Should shingles have bubbles in a new roof?

Question

I just had a roof repaired (shingles replaced) because of hail damage. As far as I can tell, everything looks good. Except for one section, there's what I would only describe as a large bubble.

Are bubbles normal on new shingles, in such a way they'll work themselves out? Here's a picture, though it might not be apparent.

There are other soft spots in the roof, but this is by far the largest.

UPDATE:

Thanks for responses. I got into the attic and this is what I found:

Uneven seam where the two pieces of plywood meet. Wood doesn't look damaged to me, though (not really a wood guy either!).

Answer 1

Bubbles in a roof like this are NOT normal. They indicate a problem underneath. Is it serious? Possibly. It will probably decrease the life of the roof.

The shingles will have been nailed down, so this is not a case of the shingles simply pulling loose. Especially if the roof is soft there, it seems this must be a case of the plywood underneath having gotten wet and as it dried out, then warping and bubbling up underneath. The plywood should have been replaced where there were problems.

Edit: After seeing the interior picture, it looks like there was some water contact there at some time. Is it still happening, or is this old, perhaps when you had the hail damage? I find it useful to use a moisture detector - Wagner Moisture meters. It is something I have for woodturning purposes, but it is useful to resolve problems like this. You may be able to rent one, since it hardly seems worth buying one for one use though.

If there is still moisture there, it is possible that water is still getting in, that the roofer made a mistake somewhere. Water can be insidious that way, getting in the tiniest of cracks.

Answer 2

This problem likely has little to do with the shingles and lots to do with sagging within the plywood decking (AKA sheathing.) I modified your picture a bit -- noise was reduced to get rid of the color/light variations coming from the shingle aggregate, and an adjustment was made to increase contrast.

As you can see, you have lines going up and down your roof. These are your rafters underneath, and the low points are caused by the sag in the sheathing. This causes your roof to be "wavey" and although it isn't desirable, it is not altogether rare. It does appear that that one area is slightly worse than the rest, but nonetheless, the problem isn't limited to that one specific area.

Any idea how old the sheathing is?

Answer 3

It's hard to tell from the picture, but the interior shot shows what looks like water on the beam, and possibly on the plywood too. It is damp to the touch? It is significantly darker than the other wood?

As you've had the work done recently I'd call the builder back in and get him to have a look. If anything needs doing - especially if it's due to a fault in the materials or the way it was fitted - he should do it for free (or at least at reduced cost).

Answer 4

I see a few issues with the interior shots:

• moisture
• missing h-clips between the plywood
• rafter spacing seems too wide (though I can't quite tell from the shot)

Answer 5

Respecting @DA01 mention of H-clips, an addition often dispensed with by skillfull sheathing installers (by the trick of the trade by which uniform gapping is achieved without clips):

At first I thought the sheet bowing was being dubiously attributed to lack of "edge confinement" by clips, their primary purpose being related to sheet expansion allowance. However, looking at where H-clips could have been, it also seems evident that there is no expansion gap between sheets--they seem to have been nailed down in snug fit by the original, very-likely-unlicensed, roof and shingle installer: the sheather installed panels wrong; the shingler failed to insist on correcton before felt and shingles went on.

After many (or even few) years of seasonal sheathing heat expansion, accompanied by sheet bowing and nail pulling/loosening, it would be no surprise to find loose and softened panel undulations more or less paralleling the rafters; and a good likelihood of water intrusion if shingles and paper tearing occurred...leading up to the need for (what can only be best described as stop-gap) repairs.

Since shingle roof repair is usually more difficult and more problematic than new roof, the likelihood of any recouping on account of the recent repair defects is slim to none--especially to unsheath and resheath an entire roof originally sheathed by another "roofer."

It would be a safe bet that most licensed roofers would spot such a defect and decline to do repairs--something which which roofers generally avoid anyway--for fear of "buying" a householder's existing problem or impairing his own license and bond.