Moisture Problems in Building Envelopes – knowing the score is key to reducing risk.

We’ve all heard the heartbreaking stories. Most of us know someone who was affected by the “leaky condo” crisis that blindsided homeowners and caused them immense hardship and loss. Between 1983 and1998, a massive failure of the building envelopes in coastal BC homes allowed moisture to enter walls and reap havoc in rot, mold and leaks. Although the damage was most prevalent in condominiums, it also hit rental units, co-ops, townhouses, high-rises and single-family homes. When all is said and done, an estimated one to two billion dollars — most of it paid by homeowners — will have been spent to clean up the mess. Public confidence in the residential construction industry went into a tailspin as a result and stayed low for many years. If you’re thinking of buying a property, you’re riding a new wave of confidence in real estate purchase. Is this confidence justified? If you buy a home today, how sure can you be that it won’t leak? True confidence in today’s market must be based on the knowledge gained from past mistakes. It means standing on solid ground and making an informed buying decision. This article looks at how the problem of moisture-ridden homes developed, what’s been done about it, and the steps you can take to reduce your risk.

Causes of building envelope failure

Several coincidental changes played a role in the disaster. From building codes to consumer protection programs, the processes in place to ensure quality building practices failed. Rapid economic expansion and a boom in housing construction led to a dramatic increase in land prices, squeezed profit margins, and a shortage of qualified developers and builders. In this fiercely competitive market, hungry developers looked for cost-effective building techniques and new housing solutions. They began to model California dwellings and to emphasize lifestyle marketing and exterior design at the expense of solid construction practice. The new designs ignored the traditional features suited to a rainy climate and instead limited or eliminated overhangs, minimized wall thickness, and incorporated ineffective building envelopes made of substandard materials. The arena in which this was occurring gravely compounded the problem. It was one in which the roles and responsibilities of the various participants in the system — the architects, engineers, developers, general contractors, city inspectors, financial institutions, warrantors and so on — were ineffectively delineated and regulated. Along with inappropriate designs and shoddy workmanship, this lack of guidelines and accountability led to a systematic failure of the building process that resulted in the deterioration in the quality of construction and the ensuing tragedy. For a detailed analysis, read the report of the Barrett Commission of Inquiry into the Quality of Condominium Construction in British Columbia:

Rain penetration control

The building envelope consists of everything that separates the indoors from the outdoors — the exterior walls, foundations, roof, windows and doors. It is meant to keep out rain and to prevent moisture from getting trapped inside the walls, leading to deterioration and decay of the building components. Building envelope technology is a complex subject, but a basic understanding of how different wall assemblies perform in terms of keeping water out can be helpful. Three factors are needed for water to penetrate into a building: water on the exterior wall, an opening through which the water can enter, and a driving force to move the water. Wind, momentum, capillary suction, and pressure due to differences between the outside wall and the interior wall cavity create the conditions necessary for water to penetrate the building envelope at any opening. Since it is practically impossible to achieve and maintain a watertight seal of the building envelope, some water will inevitably enter and must be allowed to drain out. Deflection and drainage are the primary mechanisms for protecting a wall from water penetration.

Deflection not enough

Systems that rely primarily on the deflection of water from the exterior wall are insufficient. For example, the face sealed systems widely used in this area attempt to create a completely impervious barrier to water by carefully sealing the envelope.   However, due to temperature extremes and building movement, the seals eventually fail. Wind then moves through the cracks, creating the driving force necessary to bring water into the wall assembly. Since there is no cavity for the water to drain out, it stays trapped there and causes rot. Concealed barrier systems are designed mainly to shed water from the exterior surface but also incorporate minimal drainage and venting capabilities as a second line of defense. These types of wall assemblies work well in drier climates. In BC’s wet coastal climate both systems have shown a high frequency of moisture problems in recent years. In the 1980s various new wall systems were tried that contributed to the problem. Among them, a new waterproof synthetic stucco called EIFS (pronounced ee-fiss; exterior insulating & finishing systems) came on the market and into wide use. It has subsequently been connected to concealed rot in wall cavities.

Rain screen systems go further

Rain screen wall assemblies are the best method for controlling water penetration. These designs deflect most of the water at the exterior cladding, but also have a cavity through which any water that does get past the surface wall is allowed to drain. Water entering the wall cavity typically runs down the backside of the cladding and exits at flashings and weep holes. The combination of a larger drainage cavity and vent paths to the outside improves the drying ability of the wall. Residential structures in Vancouver have been built using rain screen technology since 1999. The result is that properties entering the market since then are much more effective at preventing moisture penetration into the building components. Whatever type of building envelope is used, if moisture does enter the wall and the problem is identified early, it can be remedied relatively inexpensively. If left unattended, repair costs increase dramatically. Even if a building survived the crisis period without any complaints doesn’t mean that it won’t leak in the future. Regular home inspection and maintenance of the building envelope by a qualified professional is crucial.

New regulations to protect homeowners in B.C. 

As a result of recommendations by the Barrett Report, British Columbia now has a regulated construction industry and consumer protection mechanisms in place. In 1998 the Homeowner Protection Act was passed and the Homeowner Protection Office (HPO) established to protect consumers and improve the quality of residential construction. As of July 1, 1999, all residential builders must be licensed by the HPO and provide third-party warranties on new home construction. This mandatory coverage includes a minimum of two years on labour and materials, five years on the building envelope including water penetration, and ten years on structure. There is a public registry of all licensed residential builders on the HPO website. In addition, as of October 1, 2000, repair contractors who perform building envelope renovations on residential buildings of three units or more must be licensed by the HPO and provide third-party warranty insurance in order to get a building permit. For more information visit the Homeowner Protection Office website:

How to reduce your risk

Despite these measures and improvements in building technology, the danger still exists that you could buy a home with building envelope problems. A prudent approach is especially important if you’re considering buying a condominium. Some defective buildings have yet to show signs of moisture damage, some repairs have turned out to be as faulty as the original buildings, and there can be less-than-perfect disclosure of the property’s condition. Whether you’re interested in a resale or new unit, there are several important actions you can and should take to minimize your risk of moisture problems and maintain proper home health.

1. Investigate the property

In new buildings

  • Ask about the builder’s experience, training, and affiliation with trade associations.
  • Check the company’s reliability report with the Better Business Bureau:
  • Request a list of projects completed in the last few years and check them out. How has the company dealt with any previous problems on its projects?
  • Make sure the developer used a building envelope specialist.

In resale buildings

  • Review the property disclosure statement the developer or seller is required to give you.
  • Read strata council minutes, corporation bylaws, regulations, financial statements and budgets for the current and previous two years. If moisture problems are mentioned, find out if and how these were remedied. Are there any major expenditures planned for the building?
  • Try to determine how proactive the strata council is with regard to maintenance planning and repairs. Find out the percentage of rental units to owner-occupied units. Higher owner occupancy indicates that the building is likely to be maintained at a better standard, and the minutes will more accurately report existing building conditions.
  • Request any engineering reports, critically important since they are typically done after moisture problems have been identified.
  • Find out what kind of wall system was used following envelope repairs and discuss with a Contact Us.
  • Ask specific questions of the strata president about water intrusion and talk to neighboring unit-owners.
  • Have a knowledgeable person assist you in interpreting technical and legal documents if necessary.

2. Understand the warranty protection

If a defect occurs in your new home, a strong warranty is your only guarantee that it will be repaired. Make sure you clearly understand the type of warranty offered. Keep in mind that the market is in a period of transition regarding warranty protection and that many different types of warranties exist. For more details, refer to Buying a New Home: A Consumer’s Protection Guide, available on the Homeowner Protection Office website:  

3. Hire a professional home inspector

A professional inspection by a Primus home inspector will reduce the risk of purchasing a home that may have moisture penetration problems. Training in building envelope theories and practices, and experience in the field will enable a building inspector to reasonably predict the likelihood of existing or future building envelope failure. It must be emphasized that the only conclusive way of determining whether moisture damage is evident is through core sampling, a procedure in which test cuts are made at various locations in the building envelope to extract a core sample. This is not, however, a realistic option for buyers, nor are many vendors likely to agree to it. A professional home inspection report will give details on the likelihood or potential for moisture penetration problems in the building envelope, giving the buyer valuable objective information to confidently make a purchasing decision.   Written and published by our Vancouver home inspectorsPrimusy Home Inspections Ltd.