Questions on Dry Wall Shims

[DerbyDad03]

The description of the dry wall shims found at the site referenced below contains the following statements.

"Ideal for floating butt-joints and framing irregularities. Save time by shimming drywall to allow greater inset at joints. Ensures maximum bonding of tapes with drywall."

How would these shims help with "floating butt joints", which I assume are butt joints not centered on a stud?

What do they mean by "allow greater inset at joints" and how would this "save time"?

[hrhofmann]

Don't know the answer, but when I have had a floating butt joint, I would put a piece of plywood behind the joint before the second piece of sheetrock went up, use a couple of drywall screws thru the sheetrock into the plywood, and then put up the second piece of drywall and a couple more screws thru the new drywall into the plywood. The wood is a splice over the butt joint so there is no relative movement between the two piece/ends of the sheetrock. Pretty much like when patching a really large hole and backing the patch,

[Mike Paulsen]

The long edges of drywall are tapered and form a valley when two sheets are jointed. That valley is filled with tape and mud and results in a fairly flat surface after finishing. Butt joints have no taper, so you start with a flat surface and add tape and mud, creating a hump which must be feathered out.

If you want to float a butt joint between framing members you have to use a backer board, say a 6" strip of plywood or waferboard. That will give you the same flat surface which leads to a feathered out hump after finishing. If you add shim strips to the backer board ==-----== then the ends of the drywall will be sucked in, forming a valley much like you get joining two tapered edges.

If your butt joint is going to fall on stud B, putting a shim on studs A and C will leave stud B slightly inset, again making it easier to finish the butt joint.

[dadiOH]

Great explanation. I learned something, thanks.

[DerbyDad03]

Ditto on the "great explanation" comment.

Never heard of either of those shimming techniques before but, dammit, they sure do make sense!