Hairline cracks along meshed plasterboard wall butt joints

[kgk]

I have a few very fine vertical cracks that have opened up in my plastered walls along the (insulated) plasterboard seams. I know that these joints were meshed, and that the plaster dried slowly and did not crack or craze with age. They resulted from specific trauma

> In one case, the crack opened due to a minor structural shift during installation of a RSJ over a year ago and the crack has not expanded.

> In another case, the crack appeared after mist coating a few weeks ago and probably was a reaction to extra water being pulled into the deep fill joint at the board junction.

I understand from researching in the forum that the usual advice is to enlarge the crack by cutting out a "V", filling (red devil, easy fill, or whatever, sand, prime) and continue on.

However, I am wondering if there is anything different to consider given the specific location of these cracks? For instance ... Should I really be digging away at the mesh? That area is filled with plaster which is harder that the plasterboard to either side, does that matter?

Before moving on with the rest of the decorating, I am going to be overcoating these walls with Zinsser Gardz. This new sealing coat might bridge the crack anyway. However, even if I knew that was going to sort the problem out all on its own, I really would like to know what are some of the recommended strategies to approach this sort of a problem if I wasn't overcoating with a sealer.

Thanks!

 

[PrenticeBoyofDerry]

Please expand on explaining what the mesh product is,
is it a metal mesh or a nylon type?

 

[kgk]

PrenticeBoyofDerry, thanks for taking a look at this problem for me.

The mesh tape is just the bog standard nylon or perhaps fibreglass mesh joint tape that is typically sold for the purpose of joining seams. (It is what you would buy at any builder supply right next to the plaster board. At least that is where I found it, and my plasterer said it was the right product when I handed it over to him).

 

[PrenticeBoyofDerry]

If the cracks are hairline or minor and the butted taped joint has not been broken and the cracks are now stable. I would be tempted to either just fill the cracks in with a joint filler product or maybe a stage further would be to apply tapes to cracks and easifill and feather out application, then sand and reapply as required, until smooth and even surface.

 

[kgk]

My interpretation of your advice is that if the cracks were of any concern that you would -not- suggest digging into the existing mesh joint, but rather suggest taping and feathering over the existing join.

In this specific case, the cracks are very minor, hairline, and I have every reason to believe that they are stable. In this instance, rather than tape and feather, I think I will fill and rely upon the Gardz sealer to provide a bridging layer.

Thanks again for the advice PBoD

 

[PrenticeBoyofDerry]

I would personally, fill in any cracks prior to using sealant/stabilising primer.
The primers are not designed for crack filling.

 

[kgk]

Point taken on board.

I picked up many of my DIY skills working construction in summer jobs in the US ages ago; and, as part of that, I am used to dry walling and mud / jointing compound. I picked up some TouPret Fine Surface Filler to fill in some paint chips and found that it behaves very much like a "spackle" jointing compound -- extremely fine, fast drying, can be built in layers, sands and feathers beautifully. This is what I have been looking for in a filler for ages! Time to trash all that PFilla etc.

Anyway, working with the TouPret, I finally realised why I was so hesitant to scrim and feather the crack from the RSJ installation ... until yesterday I hadn't come across a filling compound that worked well for me in the UK.

Well, I'm a bit out of practice so it took a while, but the RSJ cracks are now scrimmed and feathered. Only problem is that they now look better than much of the surrounding wall (but this is a problem I can live with).


As for the other crack, I opened a small section to get a better look at the depth and I think it is just a surface crack. This crack only opened when mist coating so I think it was just the excess water in the joint. I am probably going to gamble and take a chance that the Gardz sealer and later layers of paint will hold.


Even if not universally implemented, the advice is always appreciated!