About Your House
Repairing or Replacing Exterior Wall Materials
Exterior finish materials are expected to protect the house
from the elements while providing an attractive appearance.
They must prevent rain and snow from penetrating the building
and causing moisture damage. Exterior finishes must be durable
enough to resist normal expansion and contraction due to
temperature changes, minor impacts from people and objects
that can occur from everyday activities and premature
deterioration from sunlight exposure. Repairing or replacing
exterior wall finishes will help protect your home, preserve
the durability and structure and make it more attractive.
Some problems are common to all exterior finishes while
others are specific to a particular material.
- Problems common to all finishes — water is the
source of many problems. Moisture can penetrate the wall due
to flawed roof elements, faulty flashing over windows or
doors and at the base of the wall, flashing and caulking
problems at penetrations or failure of the exterior finish
to act as a rainscreen. Exterior finishes may also suffer
from improper fastening or support, or problems with the
wall sheathing and sheathing membranes behind the finish.
The finish may be stained, damaged or soiled.
- Wood siding — wood siding may suffer paint
failure, splitting wood and rot.
- Metal or vinyl siding — these types of siding may
suffer from aging, fading, cracks or dents and buckling.
- Masonry — masonry problems include efflorescence
(white, chalky stains), crumbling mortar, cracked or loose
bricks and spalling (breaking off of exterior layer) or
- Stucco — cracks and loose or damaged areas are
common stucco problems.
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, ventilation 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.
If the exterior walls don’t protect the house from the
elements, further problems throughout the house can be
Failure of the exterior finishes often means that rain or
snow can penetrate the building envelope. It can also mean
that the materials will deteriorate. Failure may result from
defective materials or poor installation. However, some causes
of defects are indirect and can be attributed to a failure of
another component of the building’s systems. Here are some of
the likely situations that people encounter. However, every
situation is unique and you may need to hire a qualified
professional to do a thorough investigation, find the problems
and suggest the best solutions.
|Problems common to all
- Does the exterior finish show signs of staining,
uneven weathering or decay? Is there any sign of
damage to the interior finish in the same area?
- Is the siding deformed or displaced?
- Is there damaged siding at or near grade?
- Repair roof leaks. Check flashings and repair if
- Caulk cracks around windows, doors and
penetrations. Repair any damage.
- Remove and re-apply loose or deformed siding.
- Re-landscape to keep siding at least 200 mm (8
inches) above finished grade.
- Install eavestroughs with downspout extensions.
- Continued moisture penetration will deteriorate
exterior and interior finishes, leading to structural
- Loose or deformed siding will not protect the
building from the elements and may become detached.
- Is the paint blistered or peeling?
- Has the wood split?
- Is there any rotten wood?
- Has hardboard siding buckled?
- Keep wood siding clean, painted and sealed.
Refinish every four to five years or as needed. Seal
the walls from the inside to stop air leakage. Provide
ventilation to reduce indoor humidity levels.
- Protect ends, joints and gaps in hardboard siding.
Re-landscape to keep siding at least 200 mm (8 in.)
above finished grade.
- Wood siding that is not maintained will continue
to deteriorate. Unchecked air leakage from inside the
house will transport moisture to the outside and may
affect the siding. Excessive moisture in houses will
only compound this problem.
- Any unpainted surfaces of wood or hardboard siding
can absorb moisture, swell and deteriorate.
- Siding too close to grade may absorb water and
become stained from water splashing. Hardboard siding
may buckle. Wet hardboard and wood may rot.
|Metal or vinyl
- Does the siding look chalky?
- Is the metal siding corroded or pitted?
- Are there water stains or moss under the lip of
- Are there dents in metal siding or cracks in
- Has the siding buckled?
- Clean and paint metal siding to protect from
chalking, corrosion and pitting. Replace or paint
chalky vinyl siding.
- Check flashings and repair as necessary. Water
staining or moss under the lip indicates moisture
behind the siding. Seal air leakage paths inside the
house. Provide ventilation in rooms to reduce
- Repair metal siding dents with autobody filler and
refinish, or replace.
- Repair cracked vinyl siding with a colour-matched
caulking or replace.
- Remove buckled metal or vinyl siding and re-apply
- A chalky, faded finish on vinyl or metal siding
can give a house a tired appearance. Corroded siding
is unattractive and offers poor protection.
- Moisture behind the siding can damage both the
interior finish and the structure of the building.
- Dents and cracks are unsightly. Water can
- Buckled siding is unattractive and more prone to
water penetration. Further loosening or detachment of
the siding may occur. Appearance is important for
- Are there dirty bricks?
- Is there any efflorescence (a white, chalky stain)
- Is the mortar crumbling?
- Are there cracks or loose bricks?
- Is there spalling or flaking bricks?
- Clean bricks with high-pressure steam. This may
not be suitable for older brick or brick that is in
- Repair flashing and caulking. Seal air leakage
paths from inside the house. Moisture penetration
causes efflorescence. Provide ventilation in the house
to reduce interior humidity.
- Scrape out and repoint crumbling mortar. Maintain
flashing, caulking and chimney caps.
- Repair or replace cracked or loose bricks. If
damage is extensive, consult an engineer regarding
foundation settlement problems.
- Solve water penetration and replace the bricks.
- Soiled bricks detract from the appearance of the
- Efflorescence is unsightly and should be
considered a sign of future crumbling mortar,
spalling, flaking and structural damage.
- Crumbling mortar, cracked or loose bricks and
flashing and caulking problems will continue to allow
water penetration. More crumbling, efflorescence,
spalling and possibly interior damage will result.
- Are there cracks?
- Are there loose or damaged areas?
- Is there moss or algae on the stucco?
- Fill, then paint small cracks and blemishes.
Structural movement usually causes cracks. For
enlarging cracks, consult a qualified home inspector.
Solve the problem, then seal or repair the crack. Do
not use waterproof sealers.
- Break off and replace loose stucco. Water freezing
behind the stucco can loosen large areas.
- Moss or algae growth indicates high levels of
moisture. Minimize water paths into and behind the
- Small stucco cracks may allow water penetration
that can result in loosening of large areas and
possible deterioration of the structure.
- Structural movement causing stucco cracks may be
an indication of a much greater problem.
- Large loose areas of stucco are unsightly and
cannot protect the house from the elements.
- High levels of moisture will continue to degrade
- Repairing or upgrading your exterior finish
material can work wonders for the appearance of your
- You can enjoy renewed pride in your home along
with the peace of mind that comes from knowing that it
is well protected from the elements.
- Your home will also appear more attractive and
better-maintained to others. Resale value will be
Skills to Do the Job
A homeowner with good fix-it skills may be able to do
much of the work including:
- Keeping sidings clean, painted and sealed.
- Sealing air leakage paths from inside the house.
- Fixing dents or cracks.
- Removing and re-applying siding.
- Sealing small stucco cracks.
Hire a professional masonry contractor to clean,
re-point or replace bricks, a stucco contractor to
repair large areas of stucco damage and a professional
engineer to solve extensive foundation settlement
Use the Exterior Finish Repair Worksheet to help
you assess the problems and plan your repair
Finish Repair Worksheet|
Costing Your Project
The cost of essential repairs will depend largely on the
deterioration of the existing finish materials and the extent
of the underlying causes. These factors will dictate which
finish materials must be replaced rather than repaired and the
amount of professional labour required. Use the checklist
above to help you evaluate your options.
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 described.