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The Latest Trends in Roofing Materials – Part 1

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Low-Slope Roofs

The Jamaican roofing landscape has changed quite dramatically over the past 20 years, Modified Bitumen Single-Ply Membranes were first introduced here over 20 years ago and have progressed from being a new, revolutionary product to having a significant share of the roofing market, estimated at 50 - 60%. Most low-slope roofing contractors now specify and install this very cost effective system.

The asphalt based built-up roofing system, out of favour for awhile because of real and perceived performance and installation problems, has suffered a significant decline in popularity and usage in Jamaica. We estimate that less than 15% of low-slope roofs are being repaired using this traditional system. Jamaican contractors are leaning heavily towards the very easy to install modified bitumen single-ply membrane systems, with Sprayed Polyurethane Foam (SPF), Elastomeric coatings, and even EPDM and PVC systems also making an appearance here.

For those facility owners, managers, engineers, etc, purchasing roofs in today's market, there are two words that best describe the state of the industry, Choice and Change.

Today's Choices

Compared to the 1970's, when the only real decisions the buyer of a new roof had to make was how many plies of built-up roofing were best, the current market presents a dizzying array of choices. Following is a short review of some of the updates in each generic product line.

Modified Bituminous Systems

Modified bitumen, sometimes referred to as "mod bits" or modifieds, is a family of asphalt membranes composed of a rubber or plastic additive, combined with asphalt, fillers and felt reinforcement. The modifiers improve the cold flexibility of the membranes over conventional blown asphalt, increase the melting point and resistance to high temperature flow of the bitumen, and are formulated to improve elasticity of the roofing material.

Most typically the mod bit membranes are made in sheets three feet or one meter wide, and resemble traditional asphalt rolled roofing. Two primary modifiers are used, SBS or styrene butadiene styrene, a rubber like substance, or APP, atactic polypropylene, a waxy plastic like modifier. SBS membranes, with better low temperature flexibility, are most often specified in overseas temperate climates. Alternatively, APP membranes with outstanding resistance to high temperature flow are better suited for tropical climates such as Jamaica’s.

APP modifieds are generally torch applied and SBS membranes are mostly applied in hot asphalt. Cold adhesives for both are also now on the market, which may be helpful in places where torches or hot asphalt cannot be used due to unacceptable fire risk or environmental considerations.

The mod bit systems are increasingly being specified as multiple ply systems, with two plies being a recommended minimum. Again, there are numerous choices available to the roof designer, depending on the needs of the application. Hybrid systems, using one, two, or three plies of fiberglass felts in hot asphalt, followed by a finish ply of modified bitumen, has also been a popular development in some overseas markets. Most local contractors continue to use mod bits in a single layer as originally recommended by the manufacturers, and this remains the most cost effective waterproofing system available here. However, a move to a minimum of two plies of this material is increasingly recommended and even required by the manufacturers, and we support this trend which yields greater reliability and resistance to mechanical/chemical damage.

Modifieds have the same general sensitivity to ponding water as asphalt built up roofing, so positive sloping to drains is a necessary design feature. Modifieds are very durable, and generally have performed well over the past 15 to 20 years here in Jamaica if properly installed and maintained. They are usually warranted for 10 years but will last up to 20 years under good conditions.

Built-up Roofing

The main improvements in built-up roofing have been the shift to fiberglass felts and the use of rubber modified asphalt flashing materials. Fiberglass ply felts now come in two types, the widely used Type IV felt, generally considered the commodity felt, and the newer but stronger Type VI felt. Both have proven to work in well designed applications, and at this point the Type VI felt is positioned as the premium felt, for those inclined to buy upscale. Type VI felt systems generally are required to qualify for longer "system" warranties.

Sprayed Polyurethane Foam (SPF) System

This system was introduced to the Jamaican market about 5 years ago and is installed by a few specialist contractors with varying degrees of success.

It is applied by combining two components (Part A, Isocyanate and Part B, Polyol Resin) at the point of application on the roof using specialized spraying equipment. The components immediately react forming an amber coloured Polyurethane foam of varying controlled densities depending on the application. This foam is sprayed in multiple layers or “lifts” to create a slope for positive drainage to the drainage points. It is then coated with a reflective and UV resistant coating or crushed river stones to screen very damaging solar ultraviolet (UV) radiation. This system is generally warranted for 10 years, with a potential life span in excess of 20 years.

The SPF system properly installed is very effective and offers some strong benefits to the building owner and installing contractor. It offers the possibility of creating a waterproof, energy efficient and positively draining surface in a single application. Being seamless, it eliminates any potential issues with seams and joints, and its completely hurricane resistant and lightweight. As with many roofing systems however, the quality of the workmanship is of critical importance as the system is somewhat temperamental and requires expensive, well maintained equipment and highly trained and experienced applicators. There are no more than one or two local contractors with the requisite training, experience and commitment to quality that can successfully install this system. The market share of the SPF system is estimated at somewhere between 10-20%.

Single-Ply Systems

Single-ply systems consist of one layer of an elastic/plastic membrane usually 45 to 60 mils thick and installed in a number of ways, generally ballasted (laid dry, but held in place by gravel or pavers), fully adhered (glued in place) or mechanically fastened (anchored to the roof deck with fasteners). Chemically, these membranes are manufactured from synthetic rubber or plastic, sometimes incorporating a layer of reinforcing fabric or mesh. More commonly they are known by their primary polymer component makeup, EPDM, PVC, CSPE, PIB, EIP, etc.

Single-ply roofing membranes were adapted from other uses of elastomeric membrane materials, such as pond liners. Having excellent elongation, they were sold to disgruntled built up roofing owners as a better solution.

There are only one or two local distributors/applicators of this very effective niche system which is estimated to hold less than a 5% share of the Jamaican market.

Elastomeric Coatings

Elastomeric coatings are polymer based with a rubberized consistency, and most often white in colour. They are liquid applied with rollers, brushes or airless spray equipment, and are most often supplied in 5 gallon pails. The market is supplied by local and international manufacturers, mainly through hardware stores.

This system is for the most part a do-it-yourself one catering primarily to homeowners with concrete slab roofs. Few contractors offer this system as a long term, heavy duty option as it is not considered very durable and long lasting on heavy traffic commercial roofs. It is also particularly susceptible to ponding or standing water so prevalent on most low-slope roofs. The ideal application for this system is a residential concrete roof with excellent drainage, solid construction with minimal cracking, and little foot traffic. We estimate the market share for this system at somewhere between 5-10%.

Metal Roofing

Low slope metal roofs have come a long way from the leaky metal siding panels that were caulked together and screwed to the structural frame. Today's metal roofs are attached to the structure with concealed clips, which slide to accommodate expansion and contraction. Panel sealants are still used at end laps and some side lap locations, but the sealant is subjected to less movement stresses and is often shielded from U.V. exposure.

Metal roof systems can be used in new and some reroofing situations, but should always require a minimum 1/4" per foot slope. They are most often specified for commercial structures in various gauges of steel or aluminium, and featuring various mostly rectangular profiles. For the residential market, aluminium roofing in 26 gauge or less is commonly specified, sometimes painted. There is far more usage of this system for commercial roofs, with very few residential properties featuring this system.