# Question about Inside and Outside corners in Drywall repair work



## DIYusually (Jan 16, 2016)

I had some water damage in our house so we tore out the bottom 4 ft of drywall all around in the rooms. The studs and flooring have been well air-dried and now it's time to replace the bottom drywall.

My questions: after hanging the new drywall, when I get to the taping and mudding part, do I have to remove the old inside corner tape and the outside corner metal corner beads that remain in great shape on the top 4 ft of the original painted wall and run all new 8 ft inside corner tapes and all new 8 ft outside corner beads? Or can I just leave the corners in the top half of the walls alone and just try to transition the new corners in the new drywall in seamlessly?

I'd rather not have to go do that additional slight demo work on the existing corners and then also have to mud that too, but if people with more experience here say that's the best and only way to make for a visually seamless corner, then I will do it. Like I said, the current 4 ft top inside and outside corners show no damage now.

(Bonus question: it appears this house was originally built with the drywall installed vertically because I didn't come across any natural horizontal seams when I cut at th 4 ft high mark to remove the bottom section of drywall. I am going to lay my new 4'x8' drywall sheets in horizontally so the tapered long edges will be butting up against a full 1/2" flat butt surface of the bottom of the existing top half of the wall. Any special taping and mudding tricks or tips for this taper-meets-butt joint, or do I just build up the taper with mud and treat this like a butt joint?)

Thanks in advance, all!


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## firehawkmph (Dec 12, 2009)

If you are careful installing your outside corner bead, you don't have to tear out the top half. Make sure the bead is seated well, it should end up just slightly recessed compared to the existing with the mud on it. The horizontal joint should end up being treated like a butt joint. Feather it out wide and it should be fine.
Mike Hawkins:smile:


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## ToolSeeker (Sep 19, 2012)

They can be mated just a little more mud work to get them to blend.


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## Nestor_Kelebay (Jun 17, 2008)

Instead of installing new drywall, I would install a product made by the Georgia Pacific Company called Dens-Shield. It comes in 4X8 sheets in 1/2 inch thickness just like drywall and you can cut and install it with drywall screws just like drywall. But, it's highly water resistant so if the same water damage ever happens again, you won't have to tear apart your walls and start rebuilding all over again. You'll just have to mud and sand your joints and prime and paint. No biggie.

Also, if'n it wuz me, I would decide how tall a baseboard you want to use, and then have some spruce plywood ripped to widths about 1/4 inch narrower than your baseboards. Then, install your plywood strips first, then rest your Dens-Shield panels on the plywood strips, mark them, cut them and drywall screw them in place. By having plywood behind your baseboards, you can use much shorter (pronounced "smaller diameter") finishing nails to stick your baseboards on with. That's because without those plywood strips, your finishing nails would have to go through the baseboard, through the drywall and some distance into the bottom plate or studs in your walls. With those plywood strips immediately behind the baseboard, you just need to go through the baseboard to nail into wood.

Use construction grade spruce plywood because it won't be sanded on one or both sides to make it smooth, and that means it should be a full 1/2 inch thick instead of 7/16ths, which is what you get with sanded plywood.

So far as your semi-butt joints go, buy something called a "curved trowel". A curved trowel look for all the world like an ordinary 11 inch plastering trowel until you set it down on a flat surface or sight along it's edge and notice that the blade of the trowel is curved. It actually arches up about 1/8 of an inch in the middle. Since you hold the trowel at a comfortable angle when using it to spread drywall joint compound, a curved trowel allows a total newbie to spread a perfectly symmetrical "mound" of joint compound that's about 5/64'ths of an inch thick in the middle and tapers to zero thickness at both ends. That's more than thick enough to bury joint tape in, but not nearly thick enough to cause a visible "bump" on the wall, even if you have wall mounted light fixtures.

If it were me, I'd use a chemical set joint compound and a 3 inch wide taping knife to make a flat surface to apply fiberglass mesh joint tape to, apply your tape over that joint, and then use a curved trowel to bury the tape in joint compound, sand smooth, prime and paint. I'd probably also paint over that fiberglass mesh with diluted white wood glue as well. As the glue dries it'll bond the fiberglass mesh to both the drywall paper on one side of the joint and the chemical set joint compound on the other side of the joint. That'll ensure that the fiberglass mesh will carry any tension across the joint that would otherwise crack the compound on that joint. I'd be concerned that just applying fiberglass mesh tape over what you have would not make for a strong drywall joint. I'd fill it to start with a flat surface first, and then apply the tape.

Hope this helps.


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## Nestor_Kelebay (Jun 17, 2008)

Also, it occurs to me that Dens-Shield doesn't have contoured edges like drywall, so your horizontal joints will be butt to butt, and that lends itself well to simply applying tape over the joint and then burying the tape using a curved trowel.


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## DIYusually (Jan 16, 2016)

Thanks for all of your helpful input and recommendations, Nestor. I was not aware of such a thing as a curved trowel so I will get one of those based on your advice.

About your idea of using Dens-Shield, I had thought about doing something like that. But first a little more background of our "flood" incident: We got about 3 inches of water into the house for about 3 hours total. We were bailing like mad into plastic trashcans which we then emptied into the kitchen sink but we couldn't reduce the water level appreciably.

The water was on the hardwood floors for the 3 hours but the drywall didn't show any noticeable damage. The person who had rehabbed the house 15 years earlier following a major 3 ft high flood had ended up using high quality materials so we had 4 inch high stained and glossy (sealed?) oak baseboards throughout the house. The water level in our 3 inch "flood" never went above the baseboard and never contacted the interior wall side of the drywall directly.

A couple of days after the flood event, we started to pull the baseboards off and found only about 2-3 places in the house where the bottom of the drywall was a little crumbly but surprisingly almost all of the drywall was fine. The insurance adjuster suggested we cut out the bottom 2 ft of drywall to avoid any possible future problem from mold affecting the bottom of the drywall that must have gotten a little wet from water inevitably leaking under the baseboard molding. We decided to cut out the bottom 4 ft instead, thinking we would save time on the re-hab side by just working with standard 4 ft high open spaces.

I was considering using the Sheetrock brand UltraLight Mold Tough drywall since I thought it would at least be resistant to a 3-hr, 3-inch flood event if we had one again, and then I wouldn't have to cut it out if it got wet. The problem was that I would still have to cut that UltraLight Mold Tough drywall out if we got flooded because the insulation in the exterior walls would get wet and be an ideal place for mold if it wasn't cut out and thrown away, so that means having to cut the drywall anyway to get to the wet insulation.

I thought a workaround to that problem might be to use "Roxul" insulation which I was using for soundproofing the walls of the bathrooms, and use the Roxul also in the exterior walls as the insulation. It's not affected by water because it's made from volcanic rock (of all things!) and so is not organic and not conducive to mold.

That sounded like the solution - use Roxul insulation in the exterior walls, and UltraLight Mold Tough drywall over it; those two layers of material wouldn't be affected by future floodwaters. However, that still wouldn't be the answer to a way to keep from tearing open drywall after the next flood event - and the reason why is that even if the drywall and insulation were water-resistant, I would still have to open up the walls to air dry the studs and bottom plate that got wet.

So, my plan of attack now is to try using this UltraLight Mold Tough drywall on the sides of interior walls where I don't need to tear out both sides of the wall (i.e., I can just tear out one side to air dry the studs inside). I will pick the side of these interior walls to use the Mold Tough drywall as being those rooms where we did not have to remove the hardwood floor planks along the wall to help air out the floor. The rooms where we had to remove the first few rows of hardwood planking benefitted from having no drywall in place because that gave more working room to remove the planks.

As for your plywood tip to make it easier to finish nail the baseboards, I shouldn't have a problem because I bought a compressorless Ryobi Airstrike 15 gauge angled nail gun as well as the smaller Ryobi 18 gauge nail gun (both refurbished and at about half the retail price) to do all of the finish nailing of door and window casing, baseboard and shoe mold installation, and also re-nailing and face-nailing the hardwood floor planking that was taken out earlier to help the hardwood floor to dry. Both Ryobi guns are able to shoot 2" to 2 1/2" finish nails through even oak.

One final question I did have for you, Nestor - you recommended using fiberglass mesh tape. Why do I see many other places online where people tend to go with paper tape over fiberglass mesh? Is it because the mesh tape is thicker and requires more mud to cover it, leading to more and wider feathering work?

Thanks,
DIYusually


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## Nestor_Kelebay (Jun 17, 2008)

DIYusually said:


> One final question I did have for you, Nestor - you recommended using fiberglass mesh tape. Why do I see many other places online where people tend to go with paper tape over fiberglass mesh? Is it because the mesh tape is thicker and requires more mud to cover it, leading to more and wider feathering work?


No, it's because paper tape is a little stronger than fiberglass mesh. People who do a lot of drywalling will herald the advantage of paper tape because it's stronger. But, I've been on these boards long enough to know that most newbies find that working with paper drywall tape is much like fighting with a grizzly bear.

Chemical set drywall joint compounds dry harder and stronger than regular joint compounds, and so it's recommended that if you're going to use a fiberglass mesh tape, that you set it in a chemical set joint compound. The idea is that since the tape is a bit weaker than paper tape, you use a strong joint compound in the joint to compensate for the weaker tape.

There's also a new product out called "Fiba-fuse", which I have never used which the people in here are touting as being both strong as paper, but as easy to use as fiberglass. I would check out Fiba-fuse.

Also, from a strictly engineering point of view, I don't see why the disadvantage of fiberglass tape can't be compensated for by using two layers of fiberglass mesh over each joint. That SHOULD give you twice the strength of a single layer of fiberglass mesh. And, if one were to use a 3 inch paint roller sleeve to paint over that fiberglass mesh with diluted white wood glue, it would ensure that both layers of fiberglas mesh are bonded well to each side of the joint. That is, as that glue dried, it would glue the fiberglass mesh to the drywall on one side of the joint and whatever panel you use on the other side.

And, finally, I believe a bit of the pooping on fiberglass mesh tape is because people that are proficient at using paper tape consider fiberglass mesh to be the equivalent of Peel & Stick floor tiles; something that's made for DIY'ers that aren't skilled enough to do a quality job. But, I have yet to have anyone explain to me why two layers of fiberglass mesh tape properly bonded to the drywall paper with wood glue wouldn't result in a joint that's considerably stronger than paper tape.


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## Nestor_Kelebay (Jun 17, 2008)

Here's a picture of a curved trowel:










Now I believe this image was Photoshopped to exagerate the curvature of the blade. In the above picture, it looks like the blade arches up about 1/4 inch in the middle. On an actual curved trowel, it's no more than about half that, or 1/8th of an inch. That's what makes me think the image is Photoshopped, but the curvature at least serves to illustrate the difference between an ordinary flat trowel and a curved trowel.

On a normal curved trowel the curvature of the blade is so slight as to be unnoticable until you do something like set it down on a flat surface or sight along it's edge.

To see that curvature, place a straight edge (like a sheet of paper) on your computer screen so that it touches both the front and back corners of the trowel. You see how the blade arches away from that straight edge in the middle?

You can see how using a trowel like this over butt-to-butt joints would make easy work of burying your tape in joint compound without having to master the fine art of feathering your joint compound. And, because you hold the trowel at a comfortable working angle to the wall when using it, the curvature of the mound of joint compound you make is considerably less than the curvature of the trowel's blade.

(On one DIY TV show I was watching, the guy that was supposed to be feathering joint compound over a butt-to-butt joint ended up feathering it wider and wider until he ended up with a swath of joint compound about 4 feet wide, and I'm sitting there watching this thinking "WTF?" Whomever put that show together SHOULD have been aware of something called a "curved trowel" because what they're effectively doing is giving newbies really bad advice by telling them to feather out their joint compound that far; which is crazy.)


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## Nestor_Kelebay (Jun 17, 2008)

Here's an accurate picture of a curved trowel:










Notice that the distance from the blade to the straight line is widest in the middle and narrower at the ends of the trowel? That's how much curvature there actually is. (and that's why I believe the previous photo musta been Photoshopped to make the curvature more obvious)

It's very subtle, but the above trowel will make a mound of joint compound that's plenty thick enough in the middle to bury multiple layers of drywall joint tape in.


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## DIYusually (Jan 16, 2016)

Based on your advice and recommendation, Nestor, I actually did pick one of those up at the big orange box store the other day.

I'm going to start mudding my "test" bedroom (the smallest, least likely-to-be-viewed room in the house) today. Since that curved trowel was so expensive (about $19), I'm going to try to achieve similar results with the 6" and 10" blades I actually have from some other work first before unwrapping that curved trowel.

If it turns out it's taking too much time or I'm getting less-than-satisfactory results the "old-fashioned way," I will break out the "high-tech" curved trowel and let my DIY ego take a break....:wink2:


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## Nestor_Kelebay (Jun 17, 2008)

Here's a better idea:

Try using the curved trowel first.
And then see if you can do half as good a job using your straight tools.
That way you don't waste as much time proving to yourself that you can't.

You'll find that a curved trowel goes through an awful lot of joint compound, so you'd do well to stock up on joint compound. And, don't be afraid to thin your joint compound with water to make it easier to spread and work with.


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## DIYusually (Jan 16, 2016)

Nestor, can you explain at what step in the process to use the curved trowel. From the various YouTube mudding videos I've seen, the guys use a 4" or 6" knife to lay the first coat of mud on the joint, put the tape on that, embed the tape with the knife and some mud, and do some initial feathering.

Then on the second coat, they typically use a 10" knife, and a 12" knife on the third coat. By the time they use the 12", the outside feathered edges are 12-18" from the original joint.

With the curved trowel, I'm guessing I would still use the flat 4" or 6" knife to do the initial mud coat and to embed the tape making sure it's flat and against the two drywall pieces, and then switch immediately to the curved trowel to cover the tape and smoothly feather the first pass in one fell swoop. Is that correct?

And then I'm assuming I would still need the 10" and 12" knives to do a further feathering out on a second and third pass. Is that a good assumption?

(BTW, on one of the YouTube videos with a very quick and efficient pro doing the demo, he also suggested doing a power mixing and adding water to get a nice smooth pancake batter consistency for the first coat. I bought the same mixing paddle he had in the video and used in it a large Bosch rotary hammer drill I have and did the same mixing. However, I found myself kept adding more and more water. I must have added what seems like almost half a gallon of water when it was all said and done. 

I bought the 3.5 gallon premixed all-purpose joint compound in the box and mixed it in a 5 gal "Homer" orange bucket. I found it true what one guy said in the comments on the orange box store website about the mixer paddle - it's not sharp but it will still shave off pieces of the inside of the bucket into the compound mix. I tried to be as careful as I could not to hit the inside of the bucket with the mixing paddle but I must have a few times because sure enough, I found a few tiny half-inch orange plastic strands in the mud on the wall a few times.)


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## Nestor_Kelebay (Jun 17, 2008)

DIYusually:

Are you going to be taping a contoured-to-butt joint or a butt-to-butt joint?

If you have a contour on one side, I would fill in that contour on one side of the joint first with a chemical set joint compound, allow that to dry, and then use fiberglass mesh tape over the joint (or the fiba-fuse stuff people were recommending).

I've never used paper tape, so if you're wanting to use paper, I really can't advise you because I have no experience with it. Also, if you have a contour on one side of the joint, you'd need to fill in that depression so that the tape is flat over the joint. That's the only way the paper will carry tension across the joint; it has to be laying flat over the joint for it to be effective in carrying tension. I don't think any kind of tape (paper or fiberglass) will work properly if you apply it across a joint where you only have a contour on only one side of the joint so that the tape isn't laying flat. Better to fill in the contour on the one side and lay the tape flat over the joint.

Dunno if that answers your question or not?


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## DIYusually (Jan 16, 2016)

I am actually doing both types of joints, contour-to-butt and butt-to-butt, because I have the original drywall on the top 4' of wall and I've just hung the new drywall sheets in horizontally below them. 

I earlier thought that the original drywall was installed vertically because when I cut out the bottom 4 ft, I rarely cut into a tape joint which would have been at that height. However, last night when I was looking at the cut bottom edge of the original top 4 ft of drywall on the wall with a flashlight, I noticed that at the cut line the original drywall was about 5/8" thick and there was about 1/8" of hardened white joint compound making up that additional thickness for what was clearly visibly 1/2" drywall.

It was like looking at a cross-section of a geological cross-section! By looking at that cut edge from the bottom, I figured out that the existing drywall was originally hung horizontally because what I was looking at with the flashlight was where the original tape joint was built up at a tapered long edge. (Now, why I didn't see much tape when I cut the original drywall at the 4 ft height is still a little mystery - maybe I was just slightly off on my cut line and missed hitting the taped seam.)

Anyway, so what is now my horizontal contour-to-butt joint is because the top piece area is what was built-up tape joint originally. So not only do I have to build up the contour taper of the new bottom piece of drywall as you suggested, but the top piece I'm trying to match to is slightly thicker than 1/2" since it is the original built-up tape joint!

You suggested using some chemical set joint compound to do this build-up at the contour area; I didn't have any on hand and had already started doing the mudding for the day before I read your post so I just used more of the all-purpose joint compound I was using for everything else. Do you think there will be a problem other than it will just take overnight to dry and harden? 

What I did was build up the contour to match the "butt" top side and then added the tape. So I did both the build-up and then the tape embedding at the same time (and yes, I added the paper tape after doing the build-up so the tape is laying about as flat as is possible).

My question is, other than longer drying time, is there any inherent strength problem by piling on about a 5/32" thick layer of all-purpose joint compound all at once and expecting it to dry hard as well as it does in thinner layers?


Finally, no, you really didn't answer my other question about using that curved trowel - I was just wondering at which step do you use it in the process? After using the 4"/6" knife to put down the initial bed coat of mud and pressing in the tape? Then do you use the curved trowel at that point to put down the first feathered layer?


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## Thunder Chicken (May 22, 2011)

DIYusually said:


> My question is, other than longer drying time, is there any inherent strength problem by piling on about a 5/32" thick layer of all-purpose joint compound all at once and expecting it to dry hard as well as it does in thinner layers?


Don't do it all at once. All-purpose JC shrinks like crazy and will crack to pieces if you apply it all at once. Only apply it in thin layers and let them dry thoroughly before recoating. You want to feather this out anyway, so more thin coats will leave you with a smoother finish. I'm not sold on the need for a curved knife; this can be done with a flat blade with multiple feather coats. I use a couple of 10" knives, 6" ones in fiddly corners and other tight spots.

Hopefully a pro will come along and tell you about setting plaster / hot mud, which might let you get this filled and taped in one pass. I don't have any personal experience with it, but it sets much faster and harder and doesn't shrink near as much as all-purpose. It comes as a powder that you mix as you use, usually has a working time in tens of minutes, some up to an hour. It's available in most box stores.

Also, use paper tape. It's really not that hard to use. It is nice and strong, thin, and is much easier to blend in than mesh. One thing you must be sure to do is to dampen it (moist, not dripping wet), either with a little water or with a pre-coat of joint compound. What I like to do is coat the area on the wall where the tape will go down with a layer of mud (doesn't need to be smooth here). I then cut the tape to length and run it under a faucet or dunk it so it is all wet. I let it sit for a minute, then wipe the excess water off and place it on the mud. I then hold one end down with a knife and draw another knife sharply along the tape, pushing it hard against the seam and squeezing out most of the joint compound. That tape will be flat flat flat and, when dry, you'll be amazed at how strong it holds. You can't peel it off the wall because it will be part of the wall.

Once the tape is down and dry, you can apply a second coat of mud to either side of the tape, filling in the small ridge at the tape edge. When that is dry, go out another blade width and put another thin layer down on the edge of the last layer. Always use a sharp knife and push it hard against the wall; you want nice thin flat layers. You're not making an adobe house, you're trying to make smooth flat walls.

If you do a good job with the drywall and the mud you won't have to do much sanding if any.


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## Nestor_Kelebay (Jun 17, 2008)

DIYusually said:


> I am actually doing both types of joints, contour-to-butt and butt-to-butt, because I have the original drywall on the top 4' of wall and I've just hung the new drywall sheets in horizontally below them.
> 
> I earlier thought that the original drywall was installed vertically because when I cut out the bottom 4 ft, I rarely cut into a tape joint which would have been at that height. However, last night when I was looking at the cut bottom edge of the original top 4 ft of drywall on the wall with a flashlight, I noticed that at the cut line the original drywall was about 5/8" thick and there was about 1/8" of hardened white joint compound making up that additional thickness for what was clearly visibly 1/2" drywall.
> 
> ...


No, I don't see a real problem there. All Purpose joint compound has glue in it to make it stick better to the drywall and dry harder. I think you should just leave what you've done alone, but I'd try to use a chemical set joint compound for the rest of your work.



DIYusually said:


> What I did was build up the contour to match the "butt" top side and then added the tape. So I did both the build-up and then the tape embedding at the same time (and yes, I added the paper tape after doing the build-up so the tape is laying about as flat as is possible).


See if you can cover the paper tape with the curved trowel. Just set the curved trowel against the wall and see if that ridge where the tape is is too high for the curved trowel or not. If you can cover that tape with the curved trowel, then I'd do that as your next step. If the ridge sticks up too high for the curved trowel, then I think your only option is to spread joint compound over what you have and feather edge it as best you can.

You could also buy a tool called a "rasp" to take that additional 1/8 of joint compound off, but that may be quite a bit of work depending on how much of it there is to do.



DIYusually said:


> My question is, other than longer drying time, is there any inherent strength problem by piling on about a 5/32" thick layer of all-purpose joint compound all at once and expecting it to dry hard as well as it does in thinner layers?


No problem so far as I know. I've applied both base coat plaster and joint compound in much greater thicknesses than that without a problem. It does take longer to dry if you apply a thicker coat, but that's the only drawback so far as I know of.



DIYusually said:


> Finally, no, you really didn't answer my other question about using that curved trowel - I was just wondering at which step do you use it in the process? After using the 4"/6" knife to put down the initial bed coat of mud and pressing in the tape? Then do you use the curved trowel at that point to put down the first feathered layer?


If the curvature of the trowel is sufficient to cover the 5/8 inch thick ridge in the joint compound at your joint, I'd use the curved trowel to bury your tape as soon as you have your tape laying as flat (or as flat as you can get it) on the wall.

I'm concerned that the 5/8 inch thickness of the upper portion of the drywall will be too much for the curvature of your curved trowel to cover. Taking that extra joint compound off would be a lot of work, especially if it's painted, so I'm thinking you might just need to smooth the joint compound out over this joint as best you can freehand.


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## DIYusually (Jan 16, 2016)

Thanks for the input, TC. Well, since I already started mudding in my "test bedroom" this morning, I've already violated your first bit of advice on not putting all that mud on in one pass. I guess I'll see tomorrow how it turns out. So far tonight I've seen some microscopic air bubbles in some areas but no drying cracks yet.

I haven't taken off the wrapper on the curved trowel yet so it's still in returnable, refundable condition. However, I was thinking of giving it a shot tomorrow because with the wall setup I have, I need to get a lot of mud on the horizontal joints because I'm dealing with a factory tapered edge there. I was using a 4" taping knife to try to pack the mud on, but because of its small size, I have to keep reloading it from the pan quite often. (Oh wait, you were telling me _not_ to pack it all on in one pass...)

About the "hot mud," a lot of YouTube instructors mention it but don't exactly explain what it is. When I was on the homedepot.com site to plan on what I was buying, I read about the various joint compounds and one commenter explained that "hot mud" was called that because it dried via chemical means rather than air drying. Another very helpful commenter posted that a newbie should use and practice on regular all-purpose joint compound to get the techniques down before attempting to use any of the hot mud options. That's because although it may say "45-minute working time," in reality it's more like 30-35 minutes when it starts to harden up, so if you're not already experienced and know what to do, a lot of that hot mud stuff may go to waste on you

About the paper tape, yes I did the same process of laying down some mud, and then embedding the tape in it - that was the method in the best YouTube video I watched. I did wet the paper tape between my fingers before taping the corners for better adhesion and workability but did not do that for the long horizontal seams. I think I will do that (using an extra plastic mud pan I use for painting as a "water bath") for the horizontal seams going forward because it seems to really make the tape stick to the mud.

Learned a lot today from the experience, and appreciate picking up more tips/tricks/insights from this forum discussion! Thanks.


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## DIYusually (Jan 16, 2016)

*"You could also buy a tool called a "rasp" to take that additional 1/8 of joint compound off, but that may be quite a bit of work depending on how much of it there is to do."

"I'm concerned that the 5/8 inch thickness of the upper portion of the drywall will be too much for the curvature of your curved trowel to cover. Taking that extra joint compound off would be a lot of work, especially if it's painted, so I'm thinking you might just need to smooth the joint compound out over this joint as best you can freehand."*


Yesterday, I had tried to power sand down that 5/8" thickness of the top, existing drywall where it was going to meet the tapered edge of a new piece of drywall but didn't get much results. I think the sandpaper grit was too fine (100-120) but that was all I had on hand. I may try a rougher grit to see if this is a worthwhile option to pursue, but truthfully speaking, the horizontal joints don't look too bad tonight as they're drying - still pretty flat at this stage. Even sighting down the wall with a strong LED spotlight shining back along the wall, the wall doesn't have any obvious "tape bulging" area yet so I might be okay.

I may yet try your curved trowel idea, Nester, just for the one-pass time savings alone.


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## Nestor_Kelebay (Jun 17, 2008)

DIYusually said:


> Thanks for the input, TC. Well, since I already started mudding in my "test bedroom" this morning, I've already violated your first bit of advice on not putting all that mud on in one pass. I guess I'll see tomorrow how it turns out. So far tonight I've seen some microscopic air bubbles in some areas but no drying cracks yet.


I add dilute white wood glue to my chemical set joint compounds to make them stick better and dry harder and stronger. My experience has been that the only time my joint compound will crack is when I add too much glue. I think that's because the glue shrinks as the joint compound dries, but so far at least, the joint compound has never cracked so that it's let go of the surface it's stuck to; it only cracks in the middle as the joint compound shrinks, so that you can just fill in that crack with more joint compound.



DIYusually said:


> About the "hot mud," a lot of YouTube instructors mention it but don't exactly explain what it is. When I was on the homedepot.com site to plan on what I was buying, I read about the various joint compounds and one commenter explained that "hot mud" was called that because it dried via chemical means rather than air drying. Another very helpful commenter posted that a newbie should use and practice on regular all-purpose joint compound to get the techniques down before attempting to use any of the hot mud options. That's because although it may say "45-minute working time," in reality it's more like 30-35 minutes when it starts to harden up, so if you're not already experienced and know what to do, a lot of that hot mud stuff may go to waste on you


"Hot mud" is a joint compound that CURES as a result of a chemical set. All joint compounds DRY, but joint compounds that have a chemical set have a chemical reaction that kicks in after the joint compound powder has been mixed with water. If you get a joint compound that kicks in after 90 minutes, you'll have plenty of time to spread it and smooth it before that chemical set kicks in. When the chemical set does kick in, the joint compound will still be moist, but it'll be stiff so that you can't spread it anymore. You can't sand it without plugging up your sand paper or sanding screen, but you can scrape it down with a sharp paint scraper and apply new joint compound over top of it.

Regarding the terminology, people in the trades tend to use terms that aren't technically accurate. "Mud" is joint compound even though there is absolutely no soil in it. "Mud" will not dry to form top soil. "Hot mud" is joint compound which has a chemical set to it that kicks in a certain time after it's mixed with water. "Hot mud" is no warmer than a regular joint compound that dries entirely due to the evaporation of the water in it.


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## Nestor_Kelebay (Jun 17, 2008)

DIYusually said:


> ... but truthfully speaking, the horizontal joints don't look too bad tonight as they're drying - still pretty flat at this stage. Even sighting down the wall with a strong LED spotlight shining back along the wall, the wall doesn't have any obvious "tape bulging" area yet so I might be okay.


That sounds great.

I was concerned that the extra 1/8 inch of joint compound on the top sections of drywall were going to prevent you from using your curved trowel to finish that joint quickly and easily.


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