About Roofing Concepts – The Roof Solutions Blog
Welcome to the Roofing Concepts Blog by All Area Roofing & Waterproofing. We aim to provide Florida building owners and property managers the knowledge base to familiarize you with the sometimes bewildering jargon of the roofing industry. An array of acronyms such as SBS, APP, TPO, EPDM, PVC, or PUF and technical terms such like “wind loads” and “design pressures” may leave you wondering “what is being installed on my building?”
We will clarify those terms in a language the lay person can understand and shed light on how they can affect your budget, capital expenditures, and maintenance funds. This should provide an easy seque into the design/build and maintenance process as you encounter the inevitable need to deal with roofing and waterproofing issues.
We will also provide you timely updates on the dynamic world of OSHA and EPA regulations and compliance, storm preparedness and disaster response, and permitting issues.
Questions, comments on individual blog posts, and blog topic requests are welcome and appreciated.
EPDM Roofing Solution for High Square Footage
Since the 1960’s, an increasing number of manufacturers, building owners and contractors have searched for an alternative to the fumes, flame and expense of conventional “hot applied” roof systems. One of the original single-ply systems to provide that alternate is a synthetic rubber known as EPDM.
Ethylene Propylene Diene Monomer or EPDM, is a compound whose principal components are ethylene and propylene. This form becomes a flexible rubber when diene is added. EPDM is classified as a thermoset membrane, meaning it is cured prior to installation. The uncured form is used as flashing material and cures during the natural weathering process. Seams are chemically welded with solvent borne adhesives or specialty seam tapes with adhesive primers.
One of the early appeals of EPDM was the relatively low materials cost. The membrane is typically 25 per cent-30 percent less expensive than modified bitumen and half the cost of built-up roofs. The uncured flashing materials and lap adhesives tend to drive the price higher, however the overall cost can be considerably less than conventional roofs and this is especially attractive for large scale distribution centers or manufacturing plants.
Three choices are available in EPDM system design:
- A mechanically attached system with fasteners through the laps and into the substrate;
- A fully adhered system glued to either suitable insulation or substrate and
- A loose laid or ballasted system, fastened only at the perimeters and penetrations with either pavers or stone holding the system in place. As of the revised 2004 Florida Building Code, system 3 is no longer applicable in the state, but is used extensively in large facilities requiring less stringent wind uplift standards due to its extremely low installation costs.
As the early EPDM systems aged, several issues became apparent. First and foremost is shrinkage. Most notable is ballasted systems, shrinking membranes displace gravel, can distort wall or edge flashings and will ultimately tear the membrane itself allowing water intrusion. There are no universal methods of addressing shrinkage as the repairs required range from minor tension relief cuts to complete re-roofing. The second problem is lap failure, often due to shrinkage or improper adhesive installation. The latter problems have been addressed with the advent of seam tapes providing more uniform lap strength.
If your property is currently covered with an EPDM system, please contact All Area Roofing & Waterproofing for a free evaluation with maintenance recommendations.
The Modified Bitumen Evolution in Florida Roofing
One of the many evolutions in the roofing industry has been the formulation of modified bitumen membranes. As the name implies, modified membranes are asphalt based with modifying polymers introduced during the manufacturing process. The most common modifiers are APP or SBS, which when combined with asphalt, give the resulting membrane plastic or rubber-like properties.
In addition to providing greater tensile strength and elasticity, the introduction of these polymers allows for a single roll with coverage of 100 square feet, including the surfacing, resulting in significant labor savings during application. Modified can be installed with conventional hot asphalt, modified adhesives, open flame torches, hot air welders or most recently, self adhered. Several of today’s systems, such as Derbigum, combine the superior uplift of adhesives with the immediate watertight lap provided when torching or heat welding.
All modified bitumen membrane rolls rely on an inner scrim or reinforcement mat to hold the asphalt in place. Scrims are typically polyester or fiberglass or both and these mats are dipped into the molten modified mix, processed through a rolling cylinder and then a surfacing table and cooking bath. These mats are chosen because of their ability to accommodate the modifying polymers elongation properties. The type and weight of the mat determines the final characteristics of the roll and ultimately the price.
Since the introduction of modifieds in Florida in the 70’s, their market share has increased steadily culminating in almost 30 per cent in the 90’s. Several factors play a role in the recent decline seen in this market over the last decade. A few of these include:
- Widespread acceptance of thermoplastic systems requiring minimal slope with accompanying reduced installation cost.
- Increased insurance costs associated with open flame and 500 degree molten asphalt for SBS cap sheet installation.
- Rising petroleum costs translating to higher manufacturing prices and ultimately more expensive end user cost.
- Increased demand for environmentally sensitive “cool roofs” and more awareness of potentially harmful fumes.
Despite the items listed above, modifieds have proven performance on residential, commercial and industrial applications. The granular surfacing requires no costly maintenance coatings while making inspections and repairs very easy. Tough and long lasting, these systems are designed for Florida Owner/Managers that wish to keep and maintain rather than sell.
Build-up Roofs a Longtime Staple for Florida Commercial Buildings
Built-up roofs using coal tar pitch are the oldest form of flat roofing in existence. One hundred forty year old sketches are available showing horse drawn “hot kettles” and this form, with minimal changes, is still in use today in Tampa Bay and all of Florida.
Coal tar pitch is a distillate of coal tar and is formed of primarily aromatic hydrocarbons. This complex linking makes coal tar inherently stable chemically and allows a broad range of softening temperatures vs. the defined melting point found in asphalt products. In short, coal tar is an extremely durable roof membrane which softens at very low temperatures and this cold flow property allows the roof to “heal” itself from minor punctures and voids.
Coal tar roof systems consist of alternating layers of roofing pitch with reinforcing felts and are “built-up” in a similar fashion to asphalt BUR roofs. Because of the unique chemical composition of coal tar, it can be installed on “dead level” or poorly drained flat roofs with no ill effects on the system. Prior to the widespread use of mechanical air conditioning units, many buildings were”water cooled’ by providing raised edge details to impede water run-off and coal tar pitch was the roof system of choice for these locations.
Coal tar pitch is also utilized in several other areas of the construction industry including a below grade waterproofing mastic and pavement sealants.
Unfortunately, the past few decades have revealed some serious health concerns with coal tar products. Side effects from the vapors range from minor skin, nose and throat irritation to nosebleeds, changes in skin pigmentation, rashes, fainting and comas.
Additionally, the price of pitch has been a prohibitive factor as the installation cost is typically 2-3 times that of asphalt products and special design criteria must be met to accommodate the cold-flow characteristics.
The combination of health and cost concerns has created a marked decrease in the cold tar market. Several manufacturers’ have vacated this segment of the industry and as health insurance costs continue to rise, we’re doubtful coat tar pitch will rebound.
If you have a coal tar roof on your building and require assistance in managing this specialized system, call All Area Roofing & Waterproofing, Inc. today.
Built-Up Asphalt Roof Systems in Florida Commercial Buildings
Conventional built-up roof systems have been in use as an industry mainstay for over 100-years. These applications typically use coal tar pitch or asphalt as the waterproofing material which is installed in successive layers and reinforced with ply felts. With multiple plies, a contractor is essentially “building up” the roof, hence the terminology. This post covers the asphalt side of BUR systems.
Built-up asphalt roofs are field fabricated using hot applied asphalt in alternating layers with Type IV, Type VI or organic ply sheets. The entire assembly is then surfaced with protective coverings such as gravel, fibered aluminum or other coatings to avoid UV degradation of the asphalt in the assembly. A built-up roof is greatly enhanced with additional plies and redundancy is the key to its performance.
Layers of a Build-Up Roof
A typical BUR assembly might consist of an anchor or base sheet installed over a lightweight concrete deck or multiple layers of tapered insulation. The next step is the alternating felts and asphalt mopped in place at an application temperature within 25 degrees F of the EVT for the particular type of asphalt. Most contractors today use Type 4 asphalt with an EVT of around 472 degrees so the temperature at the mop should be within the 450-500 degree range for the optimum roofing. The asphalt is spread to allow approximately 23-25 lbs. of asphalt per 100 square feet per ply. Too much asphalt and the roof can “slip”, too little and the system will fail prematurely. The fiberglass ply sheets are porous and allow the asphalt to saturate at this temperature and this combines to form a “ply”. Four of these layers constitute a “4-ply BUR”. Finally an additional layer of asphalt is spread and gravel is broadcast while still hot at the rate of 400-600 lbs. per 100 square feet. A minimum standard is 50 per cent embedment of the surfacing gravel. This system then becomes a “4-ply BUR/G”.
Other alternatives for surfacing include a clay/asphalt emulsified coating, fibered aluminum coatings or acrylic/elastomeric coatings. All of these are acceptable, however, each is subject to deterioration and will require “recoats” at 5-7 year intervals and none have the protective properties or excellent fire ratings of gravel.
Build Up Roof Challenges
As is easily noticed from the installation guidelines, built-up roofs are extremely labor intensive. Kettles at ground level to heat the bitumen allowing it to be pumped onto the roof must be constantly monitored. Moving hot asphalt safely around a roof surface requires additional personnel and specialized equipment and to physically install ply sheets and surfacing requires a substantial team. A typical built-up crew can easily involve 10-12 men or more.
Combining the high labor costs with volatility in the petroleum market, increasing awareness of open flame and fume hazards and building department concerns over gravel surfacing becoming airborne projectiles has led to a decrease in market share for this roof type. Additional concerns include the aesthetics of a “hot kettle” at ground level and the stringent safety procedures that must be followed when dealing with open flames and super-heated asphalt with its’ resultant fire potential. Lastly, when the cost of tapered insulation (asphalt fares poorly in ponding water) are combined with high labor and increasing bulk asphalt prices it is east to have a 15-year BUR system at double to triple the cost of other systems with the same warranty period. In today’s economy, many Owners and Managers are increasingly in search of alternative systems for their properties.
For further information concerning your built-up asphalt roof, we suggest the Asphalt Roofing Manufacturers’ Association . Or please contact All Area Roofing and we will be glad to visit your site, evaluate your BUR and provide maintenance or design/build insight as needed.
Commercial Roof Insulation
Exploring the elective components of a commercial roofing system in Florida, we now take a look at types of insulation.
Roof insulation performs two basic functions:
- Acts as a thermal barrier for the top of the building.
- Serves as the base for the roof sytem.
Secodary functions include:
- Enhancing drainage through the use of tapered insulation systems and stiffened roof decks.
Poly-isocyanurate
Far and away the most common roof inulation installed, ISO is available in flat or tapered panels and is the base for many roof systems with an average LTTR value of 5.56 per 1″ of product. Polyisocyanurate features a closed cell iso core integrally laminated to fiber reinforced felt factors. Iso has a perforated facer on one side for use with hot asphalt applied systems while the non-perforated side is for use with single-ply systems.
Pros
High R value of 5.5 per inch and good compressive strength. Excellent dimensional stability and very lightwwight.
Cons
Contains CFCs or HCFCs which may be released into the environment, causing ozone depletion. It is also expensive in comparason to other insulations. Contains a petroleum by-product increasingly in demand worldwide, resulting in availability problems and lengthy lead times for orders.
Perlite
Perlite insulation is an inorganic, rigid board insulation available in 2′ x 4′ or 4′ x 4′ panels. The panels are composed of expanded volcanic glass and wood fibers bonded with asphaltic binders. Until recently, perlite was the most common insulation used in roofing. Although still popular, its low R-value of 2.78 per inch and tendency to absorb moisture have diminished its frequency of use.
Pros
Perlite has an excellent fire protection resistance rating. It also has good compressive strength which allows normal roof foot traffic. It also has great dimentional stability and the ability to absorb outgassing common in foam and iso insulations. It is often used as a cover board in hot asphalt sytems.
Cons
Very friable and relatively easy to break panels. Complete deterioration when in contact with moisture. Low R value and poor tensile strength.
Expanded/Extruded Polystyrene
As the lead times required for isocyanurate insulation increases, EPS has risen as a low-cost alternative for roofing insulation. Both types are manufactured from polystyrene, one as a fused board made of beads while the second is formed from a molten sheet pressed into shape.
Pros
- Dimensionally stable with lower water absorbtion.
- Extremely lightweight, minimizing roof dead loads.
- Easy to handle, cut, and form.
- The extruded form is used widely as a base for achitectural shapes at wallsand parapets.
- Decent R values between 4-5 depending on type.
- Relatively inexpensive
Cons
- Poor fire resistance
- Low compressvie strength equates with poor wind load resistance
- Releases potentially toxic combustion product if ignited
Dens-Deck
Dens-Deck is an ever increasingly popular roof insulating product in roof assemblies. It is the roofing version of an exterior board used most commonly as an exterior stucco backer board. This board is a mold resistant roof panel that consists of a moisture-resistant, non-combustible core of specially treated gypsum with glass mat facings.
Pros
- Approved by all manufacturers.
- Highest performance rating for fire, wind uplift, and moisture resistance.
Cons
- Very heavy board increases handling costs and deck requirements.
- Difficult to cut and form
- Primed version must be used in hot applications to avoid blistering membrane.
- Low R value
Wood Fiber
The final insulation we will examine is wood fiber. It is the oldest type designed for roofing. It is normally found in a “high density” form and is inexpensive and durable. It is also often used as a cover board over iso in hot applications to reduce outgrassing.
Pros
- Durable, easy to handle, and relatively easy to cut and form.
- Decent compressive strength provides reasonable wind uplift ratings.
Cons
- Dimensionally unstable in contact with moisture.
- Rapid deterioration when wet, also providing possible medium for mold growth.
- Poor fire rating with low R value of 1.9 per inch.
Other types of roofing material used in commercial roofs across Florida are foam-glass, gypsum wallboard, and mineral board. Please call us if you have any questions or would like a further analysis of the insulation in your roof system.
Each project and roof assembly has its’ own subtle differences that may lend itself to a particular size, type, or thickness of insulation. Additionally, the expense at insulation should be cost-factored in comparison to heating or cooling billd over the expected life of the assembly to determine the most effective insulation for a particular project. Your contractor, consultant, or manufacturer can all play vital roless in helping with the final decision based on R value needs, anticipated length of ownership, and local codes.
