One thing you can do to minimize cracks is to water the perimeter of the foundation(during warm weather). That will maintain the same soil consistancy and help minimize movement. You don't want to keep the earth wet, just moist, about three or four feet out from the foundation around the entire house. You really only need to water during long dry spells, if it rains a couple times a month, watering isn't usually necessary.

When the foundation moves, the forces are much greater than any drywall installation process can withstand---the drywall will crack. Adding layers simply adds more material for the movement to crack. Since the repair failed at the same places, it sounds as if the wall construction would have to be changed to try and make any lasting correction.

If the cracks are not huge, a flexible filler applied to the cracks may be a better way to go. At least you've done the homework and ensured it's not dangerous or going to get significantly worse.

Thanks guys. Handymac, if I understand you, your saying there is nothing in the installation of dry wall that will make the joint's strong enough to keep cracks from coming back? I spoke to the engineer about watering around the foundation. He said that although he did it himself he really doesn't think it does much good as we cannot get the amount of water down that Mother Nature does. Pjb999, am I to assume the flexible filler allows for some movement and therefore will make it less likely to crack?

That flex filler can stop the unsightliness of the crack in the wall board---but the paint still cracks.

If you water the foundation on a regular basis, you will do a better job of keeping the soil in a more stable state---Mother Nature rains a lot and then none---that is what causes the movement.

Thinking back, I seem to remember hearing that a second layer of drywall COULD help, providing the seams are staggered in relation to the original seams, but could add up to a lot of work if there are doors or windows in that wall, since it'll be a lot thicker all of a sudden and the frames would have to be shimmed. Could be ugly if not done well.

You may even find the cracks are seasonal, do they close up at other times of the year, or are they there to stay once they start?

I saw a product once that was like a canvas. You applied it like wall paper. If can find find that product it might be the solution.
No tape and mud job will fix cracks if the walls are still moving.

Found this on a thread over at the paint forum:

Here is a link that might be useful: krack-kote

Thanks for the link sierraeast. The krack-kote claims certainly look promising. Has anyone used the product?

I cant find the thread over at the paint forum, but the person who referred krack-kote stated the importance of knowing that you cant really sand it. Reading the website it states that small ridges and imperfections can be sanded when fully dry but appearently it needs to be applied as smooth as posslble, feathering the edges. Hopefully you'll get a response from someone that has used it, i never have. If it is compatible with joint compound, im wondering if krack-kote embedded in the crack leaving a minor void to be filled with joint compound would work, as it would finish better over the recommende fabric, i would assume.

When a foundation moves the wall must crack. If the joints were strong enough the crack would be in the panel. Adding another layer would only force cracks to occur in that layer. The only way to stop the cracks is to isolate the wall panels from it unstable support or float the panels on the wall that is deforming. Resilient sound channels supporting a new layer of drywall might work for awhile.

I would be concerned about why the settling has not stopped and would call in a geotechnical soils engineer. It might be possible to pump concrete under the foundation to stabilize it.

The downside to these textured finishes etc in home resale is, 1) people don't like the fact they're stuck with them, and b) they tend to highlight the fact there's an underlying issue.

Of course, we know there's that issue, so whaddareyagonnado.

I'd try the flexible filler or try what sierraeast seems to be suggesting, just use it as a filler or bridging agent.

Thanks for the advice. Since the cracks will tighten when we get substantial rain, we will wait to repair them. It is just abnormally dry here and although the engineers say the foundation movement is within tolerances, it has been enough to put a strain on the drywall. After we have some rain the foundation should move again and the cracks should tighten and then we can proceed with a stronger repair. However, based on the comments, drywall over drywall is not the answer.