Civil Engineering Reference
In-Depth Information
— PVC: Polyvinyl chloride a synthetic thermoplastic polymer
prepared from vinyl chloride.
—
TPO: a blend of polymers that may or may not contain desir-
able additives such as flame retardants or UV absorbers.
Type2
Built-up roof (BUR), consisting of multiply plies of two compo-
nents, bitumen and felts. Bitumen provides the waterproofing and ad-
hesive properties of the system. The felts strengthen and stabilize the
membrane. The roofing membrane is protected from the elements by a
surfacing layer, either a cap sheet or gravel embedded in bitumen or a
coating material.
While there are many pros and cons for each of these two types,
installedcorrectly,a5-plybuilt-uproofisfarbetterthananysingle-plymem-
braneintermsoflifecycleperformanceandeaseofmaintenance
. The BUR has
many advantages:
•
With a gravel wear surface, the roof has excellent exterior fire resis-
tance.
•
It is impact and puncture resistant—better for roofs with high foot
traffic.
•
Temperature differential stress due to water ponding is significant-
ly lower.
•
Repairs are fairly easy (and can often be done by the facility main-
tenance staff)—no special manufacturer licensing requirements for
contractors.
•
Multiple plies add redundancy for water barrier protection—a
5-ply roof is better than a 3-ply roof.
•
Service life—which can be extended by ongoing maintenance and
repair.
“Cons” associated with BUR include odors and potential fire haz-
ards during installation, it is susceptible to damage from animal fats
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