Water, Fire, Access, Power, Slope, Excavation, Vegetation, Sun, Wind, Views, Aspect. These are probably the main considerations when thinking about siting your house. Mind you there are plenty of others like privacy, noise from the motorbike next door, road dust, and stroppy neighbors although one usually doesn't find them out till after one has stepped on their toes.
Water is the primary consideration for all house sites. If you have not already decided on the type of supply needed, this is the next step. If rainwater storage will meet your requirements your choice of site will not be limited by water. But keep in mind that if your proposed site is fire prone, emergency water may well be a major consideration. If however you anticipate pumping water, then the distance from and height above the supply should be considered.
If grid power is available at the pump site it is a cheap method to lift water up to 40 meters. Otherwise a centrifugal pump, the most common being a firefighter style petrol pump, although a little noisy, is the next practicable alternative.
A fire fighter will lift 10,000 litres 40 meters, through a 40mm diameter pipe, in about 1 hour. Depending on size an electric pump will move a similar amount.
If a greater lift height is required then a "force pump" may be in order. These take various forms, the most common being a piston pump that forces water up the delivery line. Although it will move considerably less water than a centrifugal pump, the lift height is limited only by the power of the driving motor and the strength of the delivery pipe. Other forms of force pumps include gear pumps (most commonly used for moving oil within machinery) and diaphragm pumps more commonly used for moving matter somewhat thicker than water.
Most major plumbing supply and farm produce shops in rural areas will have a rural water supply consultant who can give you a realistic view of your requirements. Make sure they do know what they are talking about and are not just trying to sell their product. All pump manufacturers supply detail sheets which will give the pump's performance ratings for various factors such as suction lift (height of pump above supply), head (vertical height above pump) and diameter of suction and lift pipes. Buy a pump that will cope with all your future needs. The extra amount spent on the right pump now will save a lot of time and extra expense of changing later. This applies to installing pipelines as well. The cost difference between say 1" and 1,1/2" poly pipe is minimal compared to the amount of water that will travel through the pipe. A fire fighter pump will shift less than half the amount of water through a 1" pipe compared to a 1,1/2" for the same distance of pipe.
Note; Most rural councils now require that you, the owner, maintain fire truck access to your water tanks and provide appropriate fittings to allow the brigade to take your water!
Your water needs resolved the proposed site should next be assessed for the risk of fire. This is an omnipresent factor and must never be disregarded in the set up of a new site or when building or remodeling an environment for an existing structure.
Bushfire has a knack of sneaking up on the unsuspecting even, as events of the last decade have proven, in urban areas. What in normal times may appear to be a lush Eden may, in times of drought or sustained hot dry weather, become a major fire hazard.
As mentioned in the last issue, a visit to the local fire authority will help you decide on many of the factors that will effect your proposed site. Keep in mind that the advice you are given will probably err on the side of caution and not without reason. But also be aware that creating a desert for 100 meters around the house is not the best way to control fire hazards on your site.
There is plenty of literature available on the built environment, not the least of these being on the Permaculture system. There is a large range of fire retardant trees that may be used to protect your house from fire danger sectors. Many of these are deciduous and most are exotic however their employment in these situations can be extremely beneficial. Careful planning for the use of fire retardant vegetation will allow you to consider a site that is potentially a fire risk.
From a fire point of view, it is safer to build at the bottom of a hill. However there could be drawbacks to this. High hills limit sunlight hours and restrict summer breezes.
Building above a steep vegetated slope creates a major fire hazard in dry conditions. However by setting the house back behind an earth berm and using fire retardant species on the slope below, the risk of fire damage can be markedly reduced without losing other benefits of the higher site like view, sun and breezes.
Access to the site from your front gate is important and should be built in to the whole equation. The frequency of use will decide the quality of track required. However when building you should keep in mind that a variety of heavy vehicles will need to use the track. If it is not up to scratch then the bill for recovery costs of a wayward concrete truck may well land in your lap and could indeed exceed the initial cost of a well-prepared access road to the site.
The gradient of the driveway should not be too steep as this will create heavy wear from wheel spin and make the surface difficult to maintain. Water erosion is the most damaging factor in maintaining driveways. If a road is well cambered and kept dry, and rainwater runs off into properly built table drains the damage and maintenance will be minimised.
If you are building a new road to the house site it should be well constructed to start with. The grass should all be removed first to at least 3meters wide. Then the soil cambered up a minimum of 300mm high in the centre to shed water to the sides as quickly as possible. The graded surface should then be topped with at least 100mm of coarse gravel and rolled in well to give a longwearing surface.
Although this is generally a contractor field, many driveways have been built using a humble Fergie with a dump carryall and grader.
Get a quote for this job. Although initially expensive, a well-built drive will save many hours and $ in repairs to both the road and the vehicles using it, to say nothing of reducing the environmental damage caused by erosion.
Power supply is probably a decision that has already been made for you. Most sites have access to the grid, but when deciding on your house site be aware that the initial cost of power is a big outlay. If power to the preferred site is going to cost $1,000 or $2,000 more then it may well be worth paying the extra cost to get where you want to be. The local power authority will be able to give you a quote for the cost of grid power to the site you want.
If you are "going solar" then the only limitations will be trees or bad weather.
Check your weather patterns and try to get an assessment of the average sunlight hours for your area. It relates directly to the amount of power you will collect from your panels.
Make a careful assessment of existing trees and determine if they will shadow your house or panels at any time of day. It is critical that panels are not shadowed, as every photon of sunlight is precious. Be aware that young trees, especially eucalypts, grow very quickly and within a few years may be casting much longer shadows and be difficult, or against the law, to move. Similarly plant trees that will not grow above the shadow lines you set out for your site.
There is a lot of good information available on this in Permaculture design and other solar design books and magazines, including earlier OB's.
The Slope of the site will determine many factors in the design of your house. The best aspect for good solar design and a thriving garden is a gentle slope to the north. But with all the other considerations needing to be taken into account, congratulations if you end up achieving that as well.
The style of house that you would prefer will have a bearing on the amount of slope that you can tolerate. If you like an elevated house on piers or poles then the slope may be up to 180 or 1:3. Anything greater than this becomes very difficult to work on and could have expensive foundations. Council will require engineers' details and the engineer will ask for a Geotech report to ascertain whether the ground is stable to build on. A gradient greater than 260 or 1:2 is too steep, and it would be down right irresponsible to disturb this ground in any way.
You can measure the slope of your site with a long straight board 2 or 3 meters long, a spirit level and a tape or ruler. With one end on the ground, elevate the board till it is horizontal and then measure the vertical height of the other end above the ground. Continue this process across the whole site. Multiply the number of spans by the length of the board (say 6 x 3 meters = 18meters) and divide it by the total of the vertical measurements (say 3 meters). The slope will be 1:6 or about 70. If this doesn’t sound steep remember that a level floor 9 meters wide will be 1.5 meters above ground on the low side. If a concrete slab or paved floor is contemplated then a great deal of fill or extensive excavations will be in order.
Excavations always traumatize the site no matter how small. The disturbed material will become fill so the greater the excavation, the greater the amount of fill that will have to be disposed of. When building a house the foundation material (ground supporting the footings) must be undisturbed. The entire house must rest on solid ground. If you want to build over fill then the footings must be cut or piered through the fill into the original ground. This can become expensive very quickly and is best avoided wherever possible.
Reactive clay soils (soils that expand and contract in wet or dry conditions) are problematic when digging foundations and it is important that all the footings rest on a similar soil type. If parts of the footings are resting on reactive soil and part on rock or stable shale or sand, subsequent changes in soil moisture will cause the reactive soil to move and exert massive forces on the footings. If they are not strong enough, cracking will occur which will effect the whole structure to some degree. Generally some cracking will occur when building on reactive soils so minimising foundation movement is very important.
Excavation work will also change the water table in the immediate vicinity and so foundation soil moisture content must be stabilised at as low a level as possible. Good drainage is critical to ensure no surface water runs under the building. The back of the excavation (deepest part) must have an open drain at least a meter wide for the full length of the cut. The drain will take surface runoff or ground water seeping from the cut to the sides of the excavation, preventing it flowing under the building. In any building work even without excavation, all foundation material should be kept well drained and dry at all times. High soil moisture content also provides ideal conditions for fungal decay and termite development under buildings.
Aspect is often ignored in the building of homes. There seems, even in country situations to be an overriding need for the house to face the street or the main road. Why? Is the road the most interesting aspect of the site. What is the point of siting the house for the sun or the view then turning your back on them.
In our growing world energy crisis we should be going all out to maximise the use of natural energy available at our site. Simply orienting the house to maximise heat gain in winter and stay cool in summer will reduce heating and cooling power costs enormously. Well-designed solar houses can obviate the need for any extraneous heating or cooling.
The basic principals of solar design are very simple. In the South Temperate Zone the sun's path in summer is generally from east to west over-head. In winter it is well down across the northern sky. By facing the longest side of the house to the north we can expose the largest surface area possible to the winter sun. By having plenty of glass and/or high thermal mass materials like earth walls, masonry or concrete to the north we can absorb a great deal of the sun's energy radiating throughout the day. In summer the sun is high enough that a normal 600mm to 700mm eave will prevent any direct sunlight falling on these walls. Walls to the east, west and south generally should be well insulated and have eaves and verandahs designed to minimise exposure to summer sun. This does not mean you cannot have windows and large sheets of glass on these walls but if you do, insulation by use of heavy drapes or double glazing will reduce heat loss in winter markedly. Deciduous vines on pergolas will shade the ground around the house in summer reducing reflected heat absorption into the house.
Of the plethora of books and pamphlets available on the principals and practices of good solar design, beware of those who say, for example, "you must design in a certain way" or "you can't have windows facing west." If the best views are to the west then why destroy the view for the sake of a purist design? If you want a large sheet of glass to the west, attach a verandah or plant shade trees and deciduous vines to protect it from the summer sun and use heavy curtains in winter to keep the heat in.
Vegetation can be incorporated into basic solar design with great effect. By using deciduous trees and vines to the north, summer heat and glare is reduced. Winter sun is admitted when the leaves fall and the sun's arc is lower. Large amounts of green shrubbery will help to moderate the temperature in the immediate vicinity of the house. Use fire retardant species to help shield the house from bushfire. (Lists are available from some nurseries, forestry and some fire control departments)
Large or tall trees further away from the house will break up wind but still allow breezes through and can be used to the west to reduce heat from late afternoon summer sun. Tall trees can provide shade and still permit views. Shrubbery and trees also provide habitat for small birds and animals that help keep insects and spiders under control.
When planting consider all aspects of the site requirements Always try to ensure that the trees and shrubs you are planting will not outgrow their position and throw unwanted shadows or become a hazard and difficult to remove.
Finally, throughout all this decision-making be aware of your neighbours. They, sure as hell, will be aware of you. Try not to impinge on their space or views. Let them know what you intend to do and try to fit in with any requests they make. In most areas council will provide the neighbours with opportunities to object at development consent stage and so it is far better for them to be aware beforehand of your project. A good relationship with your neighbours is important. More often than not they will provide helpful information or just down right practical help as well as contributing to the overall benefits of the site you have selected for your home.