I have a home built with ICF (ice block) forms.  These forms use galvanized steel to hold the block together as well as screw points for drywall anchor points.  The steel is buried within the foam and not exposed to the outside weather .  I built the structure about 8 years ago.  My problem is that in rooms where the paint is light in color the screws attaching the drywall are visible as dark spots through multiple layers of paint.  Is this common?  How do I fix?  I was planning on using Kilz primer paint to cover.  Does anybody have experience with that?

Zinsser Bulls Eye Shellac does a better job of hiding than Kilz. You might need to go over the screw heads with joint compound first, or if you have screw pops, chip off the paint etc, replace the screw, and cover with joint compound, then repaint.

-Rosalinda

This a common problem with heat transfer. It happens in houses with ceiling insulation that is substandard. The screws act as a magnet drawing dirt and dust to the heads. It's also a problem with an icf made of steel. You have heat transfer from outside of the block to the inside thru conduction. I'm afraid that repainting periodically is the only course of action unless the r-value of the screw heads can be raised to stop the transfer. No real solution

The problem cannot be substandard ceiling insulation, I have R30 blown insulation. Periodic painting may not be it as well. I painted a room that was purple where I could not see or barley see any screws. I repainted the wall white and I could see all. Any ideas on hiding? I have used the Shellac solution on hiding pine knots on trim, but rolling a whole wall with it?

I didn't mean your ceiling had a problem it happens in ceilings, I gave this as an illustration of a place where this is noticable. You have heat transfer by conduction and no amount of shellac you use will cure the problem. The only way is to raise the insulation value where the screws are . Which is of course impossible in a reasonable way.

Posted By smartwall on 12 Apr 2012 07:56 AM
I didn't mean your ceiling had a problem it happens in ceilings, I gave this as an illustration of a place where this is noticable. You have heat transfer by conduction and no amount of shellac you use will cure the problem. The only way is to raise the insulation value where the screws are . Which is of course impossible in a reasonable way.

You are right when you say it is the heat transfer but it is probably the condensate that happens on the cooler screw heads that actually attracts the dust. You are also right in saying it is the steel in the ICF that is drawing the heat out of the screw and into the steel web and concrete. That is why some forms of scips and other products that use steel without an thermal break can also have this problem.

Maybe you just need to pick out a darker color paint and solve the problem that way, since that has already worked for you. I don't know if wallpaper would help, or if the cold screw heads would just cause the marks to form on the wallpaper.


-Rosalinda