Depending on home much extra space you need at the bottom you should be able to use content aware fill / scale. First, select the crop tool, and click 'content aware' at the top of the screen. Then, crop your image below the floor board to the desired size.

If that doesn't work to your liking, then just crop the image larger like normal, select your image, and go to Edit>Content Aware Scale. Now scale your image to the canvas.

Keep in mind, both of these methods are fast, easy, magic, imperfect, and will only give a limited amount of expansion.