How to Install or Replace a Window Well

by Team HomeServe
Uncovered window well with escape ladder from basement bedroom  Safety

Installing a Window Well at a Glance

  • Tools and Materials: Shovel, level, hammer drill, wall anchors, gasket, wheelbarrow, drainage rock
  • Step 1: Check backfill and window position
  • Step 2: Measure dimensions
  • Step 3: Dig hole
  • Step 4: Insert window well
  • Step 5: Add sealant or gasket
  • Step 6: Secure anchor
  • Step 7: Add drainage rock and backfill dirt

A window well is a U-shaped barrier made of ribbed metal or plastic that prevents water from pooling by your basement windows. If your basement window is at or below the grade of the ground, installing one could prevent your basement from flooding.

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Window well installation or replacement is a relatively simple process. With the right gear, most people should be able to do it themselves. Here’s the process, broken down step-by-step.

Equipment Checklist

To properly install or replace a window well, you’re going to need the right tools. Before you begin, make sure you have:

  • Shovel
  • Level
  • Hammer drill
  • Masonry bit
  • Hammer
  • Wall anchors
  • Nuts and bolts
  • Wheelbarrow
  • Drainage rock
  • Gasket (silicone sealant or expansion joint)
  • Craft knife
  • Rag or cloth
  • Tape measure
  • Pencil

How to Install a Window Well

If you’re installing a brand-new basement window, it's a good idea to install the window well first to avoid any damage to your new glass panes.

Here’s what you need to do:

1. Check Your Backfill

Before you begin installing a window well, you'll want to make sure the dirt is backfilled only up to the distance the window well will protrude from the wall.

2. Test the Positioning

Leaving enough space to fit the window well comfortably, place it where you intend to install it and ensure it fits. Your window well needs to be at least 10 to 12 inches below the window opening. You'll also want to leave at least 3 inches of the window well above the surface grade.

3. Remove the Window Well and Measure

Take the window well out and measure its dimensions exactly. Mark these on the dirt so you know where to dig. Mark the height, width and the point where the top of the window well is going to rest. Ensure it will be exactly centered in relation to the window opening. You'll need to dig down about 10 inches where you intend to place the window well.

4. Dig the Hole

Dig a hole according to the dimensions of the window well. You might want to leave 5 or 6 inches on either side to make it easier to slip the well into the hole before you fill it back in.

5. Insert the Window Well and Confirm Measurements

Place the window well inside the hole, ensuring it's flush with the foundation wall. Grab your tape measure and double-check that it's centered and in the correct position before you make any permanent fixtures.

6. Check That It's Level

Using your level, ensure that the window well sits completely flat. Then, measure 3 inches down from the top of the window well (for the part of the well that will stay above ground) and place one side of the level at this position. Place the other side of the level on the backfilled dirt. Ensure that the mark 3 inches down from the top of the window well is level with the ground.

7. Screw Anchors Into the Wall

Once you've confirmed your window well is level on all accounts, you can grab your screws and begin the process of securing it to the foundation wall. The best way to do this is with concrete anchors and a hammer drill. Start by using the hammer drill to make just the top hole on either side. Then, use a hammer to tap the anchor into place.

8. Add a Gasket or Sealant

Use silicone sealant or a concrete expansion joint as a gasket to create a waterproof barrier along the sides of the window well.

If you're using an expansion joint material, cut two narrow pieces that are the same height as the window well. Pull the window well off the wall and place the gasket where the edges of the window well will meet the foundation. The anchor you already screwed into the wall should protrude from this gasket.

If you're using silicone caulking, place this in the same spot.

9. Secure the Anchor to the Wall

Put the window well back in position with the anchor through the top hole on either side. Use a bolt and washer to fix the window well to the foundation wall permanently. Add the rest of your anchors using the hammer drill to create appropriate holes. You can position these roughly one foot apart all the way down on either side.

Once the anchors are in position, you can torque the nuts and bolts to secure the window well. You should see sealant oozing out the sides of the window well or the expansion joint material indenting where the window well presses up against it.

10. Cut Away Excess Gasket

Depending on what kind of gasket material you used, you can cut away the excess parts of it that are visible on either side of the window well. If you used a sealant, a rag or damp sponge will do the trick for cleaning up the excess.

11. Add Drainage Rock

Once the window well is fixed into position, you can add drainage rock to the bottom of the window well. There are many types of drainage rock that will be suitable for use here. The purpose of drainage rock is to help any water that ends up in the window well filter down into the dirt below, preventing it from pooling in front of the window.

12. Backfill the Dirt

Begin backfilling the dirt on the outside of the window well to bring it level with the rest of the ground around the house. At this point, check if there's any protective coating on the window well. You can remove this.

Depending on the depth of the window well, you may be required by code to install a ladder for safety purposes in case of an emergency. Check bylaws for your residential area to confirm if this is necessary.

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Do Window Wells Need Drains?

A window well often has a drain connecting the well to a foundation drainage system. Many newer homes have a window well drain that feeds to drainage tiles on either side. Ensure your grading is correct to permit this drainage. You will need a drain if you regularly notice a significant amount of water in the window well.

How Deep Does a Window Well Need to Be?

A window well should be roughly 8 inches deeper than the window sill and approximately 6 inches wider than the window opening.

How Much Does It Cost to Install a Window Well?

The cost depends on the size of the well and the material you use. Window wells can cost as little as $18 or up to $379. Costs will remain extremely low if you choose to carry out the process yourself.

Is a Window Well Replacement Different Than Installation?

For a replacement, you will need to start by digging out the dirt surrounding the existing window well and removing it cautiously. You will also need to be careful not to damage the window. Then, follow the steps laid out above.

Since we’re all home now more than ever, being prepared for unexpected home repairs with a plan from HomeServe is important. Having a plan in place gives you peace of mind knowing that you can simply call our 24/7 repair hotline for covered breakdowns. See what plans are available in your neighborhood.