What are these dark spots on shingles

Photo by Burt Hull in Tennessee.
What are the dark spots on shingles on the side of the roof that still has some frost on it? If it’s roof cement from hand-sealing shingles, it should be under the corner of each tab.

I would say roofing nails, transferring heat from the attic through the shingles.

Yep good call

That’s pretty obvious.

Makes it easy to check fastener placement. Nice image!

To answer the OP’s, Kentons question, the action of thermodynamics. Transferring heat to cold through conduction. The conductive material, steel roof fasteners.

BUT, not only the fasteners are under the 2nd law of thermodynamics; heat flows spontaneously from a hot to a cold body.
5 courses up from the roof edge you see frost melting along a laterial line, ridge to ridge, across what I consider to be a shallow eave, due to the roof deck slope, and suspect thermodynamic convection, in the eave, onto the surface of a plank or exposed sheathing the small space between the planks.

… and if you can see the fastener pattern, what would you say about the installation of this roof?

That the shingles were cheap.

Some shingles racking method installation appears to have been used.

Installation don’t look bad for a 20-year 3-tab shingle, but the sheathing looks a little wavy. Might just be the picture.

Not installed in a high wind zone, only 4 nails per shingle.

Observation: Fasteners nailed high. Fastened on the self sealing strip.
Fasteners should be between the rain notch and the sealing strip.
Recommend: Roof tune up within 12 months of purchase.
Limitations: Inspection performed by walking on the roof deck.
Wet roof decks hide flaws. Limited assessment due to frost.

NOTE: Professional roofing contractors, as well as roofing associations, recommend sloped or/and flat roof surface coverings be inspected by a certified licensed professional, and maintained on an annual basis. This includes roof tune-ups when required.
The life of a roofing system is directly correlated to how often the roofing system is inspected, how quickly small problems are identified, repaired and maintained.

An indication of two things: 1) Nail gun set too deep. 2) Not enough fasteners in each shingle.

They racked em. No fan pattern install

I agree.

Originally Posted by dwigger View Post
I would say roofing nails, transferring heat from the attic through the shingles.

That would be all that needs to be said about that picture, as far as I am concerned. :slight_smile:

You got it, Larry!

Raking is pretty common on 3-tabs, at least in my area. Nailing with 4 nails is not.

Does GAF Approve Of
The Racking Method
Three Tab Shingles… are acceptable, but it is not the preferred method of installation because of the possible
installation problems and damage if proper precautions are not followed.


Usually racking don’t prove out to be straight on the roof, but is a common installation procedure, and 4 nails is common up here for contractors that take shortcuts. :slight_smile:

The original question was:

I stand by my answer.