended. The aim of the design should be to allow the house to keep its original appearance.  The difficulty in designing and adding a larger side extension is that most semi-detached houses and many detached houses were originally designed to be symmetrical and by adding a large building to one side the appearance of the home is unbalanced and usually unattractive.

 When city planning permission is required for home additions the Planning Council in your state will take into consideration the following factors when deciding on its approval of your homes’ improvements.  It is important to remember that planning approval does not imply building regulations approval or vice versa, and work should not start on an extension or alteration until all necessary permits have been obtained.  If you are in any doubt at all whether planning approval or building regulations approval is required check with your local planning or building permits office.

Small front porches are often ‘permitted development’ for which planning permission may not be required (check with your planning Council) but, in a subdivision of identical homes, a badly designed porch can spoil the appearance of the entire street. 

The following  guidelines are based on three main principles:
(a) Taking in account of the appearance of the property being extended, and its surroundings.
(b) Respecting the privacy of the neighbors
(c) Avoiding unreasonable obstruction of sunlight and daylight to neighboring property.

Visual Effect
An extension should be designed to be in sympathy with the original building with carefully matched materials and architectural components.  Pitched roofed buildings should normally have pitched roof additions, especially important in the case of two-story additions. The size scale and shape of the extension should be compatible with the existing building and with the street scene.  An extension which increases the floor area of a dwelling by more than 50% will not normally be acceptable.

Effect on Neighbors
An extension should be designed to respect the privacy of neighbors and avoid windows that directly overlook neighbors’ windows unless separated by at least 21 meters.  The position, orientation and height of an extension should be carefully considered to avoid unreasonable obstruction of sunlight and daylight to neighboring properties.  Balconies on additions are often a source of annoyance to neighbors, and should not be considered if they would overlook or overlap other properties.

GENERAL APPEARANCE

Many homes were originally designed in a similar style to the immediate neighbors and changing the style of your home only for the sake of being different can devalue your property.  Variations of a style can be successful and often are constructed but a talented or at the very least a trained eye and mind are needed to visualize the final effect.  If you are looking for something different hire a designer that can create the appropriate and profitable environment both inside and out.  Factors to consider are the general shape and proportions of the house, the materials used, type of window and any special features.  These addition should be in harmony with the existing structure by either reproduction of elements or highly associative.  It is false economy to use cheaper materials from those used on the primary structure particularly if they will add to maintenance costs in the future. 

If you are considering a separate building on your property keep in mind that good quality matching materials and a durable pitched roof not only maintain the appearance and value of your property, but they are likely to be cheaper in the long run because of lower  maintenance costs.

 Example of this are:
“Georgian”-style windows can look completely out of place on a home with modern windows, as can a modern picture window in a Victorian terrace.

Size
An extension of modest size is much more likely to be acceptable, both for its appearance and from its effect on neighbors. If your extension will be closer 70 feet to your neighbor a permanent screen fence or wall five feet high is recommended to maintain privacy.
Scale
Problems can arise when a house has a much higher or lower ceiling than normal.  Additions with standard ceiling heights would appear out of scale.  In a large house the solution is to increase ceiling heights of the extension to match the original.  To match a small cottage, part of the roof space of a two-story addition is often used to achieve required ceiling height inside without affecting the external appearance. In some cases this technique may require special consideration when applying for the building permits.
Shape
Homes with pitched roofs: pitched-roof additions should be used in preference to a flat root because it is a reliable way to harmonize the proportions of the extension with the main house.  A pitched roof will improve the appearance should be used where no problem of overshadowing exists.

DORMER ADDITIONS

Adding light, modern high performance roof skylights can provide good living conditions at considerably less cost than dormers and they are also less obtrusive.  Adding floor space, a dormer extension can often be the cheapest and least obtrusive way of achieving extra floor space it is important however to make sure that your loft is high enough to fit new rooms.  If there is any doubt do not  attempt a dormer extension.

 EXAMPLES: Do not attempt a dormer extension if:

Dormer projects above ridge level.
The extension is much too large for the original house.
Lengthy dormers involving several windows alter a building’s roof-line and are not recommended.
Gable proportions and roof pitch are not compatible.
The extension will create an ugly gable.
New and old materials on the same plane may make an unsightly junction.
An unequal roof pitch unbalances the gable.

EXAMPLES: Dormer Additions are feasible when:

Dormers should be kept as small as possible, match the type and proportions of existing windows and line up with them. Keep gutter and fittings as small as possible.
Use pitched-roof dormers on older property.
The tops of dormers should be kept well below ridge level and set back from the front face of the wall.
You can line up the dormers with window beneath
The main roof finish should be repeated on the dormer cheeks to help the new structure appear part of the existing.
 

SINGLE STORY SIDE ADDITIONS

Match roof shape and set back from front.
This extension usually has the least effect on the appearance of the neighbors’ amenities.
if you are extending your home on the side give consideration to any principle windows which face the side of your neighbor’s property.

TWO STORY SIDE ADDITIONS

Careful matching can make an extension less obvious.  Use similar gable proportions, roof pitch and type of roof for the extension as on the main house, and try to match the roof construction, particularly at the eaves.  

Set back the front of the extension behind the front wall of the main house. This will help to avoid unsightly junctions of new and old materials which do not match exactly.

Arrange for the ridge of the extension to be slightly lower than the main ridge. This will ensure that the extension does not dominate the original house.

Two-story side additions can be unsuitable on streets where homes are very close together;  it create a terraced effect which can completely alter the character of the street.

Side additions should match the shape and proportion of the main house lower ridge line set back on front

SINGLE STORY REAR ADDITIONS

The overshadowing effect on neighbors
Rear additions can have a considerable overshadowing effect on neighbors’ property and can reduce sunlight and daylight into nearby windows. To lessen this effect, they should usually be designed so as not to project backwards more than 2.5 meters

If the extension will be to the north of the joint boundary, its effect may actually be beneficial to your neighbor.
It is worthwhile to work out the effects of your addition and discuss these with your neighbors at an early stage in the design to avoid any misunderstandings later.

If your neighbor’s windows are less than four feet from the joint boundary a single-story extension on the boundary may be very oppressive especially if there is a  kitchen or living room window. In this situation an access gap should be provided between the extension and boundary to give enough separation. There should be no windows of any sort on an extension wall situated on or close to a joint boundary.  Such windows to a habitable room that are not fire rated are usually not be permitted under most Building Regulations.

A large rear extension in a small plot may mean that there will not be enough property space for future occupants (for example for clothes drying, children’s play) even though the space seems adequate for your present needs. As a general rule no more than a third of a small rear property should be lost for an extension. In any event at least 300 sq. ft. (excluding garage or parking space) should be left as rear property.

TWO STORY REAR ADDITIONS

The same considerations apply to two story-rear additions as to single-story, with these added:

A two-story rear extension may be perfectly acceptable on a detached house, it is unlikely to be suitable on a terraced or semi-detached house where it could seriously overshadow your neighbors’ property or cause loss of privacy.

It is important to be sure that your house is sufficiently separated from houses opposite, usually at least 75 ft so that there will still be sufficient separation for privacy.

The separation of 2-story rear additions backing onto each other is particularly important where there are windows at first floor level facing down the property.

GARAGES

The design principles and illustrations of previous sections may also apply to the design of garages.

Garages should be set back behind the front building line to avoid their predominance in the street scene.

Garages fronting roads and footpaths should be designed to ensure that the door when open will not create an obstruction of the highway.

CONCLUSION

Every home addition project poses different problems.  The need for extra space is a special requirement of each family and the recommendations posted here are not intended to address all circumstances.

As mentioned in the introduction the help of an architect or experienced design professional is strongly recommended as all additions represent a large investment and mistakes are both costly and worse yet permanent.

The best test of a suitable extension is to ask yourself whether you would be happy to live next door to the extension that you intend to build and also to ask your neighbors what they think about the scheme.

We hope these recommendations will assist you in planning and building your home addition.  Everyone has a little architect inside them just remember to get a second opinion of your ideas before you start.