(hot air) to the integral joint waterstops in a combined waterproofing system.
Internal (i.e. for water retaining structures to keep water in) and external (i.e. for basements to keep water out) bonded sheet membrane syatems need to be supported and protected by the load-bearing structure itself and / or additional protection boards, so that external ground or water pressures can be adequately resisted.
It is very important with all post-applied sheet membrane systems that the substructure has a suitable substrate surface finish to apply the sheet membranes onto. The concrete slabs are again poured over this type of sheet membranes that are loose-laid on the blinding and welded at the joints. Where required they are also pre-welded to the joint waterstops, such as external waterstops or when they are being used to create a compartment waterproofing system. On the blinding and for post-application on concrete walls and other surfaces, they must be free from raised ridges and sharp corners, plus any indents or voids should be pre-filled and tie-wires etc. removed, so that overall it is finished to a smooth, uniform level surface. Brick and blockwork walls must have flush joints, or these must also be pre-filled by pointing.
ii. Liquid Applied Waterproofing Membranes
There are many different types of Liquid Applied Membrane (LAM) Waterproofing materials and they all have different application and performance advantages and limitations. these materials range from polymer modified bitumen’s (such as Remmers Profi-tight), through single pack polyurethanes, to very high performance 2 component polyurethane (such as Liquid Plastics Decothane range) and other resin based materials (designed for both New and Refurbishment waterproofing works). Details on the preparation of substrates, application rates, method statements and curing requirements are detailed on the individual Product Data Sheets.
In principle many difficult waterproofing problems 'from the basement to the roof' of buildings and many other structures can be solved with liquid applied waterproofing membranes.
Suitable protection to liquid applied waterproofing membrane systems should also be provided once it has completely cured and hardened, if it is to be exposed or back-filled, such as protective boards purpose designed for this purpose and cut to fit the external profile.
For additional advice on the suitability of liquid applied membranes for waterproofing on your project, please call any NCC Basement Waterproofing Site office and one of our waterproofing specialists will be pleased to assist you.
iii. Geosynthetic & Clay Waterproof Liners (using bentonite clay for New Construction Waterproofing Works)
Traditionally bentonite is a natural clay mineral, following similar principles to the use of clay for waterproofing as it is has been for thousands of years. The bentonite clay absorbs water and expands when in contact with water, also forming a barrier to the transmission of further water or other liquids. The bentonite is held between two geosynthetic layers and forms an impervious seal bonded to the concrete surface. They are available in two types:
- Dry bentonite liners which rely on activation taking place on site from the absorption of the groundwater once installed.
- Pre-hydrated bentonite liners, which are manufactured by vacuum extrusion and therefore they do not need to be additionally hydrated on site.
Bentonite based waterproofing materials have largely been replaced with newer and more efficient technologies for basement waterproofing projects in the UK, but they are still widely used around the world for new-build basement waterproofing due to their relatively simple installation and low cost, but NCC
find that today there are normally much more effective and efficient waterproofing solutions available.
Bentonite-based waterproofing solutions can only be used on new construction projects and where it is certain that they will always remain confined between two surfaces and they cannot ever be left exposed. The main problem with these older technology waterproofing products is that in variable water table conditions, all bentonite systems are not effective and can be washed out through cyclic wetting and drying.
iv. Mastic Asphalt Waterproofing (for new construction basement waterproofing only)
Mastic asphalt standards dictate that it should always be applied in a minimum of three coats and that concrete surfaces must be prepared. Smooth concrete surfaces will not provide an adequate key, so mechanical surface preparation is always required.
In common with many UK building owners and architects, NCC no longer recommend Mastic Asphalt, nor any other hot or flame applied materials for waterproofing works due the difficulties of application on site, due to the risk of fire and the corresponding and increasingly prohibitively high insurance costs and the onerous contractor / specifier / owner risk liability and implications.
v. Crystalline Slurries and Powders (New and Refurbishment Waterproofing Works)
Cement based crystalline slurry barrier coatings are blends of cement, sand, additives and so-called 'active' chemicals. They are supplied in
pre-batched units of slurry product, or in powder form to be mixed with water and cement and also applied as slurry coating, directly onto prepared concrete surface.
The 'active' chemicals combine with free lime and moisture present in the concrete capillaries to form insoluble crystalline calcium silicate hydrate complexes, which block the pores and also prevent water ingress. Crystalline waterproofing product of this type include materials from Remmers, Xypex and Sika.
The cement based crystallization waterproofing barrier coatings can be applied to the internal or external surfaces of a concrete structure by brush or spray. They are suitable for use on both new and existing structures, and some claim that they do not require an additional protective layer such as the modified render coats normally employed for this. However NCC's
Basement Waterproofing Site specialists believe this to be a false economy and that any surface waterproofing solution must incorporate a physical layer rather than just surface treatment by the coating alone. This is due to the variable consistence and porosity of the substrate as this can lead to wide variations in effectiveness for the waterproofing treatment, if this is not completed with the additional ‘protective’ layer.
The concrete surfaces should always be mechanically prepared to have an open textured surface and capillary pore structure, prior to application of this type of crystalline waterproofing barrier.
vi. Cement Based, Multi-coat Waterproofing Renders, Mortars and Slurry Coatings (for New and Refurbishment Waterproofing Works)
This is one of the most widely used and well proven basement waterproofing solutions for refurbishment waterproofing projects throughout the UK, Europe and the rest of the world. They are also preferred in some situations for new construction due to their ease of application and cost effectiveness.
The installation of cement based multi-coat renders, mortars and coatings should, be left until as much as practicable of the structure is built and therefore its dead load has been created. The substrate should be prepared to an open textured surface and capillary pore structure in accordance with the relevant product PDS prior to application of the system which can be by trowel, brush or spray according to the specific products nature. These products are also known as ‘cellar tanking products’ or 'basement tanking products' and the best known and most widely used in the UK is the BBA Aproved, Sika-1 prebagged waterproof tanking system. The Sika 1 Tanking system is applied as a combination of a tanking slurry and then built up with tanking renders in a multi-coat waterproof tanking system.
The slurry applied systems are also known as ‘tanking slurries’ and include the well-known and also BBA Approved, SikaTop Seal 107 tanking slurry and Remmers Profi-Tight tanking slurry. These are both applied by ‘slurry brush' in 1 – 3 coats according to the waterproofing system’s performance requirements.
Details on the cement based multi-coat waterproofing products application methods and thicknesses, consumption rates, mixing ratio and requirements, the number of layers/coats and curing required can vary quite considerably between the different products and systems. Therefore we recommend that you read the relevant Product Data Sheet (PDS) and Materials Safety Data Sheet (MSDS) and if you have any concerns, and then please contact any NCC
office for detailed information and advice for your specific waterproofing project. The substrate and structural elements should also be assessed for their suitability to withstand any increase in applied loads from future water pressure after the waterproofing is complete.
For more information on basement waterproof tanking products please refer to our ‘Basement Tanking Products
2) Waterproofing Type B Structurally Integral Waterproofing Protection Products
Obviously integral waterproofing product, systems can only be used as the waterproofing system, or as a component of the waterproofing system for new reinforced concrete structures. They can also be designed to achieve or assist in preventing water vapour ingress.
For more detailed information please refer also to the ‘Basement Waterproofing - New Construction
’ and ‘Basement Waterproofing Systems
This approach cannot normally be used for refurbishment works, as Type B integral waterproofing protection relies upon the waterproofing materials being incorporated into the structure. However they are very often ideal for use in extension situations for the potentially complex connections and providing watertight joints between new construction and existing structures.
Pipework and other service entries are particularly vulnerable to water penetration, so where these cannot be avoided, they should be carefully detailed, for example by incorporating preformed hydrophilic gaskets and swellable hydrophilic joint sealants (such as Sikaswell P profiles and SikaSwell S sealants) to minimize the risk of any future water ingress.
NCC Basement Waterproofing Site
specialists can assist you to determine most appropriate integral waterproofing solutions for your project including the complete specifications, detailing solutions and method statements.
A summary of the key component products includes:
i. Watertight Concrete Using Waterproofing Admixtures:
These are the waterproofing admixtures which increase the inherent resistance and therefore reduce the permeability of concrete to water and water vapour. Waterproofing (water-resisting) admixtures such as the BBA Approved Sika-1+ system that is used in conjunction with Sika Viscocrete high range water-reducing admixtures to achieve the necessary reduction in water permeability of the concrete..
Concrete containing a proven waterproof admixture (i.e. the BBA Approved Sika-1+ system), will have a considerably lower degree of water permeability and water vapour transmission. The concrete mix design and placing must always be adequately supervised at the ready-mix plant and on-site. NCC basement waterproofing specialists can assist with this supervision on your site.
These waterproofing admixtures are generally to be used in conjunction with the integral jointing systems below and these are normally approved and supplied by the waterproof concrete admixture producer to ensure compatability and waterproofing system responsibilities.
Waterstops are established solutions for integral joint sealing and NCC
can provide detailed advice and support to select, specific and install the right system on your project. The principal types of waterstops for construction and movement (expansion) joints can be classified as follows:
ii. a) Passive waterstop sections:
Today these are usually flexible polyvinyl chloride (PVC) or other synthetic elastomer based profiles cast into the concrete and therefore fixed into the structure on both sides of the joint, either at the concrete surface or mid-depth of the concrete section, to form a physical obstruction to water transmission; i.e. these systems basically function by greatly extending the length water has to trowel and therefore reducing the possibility of any leak occurring.
ii. b) Active ( hydrophilic) profiles:
Preformed hydrophilic profiles or sealants (such as SikaSwell P or S) applied in or concrete joint at depth in the section. The materials swell or give rise to crystal growth on contact with water providing an enhanced obstruction to its path. They can be used on their own as the joint sealing system with limited exposure to water pressure, or in a combined system with passive waterstop sections for example.
ii. c) Permeable hoses (i.e. Sika Fuko) or special sections (i.e. sika Injectoflex):
These are fixed to the construction joint surface before casting the second pour and they are specially designed to facilitate the injection of a specialist sealing resin into the joint, if and when required in the future.
All of these waterstops can be used to provide enhanced resistance to water transmission in all of the joints in the concrete structure, e.g., including movement / expansion joints; at construction, isolation or day-work joints, service entry pipe or other penetrations. The positioning of the waterstop(s) (external and/or internal) should be appropriate for the method of construction and the level of risk. Particular attention should be given to the use of waterstops in the movement / expansion joints in the concrete structure (although the requirement for these should always be avoided by design wherever possible).
Where centre-bulb waterstops are used, the methods of fixing should also be sufficient to keep the components in the correct position during the concreting operations. These must always be adequate compaction of the concrete around these internal waterproofing components to avoid actually creating paths for subsequent water ingress. NCC
can support you throughout the design and installation phases of your waterproofing projects.
3) Waterproofing Type C: Cavity Drain Waterproofing Protection Products
Type C Cavity Drain Waterproofing Protection manages water that penetrates the external shell of a structure, by collecting it in a cavity formed between the external wall or floor and an internal lining/wall/floor surface. There is permanent reliance on this cavity to collect any groundwater seepage and condensation internally, then direct it to a suitable discharge point e.g. drains or a sump for removal by gravity drainage or mechanical pumping.
Traditionally, the drainage cavity in floor construction was formed by the use of a no-fines concrete base or ceramic drainage units / channels embedded in the concrete. These are rarely used today due to cost and their dimensions in new construction, but this design might well be encountered and have to be accommodated when refurbishing existing structures.
Structural aspects of cavity drainage:
The exterior walls of the structure should be capable of controlling the quantity of water that can pass through it, in order not to exceed the drainage capacity of the system. Water entering a drainage cavity system is regulated by the structure, so any defects that might result in unacceptable leaks should be remedied before the new drainage cavity membrane is installed.
Cavity drain systems do not change the loadings on an existing structure due to water, other than where remedial measures are taken to control the level of water ingress.
Cavity drain membranes:
Cavity drainage membranes form a permanent void or ‘cavity’ between the external elements of the structure and the internal wall/floor finishes. Such cavities vary in width, depending on the design of the stud height or profile of the membrane; They are usually ≤ 20 mm according to the anticipated volume of water that they are to channel to where it is drained or pumped out of the structure.
Cavity drain membranes should be used in accordance with appropriate stud height or profile after considering the external hydrostatic pressure, the porosity of the structure and the predicted rates of water ingress though the structure's external fabric.
Cavity drain membranes have a particular advantage in that they can be used on surfaces that have been contaminated with impurities. However, in these situations, consultation should first be undertaken with the local Environmental Agency regarding any potential discharge from the system.
Before a cavity drain membrane is laid or fitted on walls and floors constructed of new concrete, the concrete surface should be treated to reduce the risk of leaching of free lime or mineral salts, which could otherwise build up over time and eventually create an obstruction of the drainage system.
Where the floor cavity incorporates perimeter channels that discharge into a sump(s), both the channels and the sump(s) should be cleaned before, during and after installation of the membrane to allow uninterrupted drainage
The regular servicing requirements for this type of waterproofing system should be clearly set out in the documentation supplied to the client, including the need for regular planned maintenance of the drainage and/or pumping systems which must never be done less than once a year
With cavity drain systems the client and their designers should always be informed that any failure to adhere to the defined maintenance schedules could result in a premature failure of the waterproofing system.
Advice on Basement Waterproofing System – All Types
Whatever your basement waterproofing and tanking requirements, for all types of waterproofing products you can contact any NCC Basement Waterproofing Site office to receive, FREE unbiased, independent advice, plus the best prices and fast delivery of the most appropriate waterproofing system solutions for your project!
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