TPO Roofing and Why Lower Cost Doesn’t Save – Part I

Today we are starting a series looking at some particular examples, from what we consider a case study, of work done poorly by other contractors. In our industry, and in the construction trades, you can often learn a lot from looking at work done by others to understand what they’ve done right and what they’ve done wrong. Because there are limited standards for enforcement of the building code and such a wide range in quality of contractors, we often see work done by others that does not follow the rules of the building code or the requirements for installation. In this particular case, we are looking at a TPO roof membrane. This particular portion of TPO was added at the rear of a building, where a HVAC condenser unit is set on top of the roof.

TPO Roofing - dupontroofingdc

In a circumstance like this, where we are examining the conditions of installation, we don’t have the ability to question or interrogate the original installer.   The original installer is gone and in most cases, even if the client reaches out to the original installer to ask them to fix their installation defects, the original installer won’t even pick up the phone.  (We suggest using a company like ours, who really values our clients.  We understand the sad truth, that when other contractors do half the work, it can be half the price but clients are left with major problems, so we don’t do that!)

We’d love to know what was going through the original contractor’s mind, why they made the type of decisions that they made and why they used the odd material choices, installing things in different configurations and uses that the materials are not intended to do.

In the picture below, it looks like instead of sealing the line set and associated control wiring and power line for the HVAC system, they cut right through the original membrane to reroute and change the location of the services.  Instead of patching it properly, they just applied a caulking. Whenever a cut or penetration must be made in a low slope roofing material, the patch must be made through an approved methodology. The building code enforces the manufacturer installation requirements which spell out acceptable methods of making repairs and here, it looks that the original damage or cut through the roof was completely unnecessary and it also looks like they completely sidestepped and avoided or omitted the proper type of patch to reseal the roof. Gun applied sealants like caulking and elastomeric type materials that are applied like caulking can be strong, in some cases, when applied properly, when the substrate is prepared properly, and when the particular material type is compatible with the substrate.  Gun applied sealants, though, have an incongruence or misalignment with the lifecycle of a low slope roof and the idea of making a patch in the horizontal plane of a low-slope roof with nothing more than gun applied sealants, is seriously incorrect.  As an analogy, it seems akin to something like drilling a hole through the hull of a boat and then later filling it with caulk, for no good reason. This is an extreme example, but it illustrates the absurdity of this kind of unnecessary cut and wholly inadequate type of repair.

TPO Roofing and Why Lower Cost Doesn't Save

A closer view of this issue follows in the next photo below.

wholly-inadequate-type-of-repair

But this small item isn’t the end of the problems with this roof installation, it’s just the beginning. In fact this cut, although made by the latest roofer on this building, it’s not the worst condition at all. And all of these problems that we’re talking about today have been created by the most recent roofer, the roofer who was there before us. It’s apparent that they had access to commercial materials, but they had no idea of what they were doing with the work.

In the next picture below, you can see the biggest problem of all is that they installed an aluminum pre-bent flashing on a flat surface at the transition between the original roof and the new roof. This also includes or involves fasteners into the horizontal area of the membrane without a permanent cover on top of the fasteners. There’s several problems with this type of assembly or application.  A few examples follow:

  1. Inconsistent pressure.  Since they have used a light gauge flashing metal, where the flashing metal is fastened down to the roof, it is in compression with the membrane, but the fasteners have space between them and the amount of pressure varies significantly and is weak at the space between the fasteners.
  2. Fasteners in the horizontal position. We’ve looked at examples and talked about this many times in past blogs, but it’s never acceptable to install fasteners in the horizontal position in a low slope roof or accessory components without a permanent cover on top of the fastener.
  3. No permanent seal. The material used here to make the seal between the aluminum and the TPO membrane on both sides of this light gauge metal flashing is just an elastomeric polyurethane type sealant which works very well for many types of applications, but in this application where is fully exposed to the sun it has a lifespan of approximately 3 to 9 years which is way less than the intended lifespan of the overall roof system. In this case, that sealant is the only water stopping or water resistant leak shield, and for it to have a lifespan of a fraction of the roof systems lifespan makes it unacceptable.

In the next blog in this series, we’ll talk about each of these three items above in more detail and explain some of the properties of the materials and why they work in a way that requires a continuous system approved type of installation. At a glance to the average building manager or homeowner, the installation below might look almost acceptable, but it’s far from being correct.

aluminum pre bent flashing

We recommend every building owner in DC who values the longevity of their roof (and their investments) and building use a contractor who values the simple and important principles of proper roof construction like Dupont Roofing DC. Learn more about our company and the proper techniques of working with roofing on historic buildings in Washington DC here on our blog at DupontRoofingDC.com, and you can call us at (202) 840-8698 and email us at dupontroofingdc@gmail.com

On Key

Related Posts

Reverse Coping Case Study

Reverse Coping Case Study

Reverse Coping: Insights from a Case Study Today, in our weekly blog article, below, we’re looking at a bunch of pictures from different angles at