TPO Flat Roofing System vs EPDM Membrane Material

Flat Roof Repair and Replacement Contracting in DC Metro

Did you know that nearly all row house and buildings in DC and Capitol Hill area have flat roofs? And all modern homes with steel frame structures and open floor plans have flat roofs? So if old and new are use flat roof construction, it must be the best material for roofing, right? 

flat roof in capitol hill dcThe demands on flat roofs are unique to other materials. Flat roofs are “flat.” At least nearly, but they do grade a tiny tiny bit. and slowly drain into stormwater management systems such as large gutters and downspout drains. Flat roofs need to be water proof because they need to hold standing water and prevent leakage into the underlying wood roof decking. Contractors who Install flat roofs are very specialized and need to pay careful attention to details. 

Premier Roofing has over 35 years of experience. We are one of a few roofers in Capitol Hill who specialize in flat roof projects. Additionally we provide flat roof services in and around the DC, MD and VA metro area. Contact us for a free estimate. 

Nearly all new flat roofs are made of either TPO or EPDM membranes. So which one is better and what are the pros and cons?

TPO or EPDM – What is the Best Flat Roof Membrane?

TPO and EPDM flat roofing60% of all flat roofs installed these days have TPO membranes. But why? What makes TPO singly ply better than EPDM systems? Some roofers believe TPO is easier to water proof than EPDM. But there are many differences in the two roofing materials and how they are installed. This page will describe how EPDM is different than TPO and the pros and cons of one versus the other. TPO is more widely used in the Maryland, DC and NOVA areas.

Premier Roofing specializes in flat roof replacement and repair. We do commercial and residential flat roof contracting. Finding a TPO specialist is important, because flat roofing is technique sensitive compared to asphalt shingle installation. Many of our projects are completed in Washington DC, Silver Spring and Alexandria. We have over 25 years of experience in the roof industry. We are happy to evaluate your project and determine what flat roof membrane and installation is best for your situation. 

Pros and Cons of EPDM compared to TPO material?

Let’s take a look at the differences in the systems. What are the advantages of TPO and EPDM?  What makes one better than the other?

epdm flat roof vs tpo

It is really best to ask your Premier flat roofing expert whether TPO or EPDM is best for your project. Usually TPO is a better product in the Washington DC metro area due to the climate. During your project assessment, Premier will make a recommendation. But the basic differences between TPO and EPDM are as follows: 

  1. EPDM has been used for over 60 years vs 20 years for TPO
  2. EPDM absorbs heat from sunlight and TPO reflects sunlight
  3. EPDM is mechanically retained by screws where TPO is glued down
  4. EPDM seams are taped together whereas TPO seams are melted together with a hot air gun.
  5. EPDM and TPO are roughly the same cost.
  6. EPDM on the average lasts 5-10 years longer than TPO. 

What is the Best Flat Roof Material?

The above facts about TPO vs EPDM speak for themselves but there are certain situations where one material may work better than another. For example in situations where there may be high winds, TPO may be better because of the higher seam strength. In situations where there is lots of intense sun and long summers, TPO may be better because if reflects radiating heat from the sun where as EPDM absorbs more radiant heat. TPO in this situation will likely prevent less heat from entering the building and reduce cooling bills. In situations where there are longer winters EPDM may be a better product for energy saving reasons as well. EPDM has a longer life on the average, so it will in the long run be the better value when it comes to longevity. EPDM is also easier to install and requires less skill. 

Single-Ply Membrane Systems 

TPO and EPDM are examples of single-ply membranes. If you see a large commercial roof that looks like a seamless sea of white, you have likely seen a TPO roof. A flat roof is a membrane that attaches mechanically or with an adhesive to the wood decking or to a root-top insulation material. Of course the two most common single ply membranes are: 

  • Thermoplastic Polyolefin (TPO)
  • Ethylene Propylene Diene Terpolymer (EPDM)

Both of these materials differ in their composition, energy efficiency, and installation techniques.

TPO Roofing Systems Installation:  

The first step in installing a TPO roof is to remove the old roofing material down to bare wood. Next step in installing insulation. There are a few different kinds of insulation that can be used:

  • Polyiso aka Polyisocyanurate – a very popular flat insulation material. It is expensive but has an excellent R-value rating, or insulation value. This will definitely help with the energy bills. 
  • EPS or Expanded Polystyrene – also has a great insulation value and is very resistant to water,penetration.
  • (XPS) Extruded Polystyrene – It’s insulation value and price are between Polyiso and EPS. It is a semipermeable material that has a perm rating of 1. It is not as good of a water and vapor barrier as EPS. 

TPO membranes come in sheet widths of 10, 12, and 20 feet. The sheets come in rolls and are un-rolled and cut to size on the job site. Once the membrane has been rolled into place and cut, the seams created are welded together with a hot-air gun. 

How Much Does TPO Roofing Cost?

There are several factors that go into the cost of TPO single-ply roofing systems:
  • Existing roof condition
  • Roof dimensions
  • Roof height and access
  • Insulation being used
  • Roof penetrations such as vents and air units, skylights, etc
Most single-ply membrane roofing lasts from 10-20 years. There are other benefits with single-ply systems, such as: 
  • flexibility in selecting different insulation options. Some products include insulation. 
  • Installation techniques – There are different ways to install a TPO roof. It can be connected directly to the roof deck or attached with adhesives. It can also be welded through heat in more difficult areas such as protrusions, projections, and chimneys. 
  • Resists growth of algae and corrosion. Very rarely does TPO need to be power-washed. 
  • Fire resistant material
  • TPO reflects radiant heat. In contrast to EPDM which absorbs heat.

Disadvantages of TPO

With the popularity of material, there are many different manufactures of the singly ply product. There are many different qualities and you really need to do your research when it comes to the track record and warranties. Long story short, the material will last 10-20 years. The material will eventually fail when is cracks and separates from material breakdown. The roof can also come undone at the seams between where the TPO pieces were welded together. Stress is placed on the seems as the material contracts and expands with changes in temperature and humidity. 

Installation Mistakes Lead to Expensive Future Flat Roof Maintenance

Finding a certified TPO specialist is important and will save you money in future maintenance and repairs. For starters, hiring a one-and-done contractor will likely never be found again, because they will have moved on by the time you need service. A true professional will use the best installation methods for your flat roof projects. The biggest mistake in flat roof installation is de-bonding of TPO materials at the seems and separation of TPO from insulation at difficult areas such as chimneys and penetrations.