Waterproofing - BS 8102:2009 The Protection of Below Ground Structures Against Water from the Ground - Delta Membrane Systems Lt


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Welcome to Delta Membrane Systems. Delta systems provide the world's foremost range of products for drainage waterproofing and underground wall protection. One of the largest manufacturers of cavity drain membranes in the world. Delta is recognised as the UK's market leader in cavity drain waterproofing systems. They are the UK arm of Dörken GmbH & Co. KG.


This RIBA approved online CPD presentation will take approximately 30 minutes which will conclude with a questionnaire. Successful completion of this will entitle the participant to a CPD certificate.


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The talk aims to explore waterproofing and in particular the use of cavity drain and air gap membranes, in a variety of different situations, from domestic basements and listed buildings to the London Underground.


Delta Membrane Systems Company Philosophy

Delta membrane systems are the UK partners of Delta Dörken GmbH, a family led business which dates back as far as 1892. Being a medium sized enterprise Delta membrane systems have an organizational structure that is clear cut and uncomplicated, giving us an unusual degree of flexibility for responding swiftly to market conditions and dependably realising the wishes and objectives of our customers.


The success of customer relations is always based on product performance. However, in our opinion it is not enough simply to deliver a range of high quality innovative products, at the right time and place. Consequently our comprehensive portfolio of branded products is backed up by a varied range of services, including: meaningful technical documentation, standard requests for tender, training courses and on the spot advice on application technology issues.


Delta systems can easily deal with aggressive groundwater conditions where basements and below ground structures are liable to flooding; or indeed where simple dampness contamination or salting problems are prevalent in above ground structures.


Other more diverse applications include turf covered roofs, barn conversions, tunnel linings or even as a barrier against radon gas. Delta systems have been used on some 30 London Underground stations. 70,000 square meters of Delta Ms have also been used in the Channel Tunnel. Delta protects property saves energy creates comfort.


BS 8102:2009 - Code of Practice for The Protection of Below Ground Structures Against Water From the Ground.

We will now take a look at the standard BS 8102:2009 that governs the waterproofing industry. BS 8102:2009 is the code of practice entitled The Protection of Below Ground Structures Against Water From the Ground. This document replaces CP102:1973 and should be of utmost consideration when designing a waterproofing system.


Other documents include the approved document and the concrete Association guidelines however BS 8102:2009 is the benchmark standard and is used as the leading document in the case of poor waterproofing design and litigation.


Key considerations for BS 8102:2009 

Key considerations under BS 8102:2009 when consideration is given to the waterproofing of a structure include:

  • The three forms of waterproofing construction, referred to types A,B and C.
  • The evaluation of groundwater conditions soil gases and contaminants.
  • The requirement for an integrated waterproofing solution between the design team and manufacturer.
  • The consequences of less than adequate workmanship.
  • Consideration to the form and feasibility of the design.
  • It should be a maintainable waterproofing system.


Forms of Waterproofing Protection


Type A - Tanked or Barrier Protection

Tanking can be applied in new build construction and refurbishment, with new construction the structure itself is constructed from concrete or masonry and offers no protection against the ingress of water and water vapour by the nature of its design. Protection is therefore totally dependent on a continuous barrier system applied to the structure.


With new build tanking can be applied externally, positive side waterproofing; or internally, negative side waterproofing. Or even sandwiched in construction when we consider new build for example, we take guidance from the British Standard Section 8C. Barrier protection should be based on the evaluation of the ability of the barrier system to accommodate movement within the structure.


Internal tanking, negative side.


Here we have two typical tanking failures in the picture on the left and Asphalt tanking system has been selected. Water pressure has come to bear and found weakness. Consequently the tanking has debonded from the structure.


In the picture to the right a cementitious tanking approach has failed due to construction joint failure. Construction joint failure can occur through dynamic movement within the structure bending stresses in the walls and flotation forces within the slab. Often tanking is only as good as the sum total of the structure it is applied to an should be of utmost consideration. Kicker or construction joint failure is common in both types A and B waterproofing.


Type B - Structurally Integral Protection

Waterproof concrete for example designed and constructed in accordance with BS8110 or BS8007 to form a water resistant shell, dependant on the chosen grade of basement usage.


Section 921 of BS 8102:2009 states one of the following factors should be considered as being of particular importance in achieving a water resistant concrete structure and thus should be taken into account.


B the quality of workmanship in preparing and placing concrete.


It is of utmost importance to avoid contamination within the construction joints during the pour process. Often this leads to construction joint or kicker joint failure which is undetected until such time as the water table rises and finds weakness within the construction, day or kicker joint.


When failures of this form of waterproofing occur, often it is necessary to carry out post-remedial work in the form of injection resins and crack injection work, which can be costly when consideration is given to disturbance of finishes.


Guarantees for this form of waterproofing often do not cover consequential loss.


Type C - Drained Cavity Protection

Type C construction is constructed from structural concrete including diaphragm walls or masonry to minimise the ingress of water and any water which does find its way into the basement is channelled collected and discharged within the cavity created by the addition of an inner skin to the walls and floor.


Here in the picture on the right Delta MS-500A high density Virgin polyethylene membrane with an impressive compressive strength of 250KN per square metre and a drainage capacity of 2.25 liters per second, there is rarely a dampness or water ingress problem that falls outside the scope of the capabilities of the Delta system.


Typically the Delta MS500 would have an inner lining such as dry lining or a metal track to support the finishes and create an ideal void for services or insulation.


Requirements for insulation should be considered and the requirement for a vapour control layer in conjunction with the appropriate level of environmental control, as referred to in table 2 of BS 8102:2009.


Here our clear version has been selected. This aids the selection of good fixing points in a more difficult application, that is random stone and friable brickwork.


The Delta fixings required to support the membrane are available in an 11mm version or new quick seal 10mm Delta plug with preformed grommet. The centre shank of this fixing is also used for subsequent dry lining applications and will take a size 10 or 12 screw.


Alternatively screw ties can be inserted into the fixings to provide lateral support to an internal skin of block work or masonry. This same detail can be used where Delta MS500 is fitted to contiguous piling.


Delta MS500 can also be used as a sub base course in civil engineering and construction projects. Often selected in Brown for this application.


Delta MS20 shown here in a floor application to the left. An impressive loading of 150K newtons per square metre and drainage capacity of 10 litres per second.


Dimpled sheeting with particularly high drainage capacity and compressive strength. Suitable for high performance seepage layers in building and civil engineering construction.


Delta MS20 can also be used as a cavity former for many types of new construction.


Build up options for subsequent flooring applications include insulation, under floor heating and screed or combination of the aforementioned or a floating chipboard floor, laid directly onto the Delta MS20. Our range of membranes have been tested to minus 30 and plus 80 degrees. Delta systems are holders of full BBA certification for Delta MS500, MS20, Delta FM and Delta PT Lath. 


Typical Waterproofing Failures - An overview

An overview of type A and type B waterproofing failures

When type A structures (tanked) and type B structures (featuring structurally integral protection) are tested, waterproofing failures often occur for various reasons.

  • Some typical external failures can occur due to debonding of the tanking due to inadequate preparation of the substrate or defective workmanship.
  • Damage to tanking during backfilling.
  • Inability to wrap the tanking under the structure in one continuous layer, hence a join has the potential for weakness.
  • Construction joint failure due to contamination during the pour.


We also take guidance from section 623 water table classification and grades of waterproofing protection.


The British standard raises some important points.

  1. consideration should be given to the form and feasibility of remedial work
  2. if remedial work is not possible the design should be altered.


With the above in mind, external waterproofing alone without a maintainable land drain should be questioned if it is a stand alone system. Typical internal failures:

  • flotation forces and bending stresses as a result of water coming to bear against the structure, resulting in dynamic movement of the structure and critical failure.
  • Debonding of the tanking due to inadequate preparation of the substrate.
  • Contamination of the substrate resulting in failure of critical bond. Often contamination lies undetected and can be a fundamental cause of failure.
  • Undetected air pocket expansion blowing the tanking.
  • Construction joint failure.
  • Defective workmanship.


Type C Overview



As the membrane systems are mechanically fixed there is no reliance on the ability of the product to bond to the substrate. The Delta system can be applied to a variety of different substrates for example over existing renders or broken down bitumen coatings. They can be used with random stone rubble filled walls, masonry, cob wall construction, contiguous piling, ICF formwork structures and bunga Roush construction as seen on channel 4’s “Help my house is Falling Down” and the Discovery Channel. Not to mention Grand Designs.


Damp pressure equalization

The studded structure of the membrane allows the dampness behind the membrane to move in all directions unhindered. Therefore the whole of the wall or floor surface takes the damp loading. Breakdown of the waterproofing created by weak construction joints is eliminated. The product does not divert the problem to other areas and can be safely and sympathetically removed from the structure at some future time if required.



In structures where movement or vibration or problem examples being under St vaults, railway arches and buildings constructed with movement joints, the Delta system can cope. The Delta membrane has an elongation break of greater than 50% and therefore can accept minor movement variations within the structure. Often induced by fluctuation in groundwater conditions.



As there is little or no preparation required the system is by comparison quick to install when dry finishes are used the system is a fast track solution. Decoration does not need to be delayed as there is no or little drying process. Delta membrane systems of the UK arm of the world's largest producer of studied membrane systems. The market leading Delta brand has a track record exceeding three decades.

Here the walls have been lined with Delta MS500, the floor with Delta MS20, the membranes have been rigorously tested to minus 30 and plus 80 degrees. An extract from BS8102: 1990, which has now been discontinued ,stated that for those seeking maximum assurance this form of waterproofing is considered to be the most effective and trouble free. It stands to reason that for 19 years this form of waterproofing has an exceptional track record and continues to be the preferred choice for designers seeking complete protection.


Grades of waterproofing protection

Table 2 from BS 8102:2009 provides guidance on environmental grades required for designers to provide the right degree of watertightness required on a project. This revision replaces Table 1 of BS 8102:1990.


623 water table classification and grades of waterproofing protection 


When selecting a type of waterproofing protection Table 2 should be taken into account in conjunction with the following point: during the life of the structure some degree of groundwater pressure is likely to build up against the chosen waterproofing system.


Grade one is for car parking, plant rooms, excluding electrical equipment, workshops where the performance level requirement states some seepage and damp areas tolerable dependant on the intended use.

B) local drainage might be necessary to deal with seepage. Grade two is for plant rooms and workshops requiring a drier environment than grade one.  Storage areas, the performance level here is no water penetration acceptable, damp areas tolerable, ventilation might be required.


Grade three protection is for ventilated residential and commercial areas, including offices restaurants etc


Leisure centres - the performance level is no water penetration acceptable, ventilation dehumidification or air conditioning; necessary, appropriate to the intended use.


Table 2 should be of utmost consideration when designing to a grade of structure and performance level.


When to damp proof and when to waterproof?

Here the picture on the left is a barn conversion previously used for agricultural use, totally above ground and not earth retaining. 


The walls have been affected by rising and penetrating dampness. typically with this application consideration should be given to contamination of the substrate from uric acid caused by livestock.


Nitrate and chloride salts associated with rising dampness resulting in capillary held moisture.


Here the ventilated system could be adopted or sealed if consideration for radon gas is a requirement.


Here we should be damp proofing BS657 six 2005 states that a protective barrier to mask the effects of contamination or hygroscopic salts should be deployed.


A tanking system or cavity drain membrane will achieve this. an important consideration when tanking is covered in typical failures.


An overview of BS 8102:2009

To the right the pictures highlight belowground situations. In both cases we should be waterproofing. We take guidance from BS 8102:2009 and where a cavity drain system is selected, drainage should be incorporated into the design to collect and evacuate the ingress of water or hydrostatic pressure.


We look closely at this during drainage considerations and observe the British standard guidance that during the life of the structure, some degree of groundwater pressure is likely to build up against the chosen waterproofing system.


Regardless of site examination and site conditions, we must consider the current conditions are a snapshot in time and a below ground structure that just appears damp on the surface can become a wet or flooded structure at a later time.


Drainage Considerations

When waterproofing a structure we have highlighted the importance for drainage when a type C cavity drain system is selected.


And indeed where we are incorporating external drainage this should be a maintainable system. the requirement for servicing of the drainage system or sumps and pumps, should be clearly set out in the documentation supplied by the designer to the client at no less than an annual increment.


The new Delta channel provides flushing ports which should be incorporated at every major change of direction of walling.


At Delta in addition to our comprehensive drainage channel with preformed corners and flushing ports. We can offer designers an alternative for the collection of groundwater within a basement or retaining structure, with the Delta detail 129.


This detail can be utilised whereby a series of 110 millimetre underground pipe work is laid underneath or within the slab depth and turned up 90 degrees to form inlets within the slab which are cut off at approximately 12 square metre intervals.


The high drainage capacity Delta MS20 would then be overlaid to the floor after the very important flood test and free lime application, using Delta polyseal TG500. This ensures complete confidence and enables contractors to remove any low spots ensuring full continuity of the drainage system.


Selection of the Delta channel or detail 129 can offer the designer's an alternative, where a channel detail could interfere with the structural slab.


External Waterproofing

We have discussed an overview of the forms of waterproofing construction. We now take a closer look at external systems and implications, taking guidance from BS8102.


The picture here indicates a concrete box fully below ground, with a buried roof and we discuss an overview of Delta systems for total waterproofing protection.

Flat soffit Waterproofing

When consideration is given to the waterproofing of a flat soffit the waterproofing should be carried out from above nowhere is the trend more evident than on the European continent where green has evolved faster than in other developed countries.


According to the international green roof Association local authorities and city councils especially in Germany have enthusiastically embraced green roofs to help air quality, protect the soil and water and to inject some additional greenery into the lives of the citizens.


The governmental bodies are doing this by offering direct financial incentives. Reducing stormwater taxes and providing relief on density regulations, to offset the green roof contributions to open space.


Delta systems can offer DELTA® Terraxx for extensive and intensive green roofs and DELTA® FLORAXX for warm and inverted roofs. Here the Delta primary waterproofing is applied to the structure after formation of the appropriate fillets and pre treatment of the substrate. DELTA® Terraxx has been selected for the soffit and is taken down 200 millimetres past the construction joins. A water bar and Delta MC slurry have been incorporated into the kicker joints.


Delta Geo drain quattro has been selected for the vertical retaining walls.


With an impressive load of 400K newtons per square metre for both DELTA® Terraxx and Geo drain quattro a diverse solution can be offered for total protection. Different design conditions often require a different approach and as such Delta can offer a range of products under the Costa envelope of waterproofing.


To include flats offered conditions ,where it may be necessary to incorporate a Type A approach with Type C waterproofing. Products for construction joints. Primary waterproofing for soffit and vertical applications. Service entry points into below ground structures to name a few.


When consideration is given to the waterproofing design of a belowground structure incorporating a type C approach whether new build or refurbishment, sealing should be carried out to minimise hydrostatic pressure into the structure.


Delta can offer a range of resin injection techniques through our network of registered installers. These can be used to minimise the ingress of water even into sheet piling applications.


Large volumes of aggressive water can be dealt with by deployment of the Delta Costa range, which complements our diverse range of drainage membranes.


Verticle Drainage Protection

Structures that are earth retaining can be damaged by moisture penetration from the outside or by water under hydrostatic pressure.


Delta membranes are available as Geo composites to deal with such problems. They act as a waterproof drainage layer and quickly remove the water to suitable drainage around the structure. They prevent the buildup of hydrostatic pressure on the structure and filter the water via an internal polypropylene filter layer. This prevents the fine ground particles from blocking the drainage facility and avoids destabilising the soil.


Delta Geo drain quattro can also be applied over the primary external waterproofing layer on certain types of structure prior to backfilling. The membrane is only fixed along the top edge and the flange on the edge of the roll is used to lap onto the next section. and is sealed using the pre applied adhesive tape. The Geo drain quattro has very high compression strength and acts as a protection layer over flexible waterproofing. It can be used up to depths of 10 metres.


Horizontal Drainage Protection

DELTA® Terraxx an extremely robust protection and drainage system has been optimised for different applications in horizontal drainage. Consisting of a dimpled sheet with a fused on geotextile the composite material forms a highly effective drainage layer. Facing up the geotextile acts as a filter protecting the air gap created by the dimpled sheet underneath. Reliability protects and insulates waterproofing layers against mechanical damage. Withstands extreme compression loads of 400K newtons per square metre. Up to type 60 heavy trucks depending on the covering.

High drainage capacity prevents Frost damage and incrustations. Water vapour pressure is drained away through the structure. Water drainage capacity exceeds that of gravel or chipping layers.


Warm Roofs with an extensive/intensive herbaceous layer

Developed specifically for use in green roofs, DELTA® FLORAXX top, an innovative dimple sheet, forms of protection and drainage layer with a high load bearing capacity, which is optimised for the requirements of horizontal drainage.


Acting as a protection, filtration and seepage layer, it retains 7 liters of water per square metre, with its thickness of 20 millimeters. This is optimal for herbaceous covers that are supposed to survive for prolonged periods without erogation.


Walkable Inverted Roofs

Used as an efficient structural drainage layer in driveable inverted roofs, paved with stones or slabs, the innovative Delta florex dimple sheet acts as a protection and seepage layer, which permits water to drain away freely.


Breathable because of the perforation which permits air to circulate the sheet prevents the formation of a coherent film of water on the waterproofing.


Thanks to its robust octagonal dimples additionally reinforced by ribs its compressive strength is as high as 200K newtons per square metre.


Levelling or bedding material may be spread directly on top of the sheet.


Packaged Pump Stations

Delta offer an extensive range of packaged pump stations to meet all sewage and drainage needs for both domestic or commercial applications.


With applications for groundwater surface water and foul water our standard off the shelf range provides waterproofing solutions for many types of applications whether it's for new or existing buildings above or below ground, including renovation, refurbishment, heritage, conservation construction, new build or retrofit basements tunnelling and civil engineering projects.


Delta membrane systems limited are the holders of BBA certificate 00/3742 we are specialist manufacturers of above and below ground package pump stations we also offer pump variants for aggressive water such as sea water or swimming pool and backwash water.


We stock all components and generally chambers can be delivered to any UK site within one week.


Below ground chambers range from 600mm deep and are fitted with a range of single or duplex submersible pumps and are manufactured in accordance with BS752 and BS12056 for installation inside and outside buildings.


We also manufacture a range of specialist pump stations, to be used in conjunction with cavity drain membrane systems. We are the market leaders in this sector and our specialist knowledge means we can deal with all waterproofing applications typically relating to basements and structures below ground level.



A full range of accessories are available from stock which include pipe work, high level alarms, mains independent battery backups and specialist venting systems, where conventional vents cannot be installed.


A Delta Text Mast can further enhance the system and will send a text message to up to five mobile phones in the event of a high level alarm trigger.


We are able to meet with architects consulting engineers and contractors throughout the UK to produce specifications for pump applications.


After sales service

We supply annual and biannual service agreements for our own manufactured equipment as well as that of our competitors. This service is operated 24 hours a day 360 five days a year.


The Original Plaster Lath

In many situations an indeed where it is not possible to use an internal dry lining system, restrictions may include lack of space, for example Delta systems introduced over three decades ago, the original plaster lath, Delta PT Lath or plaster lath, a moulded htp membrane, incorporating a polypropylene mesh. as a key for plaster render or dry lining applied on plaster dabs for use in new construction or existing buildings.


It can be used for waterproofing and damp proofing on walls and vaulted ceilings above or below ground, over a contaminated or damp background.


It can also be used externally as a waterproof support for render.


Materials that can be applied to the meshed membrane are dot and dab plasterboard, thermal board directly applied plasters, even sand and cement and lime based plaster.


Fixing centres when rendering a typically required at 150mm centre, when used externally.


250mm centres for internal re-plastering or rendering.


Where can the System be Used?

Projects include new build, listed buildings, refurbishment, ICF insulated concrete form work, underground vaults, contiguous piling, Cobb walls, stone and random rubble filled walls.


Delta systems offer a full range of products across the board, ranging from cavity drain membranes, external geotextile membranes and solutions for green roof applications.


Typical budget/cost?

A typical cost for properly waterproofing the basement would be in the region of £40 per metre squared upward.


This would exclude finishes and an important comparison between a type A tanking system and type C waterproofing system when we consider cost is the often extensive preparatory work required before the tanking can be applied to a structure whether new build or refurbishment.


Listed Buildings

Delta membrane systems have been specified and installed on many listed and historic buildings such as Kensington Palace, the Greenwich Royal Observatory and the Kodak building in Manchester to name a few.


With many historic structures the conventional approach of installing a chemical damp proof course is not acceptable and as such Delta can provide a sympathetic approach and with the air gap technology, a reversible process is achieved.


Delta FM

Delta FM is specifically designed for floor and wall applications to combat dampness and contamination the special low stud profile 3mm minimises changes in floor levels but still provides an air gap to achieve damp pressure equalization.


Delta FM is typically used in above ground situations where salts dampness and contaminants are present within the walls and floor; and as such would be classed as a damp proofing exercise.


The membrane is a fast track application that allows various floor finishes to be achieved with zero downtime.


The percent RH levels are isolated in the air gap and controlled.


Delta FM can be used in new build, remedial or refurbishment projects for floors and walls.


And can also be used in conjunction with thermal installation, sound insulation and many types of underfloor heating systems.


Radon Gas Barrier

Radon is a natural radioactive inert gas that penetrates dwellings from the surrounding soil. radon is a colorless, odorless gas which is radioactive. We take guidance from Section 4- 1 of the British standard. where it occurs in high concentrations it poses a risk to health.


In addition to our range of cavity drain membranes, which are certified as radon proof, the Delta gas barrier system, reliably and permanently protects from the ghostly threat of radon CO2 and at the same time forms a dependable protection layer against rising damp. 


Conforms to BR211, BR212 and building regulation document C.


When detailing waterproofing and soil gas protection, Delta can offer high performance dpc units, top hats and cavity trays, in order that a fully gas tight and waterproof structure is achieved.


Delta protects property, saves energy, creates comfort.


Back water Protection

Back water damage can be extremely expensive. Consideration should be given to this when designing the drainage to protect against sewer surge.


These units are relatively inexpensive. For this reason make sure all below ground areas with open fixtures are protected by a Delta Back water valve.


Available in a passive version the valve is equipped with two free hanging vertical back water flaps. These flaps ensure that a building's wastewater flows freely through the valve while simultaneously preventing any back water from backing up into the building.


All Delta back water valves type 0 through 5 and manufactured according to the EN norms and also have passed strict in house testing which requires back water valves to perform above the EN norm requirements.


Delta are members of the RIBA CPD providers network and the NBS plus scheme and also hold BBA certification in the UK.


They offer regular training courses for specifiers or contractors and RIBA approved CPD talks for those professionals requiring them.


The Delta Dörken alliance offers an extensive range of waterproof membrane systems and ancillary products including:

  • Sump pump drainage kits,
  • channel systems,
  • flood protection valves,
  • cellar tanking and more.


Delta also provides full Technical Support and can be consulted through all stages of the project.  Delta should be contacted early in the design process. Staff are available to visit sites to give advice on particularly difficult or unusual situations, where appropriate specifications are prepared to assist in the correct use of the system. We believe our technical staff to be second to none and certainly the most experienced in the UK market this service is open to property owners, architects, surveyors and specialist companies.


Delta also operates a registered installers scheme across the UK and can provide details of specialist contractors for the tendering process and to install the systems. A registered Delta installer can offer long term guarantees for the system, usually 10 years which can be insurance backed.


Whether it's new build remedial, retrofit underground extension, new basement cellar or refurbishment Delta membranes provide waterproofing solutions for basements and buildings. Should you require any additional information please contact Delta membranes mainline on 01992523 523 or visit our new and improved website on www.deltamembranes.com. Our team will be only too pleased to assist you.


We thank you for listening to our presentation and now invite you to participate with a questionnaire successful completion of which will entitle the participant to a CPD certificate. 

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