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FLAT ROOFS: PROS AND CONS
When it comes to what to do with their flat roofs, your clients have a number of options, including TPO and PVC, that were not touched upon the main article. EPDM is competitively priced and reliable, but can be damaged and require replacement in 15 to 20 years. Garden and PVC roofs are pricier at the outset, but offer long-term advantages in terms of durability and resistance to certain kinds of damage.


ROOF TYPE
AVERAGE COST MATERIALS & LABOR
PROS
CONS


- EPDM
- $3.50 sq. ft.
- competitive pricing; limited environmental impact during manufacture; does not become brittle with age, one piece (no seams); little or no maintenance
- no ponding warranty, may be damaged by falling branches; location of a leak may be difficult to find


- TPO
- $3.48 sq. ft.
- less expensive than PVC; clean manufacturing process; contains no chlorine, making it recyclable
- quality of the welds on TPO membrane is extremely important; professional installation is nearly mandatory; limited performance history


- PVC
- $6.75 sq. ft.
- hot-air welded seams; highly durable, resists punctures; can provide up to 80% solar reflectivity
- tendency to shrink over time; possible chemical release of bio-accumulative toxins during manufacture and disposal; UV stabilizers are essential to avoid shortened lifespan


- Garden Roof
- $15 to $20 sq. ft., not including the roof’s waterproof rubber layer.
- increases roof life span dramatically; increase real estate value; reduces heating of structure; reduces storm-water runoff; cuts down on airborne pollutants; eligible for LEED points
- higher initial cost; weight load requires careful engineering; structures retain water if not carefully designed


These are the links that were used to gather the information in the chart:
> http://www.costhelper.com/cost/home-garden/rubber-roof.html
> http://www.roof101.com/roofing-materials/pvc.php
> http://www.homewyse.com/costs/cost_of_epdm_roofing.html
> http://www.coolflatroof.com/
> http://www.flatroofs.org/
> http://seattletimes.nwsource.com/html/
> homegarden/2003721895_hay26.html
> http://www.homewyse.com/costs/cost_of_ib_pvc_roofing.html
> http://www.epdmroofs.org/faqs/faq_general.shtml
> http://www.researchroofing.com/tpo.html


Initial cost of various roofing systems key *Note, the price of an EPDM roof can vary greatly, depending on the price of oil. When the price of oil per barrel rises, the price of EPDM, not to mention other roofing materials, such as shingles, tar, rolled roofing and modified bitumen also increase.


** Initial cost based on an analysis distributed by Roofingcenter.org. (http://roofingcenter.org)


 


The last method is to employ ballast, which is application more appropriate for large commercial settings like grocery stores, schools and other large structures that are engineered to handle more weight.


“In the latter case, small stones are used to hold the rubber down, so basically, you’re lose-laying your insulation, loose-laying your rubber over that, doing your seams, and then spreading stone,” he says.


“We don’t do much of that,” he adds. “It’s hard work.”


That’s the reason St. Hilaire gives for preferring fully-adhered systems like glued-down sheets of EPDM—fewer complications all around.


Asked if he’s ever used liquid EPDM to affect a repair, and the fifth-generation roofer quickly demurs.


“I know that there are sprayed-on roofing systems that are really big in other parts of the country, but in my experience I’ve found that liquid products don’t have the properties they need to hold together for the long haul,” he explains. “You have to add fabric or take additional steps to make it hold up, like installing spray foam and then, after that’s cured, spraying on multiple layers of the liquid EPDM, and it’s just not an approach I prefer. Plus, with the extremes in weather we have in the Northeast, I really haven’t found that they work.”


08.2011
49

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