Source: http://www.qp.gov.bc.ca/condo/c2_ii.htm
Timestamp: 2018-11-20 21:49:14
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Condominium Construction Inquiry -- Chapter Two: II. Building Codes
In 1941, the National Research Council (NRC) published the first edition of the National Building Code (NBC). The NBC, promoted by federal authorities, is a voluntary process for application by provinces with a view to creating relatively uniform standards, nationwide. In principle, this is a worthy objective.
Under the Constitution Act, building regulation falls within provincial jurisdiction. Therefore, provincial and municipal authorities have the ability to amend the NBC.
The British Columbia Building Code (BCBC) is a provincial regulation under the authority of the Municipal Act. The current edition was adopted in 1992 and is based on the 1990 NBC, with some adjustments, after industry-wide consultation.
With the exception of the City of Vancouver, federal properties, and unincorporated areas, the BCBC is applied throughout the province. Vancouver has its own by-law, although based on the NBC and the BCBC. The most recent set of changes in the Vancouver by-law were enacted in 1997. These reflected the NBC revisions to the 1995 Code, for Part 5 (Wind, Water and Vapour) only. These amendments anticipated the BCBC adopting the majority of amendments in the NBC revisions. The amended BCBC is scheduled for release in the near future.
Most local governments supplement the mandatory provincial code through by-laws. Consequently, there is a great deal of variation among municipalities. Recently, Richmond and New Westminster adopted by-law changes which incorporate rain-screen technology in building envelope requirements.
The Provincial Code is intended to represent minimum standards regarding life safety, health, and structural sufficiency of buildings. It is neither a textbook on building design, nor a criterion for quality or workmanship. In the ensuing discussion of the Building Code, it is important to remember that the Commission is not recommending that the intent of the Building Code be changed. Part 3: Use and Occupancy, Part 4: Structural Design, Part 5: Wind, Water and Vapour Protection, and Part 9: Housing and Small Buildings, are most relevant to the Commission's work.
Part 9: Housing and Small Buildings, is detailed, prescriptive, and relates to smaller buildings (less that 600 square metres and less than four stories). Part 9 was not intended for use by developers of larger, and more complex buildings. Because it was assumed professionals would not be involved in the construction of small buildings, and because less sophisticated builders would be, Part 9 is very specific.
The size and height restrictions were meant to limit the building's scope and complexity. However, the definitions of "building height" and "building area" are such that buildings containing four stories, and floor areas greater than 600 square metres, have been built under this section of the code. The definition of "small buildings" includes exceptions for fire walls. In addition, "small buildings" over three stories can be built under certain conditions, such as on sloped sites.
All other buildings are classified as Part 3 buildings, and are required to comply with all applicable portions of the Code. This includes Part 5, which deals with building envelope design and construction. The envelope requirements in Part 5 are performance-oriented; require a higher standard of design and construction; and require Letters of Assurance as defined in Part 2.
Many Part 9 buildings, particularly the larger, multi-unit residential buildings, receive the same exposure to weather conditions as do Part 3 buildings. The critical factors determining the exposure to wind and rain are the height and form of the building.
There appears to be confusion among building officials and professionals in understanding and interpreting what the building codes have outlined. It is the Architect's responsibility to ensure that the project's design and construction substantially conform to the relevant building codes. It is the municipal inspector's responsibility to ensure the code has not been violated. However, municipal officials approve plans for permit purposes and undertake minimal on-site inspections. Inspections do not cover building envelope design, but deal with foundations, sheathing, framing, insulation, and a final inspection for occupancy. Field review activity of architects are at their discretion and, as has been suggested by various presenters vary in their calibre.
With respect to the role of professionals, prior to 1993, architects were not required to sign Letters of Assurance. Even after 1993 -- as will be explained below -- many condominium projects were constructed under Part 9 of the Building Code. This section does not always require a design professional or Letters of Assurance. This can leave the obligation for design principles to the developers or builders, who may have ceased to be in business, or are protected by numbered companies.
The Commission agrees that there is confusion regarding the responsibility for interpreting and enforcing the application of the building code. It also agrees that the provincial government must assume the major responsibility for this area as reflected in recommendations #3, 4, and 5 above.
Recently, the City of Vancouver has added some explicit, prescriptive requirements to Part 5 of its by-laws, by issuing bulletins 96-02 and 96-25, and adopting the NBC revisions to Part 5. Specifically, the provisions for a drainage cavity in wall assemblies; greater attention to detail; and the requirement of field review by a Certified Building Envelope Specialist, were introduced.
The Commission is concerned that these changes may not have improved the quality of recent new residential construction and remedial work to the degree the city intended. Further, the Commission is concerned that these changes do not apply to Part 9 buildings. Not only are substandard, multi-family units continuing to be built, but also a significant portion of the existing stock in Vancouver, as well as in the rest of the province, continue to be renovated under Part 9.
Recommendation #7. All Part 5 (Wind, Water, and Vapour) requirements of the BC Building Code be applied to all multi-unit, residential buildings, greater than two stories in building height, or larger than 600 square metres in building area (regardless of fire walls).
Recommendation #8: All multi-family buildings facing renovations to the building envelope be renovated under the provisions of Part 5 of the BC Building Code.
Recommendation #9: That the Vancouver by-law be reviewed with respect to applying Part 5 requirements to buildings, and to renovations for building envelope failures, to all multi-family residential buildings greater than two stories in building height or larger than 600 square metres in building area (regardless of fire walls).
There has been a great deal of discussion and debate concerning the use of polyethylene in residential construction and its role in the amount of rot in condominiums. The first distinction to be made is that Part 5 of the Building Code does not refer to polyethylene as a vapour barrier or an air barrier. Therefore, the use of polyethylene derives from the optional requirement for it, found in Part 9 of the code.
Part 9 states that polyethylene may be required as a vapour barrier under section 9.25.3.5(l) or an alternative vapour barrier sheet system may be used (for example, drywall and interior paint) which excludes polyethylene, as explained in 9.25.3.5.(l)b. Polyethylene, therefore, is not mandatory as a vapour barrier.
Polyethylene is also not mandatory as an air barrier. Section 9.25.3.4.(l) states, "Air barrier protection shall possess the characteristics necessary to provide an effective barrier to air exfiltration under differential air pressure due to stack effect, mechanical systems or wind." However, these vague performance criteria, regarding air pressure, are nestled in with the more prescriptive specifications regarding Thermal Insulation and Control of Condensation.
Although the use of polyethylene may be optional under the code, the Commission understands builders may have been directed by inspectors to use it, and to ensure it was airtight. The important point here is, the building code does not have to be changed to provide an option to polyethylene.
Confusion regarding the use of polyethylene can arise when it is used as a vapour barrier as well as an air barrier. First of all, a vapour barrier, which is attached on the inside of the wall, is necessary to prevent moisture from the more humid interior of the building from creating condensation inside the wall by diffusion. The Commission understands that to work properly, a vapour barrier does not have to be air tight.
By comparison, an air barrier system, which needs to be continuous, is required to ensure the amount of wind-driven rain, through holes in the envelope, is limited. Although not the only way to create an air barrier, polyethylene, coupled with sealant and other materials, has been widely used to create a continuous barrier. The need for an effective air barrier system (which includes structural support) increases with the amount of wind blown onto the side of a building. In single-family homes, often with overhangs, and protected from wind-driven rain by surrounding homes and trees, the external pressure is minimal. It appears that the polyethylene air barrier, doubling as a vapour barrier, works well and is unlikely to develop envelope problems, provided the workmanship complies with the code.
When the building envelope, prescribed in Part 9, is applied to taller buildings, exposed to wind-driven rain (many with highly-complex building facades), the problems seem to increase because the principles of building envelope science are fundamentally violated. Simply put, the principles of building envelope science require that water not settle within the building assembly.
"Rain penetration results from a combination of water on a wall, openings to permit its passage and forces to drive or draw it inwards. It can be prevented by eliminating any one of these three conditions."
Canadian Building Digest - 40, Rain Penetration and Its Control, April 1963
It should be made clear that the research and knowledge necessary to avoid the current problems have been known for more than thirty years, and that the principles of building envelope science (or enclosure design), as laid out in National Research Council studies, are built into Section 5 of the Building Code.
"Where a building assembly will be subjected to a temperature differential, a differential in water vapour pressure and a differential in air pressure due to stack effect, mechanical systems or wind, the assembly shall be designed to provide an effective barrier to air exfiltration and infiltration, at a location that will prevent condensation within the assembly, through:
(a) the materials of the assembly,
(b) joints in the assembly,
(c) joints in components of the assembly, and
(d) junctions with other building elements.
British Columbia Building Code 5.3.1.1.(1)
As well, numerous courses and workshops have been held over the years in an effort to educate inspectors, designers, developers, and builders. However, as the results have shown, these have met with little success.
The evidence suggests that significant building envelope failures in British Columbia since the early 1980s, is not the result of the Building Code. It is a result of numerous factors, including design features inappropriate for our climate; a reliance on face-sealed wall systems; a fundamental lack of awareness regarding the principles of enclosure design suitable for our climate; meaningful inspection at critical stages of construction; and a regulatory system which was unable to understand that failures were occurring and to redress them.
"The cause of many facade problems, for example, originates in the way in which materials are specified to be put together and the type of materials chosen for various parts of the building envelope. Either from lack of appropriate information about the construction sequence or from incorrect assumptions of end performance, unsuspected weaknesses appear first in architectural and engineering drawings, are carried through to shop drawings and are eventually "built in" by the construction team."
A Study of the Construction Process, Construction Canada 24, January 1982
Design features, brought in during the 1980s and 1990s, such as open walkways, arched windows, complex, intricate and visually-appealing joints and the removal of overhangs, provided more opportunities for water penetration. As well, zoning by-laws relating to floor space ratio (FSR) exacerbated the problem. Roof overhangs are included in the calculation of FSR. As a result, they were often removed from designs. The calculation of FSR from the outside of the building envelope, instead of from the centre or interior side of the wall, tended to promote face seal at the expense of thicker, heavier walls, or rain screen systems. The exclusion of open walkways from FSR prompted their construction on a grander scale, often leading to water ingress problems.
Recommendation #10: That all municipalities review their zoning by-laws, and the calculation of FSR, with a view to promoting sound building envelope design practices. In particular the following revisions should be reviewed:
(i) FSR calculations to be taken only to the inside face of the principle structural elements of the exterior walls necessary to support the building and the walls;
(ii) exclude from FSR, walkways and top floor balconies protected by roofs; and
(iii) ways and means for promoting overhangs which does not conflict with other municipal planning objectives.
Face-sealed systems, which relied on the erroneous notion that a building could be sealed with caulking (9.27.4 of the BCBC), also became widely used on condominium projects in the 1980s and 1990s.
"... it can be concluded that the face seal systems evaluated in this study are very sensitive to design and construction variables which lead to ingress of water through the cladding, and that in the environment of the Lower Mainland it may not be possible to achieve acceptable performance with face sealed systems. Concealed barrier systems are also very sensitive to water ingress through the exterior cladding and weather barrier. In order for these systems to perform adequately, significant improvement is required in the design and construction of interface details.
Survey of Building Envelope Failures in the Coastal climate of British Columbia, CMHC
In fact, the research literature has been very clear on the inability of face seal methods to be effective.
"In the Lower Mainland, the incorrect assumptions of end performance that have resulted in the need for this Commission are reliance on exterior surface treatments of buildings to prevent rain entry under the conditions of wind driven rain. It is not difficult to find well informed technical opinion suggesting that this is an unreasonable expectation:
"Basically there are two possible ways in which one can approach the problem of trying to keep the rain out of a building. One can either attempt to eliminate all the holes through which the water could pass or one can attempt to control the forces which would move the water through these holes. Under practical building conditions, we have seen that the former is more or less doomed to failure and that one can expect better result from the latter method. " From NRC, Walls Window and Roofs for the Canadian Climate, October 1971.
Thomas Morstead, Building Envelope Specialist
There also appears -- even with the amount of attention on the matter, as a result of the leaky condo crisis -- a lack of awareness regarding the need for an effective air barrier. This barrier ensures that air movement does not drive or draw rain inward. That is, the rain-screen technology that is being advanced, may be placing too much emphasis on the cavity between the outside wall and the structure. In fact, it is the entire wall system and its function as a system, which is important. The concern is, without appropriate understanding of widely-understood and endorsed building enclosure principles, future buildings may suffer from the same, or different, moisture-related problems.
As well, there may not be a complete understanding of the principles related to renovations of face-sealed buildings. Even with its problems, face seal is essentially air tight. When the outside stucco is removed and replaced with a different wall system, it is important to incorporate in its re-design and re-construction, all the functions the wall is required to perform.
Recommendation #11: That the Education and Research initiative be charged with the responsibility for:
(i) research and development of best building practices and techniques;
(ii) ensuring that the advances in building science technology are clearly identified, agreed to, and disseminated to all parties responsible for design and construction of residential buildings;
(iii) the approval of the designation requirements for Building Envelope Specialists prior to the endorsement of this specialty;
(iv) the review, interpretation and recommendations regarding the building code; and
(v) assist in the development of key issues related to the residential construction market.
Recommendation #12: That a Provincial Advisory Council be established, through the authority of the Home Protection Office's Research and Education initiative, and with the assistance of representatives from the development industry, the Architectural Institute of British Columbia (AIBC), the Association of Professional Engineers and Geoscientist Institute of British Columbia (APEGBC), the City of Vancouver, representative from other municipalities, Canada Mortgage and Housing Corporation (CMHC) and the provincial government.
Recommendation #13: That Part 5 of the BC building code, through the Provincial Advisory Council, be reviewed prior to release, and that the City of Vancouver revisit its by-law, particularly Part 5, to ensure consistency with the eventual Part 5 of the BC building code.
On Part 5 buildings, the Code requires a registered professional be engaged to accept responsibility for the co-ordination of the design. This professional must also direct the services of a team, responsible for various facets of the design, including structural, mechanical, electrical, geotechnical and, architectural aspects.
Vancouver requires a Certified Building Envelope Specialist to be responsible for the "significant ongoing inspection" of the construction of the envelope for all buildings within the jurisdiction of Part 3. This has created some confusion as the certification program is at an interim stage. However, firms that have shown expertise in building envelope design are given the designation of Certified Building Envelope Specialist, until the AIBC program of certification is fully developed and approved.
The Commission recognizes that the Architectural Institute, the Engineers, as well as the city of Vancouver, CMHC, UDI and the Home Builder's Association of British Columbia (HBABC) have, and are continuing to develop, programs, workshops, training seminars and guides to educate the industry in sound building envelope science principles. The Commission would also suggest that colleges and universities train students in the principles required for building envelope science.
Recommendation #14: That training provided through educational institutions, and continuing education, offered by professional associations, clearly identify the special requirements for multi-family building envelopes in British Columbia.
Recommendation #15: Any architect or engineer involved in Letters of Assurance and the field review process must have the qualifications, or sub-contract, the building envelope design and review to a qualified Building Envelope Specialist, to be defined by AIBC and APEGBC in consultation with the Provincial Advisory Council.
The building envelope, although technical in nature, is still considered part of the architectural design, and is included in the Letter of Assurance for "Architectural Design" and "Commitment for Field Review." An enhanced checklist should be developed by the AIBC, APEGBC, and municipal representatives, and reviewed by the Provincial Advisory Council of the proposed Homeowners Protection Office.
Recommendation #16: That the AIBC and APEGBC, revise current letters of assurance and field review process to include a more detailed checklist of building envelope components and submit to the Provincial Advisory Council for endorsation.