What to do about drywall seams cracking ...AGAIN!

[Robert Macy]

how to repaire [and prevent future cracking] WITHOUT adding a big LUMP to the seam?

The wall run is around 60 feet and 10 feet tall. the junction right in the middle is wanting to crack. Trying to keep from forming lumps on the wall, I cut down, used paper tape with a layer of mud under and a layer on top. [Many may remember the problems I had posted earlier. I tried to wet the tape first thinking of wall paper and how that shrinks to fit, but wetting CAUSED the paper to 'slide' as it dried and thus a crack, so in response I took all that out and did it again with dry paper tape, which did work better. Only had the tiniest of hairline crack form all summer long only about four feet of run on the wall only.]

Well this winter as we isolated that section of the house - meaning cooler temperatures and probably contracting drywall sheets, the crack(s) opened up with a vengence! I mean over 3 mil separation!, but worse the crack is the full floor to ceiling AND even now goes up along a ceiling section which I never had trouble with before. I suspect in the heat of the summer the crack will close back up, too.

Yes, I know houses change shape with time, but this seems too much to be caused by 'settling'. My conjecture is is that this is more caused by 'flexing'. Oh yeah, the seams are ON a stud(s), so there should be no reason for movement there.

So, my question is How do you repair/prevent cracking at drywall seams WITHOUT creating a huge lump on the surface? I already have built up 1/8 inch thick to ++ on these stupid seams.

[Frank]

I've used fiber glass tape, looks like screen, on cracks around door frames that kept coming back. OK today.

[trader4]

I don't think the thickness is going to do much. There isn't much tensile strength to drywall compound. If the drywall moves, it's going to crack. And it sounds like the movement is related to temperature and possibly humidity changes. You say the room is "isolated". What does that mean and how cold does it get? For small cracks that are persistent in 90deg corners or similar, I've used a flexible caulk type filler. don't know how practical that would be for a long, mid-wall joint though. But

[Norminn]

clipped

My simple solution to fine cracks, when I paint, is to push some paintable, flexible caulk into the crack. Usually a problem at corners.

[Tim Watts]

On Sunday 06 January 2013 14:42 Frank wrote in alt.home.repair:

+1

This is the only "proper" way to do drywall joints. The tape spreads the strain over enough area that the plaster/filler on top can tolerate it without cracking.

The only time I've seen paper tape in use was to joint drywall that was painted direct without even as much as filling the joints - eg a crap bodge (cheap 1980's apartment builders in south London). Noone who is sane and/or not cheap would do it like that now.

[hrhofmann]

You mean the wall is 60 feet long and 10 feet high, and there is a vertical crack somewhere toward the middle of the 60 feet??? That long a solid wall, without any expansion provisions is asking for cracking if it experiences a full range of temperatures and humidity. Is this an interior wall, surrounded by interior spaces on all four sides, front and back and two ends, or is one side or one end an exterior facing wall? What do you mean by isolated, isolated from what???

A better description of the entire situation would allow folks to give you a more meaningful and workable solution.

[DD_BobK]

Drywall "moves" more than steel but less than aluminum based on temperature changes.

It it also wants to move quite a bit based on relative humidity....

Thermal Coefficient of Expansion: Unrestrained: 40-100 =B0F (4-38 =B0C):

9.0 x 10=966 in./in./=B0F

Hygrometric Coefficient of Expansion: Unrestrained: 5-90% r.h.

7.2 x 10=966 in./in./% r.h.

So keeping the the drywall within a narrow range of both temp & RH will minimize the tendency for the crack to open & close.

As T4 mentions, thinkness of the "patch"/ coverage wont help much.

With finishes... if brittle, they will crack with movement. So there needs to be minimal movement OR the materials need to accomodate movement.

Flexible caulk is an option that I use at corner joints, I've also used it with success on narrow (less than 1/16") field cracks in plaster.

You might consider cutting the corner tape & using caulk in the corners. A 60' wall is quite long and suffers a huge amount of dimensional change with temp or RH... if all the movement is forced to be accomodated at single line....you'll get a wide crack.

You mention 3 mil...did oyu mean 3mm or .003"?

.003 " can easily be fixed with flex caulk 3mm (.125") is huge

cheers Bob

[recyclebinned]

I don=92t know if this relates to your problem but I=92ve been inside thous= ands of houses and all the ones I=92ve seen that were over a slope or hill = have constant movement going on all the time; some very little and others a= lot but all were sliding.

[George]

Bedded paper tape is the classic and standard way of finishing drywall seams. The tape does the job you described.

[trader4]

"- Hide quoted text -

Paper tape is widely used in the USA for drywall in both new construction and repairs. Here in the NYC area it is used almost exclusively in new construction. I can't recall seeing the fiberglass tape stuff used by pros doing construction. So, it seems to work very well overall.

I've used both tape and the fiberglass tape. I think the tape is easier to use and agree i may give some additional benefit from cracking. It's worth a try. But it's kind of hard to imagine that the tape is going to make a thin layer of mud strong enough to keep two sheets of drywall that are moving from cracking it. To me it seems like expecting a very thin layer of concrete to have significant tensile strength and keep two sections of concrete from seperating because you add some reinforcing mesh to it.

[DanG]

It sure seems like a lot of your posts indicate pretty marginal understanding of construction.

No one would expect a 60' wall to not have any relief.

Here is a link to the USG Gypsum Construction Hand Book - pretty much a bible for the drywall, plaster, and acoustic trades.

Your current question is covered in Chapter 15 -Building Sciences. The bottom line is that drywall should never exceed 30' without some type of relief. Your best solution would be to install one or more expansion joints in the wall. I prefer using Trim Tex parts, here is a link showing you how they should be installed: down to the one entitled Hide away expansion bead

This will be a nasty remodel to get the extra stud installed in the wall, but will be the best long term solution. I suspect that you have a wall or something on the opposite side of the crack that is pushing or pulling the wall at this point. and may even involve interior and exterior conditions. If it is fracturing the tape joint at the ceiling and mid wall, there is plenty of movement going on.

One stop gap approach that may last longer than what you've been doing would be to remove all tape and mudding and replace with thermal setting type compound and mesh tape.

Hope this helps you some.

[DanG]

Paper tape is the normal and usual material to use. The nylon mesh tape can be used on tapered joints, but no tapers I know would use it on butt joints or corners and so, most just use all paper usually installed with a "banjo".

[dadiOH]

That is *WAYYYY* too thick! On butt joints at least.

Step #1 is to make sure the joints are securely fastened. If they aren't, the joints will crack. One way to tell is to put your finger lightly on the joint and have someone else thump the wall lightly with their fist a foot or so away. Can you feel movement with your finger? (Note: you can't do your own thumping).

Step #2 is to bed paper tape. Use only enough mud and width to bed and slightly cover the tape.

Step #3 - after #2 is dry - is to sand as needed and apply more mud using a wider knife. You aren't trying to cover the tape with this, you are filling the gap along the edges of the tape created by the taped area being thicker.

Step #4 is to repeat #3 but with a still wider knife. By the time you work up to a 10" knife the tape hump will be pretty much invisible even if it was on butts, not tapered edges.

You mentioned that the cracks were over 3 mils. A human hair is about 3 mils so your cracks don't sound like a disaster. If the sheets are well fastened, rubbing some acrylic caulk into them before painting as Norminn suggested (she's a sharp cookie :) will fix them nicely.

[clare]

Here in north america paper tape is the norm - the drywall is paper faced with a tapered edge - the joint is mudded, the paper tape embedded, and the surface leveled with mud.

Perhaps using a "curing" compound instead of a "drying" compound would make a difference??.(Also called "Hot mud" or "quick set" or "setting type") - has a number as part of the name - like "sheetrock 45" or "durabond 90" It is higher strength.. The normal stuff is awfull to sand - but there are now easy-sand versions. I would not use the setting type for fine finishing.

[trader4]

I looked at the link and installation for that product:

I get the idea that it's a flexible strip that goes between two sheets of drywall. But they don't say anything about how it's finished? It would appear from the pic it gets covered with mud? But, if so, what good does it do? If the two sheets move relative to each other the mud at the joint will still crack? Or do you not cover the middle with mud? I think that would look a bit odd in the wall, no?

[weather_reporting]

This indicates that there will likely be a massive Earth Quake in your area very soon. Once the house is destroyed by the quake, the wall cracks will not be noticable. Your best bet is to ignore the cracks while preparing for massive destruction and possibly your death. Now is the time to buy homeowners insurance, life insurance, and prepare your Last Will and Testament, and make funeral arrangements.

[Tim Watts]

On Sunday 06 January 2013 18:03 George wrote in alt.home.repair:

It's not in the UK -

I would take that as superior to paper tape anyday - not seen paper used for over 20 years now...

[Harry K]

Agree about the butt joint. I tried it once and could discover no way at all to put a thin layer on top of it. When you "wipe" the wet joint compount the knife rides the highs and lows of he tape and that tecture shows through.

As for the OPs problem. It appears that the framing is movign and until that is cured nothing will keep the crack from coming back.

Harry K

[gpsman]

More mud =3D more cracking. Tape/mud won't keep a wall from moving.

If the wall is moving, pull that sheet off and tie the studs together, which if the studs are wood should have fire blocks installed between them already.

The bed coat for the tape only needs enough mud to paste the tape solidly to the wall; all excess should be removed, the tape should be visible through the mud.

The 2nd (and 3rd) coats should not extend beyond the taper in any direction.

You apply the 2nd coat and knife it level with the taper. The 3rd coat, if necessary, is knifed identically.

Self-sticking fiber tape is often easier for the novice to apply, and perfectly acceptable, the bed coat just goes over instead of under. -----

- gpsman

[Stumpy]

I agree about the mud. Everyone appears to dwell on the tape. Durabond for the first coat should solve the problem.