Install Synthetic Roof Underlayment

A. Finished-Work Specification

Deliverable: one continuous synthetic underlayment installation covering every accessible roof plane addressed in this work order, with first-course eave alignment, specified end and side laps throughout, increased laps or special details at low slopes, valleys, hips, ridges, walls, and penetrations, approved fastening, the Chapter 3 rake drip-edge installation completed in its required relationship to the underlayment, documented repairs, and a signed inspection record.

B. Governing Documents

Document	Confirmed Current	Notes
Underlayment manufacturer's instructions
Roofing-system specification
Chapter 1 deck-readiness record
Chapter 3 eave/rake drip-edge record
Chapter 4 membrane installation record
Adopted code and permit conditions

C. Acceptance Standards

Check	Standard
Prerequisite completion	Deck inspection, eave metal, membrane, and concealed repairs confirmed complete before this work begins
First-course alignment	Aligned to the chalked reference line and the required eave relationship on every plane
Face orientation and course direction	Matches the manufacturer-designated face and direction
End laps	Meet the specified end-lap dimension at every sheet joint within a course
Side laps	Meet the specified side-lap dimension between every upper and lower course
Special-detail laps	Increased or modified as required at low slopes, valleys, hips, ridges, walls, and penetrations
Vertical joint staggering	Staggered where required and oriented to reduce water entry
Fastening	Located only in approved zones at the required spacing, with no loose or missing fasteners
Rake drip-edge relationship	Installed immediately after the applicable underlayment course where the approved system requires metal over the underlayment
Surface condition	Free of exposed deck, reverse laps, insufficient overlap, loose sheets, and trip hazards, or each item corrected and rechecked
Documentation	Product, course layout, fastening, laps, repairs, and completion time recorded and signed

D. Required Project Sequence

1. Review the underlayment manufacturer's instructions, roof-slope limits, fastening requirements, exposure limits, lap dimensions, repair methods, and compatibility with the roof covering. Confirm the product's minimum slope rating against every roof plane measured in Chapter 1, and record the confirmed lap dimensions on the governing-documents table above.
2. Confirm that deck inspection, required eave metal, self-adhered membrane, and concealed repairs are complete. Locate the Chapter 1, Chapter 3, and Chapter 4 acceptance records. If any is missing or shows an open item, stop this chapter and route the project back to the responsible chapter before continuing.
3. Verify weather conditions and limit exposed deck area to what can be protected during the work period. Check the forecast against the estimated time to cover and secure each roof plane, and plan the work sequence so no section remains uncovered beyond that window.
4. Establish the first-course reference parallel to the eave. Measure from the eave edge using the eave relationship specified by the roofing-system specification, and snap a chalk line across the full width of the roof plane.
5. Stage rolls so they cannot slide, blow away, overload the roof, or block access. Distribute rolls within the approved roof-load limits established for this project and keep them clear of the access path established in Chapter 2.
6. Orient the underlayment with the manufacturer-designated face and course direction. Confirm orientation on the roll label before cutting or unrolling the first sheet.
7. Begin at the low roof edge and align the first course to the required eave relationship. Position the sheet edge to the chalked reference line from Step 4 before fastening.
8. Unroll a controlled length without walking backward toward an unprotected edge. Unroll in sections short enough to control, and maintain a fall-protection connection throughout.
9. Smooth the sheet without stretching, wrinkling, or trapping debris. Work from the center of the sheet outward toward both edges and both ends.
10. Install temporary and permanent fasteners only in approved zones and at the required spacing. Use the fastener type and spacing identified in the manufacturer's instructions and confirmed on the governing-documents table.
11. Continue the first course while maintaining alignment and end laps. Check alignment against the chalked reference line at regular intervals and correct drift immediately.
12. Install upper courses so each upper sheet overlaps the lower sheet by the specified amount. Measure the side lap at multiple points along each course before fastening.
13. Increase laps or use required special details at low slopes, valleys, hips, ridges, walls, and penetrations. Apply the manufacturer's special-detail instructions at each identified condition rather than the standard field lap.
14. Keep vertical end joints staggered where required and oriented to reduce water entry. Offset end joints between adjacent courses according to the manufacturer's stagger requirement.
15. Cut neatly around penetrations and integrate the sheet with existing membrane in shingle-lap order. Trim underlayment so the upper layer sheds onto the lower membrane and roofing layers at every penetration.
16. Complete the rake drip-edge installation from Chapter 3 where the approved system requires metal over the underlayment. Install the prepared rake pieces staged in Chapter 3 immediately after the underlayment course that must pass beneath them, maintaining the approved edge and underlayment relationship.
17. Fold, lap, or terminate underlayment at ridges and hips according to the ventilation and roofing plan. Leave the termination in the condition required for the ridge-vent or ridge-cap work planned in Chapter 13 or Chapter 14.
18. Repair tears, punctures, wrinkles, loose edges, and misplaced fasteners using approved patches and fasteners. Use the manufacturer-approved patch dimensions and method, and record each repair location.
19. Inspect the entire surface for exposed deck, reverse laps, insufficient overlap, loose sheets, trip hazards, and drainage interruptions. Walk the full accessible surface using the fall-protection system, checking against the Acceptance Standards table above.
20. Secure the underlayment for the expected exposure period and forecast conditions. Confirm all fastening is complete and no section remains loose before ending the work period.
21. Photograph and record product, course layout, fastening, laps, repairs, and completion time. Attach photographs to the installation record and complete the documentation form established in Step 1.