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Name this roofing material!


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Hi, everybody! Long time lurker, first time poster! [:-paperba

I'm trying to identify the material on a flat roof over an 11-story apartment building in Iowa City, IA. The building was constructed in 1980 with $35K worth of roof repairs in 1991.

I write capital needs assessments for an architectural firm in SW Missouri but have a background in English so . . . I'm kind of lost as to what this is. I'm used to seeing built-up, EPDM, stuff like that on flat roofs. I've never seen a tile like this before on a roof. Unfortunately, the "inspector" (I use the term loosely) has no clue about different building systems so his data is completely useless especially since he calls this a membrane roof.

Please take a look at the attached photos. If you have some information on this material, I'd appreciate any help you can give! For example, what is it called (generic name rather than a brand name), benefits of using this in Iowa, expected useful life of this stuff, any sort of known problems, and anything else that might be useful.


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Download Attachment: icon_photo.gif roof 2.jpg

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"Ballast tiles" or "ballast pavers". They're lightweight concrete tiles installed to secure single-ply roofing membranes (so wind doesn't lift 'em up) and to protect the membrane from UV wear. Also reduces damage from HVAC mechanics.

Those interlocking tiles look familiar. Try googling "Westile Ballast". I'll bet that's them.

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Kurt is likely right and for Reserve Study purposes that distinction is important. Bill hit the nail right on the head. Consider the exposure at the building site and info from old farts like Bill and Kurt.

I would be sure tiles were not too tight nor loose; abrasion factor and thermal effects. I have seen the system poorly done more than properly done. It is a regional thing and should be treated like that in your report.

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A reserve study is a written document describing building condition & the amounts of money that might be expected or necessary for maintenance and repair of the building (or buildings). It's the art & science of adequately planning for common area maintenance & repair costs by reviewing building conditions & projecting costs.

Reserve studies are most often associated w/condominium buildings; the board will often request a reserve study so that they can adequately plan major capital expenditures, and maintain appropriate reserves for that purpose.

Was that too wordy?

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It's a ballasted PVC single ply membrane. The ballast keeps it from blowing off and protects the membrane. Initial cost is low. Lifespan is shorter than other products, probably 10-15 yr. Life cycle cost is highest of any single ply.

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  • 2 weeks later...

Not likely,

There's typically something being used as an isolation membrane between the ballast and the pvc. They use that stuff on the roofs of the high rises in downtown Seattle and there's typically a layer of extruded polystyrene foam a couple of inches thick directly on top of the membrane. Sometimes there's even a drainage layer of pea gravel on top of the foam and finally the pavers.



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