Mudding Horizontal (tapered) joints

I can achieve 100% fill in a tapered horizontal joint, no recess and no mound, but I was told I should instead have the tiniest bit of a mound, and feather the mud back 10 inches from each tapered edge. What is the point of a tapered joint, if it's going to be treated like a butt joint? When applying a knockdown or orange peel texture, is that joint going to be visible after primed and painting the wall if it's a perfect fill in job flush with the drywall paper?

I put a lot of effort in two of the rooms to sand, mud, sand, mud to get a perfectly smooth and flat joint and don't want to excess mud and taper the joints if it's unnecessary - but I also don't want to have a problem after primed and painted.

Any input DIYers and Pros?

 

Drywall mud shrinks as it dries. So, if you wipe down a horizontal joint tight, using an 8" knife, for example, it will shrink and there will be a very slight dip when it has dried. These concave areas show up as a shadow line much more than a gradually overfilled joint would. By overfilled, I don't mean humped or crowned either. Its just a safe bet that if your horizontal joints are a very defined 6" wide white line, that they are likely underfilled... maybe not everywhere, but at least somewhere.

Texture should not be expected to cover a poor or inadequate job of filling and finishing.

 

I am aware there will be a concave or bowl from the tapered joint, but after 4 coats or so, the mud has shrank and the last layer is covering the joint and even some of the paper. Is the part where the mud shrinks the main concern, or the fact that it's a perfectly straight line that I may be drawing mud along?

 

If you've done 4 thin coats, it is probably filled. Take a 10" knife and stand it up on end over the joint. You should not see any gap anywhere. Then put one end of the knife in the center of the joint and the other end on the paper... again, no gaps, check above and below.

Horizontal joints do not need to be tapered out 10" on each side like butt joints do, no.

 

I have used my knife to check for light under it. It's flush with the paper. Like I said, I can get it flush with the paper. Each coat I fill in the joint and scrape the excess away. Each time less and less mud fill in the shrunken area. But now with it perfectly flat, am I good to go with texturing, or is it still better to have a wider joint with feathered edges?

I have ran into some issues while sanding, even using 220 grit finish paper, I get tiny little scracthes or hash marks. I can use a sponge but it take more time, cleaning the sponge out and messing with water... Should the little scuffs be removed, or do most people not worry about them after doing the last sanding job>?

 

How wide are your finished joints?

120 grit is generally fine enough for sanding j/c. The minute scratches are normally filled by the texture or paint. You might try shining a bright light on the wall and viewing it from an angle as that will often show you any defects in the finish [if they are there]

 

marksr, I am using the featherweight compound for ease of sanding. Even my 220 grit can show the scuffs in it, and 120 is okay except it's really easy to burn through too much mud and create a dip, or tear up paper around screws when sanding them.

My Butts are about 24 to 28" wide and my horizontal (tapered) range from some areas where I filled the joint multiple times until it was perfectly flat and only have mud inside the tapered edge which would be 6 to 7" wide while other areas I started trying out the method of putting excess mud on the joint and feathering the top and bottom meaning they are 12 to 14" wide. It's easier for me to just fill the joint and scrape off all the excess mud compared to trying to get an even taper. Also less sanding to just have the taper filled - but a couple people I talked to said they never do that and that it makes the seam visible after painting...

 

I usually finish bevel joints to about 8"-10" wide although the outer edges are ultra thin. 2' is usually a good width for butt joints.

How are you sanding the joints? are you using a sanding pole or at least a block of wood to keep the sandpaper flat? I like using sanding screens because they don't plug up as quick as sandpaper.

 

So you put mud on with an 8" and flatten with a 10" or just use the 10" knife with pressure on one half to feather the mud? I find it difficult to feather half the width of a knife without leaving a ripple in the mud.

I have a pole sander I bought with a foam base and a hand sander with a soft base also. I apply moderate pressure and sand either in small circles or a figure 8 to try and avoid hash mark lines from the screen. I, too, like the screens over paper because they last for ages and never gunk up. I saved my old 120 grit after I felt it wasn't very rigid for the finish sanding, but it still leaves marks in the mud.

I saw a video of a guy doing finish sanding and he referred to the last coat as the glass coat because it's smooth as glass. I know after I sand, even with gentle pressure, it feels a little course. I have areas that are glass smooth but don't recall if that was sanded or just a very clean mud job, haha. But I know after sanding with fine paper or mesh it's definitely not smooth as glass on the feel.

 

I usually tape with 3.5" knife, 2nd coat with a 6" and final coat with 10" knife.

I feel like you are over thinking it as minute scratches will get filled in with paint or texture.