Case 5

Failure of Waterproofing System

Introduction

Peeling of the paint is evident on the ceiling near the structural column. Peeling of paint can be attributed to a number of factors. A few of such factors are using too many layers of paint, improper painting surface preparation, high temperatures, water damage, poor quality of paint, failure of water proofing membrane, etc.

The failure of waterproofing can be attributed to the following reasons:

• Poor Preparation
• Incorrect Selection of Material
• Adhesive Failure
• Deterioration
• Exposed to high water pressure (Waterproofing system may not withstand the water pressure and movement)

The waterproofing membrane has failed which allows water seepage that in turn pushes off the paint film. As there is water seepage, the surface on which the paint is applied on is constantly wet or damp, which leads to poor adhesion of the paint on the surface. Pockets of trapped air and moisture expand and displace the paint film. Air and moisture passing through the dense concrete ceiling at a slow flow rate allow blisters to form. Pressures will then develop, causing a displacement and stretching of the paint when the air pocket increases in size, resulting in the peeling of paint.

Poor workmanship, including incorrect installation, can lead to leakage issues as well as the wrong product or method used. Poor preparation and installation of critical junction points in vertical and horizontal surfaces are also a major cause of failures since poor detailing and inadequate curing of the bonding solution can adversely affect a membrane’s effectiveness, where the membrane can shift and crack with the differential movement occurring over time.

Adhesive failure happens when moisture enters the waterproofing membrane which leads to the debonding of the waterproofing material.

Preventive Measures

Design:

Specify the use of a breathable paint system to reduce trapped moisture and to avoid wetness and dampness of basement walls. Fungiresistant paint is also required. Avoid the use of Alkyd based paint on concrete surfaces that may lead to saponification (i.e. the formation of oily patches)

When selecting the paint, consider substrate, environment, application method, the feasibility of surface preparation, over-coating interval, and appearance.

Construction:

The waterproofing should be carefully constructed with supervision at all stages of construction. The site conditions and construction method should be thoroughly understood before construction begins. This helps to prevent damage to the waterproofing.

Corrective Measures

Regular inspection is important to detect or identify the defects immediately, so that corrective maintenance could be carried out at the early stages to prevent further complexities. Visual inspection techniques or instrumentation techniques can be used for regular inspections.

Diagnostics of Defects:

• Visual Inspection

Inspect at reasonable intervals to identify any blistering of paint.

• Use of Moisture Meter

A Moisture meter can be used to measure the reduced resistance between two probes when they are embedded in damp materials. It can be used to trace areas of walls affected by rising damp or rain penetration. Measurements should be taken at regular intervals to distinguish between surface dampness or dampness within the wall.

• Hygrometer

The hygrometer can be used to test the amount of moisture present in the structure.

• Thermography

Thermography can be used to identify the position of water leakages. The method is based on the characteristics of the heat flow phenomenon, in a conductive medium of a specific geometry, which is intended to model predetermined boundary conditions. Thermo tracer is an advanced equipment used in thermography technology

Remedial

Before repairing the waterproof layer, the paint that has peeled should first be scraped off. The plastering under the paint peeling should then be hacked to expose other cracks or defects. 

If the area of peeling paint is waterproofed with a tanking system or admixture, Polyurethene grout injection is one of the most cost-effective repair method (Procedure of PU injection) . It will seal up the holes and cracks in the concrete as well as seal up the passage of water from the soil.

Polyurethane (PU) Grouting is specially designed for providing water control in static joints or cracks in concrete structures. The grout material, when mixed with a certain amount of accelerator, will react with water or moisture and expand to form a tough, closed-cell rubber that is essentially unaffected by corrosive environment.

Polyurethanes are products of the petrochemical industry. They are very durable when exposed to external conditions and retain their gloss well. They can be obtained as elastomers, solid and rigid materials or flexible coatings. Major cracks or localized porous concrete can be repaired by this method.

In the application, PU reacts upon with the water in the slab and expands its volume and thus fills the cracks or pores in the slab. Therefore, it acts as a sealer over the cracks. The repairing process can be completed within half a day. Accelerator agents can be used to speed up the setting time of the grout.

References

[1] Optimech. (n.d.). Why Waterproof Membranes Fail. Optimech. Retrieved from https://www.optimech.co.nz/why-waterproof-membranes-fail/

[2] Radic, I. (n.d.). 10 Common reasons why some waterproofing membrane fails. Chemind. Retrieved from https://chemind.com.my/10-common-reasons-why-some-waterproofing-membrane-fails/

[3] SS652:2019 Singapore Standard Maintainability of Facilities