Table 2-1. Steep Slope Selection Based Upon Criteria

CEMP-ET

TI 809-53

01 May 1999

Table 2-1. Steep Slope Selection Based Upon Use Criteria

Asphalt Shingles

Asphalt

Clay

Concrete

Roll Roofing

Tile

Strip/Seal Down

Laminated

Interlocking

Severe Cold

Fair

Good

Fair

Poor

High Temp & Humidity

(e)

Fair

Fair/Good

Severe Hail

Fair

Poor

Fair

Severe Wind

Fair

Good

Fair

(a)

Can Be Re-covered

Good

No

Good

No

Appearance

Fair

Good

Fair

Good

Slate

Arch.

Crafted

Wood

Metal

Shakes

Shingles

Look-Alike

Severe Cold

Fair

(c)

(d)

Poor

(c)

High Temp & Humidity

Fair/Good

(f)

Fair/Good

Severe Hail

Fair

(g)

Thickness

Poor

(g)

Severe Wind

Good

(b)

Thickness

Fair

(g)

Can Be Re-covered

No

Maybe

No

Appearance

Good

Fair

Good

(a)

Requires nose clips, extra fastening

(b)

Depends upon gauge, clips design, closures

(c)

Requires sealed underlayments

(d)

Requires soldered joints, special detailing

(e)

Algae resistance is available

(f)

Treated wood needed

(g)

Heavier gauge better

2-3.

SELECTION CONSIDERATIONS FOR LOW-SLOPE (MEMBRANE) ROOFING.

Membrane roofing is typically used on commercial buildings where the minimum slopes required

by steep roofing render them impractical for larger buildings. Low-slope membrane systems are

completely sealed at laps and flashings (figure 2-3) and can temporarily resist standing water

conditions. Choices for membrane roofing include multi-ply bituminous built-up (BUR), polymer-

modified bituminous (MB), elastomeric single-ply systems (e.g., EPDM), thermoplastic single-ply

systems (e.g., PVC or TPO), sprayed-in-place polyurethane foam (SPF), and some metal

(hydrostatic/low-slope/SSSMR) systems. Designers frequently select low-slope roofs when the

roof is expected to accommodate rooftop equipment. With the exception of foam and metal, all

low-slope systems can be incorporated into Protected Membrane Roof (PMR) designs.

2-4. REROOFING AND RE-COVERING.

a. Reroofing. The term replacement is used when the existing roofing system is to be either

partially or totally removed and a new system installed. The designer should consider any

existing problems and whether drainage and thermal performance needs to be improved.

Existing surfaces such as walls and curbs may be contaminated with bitumen, which might affect

compatibility with some reroofing options. Additional concerns (as compared to new roofing)

include whether the existing structure can handle a significantly heavier roof system and whether

construction activities of the reroof system will affect the occupants of the building (i.e., fumes,

falling debris, and noise).

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