Basements require a proficientand economical waterproofing solution to resist any unintended entry of wateror moisture into the structure, writes Abhishek Jain.

Author’sBrief – with pull quote:

“The designers, owners and project managers shouldselect the complete system judiciously and understand in detail the functioningof each component, which together shall work for designed period of life andnot just the warranty period.”

• Abhishek Jain, National Head – Specification,Sika India Pvt. Ltd.

   

  Prominent underground structures aroundthe globe require a proficient and economical waterproofing solution to resistany unintended entry of water or moisture into the underground structure,irrespective of it being a basement or a pit for equipments. Basements areimmersed in differing levels of groundwater, and aggressive influences that includedamp soil contact, percolating water, water under hydrostatic pressure plusaggressive chemicals in solution, different soil, gravel and rock, etc. Theseall require different and often specific waterproofing treatments to be appliedto the structure.

  The technologies and systems usedin this arena are generally fully adhered FPO membranes (SikaProof A+), PVC-basedmembrane systems (Sikaplan), 2-ply (layer) modified bitumen membranes (SikaBitT) and single ply bitumen membranes (SikaBit T). Various sections below wouldoutline one of these technologies, which are based on modified bitumen membranebased on atactic polypropylene polymer, generally called as APP membranes.

   

  WaterproofingSystem with 2-ply APP membranes

  The most common and successful waterproofing system isbased on APP membranes system that forms a full bond with the PCC substrate andbonded to the retaining walls. This concept utilizes single layer of APPmembrane with top and bottom finish of very thin PE film.

  Sika, well known for their innovations in specialty constructionchemicals globally, suggests the use of two layers of APP membrane, with basesheet SikaBit T 130PG with both sides PE film, which is not bonded to the PCCbut loose laid with joints sealed by torching application. The cap sheet wouldcomprise of a sand finish SikaBit T 130SG membrane, which shall be fullytorched with sealed joints to the first layer.

   

  Advantagesof 2-ply APP Waterproofing membrane system for basements

• The membrane system is notbonded to the PCC but to the screed before the structural concrete, whicheventually becomes a part of the structure. This benefits by avoiding anyapplication of the membrane in a damp environment and is not affected by anysub-structural movements leading to cracking of PCC as it is not bonded there.

• The top layer membrane is sandfinished, which creates a firm bond with the structure and ensures no lateralmovement of water in case of any unidentified damage.

• In a 2-layer system, the jointsof base sheet are completely staggered during cap sheet application, whicheliminates the probability of an open or weak joint in the torched membranesystem.

• Keeping asand finish membrane on the top, a very high abrasion resistance is obtainedwhich protects the membrane from civil activities at site before it isprotected with a protection mortar screed.

   

  Measurementof Durability – Abrasion and Bond to structure

  The designers, owners and project managers shouldselect the complete system judiciously and understand in detail the functioningof each component, which together shall work for designed period of life andnot just the warranty period. This ensures the lowest life cycle cost of installedsystem delivering peace of mind and not just the water tightness today.

  The important parameters to evaluate the purposefulfilment in basement waterproofing will be abrasion resistance of sand finishmembrane compared to plain finish and its bond with the structure. These areassessed on performing tests as per EN 12039, which sand finish surpasses bymore than four times the resistance that plain finish membrane offers(evaluated in no of cycles).

The author is anexpert in waterproofing solutions and is in the Industry for last 10 years. Theviews shared above are based on experience and technical information availableand may vary from regions to products.