Cutting Fiberglass Doors - Is it possible?

Door is too low

Occasionally you will find that your new fiberglass door is having problems clearing the floor space when it swings open. Many modern doors come prehung so all you need to do is fit it into the opening. However, some builders will not take into account that there may be rugs or mats on the interior, causing them to hang the door too low.

Can you cut a fiberglass door? Maybe

Can you cut a fiberglass door? The answer is a resounding maybe, and only if you're skilled enough to do major cutting like this. Directly cutting fiberglass is mostly not a good idea because doing so exposes the composite layers of the door.

However, certain fiberglass doors have a solid wood border which allow them to be trimmed up to an inch or so. These doors can be cut. But because of the weight and size of a door, you're going to have to tough out a big job manuveuring it onto your table and getting that saw under or over the door. A handy circular saw may be the best of this kind of job. After trimming the door down, be sure to treat it as you would with any new wood exposed to the elements. Smooth out the edges and put on primer and finish.

Raising the opening

You may not be able to cut the door directly for some reason. If so, consider cutting the opening itself if it's made of wood. You will need to remove the door from its hinges. At the top of the opening is something called a header jamb. Remove that so you get to the wood opening. This is the thing you will thin out. After removing whatever head you need, you'll have to replace the header jamb. Since the opening is slightly taller, you can shift the hinges up and remount the door for that extra space to accomodate rugs.

Raising the rough opening

Finally, the last option is to change the installation height of the door. This is a big job and requires removing the entire door system, including the frame. This leaves the rough opening of the wall of the house. The rough opening can be increased in height, assuming that the top is made of wood and not something like stone or brick.

After raising the door, the threshhold space will have also increased. Be sure to fill it with a nice piece of wood.