Whether you're installing heavy, mirrored closet doors or lightweight bypass doors, the key to mounting guides or tracks to concrete is using masonry anchors. Concrete screws are easy to install and suitable for most closet door projects. They are similar in appearance to wood screws, but require predrilled starter holes to bore into masonry surfaces. Careful measurements and layout will ensure that the screws line up with the track and the installed doors open and close smoothly.
Remove the sliding door track from the door hardware kit. Measure the track's width and the depth of the closet door opening with a tape measure. The opening's depth is the distance between its front and rear. For example, in a wall constructed of 2-by-4 lumber, the depth is 3 1/2 inches.
Subtract the track's width from the wall's depth. Divide the difference by 2. The result is the desired setback of the track from the opening's front and rear. Setting the track back from the wall's front and rear by this dimension aligns the track at the opening's center.
Mark the front and rear setback on the concrete floor on both sides of the closet opening. Measure the distance between corresponding front and rear setback marks; it should equal the track's width. Pull a chalk snap line between the two front marks, stretch the line taut and snap the string to create a line between the marks. Create a similar chalk line between the rear marks.
Lay a builder's square on the floor. Butt the short side of the square against the interior face of the opening at either side. Align the square's long side with one of the chalk lines. If the square's short side remains parallel to the interior face of the opening and the long side remains parallel to the chalk line, the chalk line is perpendicular, or square, to the opening's face.
Check for square at the three remaining intersections between the wall and the chalk line. Adjust measurements and layout lines where necessary; the lines must be square with the opening for a successful installation. Measure the width of the closet opening. Mark the width on the closet door track with a pencil. Cut the track to size with a hacksaw. Align the cut track with the chalk lines on the floor.
Press a pencil through the track's screw hole openings and use it to transcribe the holes' locations onto the concrete floor. Remove the track from the floor. Attach a masonry bit to the drill. Wrap tape or install a drill stop around the bit's shank to indicate the desired drilling depth, which equals the length of the screws' shanks minus the height of the track. Set the drill to the driver setting and bore holes through each mark, stopping at the depth indicated by the tape or drill stop.
Clean concrete dust from the holes with compressed air or a stiff-bristled brush. Attach a driver bit to the drill and set the drill to the driver setting. Align the track with the chalk lines and starter holes. Use the drill to drive concrete screws through the track's holes and into the starter holes. Drive the concrete screws until their heads grip the track and secure it to the concrete floor. Repeat the track layout and anchoring procedure for the top track and hoist the sliding doors between the tracks to complete the installation.