Repaired wall seems very soft

[Ben]

Hello, all! Welcome me as this is my first post!

First of all, here's a picture to help:

I have a "window" between my kitchen and my living room. It used to have moulding around it and a wood ledge on the inside. Me and the wife decided it's a much better idea to have flat drywall all of the way around.

So we removed the moulding and wood planks and it revealed a frame of

2x4s. There were some significant gaps the moulding was hiding between the frame and the drywall surrounding the opening. "No problem, we'll fix it with joint compound."

So we installed our drywall where the planking was. We then joint compounded the thing all of the way around, placing fiberglass tape over some of the more significant gaps. (Of course filling the hole underneath with yet more joint compound.)

After 3~4 iterations of sanding and joint compound we got to a place where the wall seemed smooth enough.

We painted part of it last night and discovered, much to our horror, that the joint compound dries VERY soft. Pressing a fingernail into it with slight force produces a knick. Is this normal? Should we not have used joint compound to cover such an area? We used the premixed stuff...is that known to be softer?

At this point we're gonna put the second coat of paint on and leave it for now...but if we get cracking or it gets banged up, we'll have to chip it all away and start again, I guess.

Help! Thanks.

[William.Deans]

Greetings,

a) are you sure it is not still wet? Did you let each coat fully dry? b) did you use the lightweight compound? -- it is softer

Hope this helps, William

[Ben]

Thanks for the response! a) We let it sit for a few days this last time...I can't imagine it isn't dry. Most coats had 2~3 gaps between them.

b) Lightweight compound! I didn't even know that existed. I will check if that is what we used. Where would one use such a product?

[Ben]

I mean 2~3 DAY gaps between coats.

[Ben]

So if I did indeed use lightweight compound and would like to harden things up, do I have to strip away the coat of paint and chip out all of the lightweight stuff? Or can I put a layer of harder compound on the top layer to protect it? Thanks.

-ben

[BobK207]

Ben-

Did you use premixed compound (comes wet in a tub or box) or did you use fast set (mix w/ water)?

Sounds to me like the compund is just not dry (could take a long time ifthe material was really thickly place) or it is indeed lightweight compound (lower density)

At think point you could just not paint & see if it hardens up.

I would roughen up the painted surface & cover the whole area with a water mix compound, behave more like plaster.

I would suggest against futher painting until you get the finger nail preformance you desire.

Whe you let the coats dry did you get shrinkage cracks? if you did then it was most likely dry, if no cracks it either wasn't completely dry or ?

cheers Bob

[Ben]

Thanks, Bob. I have looked into the matter and discovered it was indeed lightweight compound. Do I have to try to use a watermix compound to harden this up or will a regular pre-mix joint compound do the trick?

-ben

[BobK207]

Ben-

I believe the problem you are experiencing is due to having a very thick (~5/8") layer of low density material. I have "cheated" & filled a rather deep uneven suface with the regular density prmixed compound.

I was lazy & just kept putting extra coats day after day. Covering one dried / crakced layer with another that would dry & crack. Finally the layers became thinner (just enough to cover the previous layer's cracks).

I never did the finger nail check so I'm not sure if was very hard but it probably was since this is just an extreme example of th typical corner method.

So the question is now...what should you do? (or what would I do in your situtaion?

The problem is the lightweight is rather soft material so putting a very thin layer of hard over soft may not help very much. Kinda like putting a thin concret slab over a soft subgrade; might work depending on the loading.

The "correct" way was to add some supporting framing so that reasonable sized peieces of drywall could have been placed, taped & mudded.

Or you could have jammed in & secured some 1/4" x 1/4" "hardware cloth" (very coarse screen material) to act as reinforcement & then used plaster, stucco or concrete "fixall"...That is some sort of water mix cementious material.

The benefit of light weight is that is sands very easily.

It's you call at this point.........can you live with the current result? If so forget about it.

It not remove it all & start over (it will go much faster the second time)

cheers Bob ).