Should gutter guards go under shingles, or are there guards that don't?
Short answer. Gutter guards should not be slid under the shingles. Lifting the first course breaks the sealant strip that holds shingles down in wind, can crack them, and may give the shingle manufacturer grounds to limit coverage on that edge. Many guards mount entirely to the gutter, fastening to the front lip and either the back of the gutter or the fascia below the drip edge.
Why under-shingle installation is a problem
- Broken seal strips: shingles bond to the course below with a factory adhesive strip. Prying them up to slide a guard in breaks that bond, and unsealed shingles lift in wind.
- Cracked shingles: asphalt shingles get brittle with age and in cool weather, and lifting them can crack them.
- Altered drainage: a guard tucked under the shingles changes how water leaves the roof edge and can direct it behind the drip edge.
- Warranty questions: manufacturers expect shingles installed and left per their instructions, and an under-shingle guard can complicate a claim at the roof edge.
Guard styles that stay off the shingles
- Lip and fascia mount: the front edge screws to the gutter lip and the back edge fastens to the fascia below the drip edge, or sits on the gutter's back edge.
- Gutter-only mount: clips or screws to both the front and back edges of the gutter itself.
- Drop-in perforated or mesh panels: rest in the gutter's top opening and fasten to the lip.
What to ask an installer
Ask exactly how the back edge of the guard attaches, and whether anyone will lift shingles. If the gutter is set too low or the drip edge is missing, fix that first rather than using a guard as substitute flashing. If you already have under-shingle guards and the roof is being replaced, have the new drip edge and gutters set up for a gutter-mounted guard. See drip edge explained and gutter sizing, seamless gutters and guards.