# Butt joints - Floating issues



## Joeynor (Jun 5, 2021)

Hi guys!

I just signed up after lurking these forums for a while, and they have been a huge help for me as a homeowner currently remodeling half of my house.

The problem:
I have a wooden house (with wood studs all over), and after mounting drywall I have quite a few joints were the plates aren't perfectly level, as when I put a 12" knife across it rocks slightly. I got a bit discouraged by that, and realized this will be a lot more tricky than I anticipated. 
Anyway I'm working to get the hang off floating butt joints and the misaligned factory joints out so they become invisible to the eye, but I have a hard time getting the result I want. Before and after sanding I still find the knife rocking across the joint, only to a less extent than before, and conclude I have failed at floating them out properly (even though I can't feel the joint/bump with my hand).

This might be a stupid question but I wonder if the goal really is to end up with a joint where the knife wont rock? I mean, the bump will be there no matter what one does, its just a matter of visually hiding it to the eye?


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## Tonydif (May 8, 2021)

Goal is to make butts smooth + flat, not flush.

From beginning, don't slam butt joints together, it pushes them down a bit. Also, slice the factory edges, as they slightly lift

When coating butts, go wide,. Double your trowel size with each coat. Feather edges first, then flatten middle barely covering tape. Sand, repeat, sand, repeat. Don't need a big glob of filler on butts, tape is only paper thin...fill sides of tape.

A hump trowel on first pass is a DIYers best friend. Bend an old trowel over stove.


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## Joeynor (Jun 5, 2021)

Thanks @Tonydif 
I think my mistake then is that I've been trying to make the butt joint a long/wide "arc". What I understand from the videos I've seen and your reply I should be making a flat section just barely covering the tape in the middle, and go another trowel width out on each side of the flat area and feather those edges. 

Not sure what you mean by slicing the factory edges though?


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## Tonydif (May 8, 2021)

Correct, no heavy arc, just a gradual flat fill.


The edges of drywall (sheetrock) have the slightest delaminating of the paper. Causes a fine lift and sometimes gets loose. Take a sharp knife and cut that paper off. Some call it " V-ing " the butt. If take your finger and swipe that edge of sheetrock, you'll feel the paper face move sometimes....this loose paper always shows itself after tape, fill and paint.


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## Joeynor (Jun 5, 2021)

Oh yes, I've been doing that luckily. I've also prefilled after V-ing the butts prior to taping so hopefully they wont crack!


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## Njene (Jun 5, 2021)

Use fibafuse on butt joints instead of paper or mesh tape
fibafuse is super flat and actually embeds or fuses with the mud giving you the flatest taped joint possible


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## picks drywall (Apr 13, 2021)

youll need to go a lot wider than 2 knives if they really bad. i have tamed some you could put fingers under the blade. use 45min. and just keep coating and checking. never be flat but you make the illusion that it is. sometimes for noobs its easier to run both sides then next coat fill in middle. it allows you to see how thick your coat really is.

your "arch" thinking is correct but the peak needs to stay thin. it is actually a very gradual arch your trying to achieve. 

this is a good short example of how it should be run. he uses 3 times the knife strokes that he should need though. and i dont sand between coats if regular mud. fast set i scrape lap marks before dry.
how to run a but joint - Bing video

man i had to weed threw many incorrect videos to find this one. lol hope it helps ya


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## Pinkalink (Mar 19, 2017)

Butt boards are a thing, good option if you have trouble floating out a butted seam.


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## Yunggranmassa (Oct 9, 2021)

Start out running each side of the tape with a 10" knife first, let it dry, then run a 10 down the center to cover the tape & pull it tight. Brush everything off with a sanding pole once it dries.
Then skim them using a 12" knife. Start by loading each side again keeping the edges of the knife along the spine of the tape this time, & pull 2 even sheets of mud the width of your knife covering the entire butt joint. Usually where the edges overlapped pulling one side then the other, a line of mud up is pushed up along the center. Cut the edges of across the top and bottom, cut the edges where mud meets paper, then cut down the centers on each side you loaded & don't worry about it if a smaller line is pushed up again as long as it's in the center. Wipe the mud on each side and pull either it top to middle then bottom to middle, or vise versus, but leaving a "lap mark". Pull it relatively tight on each side so that your leaving some mud about 4 inches in from the centers where the tape is, & roughly about 4 inches off from the edges cut against the paper. You should be able to see about a 4 inch dead space where mud was left which is roughly going to be down the sides where the first coat met paper. Sometimes there is still a faint line of mud pushed back up to the center again, & you can re-cut the edges along the center on each side of the butt joint. Then wipe both sides one last time & lay the knife closer to flat as you pull so the knife isn't taking all the mud back off. You want to leave some, but you don't want to leave any in the center or leave a hard edge on the paper.
When that dries the goal is to hopefully be able to stand a 12 over the center and the edge of the blade stand dead flat to the face of the mud. Also check each side of the butt joint by standing the knife over the mud with the edges of the blade from the center out. You want to see the edge of the knife stand against the mud on each side without seeing a small gap of light grinning through any space between the knife meeting the surfaces; but also, you should be unable to rock the blade back & forth over both sides as well as the center. This is not going to be easy the first several times, but it is best to go ahead and learn the habit of running both sides at once.


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## Thepelletier (Nov 27, 2021)

But joints are hard. It took me 5 years to figure out how to do them right. Especially renovation massive butt joints. You need a professional


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## picks drywall (Apr 13, 2021)

Thepelletier said:


> But joints are hard. It took me 5 years to figure out how to do them right. Especially renovation massive butt joints. You need a professional


you got that rite. i have used 2 guys, 2 buckets of 45, and an 8' 2x6 to float a couple monsters in the past. lol


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## AmoryDonawa (4 mo ago)

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