The Joys of Challenging Sites
All sites have some difficulties to deal with, but most that we regularly encounter have more than their fair share.
The good news is that the challenging sites always result in interesting houses.
We can give you pre-purchase advice if you have concerns about a site you are considering.
Here are some of the issues we have encountered:
Fires in recent times have made building on affected sites a hot topic ( no pun intended ), and I have heard a lot of uninformed debate in the media.
About half of the houses that I design are on sites classified as bushfire prone . This is partly a reflection of the interesting projects that I get to work on, which are often near reserves or in bushy areas, but also because of new Australian standards that have resulted from catastrophic bushfire incidents in the last couple of decades. Typically the first step in the process is to engage an accredited bush fire consultant who will evaluate the site and provide a BAL ( bushfire attack level ) rating. These come in several categories – BAL 12.5, BAL 19, BAL 29, BAL 40 and BAL FZ ( flame zone ) – note BAL 29 = 29 kw per M2 of radiant heat. Most sites have 2 different BAL ratings, as the rating decreases with distance from the fire source, and orientation of the house.
For each level, there are construction rules to be complied, and predictably, they become tougher as the BAL level increases. Generally it is easy to comply using readily available materials, and with negligible compromises to the design.
Windows and doors that have been tested and certified for the higher categories are coming onto the market at an increasing rate, thus providing more design options. Generally complying houses look exactly the same as houses on unaffected sites, but building in the flame zone will add costs.
So in summary, this is one more hurdle to be jumped on the way to Council approval, but generally it is easy to deal with the correct procedure and attention to detail, and definitely for a worthy cause.
It is now common practice around the coast of Australia, and particularly in the Northern Beaches of Sydney for new houses to be built on steep sites that a few decades ago would have been considered to be structurally and economically unifiable.
In fact it was not uncommon for banks to refuse mortgages on these sites due to the Geotechnical risks.
Three major changes have occurred since those earlier days, so that these properties are now highly sought after.
The first major change is improved awareness of Geotechnical, Civil and Structural Engineering issues and construction techniques. A Geotech report is mandatory on any site considered to be at risk. The Geotech Engineer is obliged to thoroughly analyse all risks associated with the site, including hazards further up the slope such as unstable boulders and slopes, failing retaining walls etc, and recommend the footing design for the house, and remedial action for the external hazards. Once the project has been completed, the site is often much more stable than it was in its’ original state. The Geotech Engineer also plays a strategic role during construction, inspecting the site during excavation, and fine tuning his recommendations as required. More sophisticated and flexible excavation machinery has been developed by the construction industry in response to increased demand.
The second major change is increased land values. Steep sites that may have been worth $10 to $15,000 in the early seventies can now be worth millions, well and truly justifying the extra building costs. Most of these steep sites have spectacular views, and those views themselves have been increasingly valued by our society.
It is essential when designing houses for these sites to incorporate large balconies, as there is generally no usable level garden area.
The resulting houses can be wonderful places to live, with excellent views, balconies amongst the tree tops, and little or no garden to maintain. The steep topography usually means 3, 4 or even 5 floor levels, so virtually all the rooms can take advantage of the views.
Many of our coastal projects receive a belting from prevailing winds. This requires additional strengthening for all parts of the house ( eg windows and doors ), and careful design considerations as outdoor areas facing the ocean will be unusable once the sea breeze kicks in.
Whenever possible we incorporate an alternate protected outdoor area – see the Milpete house in the project gallery, or locate the main outdoor area on the lee side of the house with lots of glass to maintain access to the views through the house – see the Steven house.
Low lying sites on or near the water are often classified as flood prone, so it’s necessary to design the ground floor at a minimum height determined by the Council or a flood study.
The ideal site faces north to rear and that is also the direction of the best views. This is a very rare combination, so clever design is required on for the rest.
Facing south creates winter solar access problems which can be overcome by adding north facing highlight windows to the main living area – the Wallich house in the project gallery is a good example. The highlight windows will also let in the cooling summer breezes.
Facing west obviously creates summer afternoon issues, but a wide veranda roof with drop down blinds can deal with this, and in winter the sun is always welcome, and the sunsets are there all year round.
The narrowest site that we have dealt with was just over 9m wide, and was also only 316 m2. This is the Hoppe Davis house in our project gallery. The first step was to design a tandem garage ( one car behind the other ), which allowed space for a wide hall to provide long views from the foyer to the back yard, creating a feeling of spaciousness.
The secondary bedrooms are on the same side of the hall as the garage, while narrower rooms such as the laundry and bathroom are on the other side. The family room is at the rear and is the full width of the building.
The top floor contains the main living area and the main bedroom etc, with generous balconies attached to both. High ceilings and highlight windows also add a feeling of spaciousness.
No part of the house feels small or cramped.
Heritage listed buildings
Occasionally we are asked to design alterations and additions to an existing heritage listed house. The listing comes with a lot of restrictions which can limit design options considerably. However with the assistance of a Heritage Consultant, and thorough detailed negotiations with the Council, an acceptable solution can usually be achieved.
The Allen house in the project gallery is a good example. We added a second pavilion behind the existing dwelling and linked the two structures with a wide hall. This involved minimal change to the existing house as viewed from the street, so the heritage requirements were satisfied.
New houses in conservation areas will also be subject to strict streetscape controls so that they blend in with the established architectural character.