atal's Type C system is an internal groundwater management system. This is usually provided using an internal cavity drain membrane (atal Flo Board 508iR). The system relies on a cavity between the external skin and internal finish of the structure, groundwater is guided to an appropriate sump and pump system or a suitable drainage outlet with a non-return valve.
Our internal cavity drain membranes are available in 3mm (walls), 8mm (walls and floors) and 20mm (floor). Our 3mm and 8mm membranes are available with a mesh backing to provide a ‘key’ for renders, plasters, or Dot & Dab.
Although a Type C system can be used in high risk situations, groundwater should be stemmed to prevent the system becoming overwhelmed. The outer leaf of the structure should be capable of controlling the amount of water entering the cavity drainage system.
Where the walls or floors are constructed of concrete or masonry the substrate should be treated using atal Lime Inhibitor, reducing the risk of free lime leaching and obstructing the drainage system. Type C systems should be maintainable and inspected at regular intervals throughout the lifetime of the structure.
We specify a maintenance point every 10 linear metres of channel where possible, external inspection ports may be used on semi basement projects where ground gas is present. The first inspection should be within 3 months of project completion and every 12 months thereafter.
Our sumps and pumps are specified on a job-by-job basis. We expect to see one sump per 50m of perimeter channel. Once the expected flow rate into the sump is established the sump specification can be provided. Our pump systems are specified to industry best practice, this includes a suitable dual pump system (two inlets and two outlets), with high level alarm and battery backup. Depending on budget and project needs various upgrades to are available including telemetric systems.
If you need help or advice regarding any of the Type A, Type B, Type C Structural Waterproofing options for your project or property, please contact us on 01495 717202, or alternatively you can contact us online and one of our team will get back to you.