I know my view is not held by everyone but I have good reasons. The truth is, it has its place, but not on your drywall seams. Though, people who have used fiberglass tape instead of paper tape for drywall taping have helped me make a living. As a renovator and someone who has taped a ton of drywall, I have made a lot of money over the years repairing drywall seams taped with fiberglass. Thanks, folks.
Why not? Drywall seams need a rigid tape to stay closed, especially over butt joints. The fiberglass taped seam will wiggle ever so slightly and then some time down the road after finishing, all of a sudden a hairline crack develops right down the middle of the joint. The tape isn’t broken. It’s just that the drywall mud overcoat is not rigid enough or tough enough, to add the strength necessary to permanently solidify the joint.
How do I know this? Well, I have noticed that on the recessed edge drywall seams they tend to stay taped better. With those seams, the mud overcoat is thicker because it is filling the valley where the tapered edges of the drywall come together. You get some extra toughness.
I understand why people like the fiberglass tape. You can Slap it down on the crack and mud it up. No blisters, etc. It is easier to use, especially for the novice taper. And every do-it-yourself website and magazine article promotes it. I also understand that it is harder to learn to use paper tape properly. For the newcomer to drywall taping, there are issues of laying the mud on evenly, wiping the tape down properly, avoiding humps on the butt joints, and so on. These are learnable skills, and they pay back big when the job is finished and painted. Nothing is more irritating then living in your new addition or renovation and seeing cracks developing in your walls or ceilings.
As I said in the beginning, there is a place for fiberglass tape. First of all, it is the tape of choice for plasterboard seams under veneer plaster or two coat plaster. This is what it was developed for in the first place. It works very well in this setting, because veneer plaster is far harder and tougher than drywall compound.
There is also a place to use fiberglass tape in the drywall trade, and that is in the repair end of the business. Around doors and windows, cracks in the drywall are common. This is caused by a little extra movement in the framing right there. When I repair such cracks, I want some extra help in keeping it look good.
What I will do is use short pieces of fiberglass tape, maybe three inches long or so and place them in a bed of mud across the crack. I wipe out the excess mud, just as I would with paper tape. When this first layer of tape is dry, then I lay down a line of paper tape right across the fiberglass and centered on the underlying crack. Now I have double insurance: the glass for lateral strength and the paper to keep it tight to the surface. This usually takes care of such cracks, or any cracks you are particularly concerned about. Don’t forget two or more over or topping coats. I will do the same operation or something similar on bad plaster cracks.
I have talked about the importance of the toughness of the compound you use. For this reason, I like “hot mud” or a quick setting type joint compound as it is more like plaster for strength. If you are unsure of yourself and your speed, it would be good to use a quick setting compound with a longer setting time, like an hour or 90 minutes. Mix small batches and don’t forget to wash your tools and pans well between batches. Though it works well and is tougher it is also harder to use and get a smooth job. Many times I will use regular mud for the tape and the last coat and use the quick setting mud in the middle.
