Design rule for waterstops

Basic guidelines:  

• the width of internal bands (a) may not exceed the width of the construction component, (c) bands must be chosen that are not too narrow (greater seal certainty), but also those that are not too wide (due to delamination). In addition, one needs to ensure appropriate installation depth – the covering layer (h) must be equal to or greater than the single-side anchoring depth (g).
  If installation of internal sealing bands and external sealing bands is not possible, one should create a slab low point (rib in wall) to adapt the relevant component to the appropriate thickness. An exception in this case are Nitriflex internal bands with a width of 320 mm (types A and D). The DIN V 18971 norm allows concreting them into components with a width of 300 mm. This rule should be applied to components with a width of e = 300 mm.

• the shape of reinforcement and location of internal bands in the foundation slabs and in the ceiling slabs must allow installation of bands in such a way so that its arms would be bent slightly to an angle of 10°-15°.  Such a mode of installation is in place to eliminate the voids in the concrete from the sides of the ribs in the band underside.

• external bands may be arranged only on the side of action of water exerting pressure on it. Difficulties related to appropriate concreting of external sealing band anchors aimed downwards eliminate such a solution entirely. All cases of use of external bands as insulation for day joints and expansion joints in ceilings is wrong, and excludes the selection of such a solution already in the design stage.

• for internal sealing bands made of Besaflex and Nitriflex with a thickness of the expansion part (c) greater than the minimum required value as presented in the D series band table (page 44), one can use, for each additional millimetre of band, an allowable water pressure higher by 10%. Linear interpolation, however, may be conducted solely for bands with a width not exceeding the norm values indicated in the table by more than 5 mm.
• values in force for initial slit values w_nom:

• external bands: 20 mm, with flexible part from 80 mm,
• internal bands: 20-30 mm, with flexible part from 90 mm.

Closed insulation system

It is important for the bands to form a closed insulation system, and for their free ends to be routed to at least 30 cm above the highest water level stemming from site observations. In case of basins and low points, the highest water level is the maximum projected fill level foreseen for a given structure.
If the building is divided by expansion joints, then all compensation hoses at the free ends of bands should be protected (closed) by a mass allowing adaptation to their shape, and the slits above should be protected using appropriate resources.
One should take particular care that:

• the expansion joints be straight,
• band widths along the same expansion slit do not change,
• external and internal bands are not joined together at one site.

If a passage is made between bands of different widths, the joint between them has to be made in the same way so as to maintain anchor continuity. Trimming bands, angles and changes of concreting levels of bands in day joints and expansion joints should, if possible, run at straight angles.

Minimum bend angle

When installing sealing bands, one often has to face the task of adapting their course to the altering form of the division to be protected. In order to avoid bends in sealing anchors, which could cause imprecise filling of the concrete mix around the band, one should adhere to the following bend angles:

• internal bands for day joints:  r ≥ 150 mm,
• internal bands for expansion joints:  r ≥ 250 mm,
• external bands: r ≥ 50 x f mm, where f – sealing anchor height,
• closing bands: r ≥ 30 x a mm, where a – band width.

The most obvious sealing band arrangement around a circular shape or circle section is the execution of components or structures with circular shapes. if the recommended bend angle radius cannot be adhered to, one should manufacture a pre-cast joining component, manufactured at a plant by a manufacturer or at the construction site by specialist installation teams.

Band cover

In order for sealing bands to properly fulfil their roles, they must be concreted appropriately. According to indications of standard DIN 18197 ‘Sealing of joints in concrete with waterstops’, between the sealing band and the steel reinforcement a distance of ≥ 20 mm must be maintained. The designed must, when beginning his work, reach a decision concerning the appropriate material for and type of band (internal, external, closing) together with appropriately designing the component reinforcement structure.
Only when designing a joint of the foundation slab with the wall, one may use internal bands without interfering in the reinforcement. in such a case, it is required that a threshold be made on the slab in order to embed the band. Such an addition should be made during concreting of the slab and not as an additional part. The use of Bestal steel mesh as stay-in-place formwork greatly simplifies this task.

Use of an internal sealing band for day joints	Use of Bestal day joint bands
Use of type Kab sealing bands with swell profiles

Allowable deformation vector

In order to select a sealing band for expansion joints, one has to know the shearing and cutting movements that will attempt to tear the installed band. When calculating the deformation, one should consider all deformations in directions x, y and z that may emerge during construction as well as during use. One may use the following formula to describe them:

Selection of pressure and the determination of technical parameters of installation components for bands for mechanical mounting (using compression structures)

When faced with the dilemma of having to construct a tight solution of a joint between a newly-designed structure with an existing part, or with installation of bands in complex structures, where the band is supposed to provide protection at an intersection between a concrete structure with a building’s steel components, the use of mechanical assembly of bands using a compression system with a flange is both economical and appropriate in order to achieve tightness.
The selection of an appropriate sealing band, flat profiles, anchors, compression bolts and supplementary equipment should be preceded by a thorough design analysis. Having selected an appropriate band, one should determine the width and dimensions of the compression structure and the spacing and size of tension anchors. When using all the above named system components, one needs to provide a value for pressure of the band on the concrete that would be higher than the water pressure acting on the joints.

• for sealing bands for day joints, the same choice rules and design basics apply as for sealing bands for expansion joints. The band selection diagrams are not in force for bands installed mechanically.

The above information applies only to standard situations!!!

Sealing band selection diagrams

One should keep in mind that the option of using sealing bands is determined by the value of movements in the area of the division to be protected, the pressure exerted by the water acting on the band and the aggression level of the substances dissolved in the water. In order to appropriately select our products, the following diagrams show relations (scope of shift movements – water column pressure) for the individual sealing band types.
The scope of these structure shifts must be greater than or equal to the vector of allowable deformation (Vr) of the band, calculated using the formula: