What overlay means
A second shingle layer goes over the first without removing existing material. Some towns and insurers limit or prohibit it.
You keep old felt, old nails, and any soft decking you cannot see.
When tear-off is the right call
- Already two layers — NH code typically requires full removal
- Soft or spongy decking suspected
- You want ice & water membrane at eaves and valleys
- Chimney, skylight, or valley flashing needs rebuilding
- Home is a long-term hold — not a quick flip
When overlay might be discussed
Single layer in good condition, sound decking confirmed on inspection, town allows it, and budget is extremely tight.
We will say plainly what you give up — usually ventilation inspection, full ice protection, and warranty clarity.