Horizon window installation

Horizon windows are built to size, so the opening dictates the order. Measure each opening individually — even openings that look identical rarely are.

1. 1

   For pocket replacements, measure width at top, middle and bottom inside the existing frame and use the smallest number.

2. 2

   Measure height at left, center and right from the high point of the sill to the underside of the head, and use the smallest number.

3. 3

   Deduct 1/4" from width and height for pocket replacements so there is room to shim and square.

4. 4

   For new construction, size the unit 1/2" narrower and shorter than the rough opening.

5. 5

   Check the opening for square by measuring both diagonals; note any difference over 1/4" on the order.

Water that gets past the glazing or the frame must have a way out. A sloped, flashed sill is what turns a window from a leak into a detail.

1. 1

   Remove sash, stops and old hardware; scrape the opening clean and repair any rot or soft framing.

2. 2

   Confirm the sill slopes to the exterior; add a beveled shim or sill pan if it is flat or pitched inward.

3. 3

   Install a sill pan or flexible flashing that runs up the jambs a minimum of 6" and turns out over the exterior face.

4. 4

   Apply a continuous bead of sealant on the exterior stop or nailing flange contact area — leave the sill bead open at the center to drain.

5. 5

   Dry-fit the unit to confirm clearance before committing to any sealant.

A fusion-welded frame is rigid, but it will still bind if it is racked. Shimming at the balance and lock points keeps the sash operating for the life of the unit.

1. 1

   Set the unit into the opening from the outside and press it into the sealant bed.

2. 2

   Shim under the sill at each end and at the center of any unit wider than 3 ft to support the frame.

3. 3

   Plumb the jambs, level the head and sill, then check the diagonals — they must be within 1/8".

4. 4

   Shim behind the jambs at the lock and balance locations so the frame is not bowed.

5. 5

   Operate the sash and lock before fastening: it should tilt, glide and latch with no drag.

Fasteners hold the frame to the framing; insulation seals the gap. Getting either wrong shows up as drafts, condensation or hard operation.

1. 1

   Fasten through the jambs or nailing flange 3" from each corner, then every 12–16" on center into solid framing.

2. 2

   Drive screws snug, not tight — over-driving bows the jamb and binds the sash.

3. 3

   Fill the perimeter gap with low-expansion window and door foam or backer rod and sealant.

4. 4

   Re-check operation after fastening and insulating; adjust shims before the foam cures if anything drags.

5. 5

   Trim excess foam flush once cured and install interior stops or extension jambs.

The exterior seal and the siding transition are what keep the assembly dry. Finish the flashing lap sequence bottom-up so every layer sheds onto the one below.

1. 1

   Flash jambs first, then the head, lapping over the jamb flashing and under the water-resistive barrier.

2. 2

   Install J-channel or brickmould so the head piece drains to the front of the opening.

3. 3

   Seal the exterior perimeter at the head and jambs; leave the sill unsealed so the opening can drain.

4. 4

   Clean glass and frames, verify weep holes are clear, and remove all protective film.

5. 5

   Operate, lock and tilt every sash; record serial numbers for the warranty registration.