Roof Opinions

[Brandon Whitmore]

Well, according to the NRCA's 5th edition roofing manual, counter flashing is allowed to be surface mounted. Their installation detail shows a surface mounted counter flashing with a hemmed caulking lip like you would see installed against a parapet wall with mod. bit. roofing.

That pretty much answers my question as to whether it is allowed. Is this a good practice, and how long can you expect the caulking lip/ seal to last?

[BornaRoofer]

A reglet metal is always better than a surface mount.

The caulk on a surface mount should last 15-20 years if a good polyurethane is used and a it has a healthy caulk lip. But its still a maintenance item.

A 1/2" to 3/4" cut will not weaken the masonry unless its already in a poor condition. This is common practice in the roofing industry.

[Jim Katen]

Originally posted by Brandon Whitmore

Well, according to the NRCA's 5th edition roofing manual, counter flashing is allowed to be surface mounted. Their installation detail shows a surface mounted counter flashing with a hemmed caulking lip like you would see installed against a parapet wall with mod. bit. roofing.

That pretty much answers my question as to whether it is allowed. Is this a good practice, and how long can you expect the caulking lip/ seal to last?

Surface-mount counterflashing is fine on commercial buildings where there's a good chance that the building will have a property manager and a regular maintenance schedule. The sealant will need to be replaced from time to time.

I'd advise against this type of counterflashing on a residential building. The homeowner is not likely to invest in a regular schedule of inspections and replacement of the flashing sealant.

Also, while modern sealants are amazingly long lasting, their bond to 100-year old brick and mortar is not. The bond between the sealant and the brick/mortar will fail long before the sealant fails. This failure will be tricky to spot unless someone is actually looking for it.

Regular old counterflashing embedded in mortar is a time-honored and very effective flashing method. If the roofer is too chicken to cut into the mortar, hire a sweep to work with him.

- Jim Katen, Oregon

[Brandon Whitmore]

Jim& Chris,

Thanks

The weird thing is that the roofer I refer out told me that they do cut in the reglet and counter flash that way. He called me today and said they were going to do it the other way, and that the new company he works for has been doing it this way with no problems.

That is 2 roofer's in a row that mentioned insurance issues with cutting into the chimney's. Is this something new for the industry, or are they just chicken's? The roofer did mention hiring out a sweep to cut into the chimney's as an alternative.

[Ed the Roofer]

Originally posted by Brandon Whitmore

The original roofer's on this job told me that they were finished, but never counter flashed the chimney's. They told me a chimney company would have to do the work, and that their insurance would not cover them for installing the counter flashing.

I called another roofing company who told me they would counter flash the chimney. This morning they called and let me know that they were not going to cut into the chimney. They are planning on fastening the counter flashing to the chimney, and then sealing the top edges of the flashing.

My concern: The sealant will fail over time.

Their concern: Cutting into the chimney will weaken the chimney.

Question: Is their installation an allowable practice backed up by the NRCA/ ARMA or other industry standards?

Also, the SMACNA Manual finds it as an acceptable alternative, but those guys don't put their drawings or specs online to see, so you have to own the CD or book.

I agree that the exposed caulk, even if the best available is used, will dry out and deteriorate, yet if the sealant is sandwiched in behind the metal and the chimney, then it is not getting degraded by the UV Rays of the sun and will remain a long lasting compression seal, as long as the sheet metal is anchored properly to the masonry structure. I will save the information about backer rods for a future discussion.

2 problems with reglet mounted flashings:

A) If individual step reglet counter-flashings are installed, each step hads a verical seam prone top potential wind and moisture migration.

B) Cutting the reglet just a hair too deep can bypass the integrity of the masonry structure and allow seepage to enter through the cut and wick downward through the porosity of the masonry products, but now have an easier bypass for a more fluid and direct passageway.

Ed