|
|
|
Log in
Edit Distributed Request
Original Request
-
Request ID:
8543
-
Date Submitted:
June 29, 2021
-
Requested By: Phillip McClure
-
Code:
Residential
-
Edition:
2017
-
Chapter:
Chapter 9 Roof Assemblies
-
Section:
R905.2.8.5 Drip Edge
-
Topic:
Applicability of section R905.2.8.5 to shingle as well as other roof coverings where the drip edge serves the same function.
-
Question:
Since underlayment and drip edge flashing is used with asphalt shingles as well as many other roof coverings, and serves the same function in all of these roof systems, should paragraph R905.2.8.5 of the sixth edition (2017) of the Florida Residential Building Code be interpreted to mean that the installation instructions of paragraph R205.2.8.5 must be followed regardless of roof covering, when drip edge is used with underlayment in a roofing system?
-
Comments:
I have a 5V crimp metal panel roof on my house. While observing the water runoff characteristics of the roof panels during a rainstorm, for the purposes of validating a quote for the installation of gutters, I observed water running out from between the underside of the panels, and the surface of the underlay. I also observed water seeping between the fascia and furring strip.
From observation of other houses being built in the community, the construction diagram of figure 1B (attached) was drawn. This has several other best-practice violations, but those are not the subject of this request. I noted that the manufacturer of the metal panels requires felt underlay and drip edge flashing, but these were not installed per the metal panel manufacturer’s installation instructions, nor the referenced paragraph R905.2.8.5 of the 2017 Florida Building Code.
With the assembly of components depicted in figure 1B, the logical water flows of figure 1C (attached) were hypothesized. This hypothesis was verified to be occurring by applying water at differing rates to the felt above the drip edge of a small, full size section of a roof edge, that was built with the construction of figure 1B to an accurate 5.5:12 slope. Water was observed to be flowing into the unsealed space between the underlayment and the upper flange of the drip edge flashing and was draining between the furring strip and roof deck. In this configuration, the edge of the roof deck, back side of the furring strip and upper edge of the fascia will be kept in constant state of wetness, since Florida is a region of daily rainfall throughout most months of the year.
The issue that had resulted in the gross “undesirable water flows” shown in figure 1C has been partly resolved, but there are other sources of water intrusion under the metal panels. Metal roof coverings, like shingles, do allow incident rain water to leak through side seams in adjacent panels, and at peak and ridge caps, and at the open bottom ends when wind driven. Although metal panel manufacturers - and specifically the manufacturer of the metal panels used in my community - recommend the use of sealing tapes and end closures to ensure water tightness, the use of these materials is not mandatory, and apparently some roofing contractors - including this builder's - have chosen to forego their use. Water that thus gains access to the space under the roof panels will eventually drain to the roof edge. In addition, condensation forms on the upper and lower surface of the panels overnight on most nights. The condensation from the upper surfaces drips harmlessly from the bottom edges of the panels to the ground. The condensation from the lower, inside surface however, drips onto the felt underlay, runs down the felt and finds its way to the roof edge.
This continual wetness will eventually cause the roof deck, fascia and furring strip to rot, which will compromise the holding power of fasteners in this area of the roof, which is critical to windstorm uplift resistance.
If, as paragraph R905.2.8.5 prescribes, the drip edge had been installed under the underlay, or over the underlay with the joint between the drip edge and underlay sealed with roofing cement, the water could not flow under the drip edge, but would flow over the top of the upper drip edge flange and harmlessly drip off of the edge of the lower flange of the drip edge.
-
Attachment 1: Download
-
Attachment 2: Download
|
|
|
