Ground Drainage Systems - Newton Geodrain Drainage Membrane
Newton Geodrain is a external drainage membrane system used to remove water as part of a managed water removal system, or as part of a waterproofing system where either the water must be romoved, as with sheet tanking, or where the structure needs to be protected from aggressive water.
Newton Geodrain comprises of a 6mm stud Cavity Drain Membrane with Geotex a filter fabric thermally welded to the studded face. The filter fabric allows water to pass into the cavity created by the 6mm studs, but will not allow fines or sediments to pass into the cavity. Any water entering the cavity immediately depressurizes and falls down to the perforated pipe (land drain or French drain) situated below internal floor level, which in turn drains the water away to a suitable safe drainage point. The filter fabric should continue around the perforated pipe protecting it from fines and sediments also.
The Problem
Waterproofing new build cellars and basements has always been a difficult proposition. Conventional barrier tanking will fail unless the barrier is 100% defect free. In a recent landmark judgment (Outwing - v - Thomas Wetherald) it was argued that it is unreasonable for the system to be 100% defect free. A barrier system that is not 100% defect free will fail if subjected to water pressure from the surrounding ground. Even a land drain cannot effectively deal with perched or trapped water higher up against the retaining wall. With the rise in local water tables, more and more basements are being subjected to hydrostatic pressure - do you want your project to fail the test?
Where aggresive elements exist within the water, these can be damaging to the new concrete structure. Newton Geodrain isolates the water from the structure and also maintains safe water levels when used as part of a managed and safe drainage system.
The Solution
Newton Geodrain is a cavity drain membrane system specifically designed prevent water build up and water contact to the structure, and so is ideal as a means of reducing water levels where the structure needs to be protected against high water levels or aggressive elements within the water.
Newton Geodrain is strong and flexible and is so quick to install; a large basement can be waterproofed in just one day. The welded filter fabric is more secure and will not de-bond as easily as 'cheaper' glued alternatives.
Newton Geoprofile caps the Geodrain at the top of the retaining wall to give a neat and tidy finish to the installation.
Newton Geodrain should always be used as part of a designed and maintainable water management solution, and should always include a perforated pipe such as Newton GeoPipe below the level of the internal floor slab/raft. The perforated drainage pipe should have jetting eyes included at all changes of direction and should terminate into safe drainage only. Note: Any form of drainage that can 'back-up' is not safe. A common mistake is for the system to drain directly to the storm water drainage system, but when this backs-up in periods of heavy and sustained rainfall, the water from the ground drainage system has nowhere to go resulting in a rise of water around the structure.
Safe forms of drainage are:
- Soakaways or piped drainage downhill of the internal slab/raft level.
- Pumpeed drainage.
- Systems with pumped backflow protection devices.
Photo Caption: Newton Geodrain installed over applied bitumen sheet tanking terminating to a perforated land drain wrapped in geotext fabric. Note: see rodding points at major changes in direct.
Photo Caption: Protection Board applied to the front face of the Newton Geodrain as protection prior to back fill.
Protection board in front of geodrain prior to back. Photo's courtesy of NSBC contractor Protectahome Ltd.
Photo Caption: Back fill to complete project!
Geodrain as a waterproofing system
Geodrain should be used only as either as part of a water management system or where other forms of waterproofing are included in the design, as we do not recommend that Newton Geodrain be used as a stand-alone waterproofing system. Our internal drained cavity waterproofing systems are both safer and easier to install. See our Technical Guidance Note Internal V External. If you are considering using Geodrain to remove water from an external sheet tanking system, please consider points raised within this document or speak to our Technical Department first.
Application - typical basement construction
Newton Geodrain can be installed to walls only.
Advice on application
- A fillet should be formed where the basement wall meets the footing.
- Geodrain should be fixed in the top row of studs at 250mm centres.
- Place Newton GeoPipe footing drain 200mm below basement floor level.
- Geoprofile should be used to cap the top of the membrane at ground level.
- Extra Geotex fabric will be required for wrapping of the perforated pipe.
- Protect the Geodrain with backfill protection board.
- Use a well drained backfill, and protect the backfill with Geotex filter fabric.
- Slope ground away from retaining wall where possible or drain well.
- Allowance should be made for jetting/rodding points at each change of direction, and if posible, an inspection chamber at each corner.
- Connect GeoPipe to efficient safe forms of drainage as highlighted above.
Geodrain, as mentioned above, is a water drainage meduim and should be used as a belt and braces approach to structural water proofing. For technical guidance on the advantages of internal vs external structural waterproofing please visit our technical guidance area by clicking here.
