At least twice per year, property managers should inspect and conduct maintenance on their roofs. An inspection in the spring will identify any damage that occurred over the winter months, and an inspection in the fall will ensure the roof is ready for harsh winter conditions.
When conducting the inspection, take a plan of the roof and note the locations of any anomalous conditions. The results of previous inspections can be used to determine whether the roof has deteriorated since the last inspection. Photographs can also be used to document changes in the condition of the roof over time.
What follows is an overview of what to look for and fix when inspecting low-scope, conventional and inverted roofs, but first, a few words about safety:
A roof can be a dangerous place. Do not conduct roofing inspections in high winds, and never walk backwards on a roof; always watch where you are going. Unless the roof has a parapet at least 42 inches (1070 millimetres) high or a fixed guardrail, the Occupational Health and Safety Act requires that you do not get closer to the edge than two metres (six feet, six inches). If it is necessary to get close to the edge, to inspect the parapet flashing for example, you must retain the services of someone trained and certified in the use of safety harnesses and travel restraint systems. Also be aware of the location of skylights, as there have been cases of deaths due to falls through skylights.
A low-slope roof — more commonly though not entirely accurately referred to as a flat roof — relies on a waterproof membrane to prevent water penetration through the roof. Even a “flat roof” has some slope to direct water to drains.
For all types of low-slope roofs, note areas of ponded water, as standing water on a roof can accelerate deterioration of the roofing membrane. Even if there is not water on the roof at the time of the inspection, there may be stains that indicate previous ponding. Walk the roof and note any areas that feel spongy.
Remove any debris on the roof, such as branches, as it could potentially puncture the roofing membrane. Check the roof drains and remove debris from the drains if necessary.
Areas most prone to problems are penetrations through the roof, such as vent stacks. The penetrations are usually installed through a sheet metal sleeve that is flashed into the roof membrane and that is filled with a mastic material, referred to as a “pitch pocket.” The mastic can dry up over time, so check the pitch pockets and add mastic if necessary.
Have a look at the roof perimeter (see the above passage on roof safety) where the roof membrane turns up onto the parapet, which is the extension of the walls above the roof level. A metal flashing is used to protect the membrane at the parapet. With a low parapet, the flashing may extend over the top of the parapet. With a high parapet, the membrane flashing may terminate in a “reglet” and there will be separate flashing for the top of the parapet. Check the sealant at the reglet to ensure it remains flexible and fully adhered. Check the flashing to ensure it is not rusted or damaged.
Conventional roofing systems
In a “conventional” roofing system, the waterproofing membrane is installed on top of the roof’s insulation. The most common type of conventional roof is a built-up roof, or BUR. A built-up roof consists of three or four alternating layers of felt and asphalt, ending with a layer of gravel to help protect the roofing membrane from UV radiation. Signs of deterioration in a BUR include:
- Blisters or blueberries: spongy bubbles in the surface
- Ridges: long ripples in the membrane
- Splits: cracks in the membrane
- Alligatoring: a cracking pattern that resembles an alligator’s skin
Another type of roofing membrane that is typically used in a conventional system is PVC, which is a vinyl sheet roofing system that is typically white, though it can be other colours. The white colour provides some energy efficiency by reflecting UV radiation and thereby reducing summer cooling loads. The seams of the PVC are welded together with heat.
When examining a PVC roof, check the seams for fishmouths — gaps where the strips of membrane are not welded properly, resulting in an unsealed bubble. Also check for splits or punctures in the membrane.
Over time, the PVC can become dirty, which limits its energy efficiency. Therefore, it is recommended that the membrane be washed every one to three years, depending on its condition. The roof must be washed annually for it to qualify for the City of Toronto’s “Cool Roof” incentive program in the City of Toronto. There are roofing companies and roofing material suppliers that provide this service.
An SBS modified bitumen membrane may also be used. This roofing material comes in sheets that adhere to the roof structure. A torch is typically used to heat the membrane, which then bonds to the roof when the bitumen cools. Two layers are commonly installed, with the top layer having a granular surface to protect it from UV radiation. For this type of roof, look for loss of granules, bubbles, blisters, ridges and splitting of the membrane.
The other type of roof is an “inverted” or protected membrane roof. In these roofs, the membrane is located under the roof’s insulation. To keep the insulation in place, it is covered with a filter fabric and “ballast” — a heavy material — typically rounded river stone — to hold the insulation down.
While it is not possible to directly observe the condition of the roofing membrane, the roof should still be inspected to ensure that the insulation is completely covered with ballast. The wind can shift the ballast, particularly at the corners and edges of the roof. Often heavier patio stones are used along the edges of the roof to avoid this “wind scour.” If the ballast has shifted, carefully redistribute to prevent damage to the filter fabric and to prevent stones or debris getting between the boards of insulation, where it could migrate downwards and puncture the roofing membrane.
Any membrane type can be used for an inverted system, including EPDM. EPDM is a rubberized system that is typically loose-laid on the roof, meaning that it is not adhered to the roof structure, but is simply fastened at the perimeter. For this reason, it is typically used in an inverted system with the ballast helping to hold it in place. The membrane can shrink over time, so look for “tenting” at the roof perimeter, which refers to the appearance of the membrane as it pulls away from the perimeter of the roof where it is fastened.
Fall protection anchor points, more commonly referred to as roof anchors, are used as a tie off point for window washing or wall repair activities. A plan of the layout of the roof anchors must be posted near the entrance to the roof. As roof anchors are an important safety component, annual inspections are required. In addition, all roof anchors must be load tested at least once every five years. Often a number of roof anchors are tested every year so that over the course of five years, all anchors are tested. A record must be kept of the inspection and it must be signed and sealed by a professional engineer. For convenience, schedule the roof anchor inspection at the same time as either the regular spring or fall roof inspection.
By conducting regular bi-annual roofing inspections and maintenance as required, it may be possible for a roof to last past its normal life expectancy.
Dale D. Kerr, M.Eng., P.Eng., BSSO, ACCI, is a principal of GRG Building Consultants. Dale can be reached at GRG’s Newmarket office at (800) 838-8183.