Install Trim Around Windows and Doors

A. Finished-Project Specification

Scope: one complete set of side casing, head trim, and sill trim or apron installed at one scheduled window and one scheduled exterior door, joined at the corners using the approved method and sealed only at designated interfaces.

B. Required Documentation Schedule

Document	Source	Confirmation Required
Trim schedule	Design professional / siding specification	Profile, reveal, overhang, and joint dimensions confirmed for each opening
Siding specification	Design professional / manufacturer	Trim-first or trim-after sequence confirmed for the selected cladding system
Window and door flashing records	Projects 4–9 inspection records	Confirmed passed and undamaged before trim begins
Sealant schedule	Design professional / manufacturer	Designated trim interfaces requiring sealant confirmed and distinguished from drainage openings

C. Preparation Materials and Consumables

• Trim stock: side casing, head trim, and sill trim or apron matching the approved profile and thickness, sufficient for one window and one door with allowance for cutting waste.
• Fastener stock: corrosion-resistant trim fasteners matching the approved fastening schedule for the trim material and backing.
• Sealant: the designated exterior sealant identified for trim-to-siding and trim-to-frame interfaces only.
• Documentation: one trim installation record per opening.

D. Acceptance Standards

Check	Standard
Side casing	Plumb, at the approved reveal, fastened into required backing without compressing the rainscreen cavity
Head trim	Level, with the required overhang beyond side casings, and the required clearance preserved below head flashing
Sill trim / apron	Installed to the approved sloped and drained detail without sealing across weeps or sill-pan outlets
Joint fit	Corners joined using the approved butt, miter, scarf, or proprietary method with consistent, tight-fitting reveals
Clearances	Flashing clearance, rainscreen ventilation, and cladding movement gaps preserved at every trim interface
Documentation	Completed trim and flashing interface photographed and recorded on the trim installation record

E. Document Review and Verification (Steps 1–3)

1. Review the approved trim material, profile, thickness, joint design, fastening schedule, edge treatment, head-flashing detail, siding interface, and sealant plan. Confirm the current revision of the trim schedule against the project's document-control log before cutting any stock.
2. Confirm whether the selected cladding system requires trim-first or trim-after installation. Record the confirmed sequence on the trim installation record before proceeding.
3. Verify that window and door flashing, head flashing, sill-pan drainage, and rainscreen support have passed inspection. Do not begin cutting or fastening trim at any opening whose flashing inspection remains open.

F. Layout and Side Casing (Steps 4–9)

1. Inspect trim stock for damage, moisture condition, straightness, coating, and compatibility with adjacent materials. Set aside any piece with damage, excess moisture, or coating defects before it is cut.
2. Measure the actual opening, frame projection, siding plane, and required trim reveals. Take all measurements from the as-built condition at each opening rather than from the rough-opening schedule.
3. Establish reference lines for side, head, and sill trim. Mark the reveal line at the frame and the outer trim edge line at the siding plane before any cut is made.
4. Cut side casing to controlled lengths and prepare field-cut ends. Cut each piece to the length established from the reference lines and treat field-cut ends according to the trim manufacturer's requirement.
5. Install side trim plumb with the required reveal and drainage clearance. Check plumb with the level at both the top and bottom of each casing before fastening.
6. Fasten through the approved support without compressing the rainscreen cavity or damaging flashing. Confirm fastener length and location avoid the furring cavity and any concealed flashing layer.

G. Head Trim (Steps 10–13)

1. Measure and cut the head trim or head casing to provide the required overhang beyond side trim. Confirm the overhang dimension at both ends before cutting.
2. Install or preserve the rigid head flashing above the trim in shingle-lap order. Do not remove, shift, or shorten the head flashing installed in Project 6 or Project 9 to accommodate the head trim.
3. Maintain the required gap between head flashing and siding or trim components. Verify the gap with a measuring tool rather than by visual estimate before fastening the head trim.
4. Install head trim level and aligned with the side casings. Check level along the full length of the head trim and confirm consistent contact with both side casings.

H. Sill Trim and Door Trim (Steps 14–16)

1. Prepare and install sill trim, apron, or lower casing using the approved sloped and drained detail. Confirm the outward slope of the sill trim matches the approved detail before fastening.
2. Do not seal across window weeps, sill-pan outlets, or lower drainage gaps. Identify and mark every weep and outlet location before installing sill trim so it is not inadvertently covered or sealed.
3. Fit door trim around the jamb and threshold while preserving threshold drainage and required clearance. Confirm threshold weeps or drainage gaps remain open after door trim is installed.

I. Corner Joints and Sealant (Steps 17–18)

1. Join trim corners using the approved butt, miter, scarf, or proprietary joint method. Do not substitute a different joint method than the one specified in the approved trim schedule.
2. Apply sealant or joint treatment only at designated interfaces. Confirm each interface against the approved sealant schedule before applying any bead, and leave every identified drainage opening unsealed.

J. Inspection and Documentation (Steps 19–21)

1. Inspect plumb, level, reveal, joint fit, fastener seating, head-flashing projection, sill drainage, and cladding clearance. Check every measurement against the Acceptance Standards table before considering the opening complete.
2. Correct tight joints, reverse laps, blocked weeps, split trim, unsupported ends, and misaligned reveals. Remove and replace any component that cannot be corrected within the approved tolerance.
3. Document the completed trim and flashing interface. Photograph each opening from a distance that shows the full trim assembly and its relationship to head flashing and sill drainage, and record findings on the trim installation record.