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About Your House
CE 28h

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.

Common Situations

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 flaking.
  • Stucco — cracks and loose or damaged areas are common stucco problems.

Healthy Housing

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 Housing.

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 expected.

Avoid Surprises

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 finishes
Ask yourself...
  • 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?
Consider your options...
  • Repair roof leaks. Check flashings and repair if needed.
  • 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.
...and ifyou don't
  • Continued moisture penetration will deteriorate exterior and interior finishes, leading to structural damage.
  • Loose or deformed siding will not protect the building from the elements and may become detached.

Wood siding
Ask yourself...
  • Is the paint blistered or peeling?
  • Has the wood split?
  • Is there any rotten wood?
  • Has hardboard siding buckled?
Consider your options...
  • 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.
...and ifyou don't
  • 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 siding
Ask yourself... 
  • Does the siding look chalky?
  • Is the metal siding corroded or pitted?
  • Are there water stains or moss under the lip of overlapping pieces?
  • Are there dents in metal siding or cracks in vinyl?
  • Has the siding buckled?
Consider your options...
  • 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 moisture.
  • 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 properly.
...and ifyou don't
  • 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 penetrate cracks.
  • Buckled siding is unattractive and more prone to water penetration. Further loosening or detachment of the siding may occur. Appearance is important for resale value.

Ask yourself...
  • Are there dirty bricks?
  • Is there any efflorescence (a white, chalky stain) on bricks?
  • Is the mortar crumbling?
  • Are there cracks or loose bricks?
  • Is there spalling or flaking bricks?
Consider your options...
  • Clean bricks with high-pressure steam. This may not be suitable for older brick or brick that is in poor condition.
  • 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.
...and ifyou don't
  • Soiled bricks detract from the appearance of the home.
  • 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.

Ask yourself... 
  • Are there cracks?
  • Are there loose or damaged areas?
  • Is there moss or algae on the stucco?
Consider your options...
  • 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 stucco.
...and ifyou don't
  • 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 the structure.


  • Repairing or upgrading your exterior finish material can work wonders for the appearance of your home.
  • 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 enhanced.

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.
  • Re-landscaping.
  • 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 problems.

Use the Exterior Finish Repair Worksheet to help you assess the problems and plan your repair strategy.

Exterior Finish Repair Worksheet
Problem Options Advantages Disadvantages Help Required Estimated Cost

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 Corporation

Related Resources

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.

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