Determining the Age of Roofing in Multi-Resident Buildings

    By Liam Bailey, BSc. Eng. (Hons) in Construction Engineering and Management
    Depreciation Report Planner
    & Herman Kwok, BASc in Materials Engineering, MEng in Building Science
    Depreciation Report Planner

    Click here to read Determining the Age of Roofing in Multi-Resident Buildings in its entirety.

    While doing depreciation reports, reserve fund studies or building condition assessments, we often get asked how we can determine the age of a building component by looking at it. Although not without aberrations, there are some tell-tale signs that indicate the age and the remaining life of features such as windows, claddings and veneers, roofs and fencing. Architectural styles and innovations in manufacturing will also have an influence on how long certain components may last.  We have written a series of articles explaining what signs we look for to determine age and remaining lifespan for our depreciation reports, reserve fund studies, or building condition assessments.

    This article of this series talks about determining the age of sloped and flat roofing in Strata and Condo Corporations.

    Sloped Roofing

    The observed age of sloped roofing generally depends on many factors including material, workmanship, roof pitch, exposure and maintenance efforts.

    Asphalt Composite Shingles

    Asphalt shingles typically last 20-25 years, assuming preventative maintenance is done on a regular basis. Watch for the signs –mentioned below, as they will provide an indication that the asphalt roofing is approaching the end of its useful life.

    The amount of granules remaining on the shingles typically can indicate the age or remaining useful life of the asphalt shingles. The longer the shingles have been exposed to the environment, the fewer granules they will retain. Hail, windstorms and frequent running water from precipitation can cause shingles to lose their granules. Such loss will allow UV exposure, causing deterioration, reducing the shingles’ remaining life.

    As asphalt shingles age and over time the bond of the adhesive might become brittle due to wetting and drying cycles as well as temperature swings. This can allow gusts of wind to lift shingles and cause them to crease or become loose. Temperature fluctuations can also cause shingles to crack and split, eventually to the point that moisture will get in. If many shingles are damaged or missing, the roof will soon require replacement.


    Moss growth on shingles


    Shingles curled at bottom edges








    The lifespan of asphalt shingles is also shortened when organic matter is allowed to grow on them, as such matter retains high levels of moisture and keeps the shingles too wet for too long. This issue can occur as early as a couple of years after installation. Organic matter such as moss, should be cleaned from the shingles.  If excessive organic matter is observed over most of the roof, the asphalt shingle roofing is unlikely to be well maintained and will likely see a shorter lifespan.

    Wood Shakes/Shingles

    Wood shakes, or wooden shingles, used in the roofing industry are often cedar. Although this type of wood is known for its resistance to decay, local environmental factors such as heat, humidity, precipitation, and hail will eventually wear out the material. Cracks and splits will form as the shakes/shingles experience cycles of expansion and contraction from fluctuating moisture content, as well as freeze/thaw cycles. Wood stress caused by UV rays and rain will also cause the wood to curl or cup. These deficiencies will expose the roofing felt or deck, compromising its water-shedding function.

    As with asphalt shingles, organic growth on the wood shakes/shingles can accelerate its degradation. Rot caused by microorganisms, like moss, lichen or algae will often leave the bottom edge of the shakes/shingles frayed.

    As natural weathering takes place over time, wood shakes/shingles will need to be replaced.  However, their lifespan is often determined by the local climate and maintenance efforts. They can last as little as 20 years or as long as 50 years. If the majority of the roof area shows the deficiencies mentioned above, this indicates the roof is at an advanced age and replacement is imminent.

    pic 3

    Moss growth on shingles

    pic 4

    Splits and cracks on discolored shingles







    Metal Roofs

    The useful life of a metal roof can range from 30 to 60 years, depending on materials, workmanship and maintenance efforts. Metal panels and sometimes metal shingles, are usually coated with liquid-applied polymer or paint to protect the metal from rusting. Rusty fasteners and localized rusting may indicate the metal roof’s age but, as long as they are replaced/repaired in a timely manner, they should not greatly affect the roof’s overall lifespan. However, missing fasteners can allow the panels to be loosened from the framing, allowing wind damage. Damaged panels can affect the seams between panels and allow leaks to occur. Periodic painting and sealing of metal roofing as well as replacement of damaged panels and rusted fasteners can ensure the longevity of the component. Metal panels should not be exposed to the environment unless they are treated to prevent oxidation. Scaly rust is an indication that the oxidation has been present for an extended period of time and has chemically eaten through layers of the metal. If the majority of the metal roof has scaly rust it is advisable to have a roofing service provider inspect the thickness of all the metal panels to ensure their integrity before choosing between a coating restoration or replacement.


    Rusty fasteners

    pic 6

    Scaly metal roof panels








    Flat Roofs

    Flat or low-slope roofs make up an important portion of the external enclosure of a building. The potential for extensive damage if a failure occurs, makes this component one of the most important expenditures to be considered by the Strata or Condo Corporation when planning for the future.

    When preparing for a roof replacement, it is more important to determine the remaining useful life than to determine when the roof was installed.  Regardless of the type of flat roofing installed, its useful life varies greatly due the quality of material, environment, foot traffic and particularly workmanship and maintenance.

    Common types of flat roofs installed on low, mid or high-rise apartment buildings in and around the lower mainland area include: asphalt builtup, styrene butadiene styrene (SBS) modified bitumen, and single-ply thermoplastic polyolefin (TPO) roofing membranes. Generally flat roofs can suffer from these common issues:

    Overlaps – Critical in maintaining a watertight roof. Failure likely caused by inadequate overlaps and overheating during installation as a result of poor workmanship.

    Blistering/Bubbling – Commonly due to a buildup of moisture beneath the membrane, trapped air or poor adhesion at the time of installation. In some cases small blisters are deemed insignificant and do not require repair.

    Cracking/Alligatoring – Generally, appears along the surface of the cap sheet as a result of prolonged exposure to the elements. This type of defect can also be exaggerated due to a build-up of dirt/debris and standing water or ‘ponding’ along the surface of the membrane.  In most cases, standing water is a result of inappropriate sloping or poor design.

    Rips/Splits/Tears – May result from a number of contributing factors including, foot traffic, roof-top mechanical equipment, and a build-up of objects including tree limbs and other environmental debris. Regular cleaning as part of a maintenance plan with a roofing contractor can typically assist in reducing the possibility of this type of failure.

    Given the potential failures that can occur and the age of a flat roofing system, it is good practice to get regular inspections of roofing done to take into account the amount the variables that may affect the aging process.

    Share this post:Share on FacebookShare on Google+Tweet about this on TwitterShare on LinkedInEmail this to someone