Car Park Drainage & Sub-Soil Upgrade – North Turramurra
Our team recently completed a car park drainage upgrade at a property in North Turramurra after ongoing groundwater seepage began affecting the rear wall and concrete surface. Water was pooling along the back section of the car park, especially during heavy rain, creating slip hazards and long-term structural concerns.
Groundwater movement behind retaining walls can slowly weaken concrete and allow moisture to penetrate through surfaces. If left unresolved, this can lead to cracking, damp issues, and gradual deterioration of the surrounding structure.
To resolve the issue, we upgraded both the surface drainage and installed a below-ground sub-soil drainage system to properly redirect water away from the building.
Channel Drain & Surface Drainage Installation
We began by measuring and cutting sections of the existing concrete car park floor where runoff was collecting. A sand-cement bed was prepared to create a stable base for the new drainage.
New channel grate drains were supplied and installed along the longer rear wall where seepage was occurring. To ensure proper discharge, we core-drilled through the wall to create a new outlet connection to the existing stormwater system. The channel drains were connected into the downpipe line and existing drainage network.
After installation, the concrete sections were re-formed and re-poured. All channel drain edges were sealed with outdoor silicone to ensure a watertight and durable finish.
This portion of the project falls under our broader Stormwater Drainage and Channel Drain Installation services.
Sub-Soil Drainage & Waterproofing System
To address the underlying groundwater pressure, we excavated approximately 16 metres of trench behind the rear car park wall. The trench base was carefully prepared to achieve the correct drainage fall and gradient.
Builders plastic (core flute) was installed along the trench walls to protect the waterproofing layer. Two coats of waterproofing membrane were applied to the wall and footings below ground level to create a strong moisture barrier.
We then installed PVC main drainage pipework along the trench and connected sub-soil drainage lines into the system at multiple points. Inspection openings were added to allow for future maintenance access.
The trench was backfilled with 10–20mm aggregate to promote effective groundwater flow. The sub-soil drainage outlets were connected into the existing concrete stormwater pit, with all penetrations securely sealed.
These works fall within our Sub-Soil Drainage, Groundwater Management, and Car Park Waterproofing services.
In more severe cases, prolonged groundwater pressure can expose damaged pipes or structural failures. When this happens, we may recommend additional services such as CCTV Pipe Inspection, Drain Cleaning, No Dig Pipe Repair, or Pipe Relining. Fortunately, in this North Turramurra project, the drainage upgrade resolved the issue without requiring major pipe repairs.
All works were fully tested and commissioned to confirm correct operation. The site was cleaned thoroughly and left ready for use.
If you are noticing water pooling in a car park, damp retaining walls, or signs of groundwater pressure around your property, early action can prevent larger structural problems.
Call 048 391 5451 to speak with our drainage specialists today, or click Book Now to arrange a professional site assessment.
