Valley shingle overlap

In valleys, I have always called out that the larger side of the roof should be overlap the smaller side even if the smaller roof has a higher pitch, since there will be more volume and velocity of water coming down the larger roof (especially in this case).
Here is a new construction I inspected in January. The builder just came back to the buyer saying that the higher pitched roof should overlap the lower pitch.
How do you guys call out the valleys?

I personally wouldn’t call out that valley

Yes Will, I have done the same thing.

Making decisions about cutting shingles in valleys often requires some careful thinking. Here are two “tough” calls:

  1. If a 10/12 roof section forms a valley with a 4/12 roof section, and the 10/12 section is one-third the area (water volume) of the 4/12 section, you should cut the shingles on the 10/12 side.

  2. If an 8/12 roofing section forms a valley with a 10/12 roofing section and the 8/12 roof has one-third the area (water volume) of the 10/12 section, put the cut on the 8/12 side.

Hope this helps. :slight_smile:

Thanks, would you call out any types of valleys based on the way they are overlapped? If not, why not?
The reason why I called this one out in particular was because of the funnel shape at the bottom of the roof.
I also called out the fact that the builder improperly installed the starter course in the valley as he ran them down the valley with the slots perpendicular to the main slope. Water will run right up under the shingles.

This does help. It is hard sometimes as there are no real guidelines…

I definitely see what you are saying. I just think the chances of it leaking are more if you flip it around. The two higher pitches would be shedding water right onto the lip. I’m not going to do water volume, and velocity calculations. That’s just me though. Some installation instructions say things like “less water shed”.

Will, what I posted comes directly from CertainTeed applicators manual and it is called “Making The Judgement Call” and the installation viewed meets the criteria for Alternate Closed Valley Applications. :slight_smile:

I don’t worry to much these days about shingle/valley overlap as most roofer will apply ice and water shield to both sides of the valley and if there’s no evidence of intrusion in the attic it’s not really an issue.

I’ll agree with that Peter.

But sometimes that could be an assumption that the Contractor did his job like he should have done. They don’t all do. :wink:

But the Attic confirmation with a picture should keep you in the clear that there was no evidence of leakage at the time of the inspection.

Hope this helps some. :slight_smile:

Lapping shingle valleys here only last about 10 years. Snow, ice, heat, rain, will erode these areas very prematurely. Seen it hundreds of times. Your area, and opinion, may vary.

Why would that happen in Kansas and not in Maine? Just curious. :slight_smile:

YES!!! I would call that valley out. It’s commonly known as a “California Cut Valley”. It actually isn’t cut at all. It has dimensional shingles running up the valley, then field shingles ran over to them. Every 3’ joint is a chance for water intrusion (even more so if the corners aren’t clipped).
Basically, I call it out as not sound roofing practices and note that it may not perform as well as other commonly accepted valley flashing methods. Then I recommend monitoring preiodically. Also, the pictures that you show have the “valley” shingles installed backwards (see attached photo).

I’m wondering the same.

This link to the NRCA has all of the information that you need on this type of valley.
“A conventional closed-cut valley and closed-cut California valley are illustrated. NRCA does not recommend a closed-cut California valley construction in climates that experience snow loads or heavy rainfall or in locations that are exposed to accumulation of debris, such as leaves and other natural elements.”

GAF’s View:

Hope this helps.

Correct, that’s also why I didn’t call it cut but just overlap. Thanks for drawing. I guess I should look at my NACHI library more often…
I pretty much wrote it up like that but am curious to know if others write it up and why or why not.

Thanks for the link.
As far as snow, not too much worries in Houston TX.
Thanks for the links. I noticed a couple things
The first one

this is good to know. But looking at my photo, the lower slope had the highest height or the lesser height had the highest slope… So, how to call it out?
The 2nd one was that the drawing in the GAF link shows the starter course with the tab slots in the valley…

A few reasons why these do not last.

Erosion; heavy rain/show; water flow at these areas are faster than the flat shingle areas, hence the quicker erosion of the shingles.

Many shingles are not designed to be “bent”. This cracks the shingles where bent, damages the granules, and pre-maturely causes the shingles at the valleys to fail.

Some roofers “forget” to install correct underlayment, or metal, under these lapped valleys. Water flows under the edges, stays there, freezes, thaws, and causes leaks. Heavy rains/winds here cause edges to raise, causing leaks

I write them up and inform the buyer, then they decide. Newer roof valleys are written as “evaluate seasonally and maintain as needed”.

Ah. Good catch. I was wondering why it looked funny in your picture. I would definitely write that up.

I agree. Also mentioned in the Mastering Roof Inspection series along with diagram and photos. Check the bonding at the valley on these roofs, but don’t break any bonds! “increased potential for leakage”.

Some manufacturers approve of the California cut valley as long as it is not done with three tab shingles. Certainteed calls it an “alternative closed valley”. I just look for the shingles to be tabbed/bonded in the valley. If you calls these out, you be calling out about 95% of the new construction in Houston.

I generally don’t call out the reversed overlap, but that doesn’t mean you’re wrong for doing so. Certainteed valley shingling instructions state

This is consistent with what you reported. Ask the builder who’s shingles they’re using.

I would have probably made an informational comment about the roof geometry with the confluence of several planes into a very small area and the need to keep it clear of debris and free of defects.

Pay attention to the gutter below. These are the areas where the builders like to put extensions all the way around the gutter so that it floods the eave when they back up.

BTW: I’ll bet you that house doesn’t have adequate ridge vents or has mixed vent types!