About Your House
A New Addition
A new addition may be just what it takes to accommodate a
changing family or special needs. You can expand a kitchen,
add a bath or change your existing home into the house of your
As with any renovation, the construction of an addition
requires careful planning. Before you decide to go ahead with
the project, it is important to clearly identify the features
you want. Just as important is a thorough inspection of the
current structure so that any existing problems can be
Many homeowners are happy with their present location. When
extra space is needed, an addition is often a more desirable
alternative than moving to a different house. The size and
scope of additions vary widely. A simple project may involve a
larger entry area or adding a small bay onto a kitchen or
living room, while larger additions can substantially increase
the size of your home.
As you plan your addition, here are some important things
- Size and design — Before deciding on a
new addition, evaluate whether rearranging the existing
space might give you the changes you want. It is important
to determine what size the addition needs to be and how it
will integrate with the rest of the house. Homeowners often
underestimate how much space that items like stairways
require. The addition will be more appealing if the style
complements the design and architectural details of your
house and neighbourhood.
- Fixtures — Since the addition is
essentially new construction, new fixtures may be required.
- Structural problems — The addition will
often involve structural changes to the existing house,
which may involve foundation considerations, roof details or
the construction of openings in the existing building. As
part of the work, any problems found in the existing
building and foundation will have to be repaired.
- Moisture — The cause of any moisture
problems in the existing house will need to be diagnosed and
remedied as part of the renovation work. Existing problems
can affect new areas of the building.
- Plumbing and electrical — the increased
plumbing and electrical needs may exceed your existing
services, requiring significant upgrades. Remember to run
cables for telephone and computer connections, cable TV and
security or home entertainment systems.
- Heating and ventilation — Existing
heating and ventilation systems may not have adequate
capacity to handle the increased demand.
- Finishes — always pick finishes that
match or complement existing finishes and are durable enough
to take the wear and tear of daily use.
- Zoning and regulations — new work will
have to comply with provincial building codes as well as
local bylaws and zoning requirements.
Renovating is an ideal time to make your house healthier
for you, the community and the environment. When assessing
your renovation project, be sure to consider the five
essentials of Healthy
House as a System
A house is much more than just four walls and a roof — it's
an interactive system made up of many components including the
basic structure, heating, ventilating and air conditioning
(HVAC) equipment, the external environment and the occupants.
Each component influences the performance of the entire
system. A renovation provides an opportunity to improve how
your house performs.
An addition gives you the chance to use up-to-date, energy
efficient construction practices. These projects often require
changes to HVAC equipment that can improve moisture management
and air quality in the house. Some equipment such as a large
volume exhaust fan can cause combustion heating appliances to
backdraft. Structural changes may give you a chance to improve
airtightness and insulation, resulting in increased occupant
comfort and house durability.
Once you start work on an addition, changes become costly
or difficult and can lead to delays in the completion of the
project. Thorough planning at the beginning will help you to
develop a realistic understanding of the work to be done and
the costs involved. Here are some of the likely situations
that people encounter. However, it’s always wise to consider
hiring a qualified professional such as an engineer, architect
or professional renovator to assess the structural issues.
|Size and design|
- How will the addition meet the needs of everyone
in the household, including anyone with special needs,
extended family and guests? What size will it have to
be to meet current and future needs?
- How will the addition affect spaces in the
existing house, especially traffic patterns, access to
outdoors and natural lighting?
- What style will complement the design of the
existing house? Does it fit into the neighborhood?
- Will there need to be changes in landscaping, or
driveway and walkway locations?
- Plan thoroughly before you start so that space,
traffic flow and styling meet your current and future
- Consider using an architect or professional
designer. They can help you work through the problem
areas and create a flexible, properly sized design
that meets your current and future needs and
complements the style, layout and site of your house.
- Have complete scale drawings made to determine how
the addition will connect to the existing house. These
will be required for the building permit and will help
you to visualize the project better. Furniture layouts
can also be a great help in your planning.
- If you compromise on your needs you will have to
live with the results.
- Good design and working drawings are important for
maximizing the space and minimizing problems.
Insufficient planning can lead to poor results and
costly mistakes. If you don’t solve the problems
during the planning stage, it may force you into
crisis problem solving as the project progresses.
- Will new fixtures and appliances be needed? What
types are suitable? How much space will they use?
- How much and what type of lighting is needed?
- Get measurements for fixtures and appliances from
- Familiarize yourself with available products and
- Use a professional designer to help plan your
fixture and lighting layout.
- Choose lighting and appliances that are energy
- Larger than expected fixtures or appliances can
lead to costly modifications or restrictions on the
useable space in your new addition.
- Poor lighting will detract from the look, feel and
usability of the new space.
- Inefficient appliances and light fixtures waste
energy and will mean higher annual energy costs.
- Are there any structural deficiencies in the
existing house that will affect the addition?
- Does the addition design maintain a roof profile
to provide water drainage and proper structural
details? Will the entire roof have to be refinished at
the time the addition is built?
- What type of foundation will the new addition need
and how will it be tied in to the existing structure?
- Are there unusual loads that will have to be
- Can the existing foundation drainage system be
used? Will a new foundation drain system be needed?
- Will structural walls or lintels need to be
removed or upgraded?
- How will the need for stairways affect the
structure or design of the living space?
- What insulating and air sealing can be done to
provide a comfortable, energy efficient space?
- Identify any structural deficiencies before you
start. Consult with a structural engineer or
- Repair and renovate structural components so that
they are adequate to carry the new loads.
- Plan for good drainage, particularly for
- Use accepted foundation construction practices
suitable for local soil and water conditions to ensure
a well insulated, dry foundation that will carry the
loads placed on it by the new structure.
- Hire a professional renovator who will ensure that
the addition will meet all applicable building code
- Choose contractors who are familiar with the type
of work you are planning and who use energy efficient
and Healthy Housing™ construction practices.
- Unforeseen problems will lead to unexpected costs
and delays during construction.
- Structural deficiencies can lead to cracked
finishes, floor vibration, bowed or displaced walls,
floors or roof structures and possible structural
- Foundation deficiencies can lead to a damp
basement or cracks caused by settling or from the
pressures of wet or frozen soil.
- Failure to meet building code requirements may
lead to unsafe conditions in the building.
- Poor insulation and air sealing will result in
higher than necessary energy costs, possible
condensation problems and an uncomfortable living
- Is there any evidence of moisture problems with
the existing building including finishes damaged by
moisture, water stains or visible mold growth on any
surfaces, blistering or peeling paint, cracked or
missing caulking or condensation on windows, walls or
- Determine, then eliminate the source of the
moisture that is causing the problems. It may be from
rain, plumbing leaks or condensation of vapour on cold
- Clean up visible mold growth according to CMHC
- Insulate and air seal exterior walls and ceilings.
Use energy efficient windows to provide warmer inside
- Repair or replace all deteriorated finishes or
- Provide ventilation and eliminate sources of
moisture to control high humidity.
- Maintain caulking, grout and flashings to prevent
water access to the building structure.
- Unresolved water damage problems will continue and
lead to further deterioration of the building or newly
- Mold growth caused by excess moisture can be a
serious source of indoor air quality (IAQ) problems.
- Superficial cleanup or hiding moisture damage
behind new finishes will allow deterioration to
- Poor insulation can lead to cold surfaces that are
prone to condensation.
- Uncontrolled humidity can lead to condensation,
mold growth and deterioration.
- Poorly maintained caulking and flashing can lead
to water leaks.
- Does the existing plumbing service provide
adequate water pressure and drains that flow quickly?
Will the addition increase demands on the existing
- Is the existing electrical service adequate for
the increased number of outlets and circuits that will
- What are the needs for current and future
telephone and computer connections, cable TV,
security, home entertainment systems or smart house
- What plumbing and electrical code requirements
apply to the new addition?
- Repair any plumbing leaks and upgrade the existing
service as required.
- Upgrade and repair electrical service and wiring
- Equip outlets near sinks with ground fault circuit
interrupters to prevent danger from shock.
- Assess your current and future needs for wiring
and connections. Consider upgrades that will improve
the resale value by addressing trends in home offices,
home entertainment and smart controls for appliances
and mechanical systems.
- Consult with a professional to determine that
plumbing and electrical code requirements are
addressed in your plans.
- Inadequate or substandard plumbing will be the
cause of ongoing inconvenience and may be a health
- An undersized electrical service can lead to
circuit overloads that are a fire hazard.
- Wiring and controls will have to be installed
later limiting the choice of location. Surface
mounting of cables can detract from the finished
appearance of the job.
- Not meeting codes can cause costly changes during
construction and delay completion of your project.
- Does the existing heating system have the capacity
to handle the increased demand of the addition?
- Does the house have a ventilation system and will
it handle the increased demand of the addition?
- Is this an opportunity to install a more energy
efficient heating system?
- What energy efficient practices can be used to
minimize the additional heating requirements?
- What heating devices are appropriate for the new
space? Will any new heating devices that use wood, oil
or gas be subject to backdrafting? Will a new, large
exhaust fan cause backdrafting of existing or new
- Upgrade or replace equipment as required to ensure
adequate heating, cooling and ventilation for the
existing and new areas. Choose energy efficient
- Consider installing a whole house ventilation
system. Choose one that includes heat recovery.
- Build a well insulated and air sealed addition to
minimize heating requirements.
- Use a qualified, licensed installer for heating
and ventilation work.
- Test for backdraft potential. Avoid the use of
large volume exhaust fans that can pull smoke and
combustion gases in through a flue. A trained
technician can remedy or avoid this health and safety
- An undersized or poorly installed heating system
will make the addition difficult to heat in cold and
windy weather conditions.
- Improper ventilation can lead to poor indoor air
quality, lingering odours and excess humidity.
- Backdrafting of combustion equipment such as fuel
burning fireplaces, furnaces, wood stoves and water
heaters that use oil, natural gas or propane is a
safety hazard and can also lead to smoke damage of
- What types of finishes are needed and preferred
for the new addition? How will the finishes blend with
the rest of the house?
- What finishes for items such as countertops,
floors and walls are durable enough for the intended
- What floor finishes are compatible with the floor
- What skills are needed to properly install these
- What finishes and materials will minimize the
impact on IAQ?
- Do your research. There are many new and different
products on the market. Select finishes that
complement the rest of the house.
- Choose the product that is appropriate for the
location and best meets the need whether it is for
water resistance, durability or cleaning.
- Determine the preparation requirements for each
type of finish.
- Use a trained or licensed installer.
- Choose finishes that are low emission and
environmentally friendly such as paints that carry the
EcoLogo symbol or water-based adhesives.
- Selecting finishes that don’t match the rest of
the house or intended use will yield poor results. For
example, carpeting would not be appropriate to install
in a moist basement where it would be damp and support
- Improper installation of finishes will void the
- Ceramic tile or grout can crack because of
inadequate subfloor construction. Hardwood flooring
can shrink or swell if it is not allowed time to
condition to the humidity of the space before
installation or if it is installed on basement floors
or floors with radiant heat.
- Solvent-based finishes will off-gas and may cause
- What are the local land use restrictions?
- What permits are required?
- Does current liability insurance cover accidents
due to the construction work?
- Does existing fire insurance cover the new work
- Does the mortgage lender need to approve any major
- Check with your local building inspection
department for information on permits, inspections,
zoning and any other applicable bylaws. These issues
may determine the feasibility of your proposed
- Check with your insurance agent and ensure that
you have adequate coverage during and after the
renovation. Upgrade as needed.
- Secure approval, if needed, from your mortgage
- Building officials may stop your project for
non-compliance with codes and regulations. Penalties
or fines may be imposed. The work may be delayed or
have to be redesigned.
- Lack of or inadequate insurance could lead to
financial liability. Even homeowners doing their own
work may need to have workers’ compensation coverage
(if using any casual labour).
- Your mortgage may be foreclosed if a required
approval was not given.
- A warm, comfortable addition that meets your space
requirements, has good lighting and is a well-designed
living space is the result of thorough planning and
- A well thought out and executed addition will
increase the value of your house.
- Repairing structural problems, leaks and upgrading
services will prolong the life of your house and make
the addition look and work better.
- By using low odour and easy-to-clean finishes, you
will improve the IAQ of your home.
- A well-insulated addition will provide warmer
interior surfaces that will help to prevent
condensation and mold growth.
Skills to Do the Job
A homeowner with good construction skills may be able
to do some of the work on the renovation such as:
- Demolition, including the removal of fixtures,
finishes and non-load bearing walls.
- Caulking or repairing of roof and window leaks.
- Installing insulation and air sealing of the
Consider a professional renovator to manage the
project and for structural and finish work. If you are
doing it yourself, you will still need to hire
subcontractors to do the electrical, plumbing, heating
and ventilation work. You may also want to hire other
tradespeople to do roofing, window, door, cabinet and
flooring installation, or paint and drywall finishing.
Remember to obtain all necessary permits, get written
contracts that describe all aspects of the job,
including lien protection. Ensure that workers use safe
working practices, are covered by workers’ compensation
and have their licences where required. Protect
yourself, your family and your
Use the New Addition Assessment Worksheet to
consider the existing structure, elements for the new addition
and to do the preliminary costing.
Addition Assessment Worksheet|
|Assessment of Existing
|Roof and Walls of Existing Building
|Design and Permit
|Excavation, Backfill and Compaction
|Drywall Installation and Finish
|Windows and Doors
|Cabinets or Shop Work
Costing Your Project
The cost of the renovation work will depend on the
condition of the existing structure, local labour and material
costs and the extent of the work to be done. Costs of finishes
and fixtures vary widely. A good budget checklist will help
you to develop a realistic cost for the project before you
If the addition is substantial, provide a comfortable
budget contingency to allow for unforeseen work that may need
to be done. The size of contingency will depend on the nature
of the project, but may need to be 20 per cent or more of the
initial budget. This applies, regardless of how the project
contracting is going to be handled.
Other Useful Information From Canada Mortgage and Housing
Although this information product reflects
housing experts’ current knowledge, it is provided for general
information purposes only. Any reliance or action taken based
on the information, materials and techniques described are the
responsibility of the user. Readers are advised to consult
appropriate professional resources to determine what is safe
and suitable in their particular case. CMHC assumes no
responsibility for any consequence arising from use of the
information, materials and techniques