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Skylight Instructions


  • Measuring Tape
  • Hammer
  • Nails
  • Carpenter Square
  • Power Saw
  • Sheetrock / Keyhole Saw
  • Tin Snips
  • Lumber for Curbs and Headers
  • Utility Knife
  • Roofing Mastic and Trowel
  • Appropriate Flashing for Curb
  • Drywall, Insulation, etc. for Light Shaft
  • Single-Sided Weather stripping
  • Drywall "J" Molding



Before starting, read through the Installation Instructions, noting the type of building construction and obstructions (wiring / heating). The following recommended procedures are general but pertain to most applications. When in doubt, ask your building supply center for assistance.

Examine fig.1 to familiarize yourself with the construction of the roof opening, ceiling opening, and shaft.

IMPORTANT: Do not cut or remove any portion of a factory-made truss unless you have a qualified engineer design the reframing. There are ways to install larger skylights without cutting factory-made trusses. See your Western Skylight dealer.

NOTE: These instructions are directed toward attic ceilings with shake, shingle or composition roofing. Cathedral ceilings are done identically except for the light well. The installation procedures are the same for either glass or acrylic Western Skylights. For any other type of roof, consult your building material dealer for proper flashing materials and methods.



Decide on the type of light shaft to be constructed. Do not use a glass skylight on a roof with less than a 2:12 pitch.

  1. Vertical shaft - good for relatively small light shafts. Simple to construct.
  2. Slanted shaft - effective in skylight area close to or under ridge of house or in clearing obstacles in attic.
  3. Flared shaft (most common) - wall on low side can be flared or vertical (vertical shown). Wall on high side flared. Increases amount of light into the room. Best for deep long shafts.



Check area above for electrical, ductwork, plumbing, etc. If possible, remove insulation from area.

Locate proposed opening in roof in relation to interior of room below by driving one pilot nail from ceiling into attic (1). Plumb to the inside of the nearest roof after (2). Mark position between roof rafters by driving a nail at each corner through roof (2). Verify proposed opening with skylight size.

Cut ceiling opening with saw or sheetrock knife leaving ceiling joists and rafters intact.



Proceed to the roof and, using the nails protruding through the roof as a guide, carefully remove the shingles (not roofing felt) approximately 10" beyond the nails or to the next natural break on the top and two sides. Cut shakes/shingles along a line 2" below the two lower nails and the width of the space between the nails. From your reference nails, draw the "rough opening" on the roofing felt. Check these dimensions against the correct "rough opening" or inside curbs dimensions. Also determine of rough opening is "true and square".



Set the blade depth on your power saw to the thickness of the roofing material. Take care not to cut into the roof rafters. Cut out the skylight opening. Finish the top and bottom of the opening with a single cross header. Remember, there are ways to install larger skylights without cutting rafters or factory-made trusses. If a roof rafter is to be cut, it will be necessary to temporarily support the rafter until a double cross header can be installed. Where cross headers are required, measure off the inside length of the skylight +3" on both the high and low side to allow for the header to be added.



Build a 2x6 curb box with inside dimensions the same as the rough opening. Toenail curb box to roof in alignment with the opening.

Flashing is one of the most critical steps in a skylight installation. We recommend the use of "Flash It" kits made specifically for Western Skylights. Flash from bottom to top. Continuous top and bottom flashing should extend 4" beyond sides; cut and bend overage down onto roof. The first side flashing should extend 4" down beyond the bottom of the curb. For other than shake/shingle roofs, consult your building dealer for proper flashing materials and methods.



Finish the light shaft with a vertical 2"x4" framing from ceiling opening to the roof opening.

Apply finish material inside the framed light shaft to the top of the curb. Cover cut drywall edges at top of light shaft with "J" molding. Finish light shaft and ceiling opening as required.

Apply insulation to outside of light shaft studs. Be sure barrier on insulation faces toward light shaft.



Install skylight on curb, making sure the skylight frame is down tight on the top of the curb and there is an equal spacing between the skylight frame and the face of the curb.

  1. Use foam tape (sticky on one side) to seal between the skylight and the curb. Do not glue skylight to curb.
  2. Secure the skylight with a stainless steel screws (provided) through the outside frame to the curb.



Glass: Same manner as windows.

Acrylic: Do not use window cleaners, ammonia, etc. Pour liquid detergent on a wet sponge. Use RUNNING hose to flood dirt off - DO NOT SCRUB. Air dry. Tape, tar, and most other materials can be removed with mineral spirits and a soft cloth. Wash off with soap and plenty of water.

Scratches: Glass scratches cannot generally be removed. Acrylic scratches may be buffed out using automotive rubbing compounds followed by finer polishing compounds. Deep scratches will require WET sanding with 900 or 1200 grit sandpaper first.


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