Roof pitch measurement

Ok, so I needed to check the pitch/se on a roof. It had dimensional architectural shingles but looked rather low. I broke out the 6-foot level and then placed a gauge on top that showed 7 degrees which, I believe, is a 1.5/12 rise/run. My first question is, is this an acceptable way to measure? I have an app on the phone that helps in situations like this but the phone wasn’t on the roof with me. My second question is, how do most of you measure slope on a roof; is it my mechanical means or an app?

The second shot is adjusted for the angle.


There are several different apps you can get for your phone. Most can utilize photo’s as well.

Like you did it is fine, Tony. I had a 4’ level with marks at the foot locations and measured down to the roof with a tape measure.


Hey Larry, Sounds like a good tip. I have a screwdriver that I’ve marked for inch measurements. Makes sense to put marks on the level, too. Thanks for the feedback.


Anthony, i found that the roof pitch gauge is smaller than the exposure of a shingle and it would read high if you overlapped a shingle edge, or low if you didn’t. Your solution of placing a level which spans the edges is the same solution I arrived at. Then I bought a digital level that displays the slope and I don’t need to balance two tools any more.

The roof gauge is fine on its own ( or Larry’s method) for as accurate as we really need to be if you don’t want to invest in another tool.
Here is a steep roof I wanted to brag about to the buyer and I used both the pitch gauge and the fancy digital level. Notice the pitch gauge reads high because I caught the lip of a shingle. It’s off-the chart steep. I took advantage of the valleys to move around the roof.


The app you want measures the roof pitch from the ground! It’s called, “Pitch Gauge.” Also takes a picture with the pitch marking superimposed. After a while you’ll recognize when the pitch is too low for shingles and wont need to measure.


Hey Bert, I like the thought of a digital level. It’s always good to have more than one tool in the bag. I appreciate the Pitch to Degrees image. I’ve been looking for one of those. Thanks, man.


The level you want is a laser level for measuring floor slope. No one cares about the roof slope unless it has the wrong covering. The green laser shows up on film better. Make a telltale with a pole and a graduated board you can slide up and down (for pictures).

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Thanks Bob, I’ll check it out. I’ve always been a little wary of apps because I don’t know how accurate they are. But I guess if I can trust the mechanic behind a digital level then I should be able to trust the mechanics behind an app.

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I just use the"Pitch Guage" app that Bob mentioned. Works great and you don’t have to hold the phone perfectly level for it to work. I tested it against a framing square with a level on it, and it matched up perfect several times. Then again IF I put it in a report, I say “approximately” before stating the slope for fudge factor. :laughing:

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I personally think that the 2/12 Slope rule for a standard roof shingle to be installed Is too flat unless the entire roof area is covered with one layer of ice and water shield membrane before the roof shingles are installed specially in colder areas so any time I come across a roof that looks too flat I write it as to be evaluated by a licensed roofing contractor .

In most cases we don’t need the ultimate accuracy when measuring roof slope. In most cases the phone app will be fine.
Here is a case when higher accuracy mattered. A new roof was installed in November. The house sold in December and leaks were visible in the ceilings in January. The homeowner noticed that the attic was full of apparent mold. They called a mold remediation company and the mold remediation company called me to go investigate. The day I went the roofer came back and was trying to install ice and water shield at the transition from the moderate slope to the shallow slope… just a band-aid temporary repair in my opinion.
Because this is going to court unless the roofer fixes all of the things I found ( I have a whole list of shortcuts and deficiencies) it is good that I know the slope of the roof with high certainty. It is less than 2:12 and even with double underlayment or ice-water shield, laminated shingles are not the appropriate covering.
The mold remediation company quoted $9500 for clean up based on my findings and the samples I collected. It is Penicillium / Aspergillus

5.7° is less than 1.2:12 slope


Holy moldy attic Bert! Did that space have any ventilation?

I see how the low slope roof was obviously failing/leaking. But the pitched roof mold is an interesting case study. Is the moisture from the leaking roof “venting up” into the attic space? Or does “pitched” attic also have a ventilation problem?

In your second photo, I do not see the cut-out for the ridge vent.

Michael and Brian,
Yes, this was a part of the whole problem. Its a good case study of how one problem can affect the whole structure and sometimes a deficiency is not a problem until there is a change in conditions. It’s also a story of fraud. I’ll get to that.

The low slope roof was leaking and the water was dripping onto insulation and drywall ceilings below. Because of the moisture intrusion the entire attic got very humid and the entire attic is now covered in mold. This perhaps would not have happened if ventilation was correct.

Look at the outside roof picture. A ridge vent is installed along the entire ridge from left to right. Now look at the inside picture. There is no gap. The roofer installed a fake ridge vent (put the GAF cobra vent over solid sheathing so from the outside it looks well ventilated). I told the homeowner that this is fraud.

It gets better.
The roofer offered to do some “extra” work to improve ventilation. $1800 to enlarge the soffit and gable vents and $1200 to install a ridge vent.
The buyer got the original invoice from the seller and installing a ridge vent was already included in the roofing quote when they installed the new roof. It appears to me that the roofer is trying to recoup some of the money he is having to spend to fix these issues by charging for “optional upgrades”.

I have a feeling that this is going to court.

the first screen shot - customer “Curtis” sent me a screen shot from his text from the roofer offering upgrades and Curtis asked me for advice.

the second screen shot Curtis got the original invoice that shows that installing a ridge vent was included in the roof they did last year.


Wow. A fake ridge vent! It takes 20 minutes to cut for a ridge vent.

I think the roofer is on the hook for ALL of it. Especially if he modified the original roof ventilation which was likely passive or gable or both.

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I’m no lawyer, But I’d say the roofer is responsible for all of it. So many things done wrong. I wonder if they even have insurance or a license.

Here is just one more example of their craftsmanship on this roof.
They cut a plumbing boot flashing and caulked it up instead of using an electric mast boot flashing.

Lazy cheap shortcuts everywhere.


I just had a thought. Should I not be posting info about an ongoing current issue that may end up in court.
I’m no lawyer. Anyone know if I should take all this info down?
I was just posting to give examples of why its important to roof properly over low slope and why measuring accurately can be important if we need to look professional, but I don’t want to possibly do anything that might cause trouble for my customers.

You have not released any personal info. Just a case study. Go back and edit pictures from the outside and the txt message to be safe :slight_smile:

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