OSD Design in Sydney: Your Simple Guide to On-Site Detention Requirements
OSD design in Sydney is something that surprises many developers and homeowners. This often happens right when they want to get their construction certificate approved. In most parts of Greater Sydney, on-site detention is something you must do for building projects. If your engineering drawings do not show a well-planned OSD system, councils and certifiers will just send your application back. The good news is that OSD design in Sydney can be easy if you get the right engineer to help you.
RI Engineering has made OSD systems for many types of projects in Sydney. These projects range from single homes in Mosman to buildings with many units in Parramatta. All of these projects got approved the first time they were sent in.
Why Is OSD Design in Sydney Mandatory for Most Developments?
Sydney built its stormwater system many years ago, when most ground could soak up water. But now the city has grown, and there are more hard surfaces like roofs, driveways, footpaths, and car parks. This has put more stress on the drainage system. OSD design in Sydney is a solution that councils took up to help with this. Each development must now hold its extra water for a while and let it out slowly. This controls how much water goes into the public system at one time and helps stop flooding further down.
Every OSD design in Sydney should show that the water flow from your site after work is done will not be more than it was before for the main storm events. Our engineers use DRAINS modelling to work this out. They also size your detention system the right way.
What Does an OSD System Look Like on a Sydney Property?
For most Sydney homes, an OSD design in Sydney will give you an underground tank made out of polyethene or concrete. This tank sits under your driveway or garden. It connects to the roof and surface water pipes. The tank has a small opening, like an orifice plate or a pit with slots, that lets water out slowly.
When there is heavy rain, the tank fills up. It then slowly lets the water out over several hours. You do not see it working, but it helps keep your neighbours safe. It also looks after the council drainage system.
How RI Engineering Delivers Your OSD Design Sydney
We take your site survey and look at your council’s OSD rules. Then we use the DRAINS model to make full engineering drawings. These show tank size, where water goes in and comes out, and how the overflow will move. Our OSD design Sydney packages have everything you need in one place. Your certifier gets all the details to give the CC. You do not need to send any other info.
Frequently Asked Questions
Q: Does every Sydney council require OSD?
A: Most councils do this for projects that add hard surfaces like pavement. Some councils in the city look at each project one by one. RI Engineering will check what your local council needs.
Q: How long does OSD design in Sydney take to complete?
A: It usually takes about two to four business days after we get your survey data. If you need it quickly, urgent work can be done—just ask us when you call.
Q: Where is the OSD tank on the property?
A: Most of the time, it will be under the driveway or in the back yard. This helps you get the most from your space. Our design will show the best spot for your site.
Q: Can OSD design be used with a rainwater tank for BASIX?
Yes, you can use the OSD design along with a rainwater tank for BASIX. A rainwater tank will help you save water by collecting water when it rains. OSD design is for helping water flow leave your property in a better way. When you use both together, you can meet BASIX rules. This also helps the home and the environment.
A: Yes, these types of designs can meet both OSD and BASIX rules at the same time in some Sydney councils. We can check this for your project.
Q: Do I need a new OSD design if I add more to my house in the future?
A: Yes, in most cases, adding more hard surfaces will change the OSD numbers. RI Engineering can help update your design in a fast and good way.
📞 Get your OSD design in Sydney sorted today. Call RI Engineering on +61 0451 452 932 or email riengineering2155@gmail.com — fast turnaround, first-time approvals, every time.
