Thread: Horizontal Line on Shingles

I though I remember this going around but couldn't fine anything on a search. Anyone know what causes the line between shingle courses about 8 rows from the peak on the attached photo?

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The last time I saw that, it was due to 30# felt being laid atop the underlying course of shingles. Why they did it, I don't know.

some modulars are built to have the last 3-4 feet of roof added last like the top of a pyramid. this typicallly causes that line, either due to felt buildup or mis alignment of the underlayment.
or maybe they forgot the underlayment at the top and set a few rows. then to fix the mistake, they added felt and overlapped on top of the affected row, instead of tearing off the rows without the underlayment

The glue strip protective covers were left on and the next line of shingles were installed over that line.

Originally Posted by Billy Stephens

The glue strip protective covers were left on and the next line of shingles were installed over that line.

There is no need to remove the glue strip cover.

Originally Posted by Rick Cantrell

There is no need to remove the glue strip cover.

Fasterners were used on top of the glue strip.

Originally Posted by Billy Stephens

Fasterners were used on top of the glue strip.

Sorry Billy, I do not understand what you are describing.

The adhesive on the shingles did not or could nor adhere to the layer above causing the edges on this line of shingles to flair up.

The line of shingles falls just below midway on the chimney.
Below the line, shingles are under the chimney flashing
Above the line shingles are on top of the chimney flashing
I think the roofers installed too many rows under the flashing.
Then the roofers installed a row on top of the last row.
Making the row of shingles above the line two shingles deep.
One under the flashing, and one on top of the flashing.

Did I confuse everyone?
I wrote it, and don't understand what I said.

Originally Posted by Rick Cantrell

One under the flashing, and one on top of the flashing..

Interesting,

All The Way Across the roof ( on Both Sides of the Vent ) man that's some flashing.

Red represents shingles under flashing
Green , on top

The circle is the chimney / flashing
Green is over one layer of the red, causing the line

Just my opinion of what it may be.

Looks like either the sheathing is poping due to missing H clips or the piggy back trusses were installed incorrectly causing the sheating to pop up. If the piggy backs are not set right it will leave an indentation on the other side. What did it look like from the attic?

Hans Cramer
Cramer Inspectiion Group
Vermont Home Inspection | Vermont Home Inspectors | Cramer Home Inspection Group Inc. | Vermont Foreclosures

Originally Posted by Rick Cantrell

Red represents shingles under flashing
Green , on top

The circle is the chimney / flashing
Green is over one layer of the red, causing the line

Just my opinion of what it may be.

So your thinking there are 2 layers of shingles on that row?

Is that a peak vent system or just heavy ridge cap?
If it's a peak vent, then I think they may have used 30# below the peak vent, but then I think you should see a similar line on the other side of the roof. Incidentally, around here, roofers are moving away from felt underlayment.

If not that, then a close look at how the trusses are made. And a close look at the sheathing; does it appear to be the same material on the top row?

And finally, whenever I see things like this that are hard to explain, I then look for problems that could arise from it. In this case, I see little reason for concern based on the photo. This is just one of those interesting questions that makes this job fun.

Originally Posted by Hans Cramer

Looks like either the sheathing is poping due to missing H clips or the piggy back trusses were installed incorrectly causing the sheating to pop up. If the piggy backs are not set right it will leave an indentation on the other side. What did it look like from the attic?

Hans Cramer
Cramer Inspectiion Group
Vermont Home Inspection | Vermont Home Inspectors | Cramer Home Inspection Group Inc. | Vermont Foreclosures

I agree with Hans. Either the piggy back trusses or if the trusses run parallel to the line the truss may not be installed exactly vertical or slightly out of place. That causes a slight high spot in the decking and lifts the shingle a little.

I saw this recently - OSB sheathing for most of the roof, then they used plywood offcuts to finish. In the case I saw, there was no noticeable diff in height, but it could happen if the plywood had been thicker by a fraction.

Originally Posted by Door Guy

So your thinking there are 2 layers of shingles on that row?

I think if it were the framing or sheathing, Matt would have seen something while he was inside the attic. Therefore I think it is something he could not see from inside the attic.

Again, just my opinion of what it may be.

If that is a piggy back roof truss, then the problem is not with the roof truss as some seem to be laying the blame, the problem would be with the framer not laying the roof sheathing as they should have laid it.

The only way the piggy back roof truss can cause that straight line is for the roof sheathing to be laid such that the horizontal joint between structural panels was at the meeting line, and the structural panels would be required to span the meeting line to add strength to the piggy back truss. If the sheathing had been laid so that it spanned from the lower truss to the piggy back truss, there would be, at most, a slight hump in the sheathing which would not make that defined line.

Originally Posted by Brandon Whitmore

The last time I saw that, it was due to 30# felt being laid atop the underlying course of shingles. Why they did it, I don't know.

I have seen what you describe.
In one instance there was not enough material ordered, and so they brought the roofing up to a point above an overbuild and covered the last course with 30# up and over the ridge until additional material came. And on a refroof the roofer left a line at the end of his work day. Which he then cut in roof wrap in case of sudden or overnight weather. In both cases the roofers left the paper/roof wrap over the adhesive line so the following coarse could not adhere. The result was similar to the photo.

Thanks everyone for the input.... as for access in the attic it was pretty much nothing - very steep scissor trusses, basically no access to the area in question.

The house was 10 years old and there were no visible indications of a problelm other than the line on the roof. That's basically what I wrote up. Also mentioned a roofing contractor or some other contractor may be able to provide additional information and further investigation should be sought, if desired.

I still struggle with how to write things like this up.... I figure identifying the condition on the report and talking it over with the client is the best course of action. At the end of the day we aren't magicians and don't carry crystal balls.

Originally Posted by Matt Fellman

Thanks everyone for the input.... as for access in the attic it was pretty much nothing - very steep scissor trusses, basically no access to the area in question.

The house was 10 years old and there were no visible indications of a problelm other than the line on the roof. That's basically what I wrote up. Also mentioned a roofing contractor or some other contractor may be able to provide additional information and further investigation should be sought, if desired.

I still struggle with how to write things like this up.... I figure identifying the condition on the report and talking it over with the client is the best course of action. At the end of the day we aren't magicians and don't carry crystal balls.

My SWAG (can't make out much detail in yr photo...): presence of off-peak or mid-roof application of smart vents or similar product installation.

An examples of one scissors truss design...followed by examples of some "Smart Vent" application installations... I suspect mid-roof supplemental intake for the increased volume of the above the vaulted ceiling peak area of the scissor trusses. HTH.






Example:






DCI Products, Inc. - SmartVent Off-Peak Application

Example:




SmartVent Midroof Application - Do you have a ventialtion question? Call 1-800-622-4455

From SmartVent by DCI - The #1 Choice for Attic Intake Ventilation :


Q. Can you apply SmartVent to other places on the roof?

A. Yes. SmartVent can be installed at key areas on the roof where ventilation is required or needed. SmartVent can be installed at the ridge on low-sloped roofs or under any shingle coarse from soffit to ridge. This is an incredible advantage to our product. SmartVent is by far the most versatile ventilation product on the market because it is the only ventilation product that allows you to get ventilation on basically any part of your home that is necessary or that you feel looks best.


The product doesn't require continuous void slot in deck, can be drilled holes between truss chords...

Originally Posted by Kevin Wood

Even though this is a good post and I checked into this also the picture is not displaying a Smart Vent.

Huh? The pictures you copied/quoted from my post do indeed depict and/or diagram smart vent application installations.

The discontinuity (opening) in the roof deck (be it a slot or a line of spaced holes) is many inches above (aprox 6-1/2" OC plus drip edge lip) the discontinuity (opening edge) in the shingling when incorporating a SV. This would place said "line" well beyond the b-vent system -- and if chased, beyond the inner surface of the chase wall within the space and would have no opening in that "truss bay" containing the b-vent of 16 OC and if 24" OC would be beyond blocking for chase. The system also incorporates closed end caps which do not require a tapering down of the roofing for 12" or so in either direction in-line. OP has indicated a negligable and inaccessible "attic" space which implies of course: vaulted ceiling-finished (not exposed timber style) scissors trusses. The b-vent is likely chased and chase walls insulated, below the roof line to futher prevent moisture build-up in the minimal below the deck and above the finished vaulted ceiling space occupied by the scissors trusses.

Sry, don't do "u-tube" you'll need to use your words and/or a graphic to relay your point.Would expect continuous ice & watershield above/over mid-roof smart vent and ridge vent opening.

I like Smart Vent type systems and it's easy to recognize from the top, even though I rarely see it. Inadequate attic ventilation is an epidemic around here.

Originally Posted by Brandon Whitmore

The last time I saw that, it was due to 30# felt being laid atop the underlying course of shingles. Why they did it, I don't know.

Roofers didn't complete the job on same day. To protect from rain the felt is ran over last coarse for protection. Roofer forgot to cut felt back far enough when they continued next day. This wont show up until roof tabs get some sun and take.

More common than you think.

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Seattle Home Inspection