Roof Types : Case Study

Tile

Roofing tiles are composed of either concrete or clay. Both types are long life products needing little or no maintenance. Both are aesthetically pleasing. These tiles are not waterproof. The tiles shed water but do allow some water, especially in blowing rains, to penetrate the laps in the tiles which could run into the building if it were not for the underlayment. The underlayment is the real waterproofing component. When the underlayment wears out, the tiles must be removed and the underlayment replaced. This practice is referred to as a tile relay because the old tile is reused while replacing any broken tile with new tile.

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Advantages of Concrete Tile

More competitive than clay tile or slate Long life roofing product Low maintenance product Aesthetically pleasing Hail Resistant

Advantages of Clay Tile

Long life roofing product Low maintenance product Non-Combustible Aesthetically pleasing

Slate

Traditional slate roofing systems are extremely successful systems that can easily function as a waterproof covering for 100 years and, if properly constructed, 150 or even 200 years. Their longevity, however, is not their only quality. Slate roofs are made of natural materials — primarily stone (slate) and wood (boards or lath/battens) with metal fasteners (nails). They are simple and beautiful roofing systems. When they need to be replaced, they can be discarded as clean land fill, as opposed to the toxic waste of petrochemical roofs. As such, slate roofs are sought after by those who have ecological concerns. Slate roofs are arguably the least expensive roof money can buy when the entire life of the roof system is taken into consideration.

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Advantages of Slate

Long life product Low maintenance product Aesthetically pleasing

Modified Bitumen Membranes

Modified Bitumen technology developed out of attempts to widen the serviceability range of conventional oxidized roofing asphalt. Increased resistance to brittleness at cold temperatures, greater flow resistance at high temperatures, and increased elasticity can be achieved by blending synthetic rubberized polymers with asphalt in lieu of modification by blowing processes (oxidation). The result is a membrane that combines the multi-layer benefits of a built-up roof with the installation advantages of a single-ply membrane. Modified Bitumen Membranes are manufactured with basically two formulas: Atactic Polypropylene (APP) and Styrene Butadiene Styrene (SBS). Both formulas are available with fiberglass reinforcement or polyester reinforcement. They are available in smooth surfaced or granulated rolls that can be heat welded, cold applied or hot applied.

When the management of the Nowlin building at 9311 San Pedro in San Antonio, Texas decided to reroof the 13 story high-rise, they chose Cram Roofing Co., Inc. to install their new SBS Modified Bitumen Roof. The SBS roof system was chosen for many reasons:

• The old roof was to be left in place and recovered; weight was a factor.
• The roof top is a work surface for a number of other trades.
• Limited set up area and access made the use of cold application methods very attractive.

All of these challenges were met using a polyester reinforced SBS Modified Bitumen Membrane. Cram Roofing Co., Inc. was able to clear away the debris using a crane and re-roof the facility without interrupting satellite technology that is utilized within the building.

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Advantages of APP Modified Bitumen Membranes

Can be cold applied or heat welded Lightweight membrane; great for use as a recover system Because no aggregate surfacing is necessary, maintenance and repairs are easily accomplished

Advantages of SBS Modified Bitumen Membranes

High elongation properties makes SBS a good choice where building movement is expected Excellent cold weather flexibility Lightweight membrane; great for use as a recover system Because no aggregate surfacing is necessary, maintenance and repairs are easily accomplished Can be heat welded, cold or hot applied

Advantages of Fiberglass Reinforced Modified Bitumen Membranes

High tensile strength Excellent fire resistance

Advantages of Polyester Reinforced Modified Bitumen Membranes

Excellent elongation Excellent puncture and tear resistance

EPDM Roofing Membranes

EPDM (Ethylene Propylene Diene Terpolymer) synthetic, rubber roof membranes have been used on roofs in the United States since 1960 and is one of the most common types of low-slope roofing materials. This is because it is relatively inexpensive, simple to install, and fairly clean to work with when compared to conventional built-up roofs. There are fewer odors and fumes that accompany built-up roofs which appeals to many property owners and managers. The properties of EPDM - resilience; tensile strength; elongation; resistance to ozone, ultraviolet light and ponding water – make this membrane an excellent roofing material.

To assist a naval air force base with space, Cram Roofing Co., Inc. suggested using an EPMD roofing system to link together many temporary buildings.

The base had purchased these temporary buildings to form one building. Because of the flexibility of EPDM membrane, it was a perfect solution. This membrane will allow for movement without breakage.

The work performed by Cram Roofing Co., Inc. was warranted by the manufacturer for 10 years with No-Dollar-Limit. To date, there have not been any leaks on this project.

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Advantages of EPDM Roofs

Installs easily with large sheets which reduces a tremendous amount of labor as compared to other roofing systems  Lightweight; great for use as a recovery system Because no aggregate surfacing is necessary, maintenance and repairs are easily accomplished Available in .045 mil, .060 mil, and .090 mil to meet every need Traffic Resistant Fast track system for time sensitive projects

EPDM System Design Considerations

Roof must have positive drainage Roof should not be expected to be used as a traffic surface Buildings venting any type of contaminate onto the roof surface should incorporate grease traps or recovery systems

Liquid Applied Membranes (LAM)

Liquid Applied Membranes (LAM) is a waterproofing, UV-resistant coating that protects against weathering, impact damage, stress cracking and ultraviolet rays. This roofing system is applied at varying rates of thickness and is mostly used over existing metal roofs, single ply or modified bitumen roofs as an alternative to tearing off and replacing the existing system. There are many application methods ranging from roller to broom. LAM is a tenacious adhesive and is coal and tar free. 

Due to delicate building contents, The Archeological Research Center at the University of Texas at San Antonio had a metal roof that they did not want removed and replaced. Their Architect specified a LAM roofing system and Cram Roofing Co., Inc. was selected as the contractor.

The existing metal roof was prepared, power washed with all fasteners being checked, tightened and replaced if necessary with oversized fasteners. Then all the fasteners were encapsulated with an elastomeric sealer.

All the seams in the roof were sealed with an elastomeric sealer and the horizontal seams received a polyester reinforcement and an additional layer of elastomeric sealer.

All the penetrations were sealed with a double layer of elastomeric sealer and polyester reinforcement. 

With the roof, lap and penetration preparation work done, the roof was then ready for the two coat, water based LAM. A base coat was first applied then the finish coat was sprayed on at the rate of 2 gallons per square foot, per coat.

A LAM manufacturer conducted an inspection and a 10 year Roofing System Warranty was issued.

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Advantages of LAM Membranes

Significant savings over roof replacement Highly reflective white or aluminum finish membranes Lightweight design adds minimal load to the structure No interruption in building operation in the event of unexpected rainfall during construction Long term warranties

Built Up Roofing (BUR) Membranes are typically found on flat or nearly flat roofed buildings. These Membranes are referred to as built-up due to a process of overlapping several layers of roofing felts with hot or cold adhesives. BUR felts can be made of organic, fiberglass or polyester composition. The hot adhesives will be one of three main types: asphalt, modified asphalt or coal tar pitch. The cold adhesives are either asphalt or coal tar pitch based. A layer of gravel is typically the final step which protects the roof from ultraviolet degradation and provides weather resistance.

The University of Texas at San Antonio Physical Education Building had a number of chronic leaks due to water ponding on the asphalt-based roofing system. The University’s roof consultant recommended another BUR but this time around incorporated a tapered roof insulation system to improve roof drainage and extend roof life.

The project was competitively bid under a Request For Proposal method. Cram Roofing Co., Inc. was awarded the project based on total points earned from best price offered to past performance on other university projects. 

The project specification called for a four ply, gravel surfaced BUR and features a 20 year No-Dollar-Limit Warranty.

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Advantages of BUR Membranes

Long solid track record that dates back to early twentieth century Can be cold or hot applied High tensile strength reduces the possibility of roof splits Excellent Fire Resistance Excellent puncture and tear resistance Multiple ply systems

Advantages of Coal Tar Pitch BUR Membranes

System can tolerate ponding water without risking damage to the membrane Low melting point of the coal tar bitumen easily reseals small punctures giving coal tar pitch membranes a self-healing characteristic System stays flexible for years after installation Longest life system on the market

Advantages of Asphalt Based BUR Membranes

Low fuming characteristics of asphalt BUR is less objectionable to building occupants High melting point of asphalt makes for a stable bitumen that will not run into the build or down the outside walls in hotter climates Can be used on buildings with slopes over ¼” per foot without experiencing slippage of roofing felts

Thermoplastic polyolefin (TPO) membranes is one of the most popular commercial roofing materials. These single ply membranes are created by using reinforcing fabric and rubber together with state-of the art technology to be considered an environmentally safe, “green” product. TPO roofing membrane is typically installed using mechanical fasteners and plates placed along the edge of the sheet and fastened through the membrane and into the roof decking. Adjoining sheets of TPO membrane are overlapped, covering the fasteners and plates, and joined together with a hot air weld. This type of system is highly resistant to wind and other weather factors.

When the Deputy Sheriff’s Association of Bexar County needed a new roof they contacted their Architect to help them select a roofing contractor that could handle the job.  The architect wasted no time in calling on Cram Roofing Co., Inc. to help with the project. The Deputy Sheriff’s Association had used another roofing contractor previously who had left important components out of the roofing system they installed and this had caused the building to not only have roof leaks but interior damage as well. Cram Roofing Co, Inc. worked with Mr. Hinojosa to select a white TPO single ply membrane because of its reflective properties and proven track record in being a high quality state of the art roofing system. 

The TPO membranes were then fastened over the polyisocyanurate roof insulation to the wood deck achieving the targeted R-value.

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Advantages of TPO Membranes

Excellent elongation and flexibility Lightweight; great for use as a recover system Because no aggregate surfacing is necessary, maintenance and repairs are easily accomplished Available in colors Available in .045 mil, .060 mil, .090 mil and .120 mil to meet every need. Long term warranties available Fast track system for time sensitive projects

System Design Considerations

Roof must have positive drainage Roof should not be expected to be used as a traffic surface Buildings venting any type of contaminate onto the roof surface should incorporate grease traps or recovery systems

Metal Roofing Membranes

The 1990’s saw a proliferation of metal roofing membranes as the system moved from the old, tin roof, farm house your Great-Grandfather lived in to schools, hospitals and office buildings. The application of these roofs, on structures not previously considered metal roofing candidates, spawned a new set of flashing challenges that had to be solved if metal roofing was to survive as a viable multipurpose roofing system.

New thought by the metal roofing industry and the Sheet Metal & Air Conditioning Contractors National Association (SMACNA) developed new flashing details suitable for these new roof application challenges. One critical factor in selecting the best contractor to install your new metal roof is for that contractor to have his own modern, well-staffed, sheet metal fabrication facility. This is vital because although the metal roof panels are readily available from the manufacturers, most of the trim and flashings must be custom fit by sheet metal craftsmen with plenty of experience and computerized equipment to do so.

There are different profiles of metal roofing. The most common are field-fabricated standing seam, structural standing seam, snap seam systems and a variety of corrugated metal panels. Unlike the corrugated system, the seamed system is most reliable due to unexposed fasteners that prevent leaking as the system ages.

Cram Roofing Co., Inc. won the contract to put a new, pre-manufactured, standing seam metal roofing system on the City Hall in Shavano Park. The metal roof included a composite board of 3” polyisocyanurate roof insulation with a plywood laminate surface. Over the composite board, ice and water shield were laid and then the metal roof was installed. The job went smoothly and we were able to satisfy the Zoning Board as well as the City Hall Board Members.

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Advantages of Metal Roofing Systems

Lightweight  Long life Hail resistant Fire resistant Excellent curb appeal Great Life-Cycle cost Extended warranties available

Modified PVC Membranes

Modified Poly-Vinyl Chloride (PVC) membranes has been around since the mid 1970’s. Modified PVC systems share many characteristics with TPO systems in that they are easy to install, durable and energy efficient. Modified PVC roofing membrane can be installed using mechanical fasteners and plates, fully adhered in bonding adhesive or ballasted. In all applications, Modified PVC sheets are overlapped with the seams heat welded, fusing the sheets together. This type of system is highly resistant to wind and other weather factors. Because of the make-up of Modified PVC, it also is able to withstand rain and fire.

A large manufacturing plant called in Cram Roofing Co., Inc. to re-roof their facility. With many concerns around the sensitive electronics housed inside, extra care was taken in installing their new Modified PVC roofing system.

The plant had previously been roofed in asphalt and was vented. Working with the roof consultant, Cram Roofing Co., Inc. was able to remove the damaged roof, re-roof the plant in Modified PVC and not have any debris impact the work of the employees.

The job was completed and successful. The roof was granted a 10 year warrantee from the roofing manufacturer.

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Advantages of Modified PVC Membranes

Heat welding provides exceptional seam strength Lightweight; great for use as a recover system Resists normal structural movement without splitting or cracking Custom colors available Available in .045 mil, .060 mil, .090 mil and .120 mil to meet every need Long term warranties available Fast track system for time sensitive projects

System Design Considerations

Roof must have positive drainage Roof should not be expected to be used as a traffic surface Buildings venting any type of contaminate onto the roof surface should incorporate grease traps or recovery systems