Window blinds can be expensive if your house has a lot of windows. Because of the expense, it is common to take blinds with us when we move. However, the windows of the new home are likely to be a different size. With fabric and bamboo slat-type blinds, it is possible to add to the length so they can be reused in the new setting. Making these adjustments requires a few materials, but the finished blind may look even better than the original.
Turn your blind face-down on the work surface. You should see a header with two to four cords running down the length of the blinds. The cords will pass through a series of vertical rings and individually attach to a ring near the bottom of the blind. The ring will be mounted over a dowel that might be hidden by the liner, for a Roman shade. The ring will mount directly to bamboo slats for a slat-type shade.
Measure the length of the window with a tape measure and determine the amount of material you need to add to cover the window. Add 2 1/2 inches. Select a fabric that contrasts with your decor fabric and a liner fabric that matches your existing liner for Roman shades. Measure the existing width of the shade and add 1/2 inch for seam allowances. Cut your fabric with scissors.
Cut bamboo slats, threads and cords with scissors from the bottom of a second blind that is the same width. Add 3 to 4 inches above the length you need. Remove the slats from the cording above the length you need so you can tie the slats and cords of the bottom of the existing shade to the top of the new portion. Tie each thread and cord to its counterpart and add a drop of glue on each knot. Trim off the excess thread ends.
Sew a 1/2-inch seam allowance around both sides and the bottom with fabric face sides together for the Roman shade type blind. Clip your corners. Turn your fabric right side out. Fold the bottom edge up 1 and 1/2 inches and sew the folded section like a hem. You are creating a pocket.
Place the bottom of the existing shade fabric face sides together with the top raw finished edge of the new panel. There may be a dowel sewn into the bottom of the existing blind. Slide the dowel away from the bottom edge if possible to give yourself enough room to sew the two fabrics together along the bottom edge. If there isn't enough room, rip the bottom seam of the existing blind to gain seam room.
Fold the lining fabric to the inside 1/2 inch and hand-sew the lining to the back side of the seam and over the edge of the old lining with needle and thread. Measure the width of the blind and cut Roman shade tape to this length. Measure the distance between each dowel on the existing shade. Mark this distance on the new part of the shade from the bottom of the lowest dowel on the old part of the shade.
Sew the Roman shade tape horizontally across the width of the blind at your mark. Measure, mark and sew for each pleat section added by your new material. Cut a 1/4-inch dowel rod 1 inch shorter than the width of the blind and insert a dowel inside each pocket including the pocket you sewed along the bottom edge of the blind. Sew the ends of the pockets closed with needle and thread.
Cut a cord twice the length plus once the width of your blind for each ring positioned horizontally along the width of the blind (along the dowel). Untie your existing cords and note how they thread up through the ring above all the way to the top of the blind. Follow the cord across through eyelets. Remove your existing cords and replace them with the longer cords, following the same path for each existing cord starting at the new bottom ring in your blind extension section. All of your new cords should gather to one side at the top of the blind when you are finished.
Measure 8 inches from the last eyelet screwed into the bottom underside of the header board with the blind fully down. Add a cord condenser. A cord condenser is a device that converts many cords into one cord. Slip an acorn onto the single cord. An acorn is a cup-shaped device that slides onto the single cord and covers the knot. Tie a knot in the single cord. You are ready to use your lengthened blind.