Whilst most of our projects involve designing new buildings, we are also regularly approached to undertake refurbishments / renovations of existing properties. Experience has taught us that despite initial appearances, depending on the scale of renovation, in some cases full demolition and rebuild would achieve a better outcome.   This article explains some of the reasons why.

Why renovate?

There are many reasons why people choose to renovate their existing home rather than sell and purchase another property better suited to their needs.   It is often due to a desire to stay in the same neighbourhood to maintain established connections with neighbours, community services, schools, transport infrastructure etc.   The purpose of renovating could be as simple as a desire to modernise outdated finishes. Or it may be more complex involving increasing the building size or layout to suit changed family circumstances, or to improve amenity and living conditions.

The Pitfalls

Major renovations often involve design compromises. Working within the constraints of an existing building footprint, structure and services can limit the potential to achieve the best design outcome. These are some of the implications to consider.


Most perimeter walls and often some internal walls perform an important structural role in not only supporting the horizontal roof load, but also in providing bracing to resist lateral loads from wind, flood, or earthquake. Modifying or removing these walls can impact the structural integrity of the whole house. The structural load of the house is then transferred via the walls to footings within the ground. Increasing the load on the walls and foundations by the addition of an extra storey, or by changing the roof material could require further strengthening of both the walls and the footings. Fortunately, many older buildings were constructed with oversize footings which can withstand some additional loads, however this would need to be confirmed by a structural engineer.

roof removal
Current renovation underway – roof removed to allow for the construction of an extra storey


Modifying the existing building footprint may necessitate extending rooms beyond the existing roofline. Depending on the complexity of the original roof shape, modifying the roof to suit the revised layout may be difficult and could result in the need to incorporate inferior drainage solutions such as box gutters, soaker trays and complex flashings, all potential sources of future leaks. The roof structure itself would also have been designed to suit the weight of the original roofing material. Replacing a lightweight metal roof with a heavier tiled roof is an example where it could necessitate replacing or upgrading the entire roof framing as well as potentially strengthening the walls and footings.



Most renovations require some modification to the existing services. The older the house, the greater likelihood that the existing services may need to be replaced or upgraded due to deterioration through age, damage caused by pests, or simple lack of capacity to service the new design.

Hydraulic Services

Apart from rainwater drainage, most household plumbing comprises hot and cold-water reticulation and wastewater /sewerage drainage. Whilst the mains water supply will be buried in the ground, water pipes within the home are generally located in ceilings and within walls, so can be readily exposed and modified. Drainage pipes, however, are normally located within or under the floor. Relocating these within a concrete floor slab will require the slab to be cut up and replaced with resultant damage to existing floor finishes. Wet area floors are also designed to fall to drains, so relocating these drains may also require the floor profile to be modified.

rebuild services

Electrical Services

As with water reticulation, power and lighting cabling is normally located within the roof/ceiling space and within walls. In older houses, it’s not uncommon to find that the protective insulation on existing wiring has been damaged by abrasion, or eaten by rodents, so in some cases disturbing the status quo can result in an increased risk of fire or even electrocution. Fortunately, electricians have methods of drawing new wires through existing conduits to minimise damage to existing walls and ceilings, so upgrading electrical services in a renovation is generally readily achieved with minimal damage to other materials.  Major renovations in some circumstances may exceed the capacity of the existing power supply. In those circumstances, the electrical switchboard and power source may need to be upgraded, or relocated. This can be a very expensive exercise.

Mechanical Services

Mechanical ventilation typically takes two forms in domestic applications. Exhausting or conditioning air. Exhaust fans used to extract steam, odours or smoke from bathrooms, laundries, or kitchens, or air-conditioning to heat or cool rooms within the home. The extracted air is either filtered and recirculated within the same room, expelled into a cavity within a ceiling or roof space, or ducted to the outside air. Consequently, modifications during renovations are generally simple to implement.

Air-conditioning heats or cools the air and recirculates it within an existing room or ducts it from one space to another. Successful air conditioning however, relies on the capacity of the system being designed to suit the volume of the space. Reconfiguring rooms during renovations may exceed the design capacity of existing air conditioning systems necessitating replacement, or reconfiguration of existing ductwork and associated air intakes and outlets.

renovation finishes
The proposed completed finish of the current renovation


The simplest renovations involve changing internal finishes without impacting structure or services. However, even changing finishes or making simple modifications to existing walls, floors or ceilings can have unforeseen implications.


Different floor finishes have different thicknesses and bedding requirements. As an example, replacing a relatively thin flooring material (vinyl) with thicker material (timber) may affect door thresholds. This could necessitate cutting down the underside of existing doors, or grading transitions between adjoining floor finishes to accommodate differing thicknesses. This is exacerbated where new floor finishes are applied directly over existing finishes, and in some cases may result in reducing the ceiling level to a non-compliant height. Skirtings which are designed to conceal the junction between floor and wall finishes can also be affected. Even the seemingly simple act of creating a new door or access opening in an existing wall can result in the difficulty of matching floor finishes in the new threshold. Even minor relocation of walls often necessitates replacing the floor finishes in the entire room because of the inability to match the existing finishes.


Whilst painted plasterboard walls are readily modified during renovations, walls with finishes like tiles present the same issue as floors in matching old with new. Replacing existing windows or doors in external walls is also likely to damage or destroy the window reveals, sills and architraves, necessitating repair or replacement.


Ceilings constructed of painted plasterboard can be simply modified and repaired by a good plasterer and painter, however matching other finishes can be difficult. Older cornices are often a different size to modern ones making them difficult to match, resulting in new cornices having to be fitted to the entire ceiling.

house demolition house completion
Demolition   Completion


The Benefits

In some circumstances, despite the pitfalls outlined above, a major renovation can be a better option than constructing a totally new building. This is particularly the case where the existing building enjoys planning concessions no longer supported by current legislation. This often allows for reduced boundary setbacks, increased building size or height, and floor levels below the designated extreme flood requirements. In those situations, retaining components of the original building can result in maintaining those concessions which would otherwise be relinquished constructing a totally new building. There is no guarantee however that this will be the case, and the advice of a Building Certifier and or Town Planner should be obtained to ascertain what could be supported.

The Cost.

Builders often find it exceedingly difficult to accurately price renovations due to unforeseen existing conditions that may only become evident once demolition has commenced. A common example is the discovery of asbestos within the existing building which would require costly specialist removal and disposal. Whilst a pre-construction site inspection should identify any visible asbestos sheeting used for roofing, walls, ceiling soffits etc, asbestos insulation concealed within walls or ceilings is often only discovered once construction has commenced with the potential to cause costly variations and time delays.

Consequently, if the project is being quoted as a fixed price, you can expect the builder to include a contingency premium to cover the risk of any latent conditions. If however the quote is qualified to reduce the Builder’s risk, then the client is exposed to the potential for variations during construction should any unforeseen conditions impacting the project become evident. Even if no latent conditions exist, often the time and cost associated with successfully marrying old and new building elements can exceed that of using totally new materials. It is also important to recognise that partial or selective demolition takes time and incurs labour and disposal costs that would not apply with new construction.

house demolition

Total demolition, on the other hand, is quite economical with specialist demolition contractors capable of delivering a totally clean site within days of commencing. A blank canvas to start anew without compromise.


The author has successfully renovated several of his own properties, winning renovation of the year for his first home. Every project is different, there is no one size fits all solution, so contact us today for an appraisal of your proposed renovation.

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