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The problem with nails

What’s wrong with using nails for natural slate? Nothing! How could anything be wrong with a fastening system that has been used successfully around the world for hundreds of years? Traditional nailed-in-place installation of slate is an excellent fastening solution whenever the following requirements can be met:

  • Very affordable slate, because the roof will need 2.5 square feet of slate for every one square foot of roof to be covered. 60% of the slate will lie under other slate and will never be exposed to view
  • Either a roof design strong enough to support the weight of all that slate, or, light-weight slate strong enough for 50-year durability
  • A deck and underlayment that will retain integrity with two large copper nails per slate, about four to five randomly placed nail holes per square foot of coverage
  • Availability of craftsmen to lay-out and hand fasten each slate and enough money in the budget to pay those craftsmen

    Given all that, enjoy your long-lived slate roof, but be sure not to walk on it, as the nails and the many overlaps can over-stress the very strong but equally rigid slate.

Nothing’s wrong with nails, but if any of the above is a problem, then consider Nu-lok. We’re in competition with nails.

The Nu-lok Roofing System is an alternate method of fastening hard, thin, manufactured or machine-squared slates to a pitched roof over a plywood deck and waterproof membrane. Originally designed for random-width natural slate, it has since been optimized for purpose-designed 16-inch square ceramic slates. Nu-lok solves many, and perhaps all, of the design and installation problems associated with long-lived, hard-surface roofs.

The Nu-lok fastening system consists of Galvalume battens laid horizontally across a pitched roof, fastened through a counter batten into a plywood deck. A conventional waterproof membrane such as roofing felt or other proprietary product is used between the plywood deck and the counter battens. The Galvalume battens are fastened using galvanized ring-shank nails into the roof rafters. Battens are installed at 12-inch spacing.

With battens nailed down, and starting at any row on the roof, Galvalume link channels are positioned at 16-inch centers and locked into a flange on the battens without further use of nails. Each link channel contains a shallow internal drain gutter to handle seepage between slates, which will butt together horizontally over the link channels. Natural or ceramic slates are placed into the 316 stainless-steel retaining clip on each link channel to complete a horizontal course. Another course is then started, working up the roof, by locking the next row of link channels into place. Laying the slate is very fast due to the absence of fasteners and can be done while walking on the finished roof.

Nu-lok uses a four-inch vertical overlap and no horizontal overlap with 16-inch slate, for a 75% exposure ratio. Nu-lok requires only 1.3 square feet of slate per square foot of coverage, which allows for very efficient use of expensive slate, reducing installed cost by up to 30% and installed weight to less than six pounds per square foot.

Watch out nails, here we come.


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