Step 1: Make Test Cuts

Determine the location for the in-floor storage cubbies. Use a circular saw with the blade set at 3/4" (a standard subfloor thickness) to cut a hole in the floor to see what's below. Be careful not to cut into the floor joists. In this project, Karl found a second layer of flooring material, widely spaced floor joists and old insulation between the joists. Insulation can be removed or pushed aside to accommodate the storage cubby; steer clear of any electrical lines.

Step 2: Cut the Cubby Hole

Having a small hole in the floor makes it easy to determine the location of the floor joists and any wiring or other utility lines that may be in the floor. Cut a hole in the floor between the joists the desired size for the storage compartment, being careful not to cut through the ceiling below.

Step 3: Build the Box

Make sure the hole in the floor is squared off, then measure it to get the dimensions for the storage box. Cut 1/2" birch plywood to the desired dimensions and assemble the box with wood glue and nails.

Tip: Build the box slightly smaller than the opening in the floor. This will give some extra "wiggle room" for shimming the box into position. Paint the inside of the box for a more finished look.

Step 4: Check the Fit and Install the Box

Slip the box into the hole. Check the fit and determine if shims will be needed (Image 1).

Add wood shims and spacers to the hole so the storage box will be level and lined up with the hole. Position the box so that the top of the lid will be level with the top of the subfloor. Use long screws to secure the spacers, shims and box (Image 2).

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    Image 1

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    Image 2

Step 5: Attach the Lid and Cover the Box

Use a drill with a Forstner bit to make a hole in the lid large enough for a finger. Slip the lid onto the box.

With the boxes complete, the floor is ready to be covered as desired. Karl used carpet tiles to give the floor a soft, welcoming feel –without blocking access to the hidden storage.