# shrinkage in joints



## pjwooly (Aug 5, 2012)

Just set a large ceiling in an aged care centre.Boxed the thing 3 times.Taped with a banjo then 7,10 and 12 inched boxed it and the recess joints appear to have sucked back.I did blade them off very lightly after each coat.I taped with base coat and second coat then all purpose for the 3rd coat then top coat to finish.

Any ideas where i'm going wrong?
Cheers

Do my boxes need some tampering? I have'nt had them that long

pj:furious:


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## cazna (Mar 28, 2010)

How much time between coats, They need to be well dry, Airdry muds can trick you but you said you used base for taping which is usually a good start, Shrinkage continues for some time, The all purpose may have been a dud batch. Im surprised to hear you had this happen where you live, Its a prob for me as i have a damper climate, Fans, Dehumids are helpful, I had this happen but i used airdry muds in winter, Then they turned on the underfloor heating and shrunk it, Was your area heated to fast after your job was done??


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## PrecisionTaping (Feb 2, 2012)

You ran your boxes three times after your tape? And it still shrunk back? Hmm...very weird.
But ya, Cazna raised some good points.
The only thing I can see is that it was surface dry, maybe allot of humidity in the ceiling and once sanded caused it to shrink back a bit.


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## SlimPickins (Aug 10, 2010)

It could be high shoulders, or it could be that maybe you didn't wipe as lightly as you thought? It's more likely that it was high shoulders. They look like shrunken mud when they flash.


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## DLSdrywall (May 22, 2012)

WHats the weather been like? If it's been rainny and your on cement it will never dry too much humidity. did you prefill with hot mud? Is the ceiling insulated? If you had a picture might make it easier to asess. Slim is right if you have high shoulders then you'll have to pull it by hand.


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## Bazooka-Joe (Dec 31, 2010)

pjwooly said:


> Just set a large ceiling in an aged care centre.Boxed the thing 3 times.Taped with a banjo then 7,10 and 12 inched boxed it and the recess joints appear to have sucked back.I did blade them off very lightly after each coat.I taped with base coat and second coat then all purpose for the 3rd coat then top coat to finish.
> 
> Any ideas where i'm going wrong?
> Cheers
> ...



just talking to the superintendent today, wants his basement done I said I would if I can have 3 days dry time.... said I want to do it right, he agreed...

just as it sounds not enough dry time, like paper beads are not dry the next day like most think, maybe at the end of the next day if your lucky.... I always end my sequence with last coat on bead

I feel for ya...

last company wanted m,e to tape through rainy weather, what a waste of time and money


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## pjwooly (Aug 5, 2012)

_The weather is dry and cool and sunny here.Ceiling is insulated."High shoulders" i guess means the edge of the recess maybe a little peaked is that rite? Not something we usually look for here, to be honest i cant remember how long between coats but i had the 3 of four coats done in a day so there maybe is the problem.As is so typical here in this economic climate i'm on a **** rate and a tight schedule.No time to let it dry properly and materials all over the floor where i'm trying to run the boxes. The "chippies" were literally waiting for me to finish so they could have the floor space for fitout._

_Thanks for all the responses too.I will try nextime to give them moore time for drying and see if that helps._
_I did notice that some of the wall joints that we skimmed the recess with by hand looked great..and they were probly left longer to dry._

_Been in this industry now 25yrs but you keep learnin' don't ya_


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## Bazooka-Joe (Dec 31, 2010)

pjwooly said:


> _The weather is dry and cool and sunny here.Ceiling is insulated."High shoulders" i guess means the edge of the recess maybe a little peaked is that rite? Not something we usually look for here, to be honest i cant remember how long between coats but i had the 3 of four coats done in a day so there maybe is the problem.As is so typical here in this economic climate i'm on a **** rate and a tight schedule.No time to let it dry properly and materials all over the floor where i'm trying to run the boxes. The "chippies" were literally waiting for me to finish so they could have the floor space for fitout._
> 
> _Thanks for all the responses too.I will try nextime to give them moore time for drying and see if that helps._
> _I did notice that some of the wall joints that we skimmed the recess with by hand looked great..and they were probly left longer to dry._
> ...


Run 70% hot mud to reg mud when taping

yeah we keep learning but make errors also


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## pjwooly (Aug 5, 2012)

do you mean like all purpose in with the hot mud?


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## Bazooka-Joe (Dec 31, 2010)

pjwooly said:


> do you mean like all purpose in with the hot mud?


yep

I also run 60 40 first coat tight 7 box in humid days

Run fast drop the pail and clean up


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## pjwooly (Aug 5, 2012)

Yep so a quicker mud on the humid days! i got ya.

We tend not to think about what the weather is doing here really.

We just buy from our closest dist. and get on with it.
If there is miles of joints to do i tend to buy the base 60 cos i get good life from it.
And maybe add a little citrus acid for longer life


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## 2buckcanuck (Jul 9, 2010)

pjwooly said:


> Yep so a quicker mud on the humid days! i got ya.
> 
> We tend not to think about what the weather is doing here really.
> 
> ...


citrus acid :blink:, what??? you mixing orange juice or lemon aide with your hot mud or something,,,,,, interesting

Pre-filling with hot mud when it's humid out may help you too. I will let your fellow country man, Gazman explain that one to you:yes:

(term pre-fill).... we need a glossary on this site:yes:


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## Bazooka-Joe (Dec 31, 2010)

pjwooly said:


> Yep so a quicker mud on the humid days! i got ya.
> 
> We tend not to think about what the weather is doing here really.
> 
> ...


90 min is all I use

20 for obvious quick mixed 50 50


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## cazna (Mar 28, 2010)

Citric acid crystals, A few table spoons in an empty mud bucket and 4 litres of warm water will clean up brass objects like you wouldnt believe, Dont leave it in there to long though.


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## gazman (Apr 29, 2011)

Citric acid in gypsum products, not so good.
Check out this document from page 20 onward.
http://www.globalgypsum.com/pdf/eGGSept-Oct2010-nonsub.pdf

Also here is a link to the Gyprock forum.
http://www.gyprock.com.au/page_content2.aspx?g=posts&t=135

If CSR does not recommend the use of a product that means it will void the warranty. And as you can see from the first doc, they can check using a microscope. it fractures the crystals and weakens the mud.


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## gazman (Apr 29, 2011)

pjwooly said:


> Yep so a quicker mud on the humid days! i got ya.
> 
> We tend not to think about what the weather is doing here really.
> 
> ...


Dont use citric. If you want it to last longer get base 90.:yes:


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## gazman (Apr 29, 2011)

2buckcanuck said:


> citrus acid :blink:, what??? you mixing orange juice or lemon aide with your hot mud or something,,,,,, interesting
> 
> Pre-filling with hot mud when it's humid out may help you too. I will let your fellow country man, Gazman explain that one to you:yes:
> 
> (term pre-fill).... we need a glossary on this site:yes:




This is the type of prefill that 2Buck was speaking about. These sheets were hung "tight". 
The prefill will help with drying, because that "v" of mud is not behind your tape trying to dry. And it will stop that ridge that you can get down the center of a tape.


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## keke (Mar 7, 2012)

pjwooly said:


> Just set a large ceiling in an aged care centre.Boxed the thing 3 times.Taped with a banjo then 7,10 and 12 inched boxed it and the recess joints appear to have sucked back.I did blade them off very lightly after each coat.I taped with base coat and second coat then all purpose for the 3rd coat then top coat to finish.
> 
> Any ideas where i'm going wrong?
> Cheers
> ...


did you sand that ceiling? if you sand it and after that the joints were glossy and you can see the paper, that means the problem was the 3 coats applied in the same day.when you use basecoat and top cot make sure you dont apply them in the same day


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## pjwooly (Aug 5, 2012)

yes i did sand the ceiling but no the joints were not glossy at all...but i have seen that effect too


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## carpentaper (Feb 28, 2009)

i just think its dry time. it's your winter. going that quick might work better in the hotter months. cazna has had the same thing happen to him. i've had it happen to me. if it's dry time it's not so much about the products as it is about time. the surface feels dry enough to sand but underneath is just damp enough to shrink. it doesn't take much. i would rather have people be pissed because i didn't come back for a couple days than because my joints are showing.


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## cazna (Mar 28, 2010)

carpentaper said:


> i just think its dry time. it's your winter. going that quick might work better in the hotter months. cazna has had the same thing happen to him. i've had it happen to me. if it's dry time it's not so much about the products as it is about time. the surface feels dry enough to sand but underneath is just damp enough to shrink. it doesn't take much. i would rather have people be pissed because i didn't come back for a couple days than because my joints are showing.


Its the dry time and humidity, The seams dry to the current humidity of the area your working in, Mud will dry enough so you think is done and good to sand, So you do, Then its painted, Then more time goes by and humidity and seasons change so the mud shrinks back, I think it happens for quite some time and i think airdry muds are worse for it, Basesetting muds for first coats and one thin airdry coat is the most stable but then your limited with the auto tools.

Controlling the area is the trick, If your able, Just a big fan running works well, add a dehumid is great, Heaters are so so and can work against you, Lock a room up and leave a heater on over night and it can sweat, Yeah the top may crust off, but sure enough it will shrink later on so heaters need airflow to get the moisture out as well, And of course coat to fast and rush it will kick you in the arse for sure but thats just how some jobs roll, Fan, dehumid and heater is the best, Or time, Which ever works out the best.

Even the board can play up, If its fresh from the factory, hung, taped, painted etc fast then i think it can still be green, After all its made, heated, then stacked in big piles, It doesnt get any air around it till its hung, And if its subjected to damp storing conditions it will take up moisture. Were all all trying to get perfection from an unperfect product.


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## gazman (Apr 29, 2011)

Not to state the obvious, but your mud is a mixture of a dry product and water. So a % of the volume is water and when that is finally removed the volume of the product decreases. So you get shrinkage, it is simple science. So as every one has stated it needs to be dry between each coat.:yes:


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## DLSdrywall (May 22, 2012)

In the famous words of my drywall foreman ah hell Dan just give it the 60 day guarantee:blink:


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## Kiwiman (Jun 14, 2008)

cazna said:


> Its the dry time and humidity, The seams dry to the current humidity of the area your working in,


Bingo :thumbsup:


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## DLSdrywall (May 22, 2012)

my last job i did nothing dried properly, upstairs my angles were fu When they dried i was like :blink: wowo these angles are garbage, it's where the boarders smashed the nails in the angles. Here in butcher subdivisions the drywallers use nails in the angles where the flats are. This is my major argument every week. I'm like instead of me pre-filling all the nail smashes in the angles why not use screws. There like it's not productive. It takes one 2 nails for the strength of 1 screw. When you have 3 or 4 guys boarding and you can't screw off fast enough your in the wrong trade. Sorry thats my everyday rant on why i hate subdivisions. Just 30 more years then i can retire:thumbup:


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## Bazooka-Joe (Dec 31, 2010)

DLSdrywall said:


> my last job i did nothing dried properly, upstairs my angles were fu When they dried i was like :blink: wowo these angles are garbage, it's where the boarders smashed the nails in the angles. Here in butcher subdivisions the drywallers use nails in the angles where the flats are. This is my major argument every week. I'm like instead of me pre-filling all the nail smashes in the angles why not use screws. There like it's not productive. It takes one 2 nails for the strength of 1 screw. When you have 3 or 4 guys boarding and you can't screw off fast enough your in the wrong trade. Sorry thats my everyday rant on why i hate subdivisions. Just 30 more years then i can retire:thumbup:


Tell em there is a charge for fixing butchy walls, here to tape not repair, tell em 7 bucks per dent... accept 3 mistakes rest is billed for


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## moore (Dec 2, 2010)

DLSdrywall said:


> my last job i did nothing dried properly, upstairs my angles were fu When they dried i was like :blink: wowo these angles are garbage, it's where the boarders smashed the nails in the angles. Here in butcher subdivisions the drywallers use nails in the angles where the flats are. This is my major argument every week. I'm like instead of me pre-filling all the nail smashes in the angles why not use screws. There like it's not productive. It takes one 2 nails for the strength of 1 screw. When you have 3 or 4 guys boarding and you can't screw off fast enough your in the wrong trade. Sorry thats my everyday rant on why i hate subdivisions. Just 30 more years then i can retire:thumbup:


 I can screw off 2 times faster than any hatchet nailer leaving his eggholes behind...nails have there place in spots where a screw wont hold ..Yes..but screws are faster . Most hangers dont want to drag the chord around...THAT'S ALL IT IS.. but the chord is ok for there router 
The board today Is fragle..It can't much abuse...Hatchet heads leave blisters!!!!!!!!! I'm a hanger/finisher so I know both sides ,,but the hangers only know one side..The white side and the back side of that check..:yes:


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## DLSdrywall (May 22, 2012)

I just tell the foreman that i put 3 coats on them anything that dosen't pass the boardmen can coat them. The real chitty part is when i do customs i prefill all of them with hot mud, taping puts a coat, and my finisher puts a coat, and you still see them. I agree nails do have there place like if there's a dip and you need to double nail. There's a time and place for everything, it just bugs me because we're not paid to prefill and it's just another time consumer in a piecework house.


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## A smooth finish (Mar 19, 2012)

Heres one for ya I just did a ceiling taped with all purpose and did 2 coats with proform light weight. I had one spot were the tape bubled out in a ressed joint. I prefilled with 20 min be fore taping. what causes that all the other joints look fine. Just one little spot.


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## pjwooly (Aug 5, 2012)

I have found that alltho the 20 min sems dry its actually not very dry (espscially if it was a biggish hole or patch) and its not very hard also.There would have been plenty of moisture still left in that patch under the surface.


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## Drywall_King (Dec 18, 2010)

pjwooly said:


> Just set a large ceiling in an aged care centre.Boxed the thing 3 times.Taped with a banjo then 7,10 and 12 inched boxed it and the recess joints appear to have sucked back.I did blade them off very lightly after each coat.I taped with base coat and second coat then all purpose for the 3rd coat then top coat to finish.
> 
> Any ideas where i'm going wrong?
> Cheers
> ...


Hello mate, im in bundy and did you second coat too fast, if you load the mudd right away, (PLUS Load, Top coat) your joints will railroad....let the first coat dry... You can complete all coats with fiber tape, and no railroad, the one thing mesh tape is good for..


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