LOW-SLOPE ROOFING

COMMONLY USED LOW-SLOPE ROOFS

The following roof coverings are commonly used for low-slope roofs. These roofs are considered to be water impermeable or weather proof. Low-Slope roof membranes consist of three components; a weatherproofing layer, reinforcing layer and surfacing. Roofs installed at a 3/12 pitch or less are considered to be “low slope.”

SINGLE-PLYS

Low Slope Roof Single Ply

Single-Ply membranes, while newer to the market, have had very good results over the last ten years. TPO & PVC are the most widely used “white” membranes, while EPDM is the most widely known “Rubber Roof.” Many of these membranes have natural elastic properties, low-VOC install options are available, and higher energy efficiency (sans EPDM). They have multiple installation options that can fit most scenarios and budgets.

PROS & CONS OF SINGLE-PLY

PROS
  • Productive installation techniques.
  • Moderately easy and inexpensive to repair.
  • Better appearance compared to BUR and MB
  • Available with a variety of cool coatings.
  • Resistant to storm damage

CONS
  • Durability can be an issue as well as natural weathering.
  • Due to high price-point pressures, manufacturers may offer materials and details that are not as reliable as owners may require.
  • Cold fluid adhesives may have high VOC content.
  • Thermoset seams can deteriorate over time and cause sources of leaks.

MODIFIED BITUMEN (MOD-BIT)

Low Slope Modified Bitumen Roof

Modified Bitumen (Mod-Bit) roofs are made from a mixture of bitumen, modifiers and solvents. The rubber provides a “thermoplastic elastomer” that will melt and help bond the membrane/reinforcement to the substrate. These roofs require a UV reflective surface and do not tolerate standing water well.

PROS & CONS OF MODIFIED BITUMEN

PROS
  • Easily repaired and modified.
  • Durable
  • Cool Coatings exist as a surfacing option
  • Capable of being added to a BUR in order to create a “Hybrid Roof”.

CONS
  • Bonding by hot-applied asphalt may cause the membrane to use some qualities.
  • Some manufacturers may produce sub-standard product
  • Torch down installation has been known to burn down buildings during installation.
  • Cold fluid adhesives often have high VOC content.
  • Susceptible to storm damage.

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BUILT-UP ROOFS (BUR)

Low Slope Built Up Roof

Built-up roofs are some of the most time-tested roofs on the market. They are composed of bitumen (asphalt) and, primarily, fiberglass felt plies. The asphalt is typically hot-applied, however cold-applied asphalt systems are now available. When properly installed and maintained, it can be an excellent waterproofing system.

PROS & CONS OF BUILT-UP ROOFS

PROS
  • Proven History
  • Relatively easy to repair
  • Tough

CONS
  • Difficult to properly install
  • Particularly sensitive to standing water and storm damage
  • Can be dangerous to install
  • Noxious fumes

COATINGS AND FOAMS

FLUID APPLIED COATINGS

Elastomeric Coatings are excellent in the proper situations but are rarely used as a primary source of moisture mitigation. They can provide a membrane that bonds to the structural concrete substrate for a vegetative roof. They may also be used to extend the lifetime of the system that is currently on the roof, if properly installed. Once cured, they create a monolithic membrane.

SPRAYED POLYURETHANE FOAM (SPF)

Sprayed Polyurethane Foam is a very unique type of roof system and requires a skilled installer. Similar to Elastomeric Coatings, they are typically not used as a primary membrane. SPF is typically used as an alternative to removing and replacing the current roof system.