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Benedikt Aundrup
Gabor Palotas

Waterproofing of Substructures

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    UNIT 1 - APPLICATION TECHNIQUES

    • Waterproofing of substructures - Application Techniques

      COURSE 1 / MODULE 3 - WATERPROOFING OF SUBSTRUCTURES / UNIT 1 - APPLICATION TECHNIQUES

    • Introduction

      Structures in the ground must be protected from the various forms of water in the ground and its harmful effects. Hazards include soil vapour, soil moisture or groundwater. Different forms of water require different levels of protection. Typically, we assign the same level of protection for both soil vapour and soil moisture. As a general rule, all parts of the building in contact with the ground are uniformly provided with minimum protection against soil moisture. Structures below the defined groundwater level should have a higher level of groundwater protection.

      Waterproofing materials

      Bituminous membranes, plastic membranes, waterproofing mortars, waterproofing concrete, and metal sheeting can be used to waterproof against soil moisture and groundwater.

      1. Bituminous Waterproofing

      The number of layers of bituminous waterproofing depends on the functional use and the thickness of the membrane. Against soil moisture, 1-2 layers are required, while against groundwater, 2-3 layers are needed, depending on whether a 2-4 mm thick thin membrane, a minimum 4 mm thick heavy-duty membrane, or modified forms of these are used. Using modified thick membranes will require the least number of layers.

      Corners are extremely stressed areas and therefore they need special care by forming 4-5 centimetre-radius bends here. Before laying the membrane, ensure that the surfaces are smooth, dust-free, and primed with a bituminous coating or emulsion.

      Bituminous membranes are available in rolls of 10 or 20 metres with a width of 1 metre. The membranes must be folded perpendicular to the wall, cut to size, and rolled back. They can then be bonded by flame welding the entire surface, using a blow torch to melt the bitumen from the base layer while slowly re-rolling the membrane.

      The sheets must be laid with a minimum end overlap of 10 centimetres and 15 centimetres laterally, and the overlap has to be carefully rolled. It is sufficient to weld the modified sheets along the overlaps, or point by point on a horizontal surface. In the case of self-adhesive sheets, full-surface bonding is done by continuously removing the protective film.

      The sheets must be laid with a half offset for multi-layer waterproofing.

      2. Plastic Waterproofing

      In all cases, plastic waterproofing is applied as one layer, with a minimum thickness of 1 millimetre. Remove protruding particles and dirt from the surface and dust the surface. Instead of priming, use a plastic felt for levelling. At the corners, a 1.5-centimetre-radius bend has to be created. The plastic sheets are laid dry without bonding, while on the vertical surface, there is need for a hanging fixing. The overlap between the plates should be at least 5 centimetres. Joints are made either by hot air welding or by solvent welding.

      3. Waterproof Coatings

      Waterproof coating is commonly used for floors and plinths as an additional protection against soil moisture, which can be made continuous with sheet waterproofing. The required overlap is 15 centimetres. Materials can be bituminous, plastic, cementitious or resin-based. The coating is applied in 2-3 layers using a trowel. The temperature required for construction must be at least 5 degrees Celsius. In the first layer, reinforcement strips should be embedded in the coating at corners, curves and planes of different levels. The follow-on coating layer can only be applied after the previous layer completely dries.

      4. Sheet Metal Waterproofing

      Sheet metal waterproofing can be used under monolithic reinforced concrete pillars between the base of the pillar and the reinforced concrete foundation. The waterproofing sheet of the floor is fixed to the metal sheet with clamp profiles.

      5. Watertight Concrete

      Watertight concrete is another way to protect against water. In this case we even have to be careful about the connection between the individually made structural elements and the proper sealing of the joints. Use a swellable water bar (placed in fresh concrete) in the centre line between the reinforced concrete basement wall and the slab foundation. Furthermore, a flexible joint tape can also be used in the former situation, as well as, for example, for the watertight sealing of construction joints.

  • UNIT 2 - TECHNOLOGICAL GUIDE

    • Waterproofing of substructures - Technological guide

      COURSE 1 / MODULE 3 - WATERPROOFING OF SUBSTRUCTURES / UNIT 2 - TECHNOLOGICAL GUIDE

    • This section presents typical waterproofing methods under different conditions and with various materials. 

      1. Damp-proofing of a building without a basement - single-ply modified bituminous thick membrane:

      Clean the slab of dust and dirt, and repair cracks wider than 1 millimetre. Prime the dry surface with a cold bituminous coating and the wet surface with a bituminous emulsion. For the prepared slab, lay the horizontal waterproofing membrane under the load-bearing walls with a 10 to 15-centimetre overlap. The floor waterproofing follows only after the load-bearing walls are completed, thus ensuring the continuation of the horizontal waterproofing of the walls.

      On the horizontal surfaces it is enough to weld the membranes in the line of the overlapping and at various points with specific dimensions.
      The waterproofing membrane on the floor is also rolled up 10 centimetres high on the wall, and the joints are thoroughly rolled everywhere.

      2. Damp-proofing of a building with a cellar can be done by fixing the membranes to the cellar wall or by tanking.

      a) Damp-proofing of a building with a cellar by fixing the membranes to the cellar wall - using double-ply bituminous thin sheets:

      Again, first clean and repair the slab and apply a bituminous primer. Here, the horizontal waterproofing of the wall is done first, as previously described, with an overlap of 10 to 15 centimetres. The top layer of the overlap must not be adhered to allow for a double joint.

      Once the cellar wall is built, lay the floor waterproofing and join it to the horizontal wall-waterproofing, folding the sheets 10 centimetres up the walls. The sheets are laid by flame welding again with the required joint widths and they need to be rolled down in the end. Then, prime the external walls of the cellar and install the vertical wall waterproofing. The waterproofing is applied up to the height of the plinth with the required joint widths and join with the horizontal wall waterproofing at the bottom. The bottom of the sheets is folded down to the side of the foundation. Finally, place the waterproofing extruded polystyrene sheets and backfill the soil.

      b) Damp-proofing of a building with a cellar by tanking - using a single-ply PVC membrane

      For tanking, you first build the walls that support the waterproofing on top of the foundation. Then, form the bends at the junction of the walls and the slab with a radius of 1.5 centimetres. 

      Completed surfaces must be dusted, before carrying out the usual levelling: plastic felt must be laid over the entire surface. The vertical and horizontal wall waterproofing is placed simultaneously, suspending the plastic waterproofing from the wall supporting the waterproofing. To affix the sheet, we screw aluminium or tin foil tape to the wall.

      The 5-centimetre horizontal joints are secured by hot air welding. Vertical joints are made similarly, but in this case, the bottom sheet is welded to the tin foil tape screwed to the wall and the top sheet is welded over the joint, with at least a 5-centimetre overlap.

      On the horizontal surface, we also need to ensure the possibility of creating a joint by extending the sheets over the width of the future cellar wall. The corners should be given a reinforcing strip of plates around the perimeter. The next step is to build the cellar walls, which should be made of concrete blocks for partition walls or hollow concrete blocks with a 10 to 15-centimetre thickness. During construction, we fill the gap between the walls with 2 to 3 centimetres of protective-confining mortar. In the case of a heated cellar, extruded polystyrene boards can be used instead of mortar to prevent the waterproofing from sliding off. For waterproofing the floor, form the necessary joints and lay the waterproofing boards on the basement wall up to a minimum height of 10 centimetres. Finally, by proceeding further on all sides the same way, the entire floor is waterproofed against ground moisture.

      3. Waterproofing tanking against hydrostatic pressure - using double-ply modified thick membrane

      The initial step in tanking against groundwater is to create a 10 to 12-centimetre-thick reinforced concrete slab for the floor waterproofing substrate, on which the wall supporting the waterproofing can be built. The wall must be sized for the hydrostatic pressure, so a minimum of 15 to 20 centimetre-thick wall made from concrete hollow blocks must be built. The wall height should be calculated so that vertical waterproofing against groundwater can be installed 20 to 25 centimetres above the defined groundwater level. Above this height, it is sufficient to waterproof only against soil moisture.

      Dust surfaces and repair any cracks, and make a 4 to 5-centimetre-diameter bend at the corners. Subsequently, reinforce the surface with a bituminous coating or bitumen emulsion, as described above. The two wall and floor waterproofing layers are done in one phase by flame welding, with a 10-centimetre overlap laterally and 15 centimetres longitudinally. Fix the layers of vertical waterproofing with half offsets over the entire surface, while forming a reinforcing strip of plates between the two layers at the bends.

      After completing the vertical surfaces, lay the horizontal waterproofing and make double joints on the horizontal surface. Then, form the protective layers of waterproofing with 2 to 3 layers of PE film or one layer of bituminous thin sheet. Finally, build the other structures: the slab foundation and the basement walls which resist the hydrostatic pressure and prevent floating with their mass.

      To reinforce the slab foundation,  prepare a 5-centimetre-thick blinding concrete to protect the waterproofing. Place a trim of the same height as the foundation on the sides of the slab foundation. Build the cellar wall once the foundation has been poured and solidified. At the construction stage, the 2 to 3-centimetre space between the cellar wall and the waterproofing should be filled with a layer of confining mortar. After the wall is completed, the waterproofing can be continued against soil moisture above the wall supporting waterproofing. Finally, the soil can be backfilled into the working pit around the cellar.

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