T-Lock Shingle

A T-lock shingle is a type of interlocking asphalt shingle shaped roughly like a letter T. Instead of being held down by a factory-applied adhesive strip, each shingle hooks under the edges of its neighbours, and the interlocking pattern, together with the nails, resists wind lift.

Appearance

A T-lock roof has a distinctive woven or basket-weave look, with each shingle's narrow lower tab locked between the shingles on either side. They were often used to re-roof directly over an existing layer of shingles because the interlocking pattern bridged irregularities.

History

Interlocking shingles were developed in the mid-20th century, when wind resistance of strip shingles was a concern and before self-sealing adhesive strips became reliable. Self-sealing strips came into general use in the 1950s, and laminated shingles later offered higher wind ratings. According to the US home-inspection association InterNACHI, manufacture of T-lock shingles ended around 2006, although many roofs covered with them remain in service.

Repair issues

Because T-lock shingles are no longer made, damaged roofs cannot be patched with matching material. Insurers and adjusters sometimes treat a damaged T-lock roof as unrepairable for that reason, and replacement with a different shingle type is usually required. The interlocking design also makes individual shingles difficult to remove without damaging neighbouring pieces.

Related forms

Other interlocking asphalt designs included "Dutch lap" and hexagonal shingles. All have largely disappeared from the market in favour of self-sealing strip and laminated shingles.