ROOFING / WATERPROOFING STANDARDS (continued - page 3 of 3)

Professional Guidance (continued)

Slate Roofs

• Specify slate tile manufacturers who provide a 75-year material warranty. The installer shall provide a 5-year leak proof warranty for the installed cost of the roof, to replace defective flashings and tiles resulting from defects in materials or workmanship.
• Specify slate manufacturers whose products meet ASTM C406 and can certify their slate to a Grade S1 classification by providing test results which are not more than 3 years old.
• Specify 3/8” minimum thick slate in freeze/thaw, high wind or heavy hail areas, ¼” minimum thick slate in other areas. Avoid slate from Pennsylvania.
• Specify two layers of 30# asphalt-saturated felt underlayment meeting ASTM D 226 and/or D 4869 or one layer of fully adhered moisture protection 40 mil minimum butyl-adhesive based underlayment. Use a 3” minimum headlap for roof slopes between 4:12 to 8:12.
• In snow/ice climates, specify fully adhered moisture protection 40 mil minimum butyl-adhesive based underlayment extending from the eave to 3 feet from the inside face of the exterior wall, at valleys, ridges and along dormer or other walls. Use cold roof design technology if possible.
• Specify 10 gage copper slating nails, stainless steel, bronze or cut-brace roof nails and fasten with 2 nails per slate. In high wind areas or when ¾” or thicker slate is used, fasten with 4 nails per slate.
• Provide eave cant for starter course.
• Flashings shall be fabricated from 20 oz copper or 24 gage stainless steel. Open valley pan shall be formed with a “W” or “V” shaped splash diverter.

Wood Shakes and Shingle Roofs

• National Parks are slowly transitioning away from wood products as a result of increased fire danger throughout the west, the limited availability of domestic supplied material, and the reduce life expectancy of the product in many parts of the country. However, in some cases historic preservation standards may dictate the use of these products.
• Specify No. 1 premium official blue label western red cedar shingle; premium grade western red cedar shake; or pressure treated No. 1 vertical grain, all clear yellow pine shingle.
• Specify one layer (for shingles) or two layers (for shakes) of
  15# asphalt-saturated felt underlayment meeting ASTM D 226 and/or D 4869 or one layer of fully adhered ice and water protection 40 mil minimum butyl-adhesive based underlayment.  The second layer of felt is interlaced between courses when installing shakes.
• In snow/ice climates, specify fully adhered moisture protection 40 mil minimum butyl-adhesive based underlayment extending from the eave to 3 feet from the inside face of the exterior wall, at valleys, ridges and along dormers or other walls. Use cold roof design technology if possible.
• Use a 3 layer starter course for roofs with each course hanging over the lower one by ¼”.
• Specify a minimum 4:12 pitch roof, prefer a 5:12 minimum pitch and shingle widths between 3 and 9 inches.
• Specify copper or zinc sheets at ridge in humid climates to reduce moss growth
• Hand nail shakes and shingles. Nail guns and staples are
  not allowed

Specialty Roofs

• Evaluated on a case-by-case basis

Waterproofing Systems

• Specify waterproofing products, all manufactured in the United States, supplied by a single manufacturer which has been successfully producing the specified types of primary
  products with the same materials without making
  adjustments, modifications or alterations to the chemical or physical composition of the products for not less than the warranty period.
• Specify a minimum 10-year Manufacturer’s Warranty for labor and material, without monetary limitation, to correct defects in materials or workmanship. Warranty shall contain no exclusions for random occurrences of ponding water.
• Specify the use of certified contractors to apply the waterproofing system and that the work be inspected by the manufacturer at a minimum of once a week during installation
• Waterproofing below the water table may limit the selection of the waterproofing membrane.
• Select waterproofing systems that are typically used on substrates as stated in the manufacturer’s literature.

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