Roofing 101: How to keep your roof healthy
By David Katz
As the first line of defense against the exterior elements a roof must withstand the ravages of nature, including wind, rain, ice, snow and big swings in temperature. Even with routine maintenance and durable materials, every several years a roof needs to be replaced. Because this work often extends to other building components such as bulkheads, skylights, parapet walls and mechanical systems, it can be quite expensive.
What does a building owner, coop or condo board need to know to make the right decisions? What are the signs that a roof needs to be replaced? What does that work entail? The following will provide some guidance.
Roofs can be built in a variety of forms including elaborate curvilinear shapes to gabled to “flat” surfaces. We’ll focus on roofs in dense urban environments which are overwhelmingly low-slope or “flat” roofs.
In broad terms, the four basic elements of any flat roof include: the roof deck, thermal insulation, waterproofing membrane, and drainage components. The deck serves as a base for the roof system. It can be concrete slab, corrugated steel decking, plywood or other, horizontal base material. The deck is supported by the building structure which usually includes beams and girders. Thermal insulation is the material that prevents the flow of heat between the interior and exterior environments.
Depending on its location within the roof structure, thermal insulation may be soft or rigid. In older buildings, it is not uncommon to see a combination of both soft and rigid insulation to meet energy code regulations. The waterproofing membrane is the protective barrier that prevents moisture infiltration. Finally, the drainage components include drains, gutters and flashings that direct surface water off the building.
Maintenance is a key factor in keeping a building weathertight. The National Roofing Contractors Association (NRCA) recommends that roofs be inspected twice per year for signs of damage. Pockets of ponding water, spongy surface spots or damaged flashing are all signs of roof deterioration and potential water infiltration. Once water has migrated to the building interior you might see leaks or stained surfaces. There is also the potential for less visible concerns such as rotted wood beams, rusted steel, compromised batt insulation, damaged electrical components and mold.
Exploratory probes are usually recommended to determine underlying conditions. If structural damage is uncovered, corrective work might include joist repair, steel reinforcement, or brick replacement. If asbestos is found, it will need to be removed before replacing the roof. Local authorities have strict guidelines about how this can be done.
Should roof replacement be recommended, a design professional well versed in roofing can help assess the full extent of required work, develop construction documents and identify a competent general contractor to complete the work. As this work is typically regulated, the design professional will identify filing procedures and help obtain necessary permits. They will also attend site meetings while construction is underway to make sure work is being completed in accordance with approved documents.
Many factors will affect cost and timing. Naturally, if masonry walls or structure needs to be replaced it is far more expensive than work limited to the roof surface itself. Construction time will similarly vary because roof work is weather dependent. In seasonal climates with harsh winters, the work needs to be scheduled to avoid cold months. Work is likewise affected by rain so a time contingency should be added to any proposed schedule. Regularly scheduled construction meetings are helpful to push the project along to a reasonable conclusion.
Once complete, and given the cost and time associated with all the work, a guarantee that covers materials and workmanship is essential. Roofing materials are typically proprietary and manufacturers will typically provide 20, 25 or 30 year guarantees assuming the installation is carried out by a contractor certified in the specific roofing system employed. This is independent of any contractor warranties.
The addition of pavers or furniture, even potted plants all can negatively impact the necessary flow of water and the integrity of the finished roof surface and more importantly could void warranties. If a roof is to be used for recreational purposes, a protective deck system specifically manufactured for such purposes should be employed. Similarly, the installation of solar panels must consider any impacts on the roof surface.
In all cases, a design professional will be instrumental in guiding you through the design and construction process.
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