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D4COST Software

 

New Buildings that Leak
Analyzing the Causes and Pinpointing the Responsibility

Arthur O'Leary, FAIA, MRIAI
 


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The First Rainy Season 
Fortunately they don’t all leak. Nevertheless architects and contractors are always relieved when their newly completed buildings get through their first rainy season without any problems.

Building leaks are at the top of the list of owner complaints about their new buildings. Rainwater intrusion into a recently completed building is one of the most traumatic of all unpleasant events for a new building owner. It conjures up images of shoddy construction and is often construed as an indicator of other hidden defects that will undoubtedly reveal themselves later. It leaves the owner with the unsatisfactory and uneasy feeling of having been violated.

Initial Repair Efforts
There is also the general aggravation of having to call the contractor if the warranty period has not expired. After the warranty period the owner feels utterly abandoned if the contractor has given up on voluntary repair efforts. This is in addition to the usually uninsured and unbudgeted costs of mopping up and repairing damage to finishes and contents and the necessity of reparation to prevent future occurrences.

The owner is usually ill-equipped to embark on effective repair efforts without the help of the contractor or architect. Sometimes the technological problem is beyond solving by the contractor and the architect is equally perplexed. It is when the contractor and architect seem unable to solve the problem, or even worse, abandon further efforts, that the owner is forced to strike back, usually by threat of legal action. Further procrastination or ineffective repairs will result in expensive litigation. The owner is likely to prevail.

Leaks that appear immediately or shortly after completion cannot be attributed to the owner’s inadequate maintenance or abuse. Most owners would suspect that they must have been caused by ineptitude or lack of concern of the designers or builders.

Light rain might not result in leaks unless driven by wind. So some important leaks may not become apparent initially. The first heavy or persistent rainfall after completion of a building will realistically test its raintight integrity. Most rainwater intrusion is noticed only if it impinges on the use of the building and becomes obvious.

Concealed Leaking
Some leaking into attics, subterranean areas, and other hidden places will not be detected until some visual evidence is perceived in the inhabited areas. Undetected hidden leaks may do extensive damage over long periods of time before eventual discovery.

Any part of the building envelope can leak under certain circumstances. The most commonly encountered rainwater intrusions are associated with roofs, walls, windows, doors, and floors. Subterranean leaks, ranging from minor dampness to copious streams of free water, can occur through below grade walls and floors.

The building envelope is typically made up of thousands of interfacing parts, each intervening joint susceptible to some form of failure.

Leaks at the Edges
Most materials do not usually leak in the middle. Leaks occur mostly at the seams and joints where materials are self-joined and at the edges where one material abuts another.

It is obvious that windows do not leak through the glass. They leak where the glass meets the frame, at the frame joints, or where the frame meets the next adjoining material. Frames are more likely to leak at the intersecting corner joints than in the middle of the frame.

Roofs do not often leak in the middle. They more commonly leak where the roofing material meets whatever it is fastened to or abuts, such as at skylights, flashings, eaves, chimneys, vents, and vertical walls.

Most of the time the interfacing dissimilar materials are installed by different trades. This complicates the problem of assigning responsibility for a workmanship or material failure. Each trade will blame the other.

Failures of watertightness occur when there is a shortcoming in the design concept, defective workmanship, or inappropriate materials have been used. Sometimes there is but a single generic cause but is often made up of a combination of factors.

Conceptual failure is one where the design would never have worked no matter how excellent the materials used or how skilled the artisan who installs them. This would be the case when some natural physical law or phenomenon is overlooked, disregarded, or violated. These include, among others, capillarity, condensation, friction, differential air pressure, thermal expansion and contraction, normal structural movement, and the law of gravity. Violation of the shingle principle will generally result in leakage.

Sometimes the design error is based on inadequate structural consideration or disrespect for the unique characteristics and inherent limitations of each material. Insufficient consideration of tolerances, fastenings, gaskets, sealants, and weep holes can also be at the root of the design deficiency.

Workmanship failure is one where appropriate materials have been misused or have been installed not in accordance with the design. Some workmanship failures are caused by improperly trained, ignorant, or inadequately equipped craft workers while others are caused by unauthorized, ill-considered ad hoc jobsite changes in the design, usually for the purpose of making the job easier or to save money.

Material failure is one where defective or inappropriate materials, equipment, or assemblies have been employed. The design configuration and workmanship may have been adequate if the proper materials had been used. Sometimes the contractors or craft workers stray from the properly specified materials through ignorance, but more often as an expedient to save time or money without realizing that an unsatisfactory result could ensue.

Temporary repairs may be necessary to protect the building, its finishes, and its contents for the time being. However, after the rainy season has ended, a permanent repair must be devised and carried out. A proper repair should endure as long as the underlying systems would have been expected to last had there been no failure. The same repair should not have to be made repeatedly.

It is necessary to accurately identify the precise generic cause of the leaking failure before proceeding any further. It would be pointless to go directly to the constructing contractor to devise a permanent repair method. If it happened to be a design failure, it might not be recognized as such. If it had been a workmanship or material failure, the people who made the original error might not be capable of devising a satisfactory reparation method. The design architect may or may not be technologically equipped to identify and solve the problem realistically.

Instead, an expert should be sought who understands the design problems inherent in the failed system, whether it happens to be roofing, waterproofing, doors, windows, windowwalls, plastering, masonry, sealants, or concrete.

The best repair system will not always be to remove all offending materials and replace them with the proper materials. It might be more efficient, effective, conservative, or economical to devise something different in recognition of existing conditions.

This is based on a similar article originally written for the April 1996 Issue of California Construction Law Reporter.

For additional information on analyzing construction defects, repair systems, repair costs, and liability, see Who Is Responsible for Defective Construction? by Arthur F. O’Leary, FAIA, MRIAI, in the Mar/Apr 2000 Issue of Design Cost Data.

Some Common Causes of Leaks

Dampproofing versus Waterproofing. Subterranean walls and floors must be properly waterproofed if they are expected to totally exclude moisture. Dampproofing will not accomplish this. It should not be used where there is any chance of hydrostatic pressure or persistent moisture. The difference in cost is considerable, so it is necessary that the appropriate material is specified and properly used. Repair of subterranean waterproofing is usually very costly due to its commonly inaccessible location. All special details must be carefully considered and properly designed, such as joints between floors and walls and at piping penetrations.

Sealants. Some joints are designed to be weatherproof or waterproof solely by use of sealants. If the sealant fails, the joint leaks. Sealants must be properly specified and the joints must be properly designed and detailed. Some designers are not careful about this, leaving the joint design and material to the discretion of the contractor. The contractor, unless highly knowledgeable, will use general purpose caulking or mastic of modest cost. The continued integrity of the joint might be heavily dependent on recaulking or resealing from time to time. If the joint is inaccessible, this might be impossible. Failure is inevitable.

Skylights and Window Assemblies. Factory engineered assemblies such as skylights and windowwall systems are the result of careful design, experimentation, testing, and experience in the factory and in the field. Improvements are constantly being made to reflect field experience. These types of products, when manufactured by quality producers, generally give reliable service in use. When designers or contractors attempt to design such elements by field assembly of generic materials and components, there is a high risk of leaking as well as extremely high maintenance costs.

Roofing Bonds. A roofing bond will not prevent a roof from leaking. The underlying concept of a roofing bond is that the insurer will issue a bond only if the roofing specification is up to a stated minimum standard of a roofing material manufacturer and that the installation is properly supervised. If the roofing fails to be watertight during the period of the bond, the surety will pay for the repairs. Some bonds do not cover the flashings and most do not cover damage to building contents. The exact bond language would govern the conditions of the guarantee.

Flashing. Flashing always covers and protects a very vulnerable open joint. Its failure will usually guarantee a serious leak. Thus flashings must be sensitively designed and must be properly fastened so they will not blow off or dislodge in high winds and should be sealed where necessary.



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