To complete the project like that you are going to need a Petrol High Pressure Cleaner Machine (3000 psi) to achieve the best result. Pressure Cleaner Machines (3000 psi) can be hired from many companies on a daily bases. It is worth hiring a machine and get a better result then purchasing some cheap pressure cleaner at your local store. They are powerful machines and were designed for projects like that. It could also save you some time if you are working with a professional pressure cleaner machine. The pressure cleaner has to be at least 2600 psi. If it is less then 2600 psi you will not get the required result. Also keep in mind that you do not use more then 4000 psi because it may damage the surface.

Before you start make sure that you remove any items that would be in your way. Also remember to shut all the windows and doors. If you have mildew, mould, moisture on the surface, the first thing to do is to clean the area with a mildew / mould / moisture killer product. There are various products available on the market today. Simply spray the product on the area and wash it off with a garden hose or pressure cleaner. When you are ready simply start the machine and start with the guttering and fascia. Pressure wash any eaves, exterior ceilings and walls. Work your way from top to bottom. Be careful around the windows, doors and lights, try to avoid any flood. It is also important that you do not go really close to the surface as it may cause some damage. Simply go around the building and pressure wash all exterior surfaces. If you have weather board walls be careful on the areas where you have the gaps between the boards. If the weather board is in poor condition do not use the pressure cleaner on the surface as it will damage the boards. Do not point the pressure cleaner to anyone or breakable items. Windows could easily break in seconds so try to avoid hitting them. If you are cleaning wood, be careful not to point the gun into one spot for a long time. 

If you have a two story building, simply use a small step ladder or mobile scaffold to reach the higher parts of the building. They are also available to hire on a daily or weekly bases in case you do not have any. Never use the pressure cleaner on an extension ladder. It is not safe as you have to use both hands for washing.

Once you pressure washed all exterior surfaces including the fence, you can pressure wash the driveway or any pathways you may have around the building. Please have a look at the following DIY Guide to see how to pressure wash the driveway and how to remove the oil stains: Driveway Cleaning