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How to Remove an Old Window to Install Glass Block with Side Accents

Follow these step-by-step instructions to remove an old window and prepare the opening to install glass block.

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Step 1: Design the Layout and Prepare the Materials

Sketch the dimensions of your new window and take good measurements to decide the size and style of block you want to use. Computer programs are available that create 3D images to give you an idea of what your window will look like. Gather all your supplies and tools before you begin the project, remove window blinds, curtains and brackets.

Step 2: Set up the Scaffolding

Renting scaffolding for outside work may seem like an unnecessary expenditure, but it provides security and mobility that makes it well worth the expense. Removing a window while standing on a ladder six to eight feet above the ground is not an easy job.

set up scaffolding

Step 3: Score Around the Window

On the inside, cut along the drywall about an inch away from the window with a utility knife. This will keep you from disturbing too much of the wall and prevent unnecessary repairs.

Step 4: Remove the Drywall and the Windowsill

Remove all of the drywall from around the edges of the window so you can build the frame for the glass blocks. Remove the windowsill with a flat pry bar.

remove drywall from around window frame

Step 5: Mark the Locations for the Accent Windows

Mark locations for the 4-inch side accent windows. Measure 7 inches in from the side of the window and make a mark; use a level and plumb a line. Mark the vertical line with a pencil and then measure 6 inches from that line, make a mark and plumb another line with the level. Repeat this process on the other side. This should result in 6-inch wide vertical boxes that are equal distance from the main window.

Step 6: Score and Cut the Drywall

Score the drywall along the outline with a utility knife, then cut the drywall with a keyhole saw.

score drywall along outline with utility knife

Step 7: Remove the 'J-Channel'

Remove the vinyl "J channel" around all four sides of the window. You won't be using this again, so don't worry about breaking it.

Step 8: Remove the Edging

If the window edging is nailed to the house, you need to remove the nails all the way around the perimeter. Use a cat's paw to work out the nails. Vinyl siding can make it especially difficult to get to the nails, so work slowly and carefully -- if you tear the vinyl, it will create a lot of repair work. It ususally involves replacing a length of the vinyl siding with another length of vinyl similar in color (check for fading). If you have wood or cementious siding, the issues are similar but cuts are and gouges are easier to repair than on vinyl siding. Cuts and gouges on non-vinyl siding can usually be filled with fillers, spackles or other patching materials.

remove nails from window edging around perimeter

Step 9: Drill Holes to Mark the Corners

Inside the house, use a speed square to transfer the corners of the interior opening to the back of the sheeting. Use a drill to mark the holes in the siding on the outside.

mark holes in vinyl siding on outside

Step 10: Cut Away the Vinyl Siding

Use a level and draw lines on the siding connecting the holes, and then use a utility knife and carefully cut away the vinyl siding.

use a utility knife to cut vinyl siding away

Step 11: Drill Starter Holes and Cut the Sheathing

Drill out starter holes with a paddle bit (Image 1). Cut the sheathing from point to point with a reciprocal saw and take the window out. Trim away any rough edges (Image 2).Whenever cutting through an exterior wall, make sure any vapor barriers and insulation are still intact before you close the hole or otherwise limit your access.