Why does it matter how steep the property is?
If you are planning to do a project on your site it will be more expensive the more steep it is, it may even mean that the site is unfeasible. It could also make it very difficult to make it accessible or design it so that you can age in place. Steep slopes in bushfire areas can also have higher bushfire attack level (BAL) ratings as the fire races up steep slopes. It is really important to know what your slope is before you purchase because it does have cost and feasibility implications. This is how to get contours so that you can determine what the slope is. Here are the different slope types:
- Gentle: Less than a 10% grade is generally considered easy to build on.
- Moderate: 11% to 20% is moderate, and costs start to rise beyond 15%.
- Steep: A site with a slope over 20% is often considered steep and requires a more complex design.
How to find countour lines in NSW?
- Click on six maps with Topo. Click on your site, this will zoom you out to the topomap for your area. This is a way to get a rough sense of the fall across the site, the best and most accurate way is to get a contour survey of the site.
- Download the topomap for your area.
- Zoom into your property. Have a look at the contours and work out how high each contour is, in this case each contour is 10m, this was found by looking at the contours near high points. In the site below there are 2 x 10m contours so there is 20m fall across the site. To find the percentage of fall, use this guide to find the site width. The percentage fall is the fall across the site is 20m/ Site width (in this case 40m) so the fall percentage is 50%, a very steep site indeed.
How do i calculate how steep my site is?
Site steepness percentage=
Rise or fall across the site (number of contours)
Site length
To find the percentage of fall, use this guide to find the site width.