cure for twenty-eight (28) days prior to the application of sprayed polyurethane foam.
Sprayed polyurethane foam is not recommended for lightweight or insulating concretes unless tests have been made to determine that adequate adhesion can be obtained or unless an overlayment is installed.
Concrete/corrugated metal sheets must be dry on the surface, with a moisture content less than 19%. If adhesion is suspect due to moisture content of the concrete, an adhesion test should be performed.
Existing expansion joints should be inspected and repaired if necessary.
Lightning rods shall be masked prior to foaming. Lightning rod cables shall not be embedded in the polyurethane foam and should be removed prior to foaming. Electrical and mechanical conduits should be relocated or raised above the finished roof surface.
Prior to application of the foam, the surface shall be inspected to insure that above mentioned conditions have been met.
Substrate shall have sufficient slope to eliminate excessive ponding water. If the substrate does not have sufficient slope, then the ponding water must be eliminated by building in slope as well as the proper placement of drains, or a combination thereof.
The polyurethane foam application shall not proceed during periods of inclement weather.
The applicator shall not apply the polyurethane foam below the temperature and/or humidity specified by the product data sheet for ambient air and substrate. Wind barriers may be used if wind conditions could affect the quality of installation.
Spray Polyurethane Foam Application:
The spray polyurethane foam must be applied in a minimal pass thickness of 1/2 inch.
Spray polyurethane foam thickness shall be a minimum of one inch (or more if specified). The polyurethane foam shall be applied uniformly over the entire surface with a tolerance of plus.
1/4" per inch of thickness, except where variations are required to insure proper drainage or to complete a feathered edge.
The spray polyurethane foam shall be uniformly terminated a minimum of four (4) inches above the roofline at all penetrations (except drains, parapet walls, or building junctions). Foamed in place cants shall be smooth and uniform to allow positive drainage.
Detailing skylights is particularly important in that the spray polyurethane foam MUST be terminated below existing weep holes. DO NOT COVER WEEP HOLES WITH FOAM OR COATING
The polyurethane foam surface shall be allowed to cure sufficiently. The full thickness of polyurethane foam in any area shall be completed prior to the end of each day. If due to weather conditions more than 24 hours elapse between polyurethane foam and coating application, the polyurethane foam shall be re-inspected.
Surface Finish:
The final sprayed polyurethane foam surface shall be "smooth, areas with big undulations are not acceptable. These areas shall be removed and re-foamed to an acceptable surface.
Any damage or defects to the polyurethane foam surface shall be repaired prior to the protective coating application.
The polyurethane foam surface shall be free of moisture, frost, dust, debris, oils, tars, grease or other materials that will impair adhesion of the protective coating.
Acrylic Based Coating Application:
Coatings typically are recommended to be applied in two or more applications to achieve the total minimum dry film thickness (25mils).
The rate of application of a coating will be governed by the SPF surface textured.
Each coat applied to achieve a DFT of 10mils to 15mils to build up to the final desired coating thickness.
Each coat should be applied at right angles to the preceding coat. After each coat is allowed to cure, the surface should be inspected for deficiencies and repaired as necessary before applying the next coat.
A coating should not be sprayed during wind conditions that prevent uniform application of the coating or cause overspray on surfaces that are nor intended to be coated.
SPF should not be visible, and all SPF should be continuously coated without thin spots, blisters or pinholes.
Perimeters and projecting and vertical surfaces are suggested to receive an additional 12-inch-wide application of protective coating.
Foot traffic over finished areas of a roof system should not be permitted until the coating is properly cured.
Coating Equipment: coating systems typically are spray-applied, roller-applied or brush-applied.