Flat Roof Construction
Despite their name, most flat roofs are not entirely flat. For the purpose of water drainage a flat roof usually has a slight pitch or decline that’s designed to funnel water either directly off the roof or to one or more drains on the roof surface (in the case of parapet walls). The most common materials used to build a flat roof are solid wood and/or steel framing, a flat wood underlayment (usually 3/4 inch plywood), an insulating underlayment, and a waterproof membrane. In the past, the membrane was made from tar, rubber, or asphalt. Nowadays modern technology offers a few more choices, including EPDM (a strong synthetic rubber), modified bitumen, PVC, and GRP (glass-reinforced plastics, also known as fiberglass). Click here to find a more in-depth look at flat roof membrane options.
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Common Flat Roof Problems
A leaky roof is always a major concern, as it can lead to significant damage to the inside of the structure. When a roof leak occurs water often appears in the home in a different location than where the actual leak is located. Finding the source of the leak can be difficult on a slanted roof, but it’s even more difficult on a flat roof. That’s because unlike a slanted roof, where water predictably flows downwards, water on a flat roof is prone to flow in one of many directions. There are, however, areas on a flat roof where leaks commonly develop, including the following:
- Flat roof seams (where one section of membrane overlaps the next) are prone to leaks. While roof sealant and/or adhesives are used along seams to discourage leaks, they often wear out.
- Protrusions in the roof such as vent pipes, skylights, and roof drains are also susceptible to leaks. Flashing and adhesives are used to prevent leaking, but as with seams, these applications can fail over time.
- Weather wears down the adhesives used on the edges of roofs and interior parapet corners. As a result, moisture can find its way into the roof’s interior.
- If your flat roof receives any foot traffic make sure that dirt, rocks, and other debris that could puncture the roof membrane are cleaned off.
- Severe weather and falling debris can easily damage a flat roof. Check your roof periodically and after any weather phenomena for damaged sections.
Roof Repair Costs
Because state and local licensing and business registration laws affect the hourly rate roofers charge, the cost to hire a roof repairman varies by location. Prices in your area may be higher or lower than those below.
- Professional roofers charge $50 to $75 per hour. There may also be a service charge fee of $75 to $100 as well depending on the company you hire (especially for a small job).
- Finding a simple leak and repairing it may take a professional only an hour or two; expect to pay $75 to $150 for a repair that takes one hour to complete.
- A leak that causes damage to the internal structure of the roof might necessitate plywood and framing repair. Such a job could cost hundreds or even thousands of dollars.