Basement doors are often narrow and, coupled with thin, steep staircases and low ceilings, moving a sofa down into the basement can be a tricky project. There are a few methods for accomplishing this task -- the best one to use depends on the dimensions of your sofa and the tightest space you have to get through on the way to the basement. Use a few special tricks to get a sofa to fit through any tight space.
Measure the three dimensions of the sofa. You want to know its height from the floor to the highest point on the back, its depth from the front to the back and its length from one arm to the other. Doing this before you get the sofa to the doorway helps you make a plan.
Measure the dimensions of the tightest space you need to get through on the way to the basement. If your basement has multiple entrances, measure each one. For example, many basements have both the interior stairway and an exterior entrance. Often the exterior entrance is wider or easier to navigate through.
Compare the smallest dimension of the sofa to the smallest dimension of the doorway. If the sofa is smaller than the doorway and you have enough space on either side of the doorway for the sofa length, then it will definitely fit. This makes the rest of your move easy and you can skip to Step 6.
Measure the distance from the bottom of the sofa to the top, ignoring the legs. If this is smaller than the doorway, remove the legs from the sofa to take off those extra few inches so the sofa will fit. Skip to Step 6.
Compare the sofa's length to the doorway height. If the sofa is shorter than the doorway, but its other dimensions don't fit through, you still might be able to stand it on its end and get it through the doorway by putting it through at an angle and rotating it halfway through the doorway. It is hard to measure whether this will work, so you will probably need to just try it.
Gather at least one other person to help. Ideally, with a heavy sofa, you should have a total of four strong people.
Remove the sofa cushions if possible and set them aside. Move the sofa to the doorway to the basement. Have half of the helpers go through the doorway and the other half stay on the upstairs side with the sofa. If you have an odd number of helpers, send the extra person down because people on that side have to handle more weight.
Orient the sofa so the dimension that fits through the doorway lines up with it. For example, if the sofa's height is the smallest dimension, rotate it so the back of the sofa faces straight up or straight down. If you will be standing the sofa on its end, do this now and orient it so the top back of the sofa will go through the doorway first.
Pick up the sofa and gently carry it through the doorway. If it is standing on end, push it through the doorway until the seat or arm of the sofa hits the door frame, at which point you should rotate the sofa until the bottom rear edge clears the frame. Then just carry the sofa the rest of the way through.
Go down the stairs one step at a time, with the people on the bottom setting the pace. If possible, have a spotter below them to let them know how many more steps there are and jump in to help if the sofa gets too heavy.
Position the sofa in the basement and reassemble it, including reinstalling the legs and putting the cushions back on.