Preventing Cracks Along Beam Joints

The problem is that metal beams are going to expand and contract with temperature variations, concrete and plaster don't, (at least not much). Best thing to do would be to pull off the mesh and use caulking in these joints. It will give and take with any movement.

When a facade of this type is made, one way to prevent cracking is it must be suspended away from the steel by some sort of flexible attachment that allows differential movement. These motions are small, but they are inexorable.

Another way is to use something that is inherently flexible. The requisite fire protection will be beneath this facade.

A little googling should help here

Today on this old house a southern CA. segment had a man making an INDENTION in the mortar mix using his trowel where the separation of the two boards came together on a cabinet that had one of those "plaster look" pieces attached at the bottom of it,He specifically stated it was to prevent cracking..ds

Pre-make an artistic crack.

There are plastic edgings for drywall to allow finishing with a clean line.

We have a 2 story stucco house. The stucco is interrupted betwwen floors with a flashing to allow differential expenasion and flexing.

(Stucco is evil stuff!)

TKS FOR UR REPLIES.I MEANT THE CRACKING IS IN PLASTERING ONLY AND NOT IN BEAM OR COLUMN CONCRETE.IT HAPPENS UNDER THE ROOF BEAM WHERE THE HOLLOW BLOCK WALL CLOSES WITH BEAM.SAME WAY WALLS BETWEEN COLUMNSALSO.

This sounds to me like a deflection problem. I don't know where I hid my AISC Steel Design Manual, but they had deflection limits which were quite a bit tighter when a plaster ceiling was involved (L/360???); it might have been under a heading such as serviceability. This didn't affect my work much as we did industrial mezzanines.

In the design phase this could be fixed; I don't know about post-design.

Best not to try. Make the edge of the join smooth and good looking by using any of a number of proprietory products for this purpose.