2. CMHC HOME TO CANADIANS
Canada Mortgage and Housing Corporation (CMHC) has
been Canada’s national housing agency for more than 65 years.
Together with other housing stakeholders, we help ensure
that the Canadian housing system remains one of the best
in the world.We are committed to helping Canadians access
a wide choice of quality, environmentally sustainable and
affordable housing solutions that will continue to create
vibrant and healthy communities and cities across the country.
For more information, visit our website at www.cmhc.ca or
follow us on Twitter, YouTube and Flickr.
You can also reach us by phone at 1-800-668-2642 or by fax
at 1-800-245-9274.
Outside Canada call 613-748-2003 or fax to 613-748-2016.
Canada Mortgage and Housing Corporation supports the
Government of Canada policy on access to information
for people with disabilities. If you wish to obtain this
publication in alternative formats, call 1-800-668-2642.
3. CANADIAN WOODFRAME
HOUSE CONSTRUCTION
CMHC offers a range of housing-related information.
For details, call 1-800-668-2642 or visit our website at www.cmhc.ca.
Cette publication est aussi disponible en français sous le titre :
Construction de maison à ossature de bois – Canada (n° de produit 61199).
4. aterials and techniques carefully and to consult appropriate professional resources to determine
ourses of action suitable for their situations. The figures and text are intended as general practice
uides only. Project and site-specific factors of climate, cost, esthetics and so on must be taken into
onsideration. Any photographs in this book are for illustration purposes only and may not necessarily
present currently accepted standards.
brary and Archives Canada Cataloguing in Publication
urrows, John, 1948-
Canadian Wood-Frame House Construction—Rev. ed.
Third Combined Imperial/Metric Edition”— T.p. verso
pdated to conform to the 2010 National Building Code of Canada and enhanced by John Burrows,
F Burrows Consulting Inc., cf. Acknowledgements
sued also in French under title: Construction de maison à ossature de bois – Canada.
ncludes bibliographical references and index.
SBN 0-660-19535-6
at. no.: NH17-3/2005
Wood-frame houses—Canada—Design and construction.
Wood-frame buildings—Canada—Design and construction.
House construction—Canada. I. Canada Mortgage and Housing Corporation II. Title.
H4818.W6B87 2005 694 C2005-980262-6
1967 Canada Mortgage and Housing Corporation
hird combined metric/imperial edition
evised 2014
his document, or any discrete portion of this document (such as a chapter or section) may be
produced for redistribution, without obtaining the permission of the copyright owner, provided
hat no changes whatsoever (including translation) are made to the text; that the entire document or
screte part is reproduced; that this copyright notice is included in its entirety in any and all copies
the document or any discrete part of the document; and that no use is made of any part of the
ocument, or the name or logo of the owner of the copyright to endorse or promote any product or
rvice. For any use of this document other than reproduction or for the general reference purposes as
t out above, please contact: the Canadian Housing Information Centre (CHIC) at chic@cmhc.ca;
13-748-2367 or 1-800-668-2642. For permission, please provide CHIC with the following
formation: Publication’s name, year and date of issue.
rinted in Canada
roduced by CMHC
5. anada Mortgage and Housing Corporation
knowledges the individuals and organizations
hat contributed to this latest edition of
anadian Wood-Frame House Construction.
he following people served as reviewers and
erformed the important role of ensuring the
curacy and usefulness of the publication for
omeowners, builders and educators.
Richard Lind,
Everts Lind Enterprises, Lunenberg, N.S.
David Ricketts,
RDH Building Engineering Ltd.,
Vancouver, B.C.
Jasmine Wang,
Canadian Wood Council
Chris McLellan,
Natural Resources Canada
Barry Craig,
CMHC Policy and Research Division
CMHC also expresses its appreciation to
John Burrows of JF Burrows Consulting Inc.,
who updated this edition to conform to the
2010 National Building Code of Canada (NBC
and to the energy efficiency requirements in
the 2012 Interim Changes to the 2010 NBC,
and who enhanced this edition significantly by
adding new features.
CMHC gratefully acknowledges the National
Research Council and the Canadian Wood
Council for the use of their information
included in the tables of this publication.
23. anadian Wood-Frame House Construction by
anada Mortgage and Housing Corporation
CMHC) has been a popular publication for
uilders, homeowners (current and prospective)
nd students of housing technology since its
rst edition appeared in 1967. It continues
be a widely used reference for numerous
ollege and university courses and is one of
any continuing efforts by CMHC to provide
cessible, affordable and sustainable housing
r Canadians.
HOW TO USE THIS BOOK
anadian Wood-Frame House Construction is
concise description of Canadian wood-frame
ouse construction and references several
her publications that provide additional
formation. This book is not intended to
e a complete reference on wood-frame
house construction, but it is an introductory
book for understanding and applying
wood-frame house construction principles.
Though Canadian Wood-Frame House
Construction is based on the requirements
of the 2010 edition of the National Building
Code (NBC), it is not a substitute for the
NBC. Readers are encouraged to refer to
the housing-related codes and standards
in their jurisdictions for a complete set of
requirements. The book also provides some
recommendations that go beyond the
requirements of the NBC.
The organization of Canadian Wood-Frame
House Construction generally corresponds
to the construction sequence for a typical
house. In this updated version, information
about the functions of the building envelope
has been moved close to the front (see Chapter 5
24. anning process.
he chapters are based on major aspects of
ood-frame house construction and reflect
pical practices, some of which vary across
anada. Readers are urged to consult local
uilding departments, trades and suppliers
r additional direction.
deally, users of this book should read the
ook from start to finish. However, if specific
formation is required, each chapter has
een developed as a stand-alone reference.
n order to keep this book to a manageable
ze, a glossary of the numerous housing
rms used in this book is not included.
eaders should consult CMHC’s Glossary
Housing Terms.
valued, to:
Canadian Housing Information Centre
Canada Mortgage and Housing Corporation
700 Montreal Road
Ottawa ON K1A 0P7
chic@cmhc-schl.gc.ca
NEW FEATURES
This edition of Canadian Wood-Frame House
Construction has been updated to reflect the
residential requirements of the 2010 edition of
the National Building Code of Canada (NBC),
including new energy efficiency requirements
in the 2012 Interim Changes to the 2010
NBC. Many other changes have been made
to bring the book in line with current building
science research, construction methods and
construction materials.
This edition also includes “Choosing the
Size and Spacing” text boxes that provide
examples for sizing the typical wood structural
components of a house based on the tables
in the Appendices. For situations not covered
by the tables, consult a structural engineer.
CHOOSINGTHE SIZE AND SPACING
CMHC is committed to providing the Canadian
housing industry with reliable information
on appropriate housing technology that
responds to people and the environment.
In this edition, practical considerations derived
from CMHC’s sustainable housing initiatives
have been included in “Sustainable Housing
Insight” text boxes like this one. These include
technologies, building methods and products
that would make a house more sustainable
or improve performance beyond industry
standard practice.
SUSTAINABLE HOUSING INSIGHT
25. MPERIAL DIMENSIONS
anadian Wood-Frame House Construction
rovides both metric (SI) and imperial units.
he National Building Code of Canada
ses metric units and these govern whenever
rict interpretations of Code requirements
e required. Imperial units of measure
eet and inches) are still commonly used
r wood-framing materials and house
onstruction technology.
mperial sizes for lumber are nominal sizes
he rough sawn sizes before planing and
mensional changes resulting from drying).
or example, a wood member with a nominal
ze of 2 × 4 in. has a finished size of about
⁄2 × 31
⁄2 in. The metric dimensions for lumber
e actual sizes (for example, 38 × 89 mm).
very reasonable effort has been made to
rovide accurate conversions of metric
mensions to imperial equivalents; however,
remains the responsibility of designers
nd builders to comply with building code
quirements. Some conversion factors are
ven in Table 1 (Appendix A).
onsult the local building department to
etermine the units measurement required
r house plans.
26. Wood-frame construction has been the option
hosen for millions of houses in North America
nd provides some of the world’s most affordable
nd comfortable housing. From the days when
rly settlers used abundant forest resources for
ousing materials, wood-frame construction has
nce become a sophisticated technology supported
y a wealth of research and is capable of meeting
r exceeding all building science challenges.
ADVANTAGES OF
WOOD-FRAME
CONSTRUCTION
Wood-frame construction can incorporate
mension lumber, engineered wood products
nd structural wood panel sheathing into
all, floor and roof assemblies that are robust,
onomical and fast to build. Current wood-frame
chnology is the result of many years of
evelopment and improvement and extensive
search by the National Research Council,
Like any other building system, wood-frame
construction requires reasonable care in its
design and construction to provide lasting
shelter, comfort and safety. When well-designed
and constructed, wood-frame construction is:
fast and easy to build and renovate;
durable;
built from a renewable resource;
a natural insulator that is easy to insulate to
minimize heating and cooling costs;
strong, light and flexible using basic tools
and fasteners;
easily tailored to the range of wind and snow
loads found throughout Canada;
easily reinforced to withstand extreme wind
and earthquake loads;
adaptable to all climates ranging from hot and
humid to extremely cold climates; and
mportant General Information
27. Wood-frame housing may be built to
arious designs and specifications. Whether
standard design is used or a custom design
created, building code provisions and good
esign principles must be observed to provide
durable house; to maximize occupant health,
omfort and safety; and to reduce a building’s
nvironmental footprint. Building design
hould provide easy access for people of diverse
hysical capabilities and adapt to occupants’
hanging needs. Obtain professional design
sistance for special requirements such as
arrier-free access for people with disabilities.
TRUCTURAL DESIGN
o agree with the National Building Code,
he metric spacing of wood framing members
expressed as ‘soft’ conversions from the actual
mperial dimensions. For example, spacing of
2, 16 and 24 inches on centre are converted
300, 400 and 600 mm on centre, respectively.
n order to suit the imperial sizes of common
220 × 2440 mm (4 × 8 ft.) panel products, such
gypsum board, OSB and plywood, the actual
pacing of framing members has been adjusted
approximately 305, 406 and 610 mm on
ntre, respectively.
he NBC contains provisions for bracing
resist lateral loads from earthquakes and
gh winds. The provisions are based on a
hree-level risk-based approach developed
om environmental load data. There are no
pecial requirements for areas where the risk
low to moderate. This means that normal
heathing, cladding and finishes provide adequate
sistance. Most of the new requirements apply
areas of high risk, mainly the coastal area of
ritish Columbia. For these areas, builders can
corporate adequate lateral load resistance
ithout the need for further structural engineering
supporting foundation, slab or subfloor to the
underside of the floor or ceiling above. There is
also the option of designing in accordance with
NBC Part 4 or good engineering practice such a
that provided in the Canadian Wood Council’s
Engineering Guide for Wood-Frame Construction
2009. Refer to Chapter 10 for more information
In the few Canadian locations where risk is
extreme, bracing to resist lateral load must be
designed in accordance with NBC Part 4 or
good engineering practice such as that provided
in the Engineering Guide for Wood-Frame
Construction 2009.
FIRE SAFETY
The NBC does not explicitly require fire-rated
floor or wall assemblies in single-family houses.
Wood-frame construction is considered to
provide an acceptable level of fire safety,
dependent to a degree on gypsum board
finishes, which provide essential fire protection
of structural components for a certain period
of time. In addition, occupants are considered
to be familiar with hazards and safety features
of such buildings and to know how to safely
exit the house.
Wood-frame construction can satisfy the fire
safety provisions of the National Building Code
Fire safety is a combination of many factors,
some of which can be minimized by building
requirements, and others that can only be
controlled by the occupants. Examples of
building code fire safety measures include:
limiting the area of unprotected openings
(windows and doors) in buildings close to
property lines to reduce the chance of a fire
spreading from one house to another;
requiring smoke alarms on every floor and
28. bedrooms to help occupants escape in the
event of fire; and
providing clearances around heating
and cooking appliances to prevent fires
from starting.
ccupants can minimize their exposure to fire
sk by:
maintaining smoke alarms in working order;
ensuring all occupants are aware of escape
routes and of the outdoor gathering point in
the event of fire; and
exercising care when using cooking and
heating appliances.
he requirements for attached housing such
duplexes, houses with a secondary suite,
wnhouses and apartments are often more
omplex because a fire in one unit could spread
an adjacent unit without the occupants in the
fected unit being aware of a problem.
pace between Houses
re spreads from one building to another
rincipally by thermal radiation through
indows and other unprotected openings.
Many things contribute to radiation intensity,
nd several are more significant than cladding.
t any given distance, radiation intensity will
rimarily depend on the total area of windows
diating heat.
he intensity varies inversely as the square of
he distance from the source—if the distance
doubled, the radiation intensity will be only
5 per cent that of the original spacing. For this
ason, the closer one building is to a property
ne or an assumed line between two buildings
n the same property, the smaller the area of
indows and other unprotected openings
the design and construction of overhangs, and
the types of exterior cladding materials that
are permitted. Restrictions generally apply for
houses situated within 2 m (6 ft. 7 in.) of a
property line. Consultation with local building
officials is recommended before applying for a
building permit.
SOUND CONTROL
Sound control between rooms of a house
is provided by means of the materials used
in the floor and wall assemblies and by
reducing flanking paths so that noise is not
transferred around assemblies. There are no
code requirements for additional sound control
measures in single-family houses because house
occupants can take measures to reduce noise.
When a higher level of sound privacy is needed,
acoustical insulation can be installed or other
measures taken with respect to floors and
partition walls.
Houses with a secondary suite are required to
have a higher level of sound privacy because
there could be two separate groups of occupants
in one house. Walls and floors between adjacent
dwellings must have sound-absorbing materials,
resilient channels on one side, and 12.7 mm
(1
⁄2 in.) thick drywall on ceilings and both sides
of walls.
If a house is to be built in an area with a high
level of traffic or airport noise, an acoustic
engineer should be consulted to devise a means
to reduce external noise.
In multi-family buildings (such as semi-detached
or row houses or apartments), sound control
measures are required between all dwellings to
improve occupant comfort.
For more information, refer to the 2010 Nation
29. secondary suite is located in a house, townhouse
r semi-detached houses (two side-by-side
welling units) and used, for example, as a rental
nit or to accommodate family members in an
dependent area of a house. A secondary suite,
hich may also be referred to as an accessory
uite or secondary unit in some jurisdictions,
ay occupy more than one storey or be on the
me level as or above/below the principal suite
the house.
ome special building requirements apply to
condary suites because the occupants’ activities
one suite can affect the health and safety of
hose in the adjoining suite. These requirements
e simpler and less costly than those pertaining
apartment buildings, for example, and strike
balance between practicality and cost, and the
ealth and safety of the occupants. Consultation
ith local building officials is required before
secondary suite is built. Some of the
onsiderations are as follows:
A secondary suite is a living space and the
ceiling height must be at least 1.95 m (6 ft.
5 in.) and not less than 1.85 m (6 ft. 3
⁄4 in.)
under beams and ducting.
Occupants of both the principal and the
secondary suite must be provided with
adequate escape routes for use in the event
of fire. This means adequate stair, ramp and
door widths and adequate handrails and
guards must be provided.
A continuous smoke-tight barrier consisting of
not less than 12.7 mm (1
⁄2 in.) gypsum board
must be provided between the suites.
Smoke alarms must be interconnected so that
residents in one suite are alerted by a fire in
the adjoining suite.
a secondary suite must be provided.
Heating and ventilating ductwork can spread
smoke and/or fire from one suite to another.
For this reason, separate and independent
forced-air furnaces and ductwork must be
provided for the house and the suite, or,
an alternate heating system such as hot
water or electrical heating must be provided.
If the house has a forced-air heating system,
the easiest way of meeting this requirement
is to heat the secondary suite electrically.
ROOM HEIGHT
Building codes establish minimum ceiling heigh
for living area rooms. In general, the minimum
ceiling height is 2.1 m (6 ft. 11 in.). Unfinished
basement areas must have ceilings at least 2.0 m
(6 ft. 7 in.) high in any location that would be
used for passage.
RADON
Radon is a colourless, odourless, radioactive
gas that occurs naturally in the environment.
Outdoors, its concentration is negligible, but it
can accumulate in buildings to levels that pose
a health risk. Radon can seep from the ground
into buildings through cracks and unsealed
penetrations in the floor and walls abutting
the ground.
Although there are regions in Canada with
high radon levels, all new residential buildings
are now required to provide measures for radon
mitigation because (a) there are no reliable
maps showing where radon is present; (b) high
radon concentrations can be found in one
building and not in neighbouring buildings;
and (c) it is very difficult to detect problematic
30. ter construction could be expensive, taking
easures during construction can increase safety
nd reduce the cost of future mitigation.
he basement can be protected against radon
an air barrier connecting the basement slab to
he walls is installed to keep radon from entering
he living space. A roughed-in, capped pipe
xtending under the floor slab should also be
rovided, as it could be used to ventilate the
pace below a basement floor later, if radon
ere to become a problem.
nheated crawl spaces do not need to be
rotected against the ingress of radon
ecause required ventilation can prevent radon
cumulation. Rough-ins for a future radon
xtraction system are not needed for heated
awl spaces if they do not have a concrete floor
ab and if they remain accessible. This way,
person could easily install a connection to
he sub-air barrier space to be used for the
don extraction system.
he building owner can easily test the house
r radon. The test equipment is relatively
expensive, and test kits can be ordered
ver the Internet. If test results indicate an
nnual average concentration exceeding
00 Bq/m3
, it may be necessary to complete
he subfloor depressurization system to reduce
don concentration. This requires that the
oughed-in pipe be uncapped and connected
a ventilation system exhausting to the
utside. The building should be retested for
don once the depressurization system has
een completed and activated.
or further information on how to measure
nd remediate existing houses, refer to
ealth Canada’s publications Guide for Radon
Measurements in Residential Dwellings (Homes)
nd Reducing Radon Levels in Existing Homes:
IN HOUSING AND
SMALL BUILDINGS
Once adopted by the provinces and territories,
changes to NBC Part 9 will require that
building envelopes, heating, ventilating and
air conditioning systems and service-water
heating systems meet or exceed minimum
energy efficiency performance requirements.
Where adopted, the new provisions will have
an impact on the design and construction
of houses, so builders should stay alert for
building code amendments in their areas.
MATERIAL COMPATIBILITY
Many types of building materials are used in
a house. Experience has shown that materials
such as sealants and metals can adversely affect
an adjacent material at times, resulting in
premature degradation.
Many sealant products are suited to a wide range
of applications, and there is no simple and
universal product labelling system. Improper
selection can lead to problems such as paint
failure or damage to window frame finishes.
Connecting different metals can cause galvanic
corrosion, leading to premature failure.
Premature failure can also result from job
site-imposed conditions or deadlines. For exampl
in the rush to apply paint in unheated condition
a painter might ignore the temperature range
recommended by the product manufacturer,
resulting in a costly recall.
CONSTRUCTION SAFETY
Care should be taken during construction to
avoid injuries, and the following require attentio
Site work—Chainsaws and other mechanical
equipment must be used with care, and
31. adequately back-sloped or shored to
prevent slope failure.
Foundation—Concrete formwork must be
strong enough to resist the weight of the
concrete while it is being poured.
Framing—Care is required for the placement
and temporary bracing of wall sections.
Wood trusses are unstable until they have
been braced.
Exterior finishes and roofing—Since this
involves working at heights well above ground,
those doing this work must take proper care
and wear fall protection devices.
Electrical and mechanical—Wiring, gas piping
and heating and electrical appliances must be
installed by qualified personnel to ensure safety
during construction and over the lifespan of
the house.
General—Follow the manufacturer’s
instructions for the use of all equipment
and tools and obtain practice and experience.
Use eye, breathing and hearing protection.
Fall protection and the securing of ladders
and scaffolding are important steps to ensuring
safe construction.
PROTECTION AGAINST
MOISTURE AND TERMITES
Wood-frame construction has a record of
ng-lasting performance. Like all materials,
ood has advantages and disadvantages, and
me precautions are needed to ensure long
rvice life.
Wood will not decay in conditions where it is
ept dry or, if wetted, has an opportunity to
ry. Protection is ensured through good design
service conditions.
Many of the chapters in this book cover, to som
extent, the building materials and principles
intended to reduce damage from moisture
such as:
Chapter 3—Concrete: Good concrete
mix design, placement and curing is
essential for preventing water leakage
in foundations.
Chapter 5—Functions of the Building Envelope
Water, Air, Vapour and Heat Control:
The building envelope must prevent the
movement of water and vapour.
Chapter 7—Footings, Foundations and
Slabs: Foundation dampproofing and,
where high water tables occur, waterproofing
are essential for keeping basements dry.
In addition, roofing, cladding, flashing, vapour
barriers, air barriers, ventilated roof spaces,
windows and doors all play a role in keeping
building materials dry, and they must all work
together as a system.
Separation from Wet Conditions
Wood can be used in exposed locations
without having to be preservative-treated if it is
kept off the ground and installed so that drying
is possible between wettings. Here are some
examples of separation:
Foundation walls should be kept at least
200 mm (8 in.) from the ground where wood
sidings or wood-base sidings are used.
The ground level in a crawl space should
be at least 300 mm (12 in.) below joists
and beams.
