Basement Waterproofing - New Construction
NCC Basement Waterproofing Site spend most of our time today working on the more complex area of waterproofing in refurbishment projects, however our waterproofing experts have a full knowledge of the approach and systems for new build projects and so we provide some of this useful information on these pages for the guidance and assistance of our customers and their clients.
Waterproofing systems for new construction projects can include externally applied waterproofing barrier protection, integral watertight construction and internally applied waterproofing barrier protection.
Waterproofing Type A: Barrier Protection - Externally Applied
(in accordance with BS 8102: 2009 Type A)
This is the most widely used, the most cost effective and easiest applied basement waterproofing solution for waterproofing below ground in most new construction works. Externally applied basement waterproofing barrier protection systems, include traditional and polymer modified bitumen coatings, polymer modified cement slurries or synthetic resin based waterproofing coatings, which all have different characteristics. However they all require adequate access to the base and external walls before, during and after their construction, followed by additional protection being provided before backfilling with soil. Careful detailing, the connection and sealing of any joints, pipe entry’s and service ducts is also essential. [Unfortunately this is not so common!!]
If you have any other specific questions or you need more specific information or advice on externally applied Type A: Externally Waterproofing Barrier Protection products or systems, please call any of our offices and one of our waterproofing experts will be pleased to assist you.
Waterproofing Type B: Structurally Integral Protection
(In accordance with BS 8102: 2009)
Type B: Structurally integral Waterproofing is generally only suitable for new basements and below ground structures that can be designed and built to prevent water ingress, together with the additional prevention of water vapour ingress when required. This is because the waterproofing strategy and its elements are designed and built into the new structural framework and external building envelope.
Service entries are particularly vulnerable to water penetration, so where they cannot be avoided, they should be carefully detailed, for example by incorporating hydrophilic gaskets and sealants to minimize any risk of future water ingress.
Obviously this is not normally possible with an existing structure and building envelope. In refurbishment situations, then Waterproofing Type A: Barrier Protection or Waterproofing Type C: Cavity Drained Protection, or a combination of systems, is likely to provide the best solution – According to the specific project’s requirements. For more details please refer to the ‘Existing Basement Waterproofing’ Page of this website.
The Component Materials for Reinforced Concrete Basements and Structures with Type B: Structurally Integral Waterproofing Protection
The reinforced concrete itself plays a major part in Type B Structurally Integral systems and this is achieved by a combination of important factors in the structures design and construction. These include ensuring the correct concrete thickness and reinforcing steel dimensions and positioning, plus the concrete mix design and the correct placing and curing of the concrete.
Reinforced concrete should now be designed and constructed in accordance with BSEN1992. Concretes meeting at least the minimum design requirements for structural use and durability in the ground, and that are properly placed and compacted are likely to have good resistance to the transmission of liquid water. A degree of resistance to water vapour transmission is also achieved by such concretes, dependent primarily on the section thickness. However the many variable factors involved mean that achieving such a ‘waterproof’ concrete in this way has considerable risk and it is recommended to take the additional step of using a watertight concrete design mix that includes a waterproofing additive such as Sika 1+ or Sika Waterproofing Powder, together with a high range water reducing admixture such as Sika Viscocrete.
Crack widths in the concrete should also be controlled by using the appropriate design, concrete mix (for example a minimum of 350kgs OPC, the addition of micro-fibres and a water : cement ratio of 0.45 or less, etc.), close supervision of the concrete placing, compaction and curing, especially in relation to temperatures and winds that can cause excessive rates or levels of evaporation to adversely affect the quality of the concrete surfaces.
The pattern of leaks and seepage encountered in such structures is often associated with poor joints, cracks or other discontinuities such as service penetrations. Service entries are particularly vulnerable to water penetration, so where they cannot be avoided, they should be carefully detailed, for example by incorporating hydrophilic gaskets and sealants (e.g. SikaSwell P Profiles and SikaSwell S Sealants – available from NCC Basement Waterproofing Site) to minimize any risk of future water ingress.
1. Watertight Concrete Using Waterproofing Admixtures
There is a range of products, generally categorized as waterproofing admixtures, which increase the inherent resistance of concrete to water and water vapour.
In a recent USA report ACI 212.3R - 10 ‘Report on Admixtures for Concrete’ - There is a new addition of ‘Chapter 15 - Permeability Reducing Admixtures' - (PRA's). This is interesting because it clarifies the differences between the alternative materials used to produce waterproof concrete.
Firstly it defines two Categories of PRA (Permeability Reducing Admixtures): PRA-N's - For use in Non-hydrostatic pressure situations, and PRA-H's - For use in Hydrostatic pressure situations.
This American report then defines 3 types of PRA materials:
- Hydrophobic water repellent materials (includes stearates - i.e. Sika Waterproofing Powder & Sika 1+). Mostly these are PRAN's except the 'Polymer' types which can be PRAH's (i.e. Everdure Caltite). However when combined with high range water reducing admixtures these are also PRAH’s, suitable for hydrostatic pressure situations.
- Fine solids or densifiers (includes colloidal silicates - i.e. Sika 1 Liquid). These are also generally PRAN's, again until combined with high range water reducing admixtures, when these materials are also PRAH’s, suitable for hydrostatic pressure situations.
- Crystalline growth products - 'active' hydrophilic materials that form Calcium Silicate Hydrates in the pores (i.e. Xypex / Kryton type) These are actually PRAH's in their function, but these materials need to be used in conjunction with high range water reducing admixtures to control the other workability, compaction, curing and crack control demands of the concrete.
In summary all 3 types of materials are suitable as water permeability reducing admixtures, but their correct use is dependent on the overall concrete mix design and the other specific concrete and project requirements. Therefore this mix design should be developed with a single manufacturer’s materials that are designed for this purpose. In the UK and ROI, the NCC Basement Waterproofing Site specialists usually work with the concrete technologists at Sika to achieve the optimum solution for our customers and their clients.
Waterproofing admixtures for use in concretes for Type B: Structurally Integral Waterproofing systems should always be used in conjunction with the right selection joint waterproofing systems and systems to ensure that any penetrations through the concrete, such as service ducts etc., are also securely watertight. Generally we recommend that these components are also supplied by the same overall ‘Waterproofing System’ manufacturer and will include a whole range of ‘Waterstops’ including Waterbars (e.g. Sika PVC and Elastomer Waterbars), Injection Hoses (e.g. Sika Injectoflex and Sika Fuko Hoses), Hydrophilic Profiles (e.g. SikaSwell P Profiles) and Sealants (e.g. SikaSwell S Sealants and Sikaflex Construction Joint Sealants).
2. Joint Waterproofing Systems – Water-Stopping Solutions
Waterstop systems should be used to provide enhanced resistance to water penetration at all joints in the reinforced concrete structure, e.g. at all of the construction or day-work joints, service entries or other penetrations, in addition to all of the movement / expansion joints.
The positioning of the waterstop(s) (external and/or internally mounted) should also be appropriate for the design exposure, the method of construction and the level of risk or seepage that is allowed. Particular attention should be given to the waterstop(s) in movement / expansion joints although these should normally be avoided by good design wherever possible in water retaining basements and other structures.
In accordance with the recommendations of BS 8102: 2009, the principal types of waterproofing systems to ensure that all of the joints and any penetrations are securely watertight can be classified as the following.
a) Passive Waterstop sections:
These are Waterbars (sometimes also confusingly called ‘waterstops’ which is the term used to cover all types of joint waterproofing system generically):- Mostly they are produced as extruded flexible profiles of PVC, or Elastomer (vulcanised synthetic rubber) that are designed to be cast into the concrete on both sides of the joint, either at the concrete surface or in the centre of the reinforced concrete section, where they form a physical barrier to water penetration. This is done primarily through greatly increasing the length of path any water ingress would have to take. In addition to the PVC and Elastomer types of waterbars there are also special steel and other metal sections that are sometimes produced for extreme situations and even hybrid combinations of the metal and plastic types for special situations in major civil engineering works.
b) Active Waterstop Sections - or Hydrophilic Seals:
These waterstop sections are usually preformed extruded profiles or gun-applied sealant grade of hydrophilic material that is fixed or applied on one side of the concrete joint or penetration in the centre of the section before casting the next concrete pour. The hydrophilic material is then designed to swell on contact with water effectively sealing the joint, if and when any water is able to penetrate to this point in the joint. They can be used as a sole joint waterproofing and sealing system, or as a composite product or combined solution with passive waterstop sections.
c) Injectable hoses or other sections:
Injectable hoses or other sections are usually produced from PVC or other plastic material and they are available in a range of different profiles and sections. These include local simple or complex valve systems, which allow micro-cement or resin based injection sealing materials to be injected and in some instances, re-injected, to seal any voids or leaks in the joint. These waterproofing hose sections are fixed to the construction joint surface before casting the next concrete pour. The injection of the sealing solution into the joint can be scheduled on completion of the structure, or for if, as and when required.
The nature of all of these structurally integral waterproofing systems is such that they must be always individually designed and specified on each structure As a result, many components such as connection pieces, terminations and complex watertight joint details can also then be custom made / prefabricated under factory conditions, for delivery and rapid, easier and more secure assembly on site. The installation of these systems on site should also be monitored and supervised by the Waterproofing Specialist in the project professional team.
NCC's Basement Waterproofing Site provides additional information on all of these different waterproofing systems and components in the 'Basement Waterproofing Products' and 'Basement Tanking Products' pages of this website.
Individual project waterproofing advice for each project is always required. Fortunately this can be given by the experts in any of our offices, so please call any of our offices (telephone numbers on the left of this page) and one of our waterproofing specialists will be happy to assist you.
Remedial Works in New Construction Basement Waterproofing:
When the External (Type A) or Integral (Type B) waterproofing system has been damaged – for example during installation and there is no longer a possibility to replace it, or if a decision is made to upgrade the level or Grade of waterproofing during the construction works on site; (this is not so unusual in our experience of projects who did not initially prepare and plan correctly, but that we have been eventually invited to assist and able to rescue!) -Then it is generally a Type A Barrier Waterproofing solution that is required, but this time internally applied.
Waterproofing Type A: Barrier Protection - Internally Applied (in accordance with BS 8102: 2009 Type A)
These systems are primarily designed for use refurbishment basement waterproofing works, but they may also provide useful solutions for other remedial and repair actions in new basement construction projects i.e. leaks or other problems due to the waterproofing system or components being damaged during the concreting or other work by different trades working on new construction projects. (Electricians and Plumbers can be the biggest potential ‘waterproofing criminals’ from our experience, or the installers of new plant and equipment drilling holes in the structure for their holding down bolts!)
More information is included about these internally applied waterproofing barrier protection systems and materials, also commonly now referred to as 'basement tanking systems' on our 'Basement Waterproofing – Exisiting & Refurbishment' and ‘Basement Tanking Products’ pages of this website.