Frequently Asked Questions

Delta Membrane Systems Limited has a dedicated team of Waterproofing Design Specialists.  Our trusted Technical Team offer knowledge and experience and are able to provide expertise in Structrual Waterproofing.  As a Waterproofing Specialist Manufacturer, we work with architects, surveyors, contractors and engineers alike to provide a design service which complied with BS8102:2009 and offers the highest level of technical expertise and assurance.

Our staff are able to provide assistance on projects of all sizes, whether you require some general advice about damp or waterproofing or support with technical drawings and specifications.

Almost all of the Delta and Koster range is available on a next working day delivery (Mon-Fri) if you order before 2:30pm (early deliveries available at an additional cost).

The sump must be provided with duplicate pumps together with UPS (uninterruptible power supply), usually consisting of an automatically trickle charged battery system. A high water level alarm is also essential, and if the property is frequently left unattended for long periods, then it would be wise to include a Telemax SMS messaging system for remote warning.

Please note that remote warning should also be considered for rainwater and surface water applications.

Small sheltered catchment areas up to 12m² (such as Lightwells or Stairwells) can normally be served by the same pump station that serves the cavity drainage system. For larger or more exposed catchment areas separate pump stations are advisable, and it is also important to ensure that adequate provision has been included to prevent internal flooding of the building in the event of a 24hr disruption, e.g. power failure. We will be pleased to provide further guidance if required.

The answer is yes but this is a risky strategy as you will be de-watering below the top of slab level as water enters into the chamber through the ring interfaces. Call us on 01992523523 and ask for our pump department for further advise.

No, we advise to keep these systems separate for the following reasons:

Blockages – if the Foul Sump blocks due to liquid fats and/or foreign bodies (wet wipes, nappies etc.) you can stop using the basement toilet and kitchen facilities and there is no immediate emergency and there should be no damage caused. The Groundwater/Surface water sump needs to be operational at all times otherwise if the mixed system blocks the build up of water behind the membrane system can back up into your basement causing significant damage which could be very expensive to rectify.

Foul smells – if a mixed system the smells from the foul system can travel back behind the membrane which can enter the residential parts of the basement.

Larger chamber – Deeper excavations especially in basements where there are water table problems can be more problematic and costly. It is often more economical to install two smaller separate chambers as opposed to one large chamber.

Heating and Ventilation: The environment in basements should be controlled by having balanced heating and ventilation to combat the small risk of condensation. All habitable rooms, kitchens, utility rooms, sanitary accommodation and bathrooms located within the basement, should follow the ventilation provisions of the Building Regulations 2000 part F1.

If the floor level is below street level and contains habitable rooms then it is usually considered sensible to incorporate a sump station. The pumped main should be arranged to form a back flow loop so that it is higher than the flood level. If the flood level is unknown, we normally recommend the invert of the loop is at least 300mm above the surface of the adjacent road. This will provide the best flood protection in the event that the sewer becomes surcharged (full and pressurised).

Please note that anti-flooding valves should only be used for flood protection when the rooms are of minimal importance and the occupants have access to other sanitary appliances above street level that do not discharge via the anti-flooding valve.

Delta have a nationwide network of registered installers. Please call 01992523523 or complete our contact us page and we will be happy to give you information on local contractors.

Where possible this is always recommended as the building is the first line of resistance and every attempt should be made thus reducing the work the internal sump is required to do.

See section 15.2 of our BBA certificates;
The concrete base must have a surface regularity with a maximum permissible departure of 5 mm from the underside of a 2 m straight edge, resting in contact with the floor, in accordance with BS 8204-1: 2003.

After carrying out a flood test to determine any depressions, and falls, they should be made good in accordance with Clause 15.4.  In any event ponding should be avoided.

Virgin HDPE tested to ISO 14/15 so they are pressure resistant and spun bonded so there are no joins on the chambers.

Structural waterproofing deals with a range of  below ground problems for example basements/cellars, underground vaults, tunnels, car park decks etc. Any structure that has retaining walls (walls that have soil behind them).

Damp proofing deals with problems at ground level and above.

The Delta PT has a thermicaly bonded mesh which provides a key for either directly applied plaster or a dot and dab thermal or plasterboard. The MS 500 is designed to have dry lining in front of it, either independent or timber battens screwed into the Delta plugs.

Virgin High density Polyethylene, it is not recycled but recyclable. Beware some similar looking products imported by other as these are often made from Polypropylene and can get brittle and crack below 5 degrees.

13 amp non switchable spur, ideally not off the basement ring main.

8 and 20mm

You can use our Delta PT-Lath meshed membrane to waterproof a lightwell