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How to Apply Tri-Ply Roofing

Denise Brown

Tri-Ply roofing material, produced by GAF Materials Corporation, works well as a cover for a flat- or low-slope roof. Tri-Ply comes in rolls that you nail to the roof. The Tri-Ply application is then further weatherproofed with the application of special sealers.

While you might hire a professional to install Tri-Ply, an experienced do-it-yourselfer can also apply it to the roof. Tri-Ply must have base sheathing that is at least 1 inch thick. If installed over plywood, the base must be at least four-ply and exterior grade. Joints should be no more than 1/4 inch apart.

  1. Fill all gaps between plywood as well as knot holes in the plywood with sheet metal nailed to the sheathing with roofing nails. Set all nail heads at or below the surface of the plywood.

  2. Sweep any debris from the roof’s surface with a broom.

  3. Cut perlite insulation sheets to fit on the roof with a utility knife. Butt edges together and stagger joints.

  4. Unroll Tri-Ply #75 base-sheet material and cut it into 12-foot sections. Stack the cut material into a pile for easy access.

  5. Place the first strip of base material along the lowest edge of the roof. Overlap end joints, as necessary, by at least 6 inches. Leave 2 inches extra at both ends of the roof. Attach this base sheet and the insulation below it with Tri-Ply nail fasteners that have a 1-inch diameter head. Space fasteners 9 inches apart along the edges of the Tri-Ply.

  6. Place a row of fasteners in a row 12 inches from the edge of the sheet. Space fasteners 12 inches apart. Set another row of fasteners 12 inches from the other side of the sheet. Stagger the placement of fasteners with the fasteners in the adjacent row.

  7. Start another row of Tri-Ply covering. Leave 2 inches at both ends. Overlap side joints by 2 inches. Stagger all vertical joints. Nail the edges and middle of the strip with Tri-Ply fasteners as you did in Steps 5 and 6.

  8. Continue placing rows of Tri-Ply on the roof until you cover the entire roof. Cut the Tri-Ply, as necessary, to fit around vents and other objects on the roof.

  9. Cut strips of Tri-Ply SBS membrane. Stack them in a convenient location.

  10. Apply a layer of adhesive slightly wider than a strip of SBS membrane, using a long-handled squeegee. Cover the adhesive with a strip of SBS membrane, leaving a 2-inch side lap. Overlap ends at least 2 inches as well.

  11. Add more adhesive for the next row of membrane. Set the second row of SBS membrane in place, overlapping edges with the first row by 4 inches. Continue applying adhesive and setting membrane until you cover the roof.

  12. Seal the SBS material in the adhesive by running a weighted roller over the entire roof.

  13. Tip

    Apply Tri-Ply roofing material to a dry roof deck.


    Some Tri-Ply products are installed and then heated to seal the edges of the material. Do not attempt to do this without proper training or you may set your house on fire. Use only cold adhesive and SBS material for this project.