I'm a new member who is in the construction phase of an ICF house.  I'm using TF System for both the below grade (basement) and above grade exterior walls.  I will soon be at the point of installing 1/2" gypsum board inside and am not sure how best to fasten the drywall to the ICF walls.  Is there consensus on a best practice?  If not, what techniques have proven effective?

FYI, TF System incorporates a continuous vertical 2" wide PVC "stud" 12' o.c.  5/8" below the foam surface.   The holding strength of a course thread drywall screw in the PVC flange is around 300#.

My thought at this point is to glue and screw each gypsum panel after rasping down any significant irregularities at the foam's surface. 54" wide gyspum boards will be oriented horizontally (9' wall height.)

Questions:

1.  What type of screw should I use? Gauge? Length? Thread? Point type?
2.  How many screws per panel?
3.  What type of adhesive should I use?
4.  Do butt seams need to be over a stud?


When I experimented with a standard philips head 1-5/8" course thread drywall screw using a power driver, I noticed that it takes several revolutions of the screw before it "bites" into the PVC.  In the mean time, an amount of gypsum dust is drilled out by the screw.  Aside from the mess, does this action weaken the screw's hold on the drywall enough to be of concern?  Has anyone found a screw that penetrates the PVC tie quickly?

although I'm a builder and not a rocker here goes--1/2" rock+5/8" recess=1-1/8" so I would suggest 1-3/4" coarse thread standard sheetrock screws. Local code will dictate number of screws per panel, but here in SC you are looking at one every 12" on the edge due to 24" being too wide and your having 12" ties and 16"in the field. You can use any adhesive as long as it doesn't "eat" the foam.(no petroleum products) TEST THIS!!! And the beauty of icf--no you don"t have to butt over a tie as long as you use adhesive.

Most ICF screw points are recessed 1/2 into block so 1 1/2 inch screws coarse thread.

PL-300 is the cheapest foam friendly adhesive. Seams do not need to be on a tie or glue.

Follow-on question.

Suppose you get the drywall up and plastered over.  How do you find the studs ... er, webs then?  I trust knocking on the wall with your knuckles doesn't work any more.

You can find ties with a stud-finder. But if you want to hang a picture use the needle type picture hooks, you can hang them anywhere and they will hold a hundred pounds. I use them to hand animal heads.