What does 'floating' the inside corners mean when hanging, and why do it?

"Floating" inside corners means not taping/mudding the joint where two gypsum board panels meet at an inside corner (e.g., where two walls meet, or wall meets ceiling). Instead, the corner is left open or only minimally finished.

Why do it?

1. Movement Accommodation: Inside corners are prone to cracking due to building settling, temperature/humidity changes, or wood framing expansion/contraction. Leaving the joint "floating" allows the panels to move independently, reducing stress and crack formation at the corner.
2. Ease of Future Repairs: If cracking does occur, it's easier to fix a floating corner than a fully taped one, which might require cutting out the tape.
3. Cost/Time Savings: Skipping taping and multiple mudding coats at inside corners reduces labor and material costs, especially in areas where a perfect finish isn't critical (e.g., closets, garages).

When to Float vs. Tape:

• Tape: Use in visible areas requiring a clean, durable finish (e.g., living rooms, main walls).
• Float: Acceptable in less visible areas or where movement is expected. However, local building codes (e.g., IBC Section 803.2) may require taped joints in fire-rated assemblies for safety. Always check if the assembly is fire-rated—floating corners in such cases could compromise fire resistance.

Note: Floating corners are a trade-off between practicality and finish quality. For safety or code compliance in fire-rated walls/ceilings, consult a licensed contractor or inspector.

What it means: "Floating" an inside corner means not taping the corner joint. Instead, you apply joint compound to each wall separately, running the mud into the corner but leaving the paper tape off. You finish each wall to a crisp, clean arris (edge) where they meet, often using a corner roller or wide knife to sharpen the intersection.

Why do it (Code & Performance):

1. Movement Control (IRC R702.3.1 / ASTM C840): Inside corners are high-stress zones where framing lumber shrinks, twists, or settles differentially. A taped joint creates a rigid bridge. When the framing moves, that bridge cracks—usually right down the center of the tape. Floating creates a hinge. The two wall planes can move independently slightly without fracturing the finish.
2. Crack Prevention: It eliminates the single most common callback: the hairline crack running down the inside corner.
3. Caulk Compatibility: It leaves a clean, deep V-groove perfect for paintable acrylic latex caulk (not silicone). Caulk flexes; mud and tape do not.

How to execute:

1. Hang board tight to corner (no gaps > 1/8").
2. Coat each wall side independently. Feather mud 12–18" out.
3. Do not embed tape. Use a 10–12" knife or corner roller to cut a sharp, clean corner arris on each side.
4. Sand smooth. Prime.
5. Caulk the corner after priming (per ASTM C920, Class 25 minimum).

When NOT to float:

• Fire-rated assemblies (UL designs): Tape is usually required for membrane integrity. Check the specific UL assembly.
• Level 5 Finish (GA-214): Requires skim coat over tape for critical lighting.
• Ceiling-to-wall corners: Often taped to hide ceiling joist deflection cracks, though floating + caulk works there too.

Pro Tip: If the corner is significantly out of plumb (> 1/4" in 8 ft), float it. Taping a crooked corner guarantees a visible wavy line.