4  FM quick reads on roofing

1. How Does Water Get Under a Roof Membrane?


Today's tip is about how water can get underneath a single-ply roofing membrane. Because knowing is half the battle, understanding these three common causes can be the first step toward prevention.

First is lack of redundancy. If the seams on single-ply membranes aren't formed correctly, water has a good chance of getting underneath the membrane and leaking into the facility. Single-ply membranes - because they are really only one layer - really rely much more heavily on proper installation than do multi-ply membranes. Ensure that good specifications are written for the installation, and that the installer has plenty of experience installing your particular type of roof.

The second cause of water intrusion is failed flashing. Especially with EPDM single-ply membranes, shrinkage can cause the membrane to pull apart from the vertical flashing and the roof. This unseals the flashing and provides and easy avenue for water. With PVC and TPO membranes, it can be difficult to form flashings around unusual penetrations, like square posts or wide-flange beams. So, again, flashing installation is incredibly important. Make sure your contractor has experience and can show you exactly how he plans to build the flashing and why that construction will be successful at keeping water at bay.

And finally, the third cause of moisture getting underneath single-ply membranes is water vapor diffusion. What exactly does that mean, you may be saying? Basically, water vapor can flow through solid surfaces when the difference in moisture levels, say, in the air outside a building is much greater than inside a building. This happens mostly in temperate climates. That water vapor can then condense underneath the membrane and leak into the building. A solution for this problem is including an appropriate vapor barrier as part of the single-ply roof assembly.


2.  High-Performance Products Make High-Performance Buildings

Today's tip is about high-performance building products.

In an ideal world, high-performance buildings would always be constituted from high-performance building products. But what does "high-performance building product" mean? A roof that lasts longer than it's competition? A more energy efficient chiller? A paint that doesn't off-gas? A flooring product with a particular green certification?

Especially in the last two years or so, with the advent of LEEDv4, and its controversial new credits on selecting building products, the already strong opinions about what really is a high-performance building product have gotten stronger...and louder.

When it comes right to it, however, a high-performance building product is exactly what you think it should it be. That's not a cop-out, it's a truth. If your organization is worried about its supply chain, and therefore the raw materials and embodied energy in products, then those two criteria will be part of your high-performance definition. If your organization is working on inventorying its greenhouse gas emissions, and as part of that, needs to calculate the emissions required for products entering its facilities, well, then finding that information will be a priority. For many organizations, good old stalwarts like cost and performance are the hallmarks of high-performance. And that's fine too.

More and more resources are available these days to help facility managers make more informed decisions about. You've probably been hearing about Environmental Product Declarations (EPDs) and Health Product Declarations (HPDs) for awhile now. These "nutrition labels for building products" are a great way to help weigh different product criteria against each other.

For long time, EPDs and HPDs had been the victim of the "which comes first, the chicken or the egg?" type issue — manufacturers weren't subjecting their products to be tested and certified for EPDs because no one in the industry was asking for them, and no one in the industry was asking for them, because they understood that very few manufacturers had them available.

That's changing very quickly, as LEEDv4 now offers points for collecting EPDs and HPDs for building products. All you need to do find out how quickly this has changed is to make a stroll through and building products exhibit hall these days. You may be surprised how many manufacturers really do have EPDs and HPDs available. And therefore, many more in the industry — both architects and end users — are incorporating this criteria into their product selection process.

3.  When is Reroofing the Best Option?

If you have walked your roof and determined that the roof is still in fairly good condition, you may want to consider coating the existing roof to avoid the cost of reroofing for another five to 10 years, depending on the coating and the condition of the original roof. A coating usually has a five-year life over an aged roof system. However, before doing so, a moisture survey is a necessary step.

Recoating has the advantage of being least costly of the options for reroofing and, because they are generally light-colored, coatings can reduce air conditioning costs. However, a wet roof should never be recoated. So before you make the decision to coat the roof, get a moisture survey done to determine the percentage of wet roofing. If the roof is more than 25 percent wet, don't waste your money coating it. Keep reading for some other possible solutions.

If your roof has many of the above problems and has been leaking for a while, you can safely assume you need a new roof.

Three steps can help you decide whether reroofing is a better investment than repairing the existing roof.

  1. Figure out the amount of money you have been spending on repairs each year over the last few years. Divide the total by the number of years you have included in your analysis.
  2. Figure out the cost to reroof and divide by the number of years the roof is expected to last. A good suggestion is 15 because that is an average warranty length.
  3. If No. 1 is more than No. 2, it makes economic sense to reroof because it is costing you more per year to keep the old roof in place than the yearly cost of a new roof. It is time to reroof.

4.  When Should a Roof be Replaced?

Workers performing roof assessments should take new photos each time to record the progress of deterioration or, after repairs or coring, to show the condition after the repair and to document the date completed. Another advantage of infrared scanning is that workers can store data and images or send them to other locations for management review and decision making.

If an assessment indicates any actions — for example, resealing loose flashing — the result should be a work order created to do the repair. The roof, as well as exterior components located on the roof, should have a chronological history record that tracks changes to its condition over time.

Managers should divide the roof into distinct areas with appropriate identification codes to designate the type of roofing and specific area shown on a layout. In this way, managers can tell the areas most frequently damaged and requiring the most attention. This system also helps technicians find the repair site when responding to a work order.

Frequent damage also offers a clue to which areas need special reinforcement to resist deterioration. Workers should check these roof and upper wall areas to uncover problems before they get too big and damage spaces below.

Roof assessments are essential components of roof management because if the cause of a leak is not detected quickly on the exterior, exterior damage can occur for a long time — ruined insulation, damaged or loose membrane from bubbling, and rusted or rotted deck and joists — before interior damage becomes visible.


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