Wavy roof

WHAT DOES THIS LOOK LIKE?

THE SURFACE IS WAVY, BUT INSIDE THE ATTIC THE PLANKS APPEAR FLUSH…

Am i right to suppose there could be a problem with the UNDERLAYMENT??

How should i write this one up?-
( also consider part of the roof is covered in snow)

Looks like multiple layers of shingles Joe…

No nails showing on the underside either. Nails too short, and starting to pop possibly, and multiple layers, equals wavy.

Good observation Ian- that hadn’t occurred to me yet for some reason,

Multiple layers. The vent appears to have it’s flange buried, as opposed to the pipe collar.

Nails aren’t supposed to come through planks. That’s a plywood requirement due to it’s lack of holding power.

Thanks Frank, you are right on the planking. My bad.

Frank,
As an expert, would you comment on this thread, please. Thanks.

In your second photo, I am seeing edges of the horizontal side of the plywood and the first photo appears to show waviness along the horizontal line. Some of the plywood panels appear to be narrower than four feet wide and do not have H clips. All of these could be contributing to waviness, although I would not disagree with multiple layers and nail pops. That WAS a cool observation Ian.

thanks frank! :slight_smile:

It’s gotta be wavy due to multiple layers of roofing.
Joseph, were you able to pull up the shingles at the overhang to check for multiple layers.
Matthew, it’s planked boards not plywood so that’s why there is no ply clips.
Out of couriosity how old is this house? Off the subject, It looks like another older house where they used the foundation form material for roof framing material. Isn’t that a concrete film on the rafters and bracing?

Roof waving is caused by many factors, some mentioned here. Poor quality shingles is another. Shingles installed tightly on a cool day can cause waving when the roof gets hot, and the shingles expand. Lack of underlayment (tar paper), multiple layers, weight of a previous snow fall, etc.

The house was partially covered in snow and exceptionally tall -so no go on ladder, i had to rely on visual.

The Home was built in 1940.

That very well could be concrete film on the rafters- that crossed my mind.

Typical of a roof with multiple layers, especially one with comp shingles installed over wood shingles. Look closely at the edge of he roof.

I would think multiple layers also. but were there any ventilation in the attic. looking at pic I don’t see alot and that’s a good size area

Multiple layers.

I’d use a variation of this: “The roof sheathing appears to have a dip or sag or raised area at the LOCATION(roof). We can elaborate on the possible reasons for this, but you should have a roofing contractor evaluate the roof or comment on this specific feature.”

You don’t have to determine the cause. Just need to describe the issue and let a roofer figure it out.

You don’t have to determine the cause. Just need to describe the issue and let a roofer figure it out.

It’s a visual Inspection so describe as having “Multiple layers” and to have it evaluated by a Licensed roofer.