What joint compound should I use in the flat boxes?

Whether you are completely new to finishing drywall, or whether you are making the transition from finishing by hand to using automatic taping tools, this article is meant to give you some basic pointers on the pros and cons of different types of joint compounds.

What are you used to?

If you have already been finishing by hand, when making the switch to automatic finishing tools, you can utilize pretty much whatever finishing system you used prior. You won't have less options, you will just spend less time doing it!  We will go over pros and cons of light-weight compounds, mid-weight compounds and full-weight all purpose compounds. But first let's address the most common question we get on this topic...

Can I use set-type compounds in my flat boxes?

The short answer is yes. We know of plenty of guys in the field who have used set type compounds in their boxes (including myself), and even in their automatic tapers. You definitely want to be sure that using set mud will actually help your productivity, and you want be smart about how you do it as these tools aren't cheap. Here are a few pointers to help do it successfully:

  1. Use plenty of lubricant to keep the compound from adhering to your tools, 
  2. Have a hose available on site where you can spay the tools off, rather than trying to clean them by hand in a last second scramble.
  3. Know well the working times of the compound you ae using, and also know what can affect those working times (heat, hot water, wind, etc.).

You should also be mindful that just because set-type compound is hard, it doesn't mean that it's dry. Set-type compounds such as Sheetrock DuraBond, Sheetrock Easy Sand, or ProForm Quick Set Lite all have an accelerant in them to help them harden fast, but applying a second coat over the top of hard, but still wet compound can cause air bubbles in you finish coat. It's also important to know the difference between some of these set type compounds. We often hear guys in the field refer to Sheetrock Easy Sand, or ProForm Quick Set Lite as "Durabond" or "bond". Sheetrock DuraBond is completely different than the other light-weight set type compounds. According to Sheetrock's website, DuraBond  is specifically designed for high humidity resistance. This makes this compound especially resistant to water, and extremely difficult to clean off should it set up too fast on you. Since you need to clean your tools fast and thoroughly when you use set-type joint compound in them, we highly recommend that you not use brown bag durabond in any of your automatic taping tools.

What about full-weight, mid-weight and light-weight compounds?

  • Full-weight compound is nice in that it provides a harder, more scratch resistant finish than mid-weight, or light-weight compounds, and it also has a longer working time before it skins over than lightweight mud. The downside to it of course is that it's heavy. It's also hard to sand, and it shrinks significantly more than mid-weight or light-weight compounds. This will mean you will more than likely need 3 coats to fill and finish a flat joint.
  • Mid-weight compounds are designed to be a "middle of the road" option providing some of the hardness of full-weight and some of the ease of working you find with light-weight.
  • Light-weight compound is nice in that it's low weight creates less wear and tear on you body, and it's also easier to sand. It also shrinks significantly less than mid and full weight compounds, which means if you have your box settings dialed in, you can apply 2 coats after tape, and be done! The trade off is that because it is soft, it can scratch more easily. This can create difficulty on high traffic commercial jobs that sit unprimed for a long time.  

Some guys use a lightweight mud for their bed-coat (after tape) to get the benefit of low shrinkage that lightweight compound has to offer, and then apply a finish coat (or two) with mid-weight or full weight to get the harder, slicker surface finish.

All things considered, what joint compound you use for your flat boxes, as well as for coating your angles will come down to what finishing system you have proven to be effective in your working environment.