External tanking drainage

atal realise that the most cost effective form of below ground waterproofing is external tanking.  Traditional methods using self-adhesive bituminous membranes are still relevant in the waterproofing industry but the various forms of Sodium Bentonite ‘blanket’ are currently in favour, due to their ease of use and self healing qualities.

External tanking not only provides protection to water ingress but protection to the concrete and steel from chloride attack.

As with all waterproofing membranes, lapping and detailing is the most important aspect, it is important to choose a membrane with secure laps and not just reliant on a bituminous tape.  When groundwater reaches a lap within a Bentonfix system on the outside of a below ground structure, bentonite clay within the lap expands to form a homogenous, self sealing system.

The recent changes to BS8102, the guidelines for below ground waterproofing, recommends that in high risk situations i.e. a full four-sided basement built within the water table, two levels of protection are used.  The code demonstrates three classifications of basement protection:

A. Barrier protection
B. Structurally integral protection
C. Drained protection

The code defines three levels of protection:

  • Grade 1 – Some seepage and damp patches tolerable, e.g. car park
  • Grade 2 – No water penetration acceptable, damp areas tolerable eg. plant room
  • Grade 3 – No water penetration acceptable. Ventilation, dehumidification or air conditioning required.

The most cost effective and reliable way to waterproof a high risk, Grade 3 basement is to combine classifications A and C.

All materials are warranted and come with a high level of service, including on site training and reported site inspections.  During our site inspections we ensure materials are installed as per details and data sheets thus eliminating the biggest risk associated with structural waterproofing – a poor installation.

atal Products Used…

Internal cavity drain systems

Internal systems can be used on both new and existing structures.  The structure should be capable of resting water ingress in order not to exceed the drainage capacity of the system.  A cavity drain system utilises high density studded plastic membrane to line walls, floors and ceilings where required. The studs ensure an air gap which allows water to be guided to a desired outlet or pump. A plaster finish can be applied or an internal skin can be fixed through the membrane by means of sealed plugs.


When a cavity drainage system is installed within a full basement a sump with pump is required to discharge groundwater collected in the system.  In all circumstances atal recommend the use of a dual pump system with high level alarm.  A battery backup system can be installed where a large quantity of groundwater is expected.  Sump specification should be so that the sump has the capacity to hold 24 hours of groundwater at the anticipated flow rate from the point at which the high level alarm is triggered, if this is not possible a battery back up system should be utilised.  Various add ons are available depending on budget and project specific requirements including, telemetric systems and generators for areas in which lengthy power cuts can occur.

Cementitious coatings and renders

The traditional method of tanking an existing basement would have been to use an SBR modified sand/cement render, a tried and tested method, that can only be as good as the preparation of the substrate.

atal recognise that preparation is key to a successful installation. Once preparation is complete we would always recommend using an elastomeric, cementitious coating, as the bonding quality is phenomenal and is also able to bridge any future cracking that may take place within mortar joints.

atal products used…

  • atal Flo Board 508i
  • atal Smentlastic
  • atal Lime Inhibitor
  • anti-Condensation Coating

Basement conversions

Basement conversions are a growing trend, as waterproofing methods and material technology have made cellar conversions affordable.  Damp, dark cellars can now be transformed into comfortable habitable areas.  Investing in a basement conversion does not require the rigours and cost of planning permission and is much more cost effective than a conventional extension or loft conversion.

The level of water ingress into the basement will determine the most appropriate system, whether it be a cavity drained system or a render/coating system. It is important to note, consideration must be given to drainage as a sump and pump maybe required. atal are able to design and complete basement conversions in their entirety to a finished specification.

Converting basements not only allows for more living space within a building but providing the work is of the highest quality, a below ground conversion can increase the value of the property.

atal basement conversions carry a 10 year warranty and a BBA certificate stating the materials used will perform for the lifetime of the structure.

The tanking element of a basement conversion should always be carried out by trained contractors.

atal Products Used…

  • atal Flo Board 508i
  • atal Smentlastic
  • atal Lime Inhibitor
  • atal Anti-Condensation Coating

Leak repairs

Leak detection and repairs can be carried out by atal.  Water ingress can be halted by various means and is a process of elimination.  Each leak needs to be investigated and rectified using a variety of methods.  atal will visit the site whether it be domestic or commercial at no cost for initial survey and provide a quotation for further investigation and potential works.  Please contact us to arrange a meeting to discuss your specific requirements at your convenience.

atal Products Used…

  • atal Aquaplug
  • atal KB Flex
  • atal Injection Resins
  • atal Smentlastic

Maintenance  and servicing

Maintenance of the internal cavity drain and pumping system throughout the lifetime of the structure is an integral part of the system’s performance.  This should be completed annually as a minimum.  atal maintenance services will be bespoke for specific projects.