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The Roofing Professionals

National Grid – Reconditioning an existing Spray Foam Roof System

National Grid 3Client

National Grid – Eastern Region Headquarters
Albany, NY

Existing Roof

42,000 SF Spray-Applied Polyurethane Foam (SPF) Roofing System


S. D. Carruthers installed the existing Spray Foam (SPF) roofing system over the facility’s old tar and gravel built-up roof in 1984.  While still performing well, the system was starting to show the effects of normal weathering, and the roof system’s warranty had long-since expired.


Recoating with new Spray-Applied Silicone Membrane.


Spray-Applied Polyurethane Foam (SPF) roofing is acknowledged to be one of the most “sustainable” roofing systems available.  With today’s environmental concerns, and a greater emphasis on life-cycle costing, the ability to renew and rejuvenate an aging SPF roof is a tremendous benefit.

National Grid’s facilities group understood the value of maintaining their SPF system, opting to take a proactive approach to extend the roof’s service life.  An infrared moisture scan was commissioned to determine the extent of any leaks and areas of wet insulation that may have developed.  In spite of nearly 20-years of “wear and tear”, the scan revealed less than 3% of wet insulation.  With this information in hand, a technical specification was prepared and bids were solicited for “recoating” of the roof.  After review and award of contract to S. D. Carruthers, work proceeded as follows.

  • Areas of wet insulation were first removed and replaced with new foam insulation.
  • The new foam insulation was then scarified to match the level of adjacent surfaces.
  • The entire roof was power washed, removing all loose granules, dust, dirt and debris.
  • All joints in the building’s ceramic tile coping were checked and caulked as required.
  • Two layers of new silicone membrane coating, in contrasting colors, were spray-applied to the specified thickness.
  • New ceramic granules were broadcast into the topcoat, providing enhanced durability and a non-skid surface.
  • New protective walkway pads were installed where indicated in the project’s specifications.
  • Upon completion, a new 10-Year full-system labor and materials warranty was provided.


Having elected to recoat at the proper time, National Grid was able to significantly extend the life of their SPF roof, while avoiding the high cost of removal and replacement.  Publicly committed to promoting energy efficiency for their customers, they now continue to benefit from the superior insulating properties of their seamless, closed-cell SPF system, all with a renewed 10-year full system manufacturer’s warranty.

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