Garden Window Installation

How to Install a Garden Window

1. 1 Prep site, remove existing trim

   

   Prepare the project site and remove the interior and exterior trim, then remove the existing window.

2. 2 Verify correct window sizing

   

   Check the rough opening measurements to verify the correct window sizing. The rough opening should be about 1⁄2" larger than the window height and width. If necessary, attach wood strips to the rough framing as spacers to bring the opening to the required size. 

3. 3 Level

   

   Use a level to check that the sill of the rough opening is level and the side jambs are plumb. Use a framing square to make sure each corner is square. The rough framing must be in good condition in order to support the weight of the garden window. If the framing is severely deteriorated or out of plumb or square, you may need to reframe the rough opening.

4. 4 Use framing square

   

   Use a level to check that the sill of the rough opening is level and the side jambs are plumb. Use a framing square to make sure each corner is square. The rough framing must be in good condition in order to support the weight of the garden window. If the framing is severely deteriorated or out of plumb or square, you may need to reframe the rough opening.

5. 5 Positioning window sleeve/shim

   

   Position the inside edge of the window sleeve to be flush with the interior wall surface. Check the sill of the garden window for level. Shim beneath the lower side of the sill, if necessary, to make it level
   

6. 6 Trace and cut siding down

   

   Make sure the garden window is level, then hold a piece of window trim in place along the exterior of the window and trace the outline onto the siding. Remove the window. Cut the siding down to the sheathing using a circular saw. 

7. 7 Building paper

   

   Install strips of building paper between the siding and the sheathing. Wrap them around the framing and staple them in place. On the sides, work from the bottom up so each piece overlaps the piece below. Reposition the window and reshim. Make sure the space between the window and the siding is equal to the width of the trim on all sides.

8. 8 Drill holes through window sleeve

   

   Drill countersunk pilot holes every 12" to 16" through the window sleeve into the rough header, jack studs, and sill. 

9. 9 Insert shims and fasten window to framing

   Insert shims between the window sleeve and the rough frame at each hole location along the top and the sides to prevent bowing of the window frame. Fasten the window to the framing using 3" screws. Continue checking for level, plumb, and square as the screws are tightened.

10. 10 Support brackets

    

    Locate and mark the studs nearest the edges of the window using a stud finder. Cut two pieces of siding to fit behind the brackets, and tack them in place over the marked studs with 4d siding nails. Position the support brackets with the shorter side against the siding and the longer side beneath the window. Fasten the brackets to the window and the studs using the included screws.

11. 11 Trim and seal

    

    Cut a piece of drip edge to length, apply construction adhesive to its top flange, and slide it under the siding above the window. Cut each trim piece to size. Position the trim and attach it using 8d galvanized casing nails driven through pilot holes. Seal the edges of the trim with a bead of paintable silicone caulk approximately 3⁄8" wide.

12. 12 Cut shims flush with utility knife

    

    Cut all protruding shims flush with the framing using a utility knife or handsaw. Insulate or caulk the gaps between the window sleeve and the wall.  Finish the installation by reinstalling the existing interior trim or installing new trim.