Cracks and leakage are among the sore points of contractors during waterproofing of roofs.

Conventional waterproofing methods alone are rarely adequate for waterproofing of metal decks. Most of the waterproofing materials available in the market are not compatible with metal deck materials. In most of the cases metal sheet roofing is not waterproofed initially, as they are, in general gable roof or roofs profiled at curvature.

Treatment of joints: a cost-effective solution
Basab Bandopadhyay, DGM – Technical Service, ADO Additives Mfg Pvt Ltd, says, “The most cost-effective but efficient solution lies in treatment of joints. The gaps created at the joints are filled with gun grade, self-expanding, PU foam ADO Fill-O-Fix Multifoam GHY. The material is self-expanding and fills up the open space available. A six inches strip of both the sheets are coated with ADO aqua protect – a modified silane based waterproof coating of paste consistency. All holes and kinks are coated with ADO aqua protect. The treatment will provide effective and long-lasting solution for metal roof leakage.”

ADO Cool R
ADO Cool R is a UV resistant, single component, seamless waterproofing coating. When applied with spray, this material provides a grey coloured coating over the surface which is a very effective waterproofing treatment over metal decks.

Finding and fixing leaks
Arunabha Dey, National Manager, Waterproofing and Roofing, Sika India Pvt Ltd, informs, “ Finding and repairing the leaks is a challenge. Most solutions, such as caulking, are temporary at best. One needs a permanent solution that will eliminate leaks, have a long service life, and offer low costs.”

Caulking the joints and applying a waterproofing coating – This is the quickest and initially most inexpensive solution. It involves using caulking or other sealants to seal the joints and applying a coating to the roof surface. While this might stop leaking for the short term, the roof will continue to expand and contract with temperature changes.

Insulate the roof with spray urethane foam and apply a sealant – To help stop condensation, urethane foam with a waterproof coating can be applied on the rooftop to help insulate the roof. However, the foam often creates irregular surfaces that make the roof susceptible to water.

Replace the roof – One could replace the roof entirely with another metal roof, but this option is expensive and disruptive.

Sika Sarnafil: a cost-effective, long-term solution
Recovering metal roof with Sika Sarnafil is a cost effective, long-term solution. Sarnafil’s hot-air welded seams and flashings remain watertight. When the membrane is hot-air welded, the watertight seams that are created are permanent and they are even stronger than the membrane itself.

Epoxy-based or PU: confirmed solutions for metal sheet roofs
Generally, all warehouses and industrial shades roofs are covered by metal sheet which are painted with various colours but not with waterproofing treatment so need to do the waterproofing treatment special for metal sheets.

Krishna Mestry, Proprietor, K. R. Waterproofings & Polymers says, “Like normal waterproofing systems, polymers, bitumen coating or bitumen membranes are used for metal sheet roof for waterproofing purpose but these are very basic waterproofing treatments and need to do before every monsoon season. Due to changes in environmental effect the bitumen gets cracked and damaged. Changes in environmental and temperature variations, metal sheet get corroded and micro pores develop on the metal sheets and start leakages at monsoon period.”
He adds, “Epoxy based or PU (Poly Urethane) based products are giving confirm solutions for metal sheet roofs, as these products are chemical react with each other but not any chemical reaction on metal sheet.”

Major advantages
• Good waterproofing and watertight property with anti-corrosion property.
• No any effect of natural changes like monsoon, summer, cold on epoxy based waterproofing system.
• Very good bonding with metal sheet surface for long lasting performance. Over 10 year +
• Economically viable for industrial and commercial shades.

Challenges faced while waterproofing different types of roofs structures

Dey outlines various challenges faced while waterproofing different types of roof structures

Environmental challenges
• UV rays
• Wind forces
• Temperature changes
• Rain and humidity

Mechanical challenges
• Vibration and movements
• Load and overburden
• Utilities

Design challenges
• Creative designs
• Detailing

Appearance of cracks
Appearance of cracks after waterproofing and are major concerns faced by contractors during waterproofing of roofs. Most of the elastomeric materials having very high elongation property do not effectively work after being applied on roof. This happens, as the materials when applied as a fully adhered system, cannot work as flexibly as they were behaving independently. The very thin waterproofing layer cannot withstand the stress developed due to cracking of concrete substrate and ultimately cracks. The causes of crack development on concrete may vary due to design flaws to numerous material properties.”

The solution to this lies in applying loosely laid systems like membranes. PVC and even APP membranes when applied over such type of roofs should be applied as loosely laid systems, with the joints only being sealed properly. The APP applied, should be reinforced with polypropylene only. The junction between horizontal and vertical surfaces must be doubly reinforced with two layers of membrane and should be applied over properly rounded edge.

Bandopadhyay adds, “Materials like ADO Cool may be applied in two layers. Spray applied polyurethane and polyurea coatings will also be very effective in these cases as they have a very high tear resistance. However, all such waterproofing must be applied after conducting trials in a zone and being observed for a certain period.”

Need to understand the basic information first
Mestry opines before treatment of any type of roof waterproofing of any structure, need to understand the basic information about structure, like
• Type of construction of the structure
• Age of the structure to waterproof
• Foundation condition
• Type of waterproofing problem

Challenges of application waterproofing system
• Detection correct leakage problem
• Suggestions of correct methodology to leakage problem
• Treatment of leakages as per methodology and using correct waterproofing products
• Retest the problem after treatment.

Finding and repairing the leaks is a challenge.
Arunabha Dey, National Manager,Waterproofing and Roofing, Sika India Pvt Ltd

The most cost-effective but efficient solution lies in treatment of joints.
Basab Bandopadhyay, DGM – Technical Service, ADO Additives Mfg Pvt Ltd

Epoxy-based or PU (Polyurethane)-based products are giving confirm solutions for metal sheet roofs.
Krishna Mestry, Proprietor, K. R. Waterproofings & Polymers