Why does a flat roof need maintenance?

Any roof system is constantly exposed to all forms of environmental stress. The effect of these forces causes the aging of the roof. Minor problems that are caused through negligence, abuse, and lack of maintenance will result in a shorter life span. It is an essential practice for the property manager to establish a regular roof maintenance inspection. Proper implementation of such a program will not only protect the owner’s investment but also establish a long term plan of maintenance and capital requirements for each building. Common deficiencies which can visually be detected on a flat roof are:

Roof Ponding:

Subjects the roof to constant surface saturation which increases substantially the rate of deterioration of the roof system. Ponding provides a serious supply of water, which would further damage the interior when a leak occurs. This is usually the result of structural settlement and localized roof failure. The practice of installing tapered insulation has been widely employed to correct this deficiency, as it is difficult to add drainage to existing structure.

Roof Splitting:

Refer to the long cracks in roof membrane, and are usually parallel to felts and insulation joints. Splitting of membrane is usually spongy. The cause of this deficiency may be attributed to physical stress, ponding, freeze-thaw, cracking substrate, or bad workmanship.

Roof Blistering:

Most common in Built-Up-Roofs (BUR) and modified bituminous roof systems. It usually occurs between layers of felts or between felts and substrate. It is raised contained swelling and it feels spongy when pressed. The entrapment of air causes movements when temperature rises and subsequently separates the felts.

Roof Ridging:

Also, referred to as wrinkling and buckling. It occurs in bituminous roofing, and normally found above joints of insulation. They are usually narrow and long. This is resulting from interior moisture condensing on the underside of the felts. Ridges and wrinkles on single-ply loosely laid membrane may be found around drain areas, and roof protrusions. This may be attributed to inadequate attachment of the single ply membrane and/or using inflexible flashing, which has a memory of its original shape.

Roof Fishmouthing:

It is the result of lifting of laps at edges in bituminous roofing, or unbonded edges in PVC roofing due to inadequate heat welding.

Puncture:

Found where blisters have broken or as a result of rising nails/screws or other exterior mistreatment. If punctures were found throughout the roof, assume that a considerable amount of water has penetrated the membrane.

Loose fasteners:

Common in mechanically fastened systems, where the fasteners have backed out. This could happen as a result of the insufficient thickness of the fasteners, workmanship, and/or deterioration of the roofing components due to saturation. This deficiency was also observed where major structural settlement has occurred.

Roof Felt Movement:

That may be one ply to another or all plies to a substrate. This may be attributed to the usage of wrong bitumen, excessive heat or other structural factors.

Failure of Flashing:

Punctures, deterioration, open laps, ridging, and blistering can be found when flashing is inspected.

Sheet Metal:

Copings are sheet metal cover for all wall systems. It is applied to protect the flexible flashing from wind forces. Any movement of wall systems and settlement may create opening in the sheet metal. Counter-flashing is metal installed over the flexible flashing at the adjoining walls. This prevents the water from contacting the top edge of flashing. Any punctures or loosening of sheet metal may allow water penetration into the wall.

Blocked Roofing Drains:

Shall be cleaned regularly.

Roof Safety Anchors:

Shall be inspected annually by a professional inspector. Engineered drawings must be posted near the roof entrance, and a log book of inspection must be available on site at all times.

Typical components of Roofing System:

Deck: Concrete, steel, wood Vapour Barrier: Laminated Kraft, Fibreen, Asphalt felts. Membrane: 4 Plies asphalt felts or glass felts, 2 plies modified bitumen, EPDM, PVC Insulation: Wide range of insulation is available. Most commonly used are Fiber-glass, Phenolic foam, Iso-Cyanurate, Extruded Polystyrene (used in Inverted Roofing Membrane Assembly IRMA), Expanded Polystyrene (used in Loose Laid Ballasted System), and High Density Fiber-board Ballast: Pea gravel on Built Up Roofs, River Washed gravel on loose laid ballasted, and Concrete Pavers.

Roofing Systems:

Conventional Built Up Roofs: Applies to bituminous roofing Loose Laid Ballasted: Single ply Fully Adhered (no ballast): Single Ply Inverted Roof Membrane Assembly: Bituminous and single ply

Establishing a Roof Maintenance Program:

A planned maintenance program is an essential tool for the property manager. A historical file must be produced for the roofing system. The file must include the following: A detailed description of all roofing components, the date of installation, the name of roofing contractor, the “as built” specifications and drawings, all reports by the roofing inspector during the construction of the roof, all maintenance performed, the record of mechanical equipment and the date of installation, and all roof guarantees from manufacturers and the roofing contractor. If this material is not available, the property manager may be required to hire a Professional to conduct a survey and have all this data updated. Routine inspection by site staff shall be carried out on a regular basis (two months). A visual inspection and a completion of a check list must be performed. The following items must be included in the check list: General appearance, debris, drainage, bare spots, cracking, blistering, ridging, fishmouthing, loose felts, loose fasteners, punctures, condition around all roof protrusions, flashing and counter flashing conditions, rusting, caulking, pitch pans, and irregularity.

Scheduled Maintenance is determined when site staff observes any deficiencies that require a professional roofer to rectify. Following such procedure will protect the owner’s investment and extend the life of the roofing system. Unscheduled Maintenance is determined when your site staff discovers major deficiencies. This should be repaired/replaced as soon as possible to avoid any interior damages as a result of water penetration. Those circumstances you will require external help. Be certain of your professional’s technical competence, and the ability to do what you want done within a time frame and any budget limitations that best fulfills your corporate needs.

Roof inspections and repairs will add years to the life of your roof. A roof maintenance program will help your organization in allocating the proper capital over an extended period of time, and budgets for repair/replacement will be readily available when needed.

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