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New Construction Roofing Guidelines

New construction roofing and waterproofing generally presents an application environment very different from a reroofing project.

The NRCA publication "HARK" — The Handbook of Accepted Roofing Knowledge" presents a wealth of information and guidelines applicable to successful completion of new construction roofing work.

It is a very common problem for General Contractors to direct roofing or waterproofing contractors to install moisture protection prematurely or to "phase" the installation with the G.C’s objective, to allow interior trades to proceed, being the primary concern. This often results in a substandard roofing installation.

Another common problem, especially on large projects, is damage to the moisture protection system by construction traffic of other trades.

These are avoidable problems if properly addressed. The best approach is to conduct a pre-installation meeting attended by all interested parties, i.e., owner's representive, G.C, Architect, plumber, electrician, roofing materials manufacturer and the roofing contractor. The NRCA pre-roofing conference checklist includes:

  • Establish trade-related job schedules, and appropriate trade sequencing, including timely installation of any rooftop mechanical equipment, to avoid or limit traffic on the roof.
  • Establish construction schedules and work methods that will prevent roof damage; these may include provisions for installation of a temporary roof, for installation of traffic paths or walkways for protection of finished roof systems, and for the use of mechanized roof application equipment.
  • Establish the conditions under which a temporary roof or traffic paths will be used, and who will pay for them.
  • Require that all walls, curbs, drains, and other penetrations be in place prior to installing the roof system.
  • Establish those areas on the job site that will be designated as access, staging, work, and storage areas.
  • Establish weather conditions and working temperature criteria to which all parties must agree.
  • Establish provisions for on-site monitoring after the roof application is completed to assure that the finished roof is not damaged by other trades. Establish provisions for payment for repairs in the event that damage does occur.
  • Establish and review all related EPA and OSHA regulations and other safety requirements, including considerations for safety of building occupants.
  • The pre-installation inspection should include surface inspection of the structural deck.

If changes to the agreed upon conditions are desired, the party requesting the change should:

  • Give written notice of the desired changes to all parties.
  • Secure written agreement to the changes from the project designer and all other parties affected by the change.

 

Preinstallation Deck Inspections


Metal Deck:

The inspection team should walk all deck surfaces and observe the general installation, checking that the:

  • Metal deck is properly aligned
  • Roof openings are properly reinforced
  • Deck appears to be properly secured with fastners or welds
  • Drains are properly installed and clamped at correct elevations
  • Deck is proper spaced at walls and expansion joints
  • Deck is not damaged or deformed

For further information please consult Steel Deck Institute


Concrete Deck:

  • The deck should have a wood-trowel medium smooth surface finish, without significant depressions or surface irregularities, such as fins or ridges. Consult American Concrete Institute Section 301 — 11.7.3 for precise specification.
  • The deck must be properly cured with moisture content andhave a dry surface. The concrete deck surface must be free of any laitance, oils, dust, dirt, frost, unapproved curing compounds or other foreign matter detrimental to the adhesion or performance of the membrane.

Moisture content tests are required following ASTM D-4263 procedures (plastic film test).

Recommended deck curing time of 28 days is somewhat arbitrary but should be used as a guideline. Do not use any curing agents, which are not approved, in writing, from the curing agent manufacturer and from Barrett. A burlap wet cure is highly recommended as the preferred method of curing concrete. The concrete deck surface must be free of any laitance, oils, dust, dirt, frost, unapproved curing compounds or other foreign matter detrimental to the adhesion or performance of the membrane. The General Contractor shall certify no unapproved curing compounds have been used.

For further information consult ACI@.


Wood plank and Plywood Decks

Wood decks must be stable, well seasoned or Kiln-dried solid sawn lumber. Plywood should meet American Plywood Association (APA) standard APA PRP-108, C-DX exterior grade. Wood plank should be a minimum of one inch thick, or greater, consistent with support spacing; plywood should be a minimum of 1/2" inch thick, consistent with support spacing.

Prior to installing rosin paper and mechanically fastened a base sheet or insulation, inspect surface and edge conditions for proper fastening and tight joints.

For further information consult American Plywood Association or NRCA

For specific information on:

Tectum — Cementitious Wood Fiber Decks

Lightweight Insulating Concrete Decks

Gypsum, poured decks

Gypsum panel decks

Thermosetting Insulating Fills

Please contact Barrett Technical Services

The keys to successful moisture protection are quiet simple:

  • Proper Design
  • Quality Materials
  • Quality Workmanship
  • Regular Inspections and timely Maintenance

Barrett offers

  • Design assistance to Architects
  • Highest quality materials
  • Approved contractor network
  • Inspecton services
  • Maintenance programs
  • Long term warranties
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http://www.barrettroofs.com
Last Updated : 12.12.14
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