How to build a drop ceiling window well slope in your basement

By Timothy Chapel

Basement drop ceilings seem to always have a complication when being installed. Nothing is ever easy, right?

In most basements maximizing head clearances is a priority because they never seem to dig those things deep enough.

window1Another thing basements need desperately is natural light. Most basements lack natural light and when installing a drop ceiling the easy thing to do is just build the ceiling over the window and keep on going.  That’s a choice most people regret because they miss out on two things: Natural light and being able to use the window.

It’s really not that hard to build a window well slope, anybody can do it. Follow these step by step instructions and your project will look like you hired a professional.

Step 1   Determining the size of the window slope

Begin by assessing the design and layout of the grid and determine where the last tee or main runner is located.

window2Next…determine the depth of the slope. It’s always best to start the slope on a tee line but for basement windows, you typically don’t want the depth to exceed 24”. Try to stay within 12” – 24”. If for some reason you can’t stay within these parameters, you can break the pattern of the grid and install a main runner or 4’ cross tee closer to the window.  Just remember to support it with ceiling wire if the distance exceeds 4’.

Step 2 Installing the vertical and top angles of the slope

As the main portion of the drop ceiling continues over and meets the window well opening, you’ll need to install a piece of wall angle molding on each side of the window well.

  • Cut a piece of wall angle and create a 90 degree bend taking it upwards to the top of the window itself. Secure it to the wall.window3
  • Measure the width of the window well. Cut a piece of wall angle to fit the inside of the window well and make sure it’s above the window frame if you plan on opening the window.
  • Install the side angle pieces that fit into the 90 degree bends you made. Be sure to use a speed square up against the cross tee to keep them straight.
  • Pop rivet them to the 90 degree angle and the cross tee.

Step 3 Install the sloped tees in window well

Once all of the wall angle is installed and the side angle pieces, you’re ready to begin installing the ceiling grid.window4

  • Cut and install 2 sloped tees to fit the angle of the window slope. These angled cross tees will butt up to each side of the window opening. Notch out the bottom of the cross tee about a ½” and bend the tab to meet the angle. Install and pop rivet into place at the top and bottom.
  • If the window is larger than 24” in width, you will need to install another sloped tee somewhere in the center of the opening. Look at where there is a cross tee on the main portion of the ceiling grid and keep the sloped tee in-line with that so all the tees line up.
  • If the depth of the slope exceeds 24” or you want to break up the layout of the slope, add a cross tee perpendicular to the sloped tees. Pop rivet into place.

Step 4 Installing the ceiling tile into the window slope


  • Install the ceiling tiles into the slope first. Use hold down clips if necessary to keep them sitting flat. If you’re using revealed edge tiles make sure to keep the cut edges of the tiles facing away from where people could see them.
  • Back-cut the edge of the tiles at the beginning of the slope so they sit flat into the ceiling grid.
  • Install the vertical tiles on the sides of the slope next. Use hold down clips or adhesive caulk to hold them into place.
  • Install the remainder of the ceiling tiles on the main portion of the grid last.

Sometimes reading something isn’t as good as seeing it. Take a look at the full video to get step-by-step instructions on exactly how to install a drop ceiling window slope in your basement.

Good luck installing suspended ceilings! –Tim

*No Claim is made to the exclusive right to use “CEILINGS” apart from the mark as shown.