Can a new roof be installed over old shingles?

You should never install new shingles over the old shingle roof system. Installing over the old shingles can cause unusual shapes to form in your new roof system and the roof system will not look smooth and level.If the old roof system is not removed it will not be possible to inspect the plywood deck sheathing for rot or deterioration that can become a much larger problem in the future. Moisture from the previous roof system can be trapped under the new system and the increased surface temperatures from having two layers of shingles can accelerate roof aging.


Where should ice and water membrane underlayment go?

The purpose of ice and water underlayment is to stop water from passing through the roof system into a home. Ice and water membrane is needed most to address ice damming issues during the winter.

Ice can build up on a roof slope, usually at the unheated area at the eaves, forming an ice dam that prevents water from draining off the roof. In turn, this water can creep up under the shingles causing a roof leak. Ice and water membrane must be installed far enough up the slope to cover the first few feet of heated space.

Ice and water membrane should be installed at least six feet up the slope of the roof from the eaves, 6 feet wide in all valley areas, and around any heat source such as a skylight, chimneystack or flange. Ice and water membrane is a good investment and strongly recommended on roof rafters longer than twenty-five feet, on roof pitches below 4/12, and above cathedral ceilings.


How do I know for sure I need a new roof?

Older roofing shingles and wood shakes typically have a 15- to 30-year lifespan depending on the shingles’ quality, the location and tree cover of your home, and how well the roof was installed originally. Direct sunlight, weather/wind, and poor roof deck ventilation are rough on Bay Area roofs.

Though the IKO shingles we use today have lifetime warranties, they didn’t a decade ago. We tell our customers that 12 years is a good rule of thumb to go by. At that point, check for these warning signs:

  • Curling shingles
  • Loss of the asphalt granulation (looks like bald spots)
  • Evidence of leaking on your ceilings
  • Cracked or discolored interior drywall (painted or wallpapered)
  • Decaying shingles
  • Missing shingles
  • Visible cracks
  • Wind damage
  • Broken or damaged shingles
  • Rusted or missing flashing

If a residential roof is over 15 years old, we recommend you call us out for a look. Sometimes damage isn’t visible to the untrained eye on the ground, and catching it early can avoid expensive interior repairs in the future.