Roof Systems Comparison

After more than 18 years in business, we’ve encountered a wide variety of roof systems on commercial buildings. Whether it is a metal roof, tar & asphalt roof,  pitched or flat roof, some are in good condition while others have serious problems.

What we’ve found is that no roof systems are ideal for all cases. At Tillotson Enterprises, we take the time to sit down and discuss all of the options with you and arrive at the best solution for your building together.

The following is a brief discussion of the pros and cons of the various systems offered by Tillotson Enterprises and our competitors.

Single-Ply Roof Systems

About half of the low slope (or flat) roofs in the Midwest use a single-ply roof technique. This is due in part to the relatively minimal equipment cost and experience required by the contractor to install, as well as the relatively low material cost. On most sheet systems the cost of the sheet is only 25% of the total bid.

The most common application for single-ply roof systems is over tar or tar and gravel roof systems, as these can wear out. Single-ply roof systems are also installed over other single-ply roof systems that have deteriorated.

Sometimes, single-ply roof systems are installed over metal roofs, but this is not a recommended application. To make this work, boards must be screwed or glued down to fill the flute of the metal, insulation board is installed over that, and finally, the single-ply sheet is installed on top. Thousands of new holes have just been made by doing this, and now there is only a thin layer of material keeping water out. There are a variety of chemistries for single-ply materials.


In layman’s terms, EPDM (ethylene propylene diene monomer) is called a “rubber” roof because it is usually made of black vulcanized rubber much like the old car or bicycle inner tubes. These roof systems are designed to work in one of three ways.

The first roof system lays insulation board on top of the roof deck. The rubber sheet is then placed directly on top of the insulation board and held down by what is called ballasted material (usually river rock) which can weigh from 8-12 pounds per square foot depending on code specifications.

The second roof system involves mechanically fastening the insulation board to the rubber sheet with screws and plates that are spaced at least every two feet (depending on wind uplift ratings). These screws are, in addition to the screws that are already holding down the sheet itself.

The third roof system is called fully adhered or glued in place. In this application, the insulation board is mechanically fastened down and the rubber sheet is then adhered with slow rise foam or some other form of adhesive.

While there are cost advantages to EPDM roofing, there are also significant disadvantages.

  1. These systems can shrink as much as 6% per year. This causes pulling on the edges of the building which in turn causes termination bars, parapet walls and side walls to be pulled out. Seams can be pulled apart and vent pipes can be pulled over, among other problems.
  2. We often see screws back out of the roof deck due to expansion and contraction of the roof. They eventually poke their heads up through the sheet itself, creating holes that water can seep through.
  3. Weather cracking, caused by temperature fluctuations making the sheet brittle after several years.
  4. Wind damage, which often goes unnoticed on ballasted and glued roofs. Over time, the wind can cause the sheet to become unfastened from the substrate.
  5. The seams of EPDM are sealed with water-soluble glue which can cause seam failure over time.


PVC (polyvinyl chloride) sheet systems are typically white or tan in color and are usually fabric reinforced to make them stronger than EPDM roofing. However, in our experience, the chemical makeup of these systems can cause them to become brittle with age. These systems are usually mechanically fastened, and although they do not shrink, they have many of the same problems as an EPDM roof: screws can back out creating holes; and wind damage is not uncommon.

On a positive note, the PVC sheet is usually white, which reflects rather than absorbs the sun’s energy. The seams are also heat welded, rather than glued, which results in a significantly stronger seam.


Thermoplastic olefin (TPO) is a relative newcomer to the single-ply market. TPO was designed to replace EPDM at the low end of the market, because PVC roof systems are typically higher in cost than an EPDM roof. The overall performance for TPO is generally in between an EPDM roof and a PVC roof.


Hypalon is a system that cures on the roof and does not become weak and brittle like other single-plys, making it one of the best sheet systems on the market. It can be held down using a ballast, mechanically fastened, fully adhered, or held in place with air pressure. Mechanically fastened is by far the most popular method. This sheet is also heat welded at the seams. Hypalon sheets are very chemically resistant and are the roof of choice in cases where chemicals may be deposited from vents or pipes. However, as with all single ply systems, once it has a hole in it, water is free to migrate.

Spray Polyurethane Foam

Spray Polyurethane Foam (SPF) roof system is applied using a specific spray gun that mixes two chemicals as the trigger is pulled, causing a chemical reaction that produces the end product. Spray foam is usually applied in thicknesses from a minimum of one inch to several inches, depending on the amount of insulation value that is desired. Polyurethane foam is a plastic and is waterproof after it is applied, however, it needs protection in the form of a coating system or a layer of rock to help it resist the UV rays in sunlight and to keep it from deteriorating.

SPF can be made as soft as a pillow or so hard that you could not drive a nail into it. Spray foam used for roofing is flexible enough to be able to move with the expansion and contraction of the roof but hard enough to withstand foot traffic, impact, wind and weather. Spray foam is able to be applied over a variety of substrates with ease.

As a roofing material, SPF is difficult to beat if the applicator is using a high quality coating and properly applying the product. If, on the other hand, substandard equipment is used and the ratio between the chemicals is incorrect, it can cause bubbles or blisters in the foam potentially creating problems down the road. The same problem can occur when applying foam roofing over a wet substrate. Tillotson Enterprises applies SPF at a thickness of no less than 1.5 inches, half an inch above the minimum one inch recommended by the Spray Polyurethane Foam Alliance (SPFA). The SPFA is the governing body of the foam industry. Some contractors will apply a half-inch or less which will lead to problems and added cost to properly repair.

Among the advantages of SPF is that it creates a continuous and seamless membrane; with every square inch fully adhered to the roof deck. This means that if a puncture is created in the coating layer it will not create a leak because water cannot travel through the foam. In fact, if a hole is made all the way through to the roof deck, a leak still may not occur because the foam is fully adhered at every point. Yet if the same hole were formed in a single-ply roof, the water would spread throughout the roof deck, finding any number of holes caused by the screws holding down the sheet system.

SPF roofs are also referred to as a renewable roof system, because if the roof has gone too long without attention: any bad areas can be cut out and re-foamed, and settled areas can be filled in with additional foam.

The largest savings from utilizing SPF on a roof, comes in the form of energy efficiency. Each inch of foam roof has an R-value of around R7; and then a white protective coating system is applied which helps reflect sunlight and make the roof even cooler. R-Value is a measure of insulation’s ability to resist heat traveling through it. Most SPF systems pay back the cost of the roof due to energy savings alone in just a few years.

In addition,  the cost of renewing the coating system over the SPF roof will be substantially less expensive than re-roofing over other systems.

Metal Coating Systems

Metal roofs wear out over time due to a number of things  which can lead to water in the building. The neoprene washers on the screws or nails wear out, and the screw holes become oblong due to the expansion and contraction of the metal. The mastic that is put between the sheets along the seams will eventually get hard and crack. Skylights and seals around penetrations such as vent pipes are also a common cause of failures.

The system that Tillotson Enterprises use to solve the problems previously stated is called the Metal Restoration (MR) System. The roof is first power washed to clean the substrate. Screws are tightened and in some cases added to ensure that the substrate is secure to the building. Patches are added to bad sections of rusted out metal or breaks in the metal. A rust inhibiting primer is applied to any of the metal that is showing rust or signs of rust. In some cases, this primer is applied to the entire roof. Fabric and coating is then applied to the vertical and horizontal seams and also around the penetrations and skylights. This adds strength to the seams so that when the metal expands and contracts it does not tear the coating. Every screw is then treated with a fastener-grade coating. Finally, the entire roof is sprayed with a white coating. This white final coating makes the entire roof seamless and the complete system makes the roof waterproof.


Some contractors use cheap coatings which will not last. Some coatings get brittle with age, turn chalky; or get hard and crack over time. Some contractors try to cut corners by not using fabric for reinforcement on the seams. Due to product or application errors, the coating doesn’t stand the amount of elasticity required, and cracks appear on the seams which causes system failure.


This system does not add any additional holes in the roof. It is anywhere from one third to half the cost of other alternative roof systems (single ply, new metal roof, spray foam). This system is lightweight and the white top coat makes the interior of the building 10-15 degrees cooler. The MR system stops leaks! This may sound funny but we have repaired some new metal roofs which were leaking even before they were completed. The MR system solved their problems! The installations of a MR system will not interrupt the purpose of the building being roofed.

A new metal roof doesn’t come with a “leak free” warranty with many contractors. The roof may come with a 20-year warranty on the building but read the fine print, this is not for a leak free roof. They will come out for about a year and put caulk on seams, etc. to show effort to stop leaks until you finally get tired of calling or they say their obligation is up.

With the Tillotson MR system you can get a 10-15 year “leak free” warranty on material and workmanship.  The roof system can be written off in one year in taxes as “maintenance and repair”; and does not depreciate out like a new metal roof, single ply; or foam roof needs to be.

Metal over Metal

This is where a new metal roof is placed over the old metal roof called (retrofit) or the old metal roof is torn off and a new one put in its place. This is fairly self-explanatory. There is, however, some misconceptions about this process. When we started roofing over 20 years ago, the type of roofs that we applied the MR system on were about 20-30 years old. In the last several years the age of the metal roofs has drastically decreased to 10 years old to not even finished. Yes, you read correctly, not even finished. Today’s material and labor in constructing buildings is not of the same standard as buildings constructed 20-30 years ago. I believe that our industry suffers from a lack of experience and pride of workmanship. Another problem is that all the screws today are put in by electric drills which may not be set property causing screws to be over-tightened. All together, this makes for less than quality work. Don’t get me wrong, there are still good roofs put on by good crews, but I don’t think you can assume a leak free roof every time. The roof may come with a 20-year warranty on the building but please read the fine print.

Tar (BUR)

Tar roofs have been popular from the beginning of the commercial and industrial roof systems age. Again, in my opinion these types of roofs are dated technology. These kinds of roofs were being put on before man ever walked on the moon and, basically, the process has not changed. Actually, this process is not even as good today as 30-40 years ago. The tar used today does not have as long of a lifespan as the tar used years ago, due to EPA regulations. Another problem is that today’s worker will not labor under the conditions necessary to perform the work needed to accomplish this type of job. On a 90 degree day in the summer working on a black surface around hot tar, it is very possible that the roof temperature can reach 150-170 degrees.

These systems, which used to last 20 years, are now only lasting 10 years. Once they wear out you tear them off and replace them with a new one. They are black, not white and are not energy efficient. Rock is put in the tar on these systems for two reasons:  to protect the roof from the weather and to re-heal itself from when the tar gets hard in cold weather and then warms up and re-melts and flows back together again. Due to EPA regulations, tar does not have the ability to get hard and re-melt over and over like it used to.

Torch down

This roof system is often associated with stories of roof contractors burning down buildings. This system is an attempt to modernize the tar industry. Tar and rubber emulsion are combined and then blended together to make a hybrid roof system. This is accomplished by taking the sheet provided by the factory and heating it to the point of melting with blow torches which glues the sheet to the roof. Three major problems occur with this process. The first of these is obvious, wherever you have fire on a roof the fire can get out of control and potentially spread faster than anticipated. Next the seams tend to be a weak spot of this system causing roof failure. And finally, the sheet does not always become hot enough to properly adhere to the roof, which causes bubbles.


We hope this information has helped you to make your roofing decision. At Tillotson Enterprises, we offer only the roofing systems outlined on the Tillotson Roofing Systems page of this website. The two most popular roof solutions are the MR System and the spray foam roof system. We like these because the MR system is less expensive than all other options, and the finished product, for the money, is an excellent buy. The spray foam roof system really offers more than we could ever put into words. When installed correctly, a foam roof is by far a superior roofing solution.

Tillotson Enterprises focuses on employing a quality workforce that shows attention to all of the details that go into creating a quality roofing application. Our employees have gone through training and obtained certifications allowing our company to ensure that you, the customer, will be completely satisfied. In a roofing season; we spend less than one percent of our time on warranty work. The people we employ to sell our roof systems are the same people who are there to perform the application and to ensure that it is being done properly. We look forward to working with you; and being the solution to your roofing problems.

Have a Question?

For more information or to inquire about an estimate, please contact us!

Tillotson Enterprises, Inc.

Kearney Shop Address
2069 25 Rd
Kearney, Ne 68847
Phone: 308-234-6685
Toll Free - 800-643-5731


Tillotson Enterprises, Inc.

Mailing Address

715 Huron Drive

Kearney, NE 68847


Tillotson Enterprises, Inc.

Lincoln Shop Address
8000 Fletcher Ave, Suite 100
Lincoln, NE 68507
Phone: 402-466-7038