Were my shingles properly nailed?
Most roofers do a very good job of installing shingles, and they stay on the roof for a very long time. If the shingles are not properly nailed, however, there can be problems several years down the line. Maybe the house has been sold, or the roofer for whatever reason can’t be reached.
For that reason, a good home inspector will try to look at the nails of several shingles. Pneumatic nail guns must be level and set for proper pressure. Otherwise, the nails will be over or under driven, or crooked. Minnesota code forbids the use of staples, because staples are notorious for being installed crooked and are rarely installed properly.
Under driven nails will keep the shingle above it from laying flat, and wind can lift and cause damage. Because the raised shingles are so obvious, under driven nails are less common.
Under driven and crooked nails allow the shingle to tear. Exactly when is hard to say. A strong wind could tear off a couple of shingles today, or 5 years from now.
Of course, there are plenty of times when a complete inspection of a roof is not possible. Snow cover, ice and leaves will hide shingles, and some roofs are too steep to walk.
When possible, a roof inspection includes lifting a representative number of shingles to examine the nails for proper placement. It’s best to remove a nail or to to check for proper length.. Standards require 1 1/2 inches. I find nails much shorter than that a lot.
Want to learn more? The Family Handyman has a great article of DYI roofing. Click here.