Understanding your result
The headline is the number of 12 ft pieces of resilient channel, and the line under it gives the rows, the run length and the total linear feet. The tiles give the rows, the screws into the framing and the screws for the board.
Two screw counts are on purpose. The channel is fixed to every stud or joist it crosses through its mounting flange; the drywall is fixed only to the channel, with screws short enough that they cannot reach the framing behind. Keeping the two sets of screws apart in the shopping list is the simplest way to keep them apart on the wall.
Rows are counted with one row near each edge and the rest at the spacing, which is how tested assemblies place them. The STC that an assembly with channel achieves is a property of the whole assembly, which the soundproofing assembly calculator looks up from published listings. For ceilings, the isolation clip calculator counts the alternative; plain furring strips are counted the same way but do nothing for sound.
How we calculate this
The first row sits within a few inches of the floor (or the wall, on a ceiling) and the last within 6 in of the top, so the edges of the board are supported; the rows between are at the spacing. Pieces are spliced by overlapping their ends over a framing member, which is the overlap allowance. Board screws are at 12 in along each channel, the common spacing for board on channel; the spacing for your assembly may be closer. The sound and fire assemblies page lists published assemblies that include channel, and the fastener spacing table has the board screws.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Channel spacing | 24 in on centre | Common in GA-600 tested assemblies with channel; 16 in in some |
| Edge rows | Within 2 to 6 in of the edges | Manufacturer installation instructions |
| Piece length | 12 ft | Standard stock length |
| Channel to framing | One 1-1/4 in screw per crossing | Manufacturer installation instructions |
| Board to channel | 1 in Type S fine-thread, 12 in apart | Manufacturer installation instructions |
| STC gain | About 5 to 10 points over the same wall without channel | GA-600 and manufacturer test data for wood-stud assemblies |
| Overlap and waste | 10% | Splices over framing members |
Assumptions last reviewed October 8, 2026.
The calculator does not tell you the STC of your wall; that depends on the studs, the insulation, the board and its layers, which the assembly calculator and the guides cover. It does not handle channel on steel studs differently, though the screws into steel are fine-thread. Penetrations, outlets and gaps leak sound around any channel; the soundproofing basics guide explains why, and the ceilings guide covers the floor-ceiling case.
Two worked examples
A 12 × 8 ft wall, channel 24 in apart on 16 in studs
- Rows: ⌈(96 − 6) ÷ 24⌉ + 1 = 5
- Linear: 5 × 12 = 60 ft; pieces 60 ÷ 12 × 1.1 = 5.5, rounded up to 6 pieces of 12 ft
- Screws into framing: 5 rows × 10 studs = 50
- Board screws: 5 × 13 = 65 of 1 in Type S
The board on this wall is screwed only to the five rows of channel. A finisher used to screwing into studs will look for them; tell them not to.
A 20 × 14 ft ceiling on 24 in joists
- Rows: ⌈(168 − 6) ÷ 24⌉ + 1 = 8
- Linear: 8 × 20 = 160 ft; 15 pieces of 12 ft
- Screws into framing: 8 × 11 joists = 88
- Board screws: 8 × 21 = 168
On a ceiling, two layers of 5/8 in board on channel is a common assembly; the second layer is screwed into the channel too, with screws long enough for both layers but still short of the joists.
Where to find your inputs
Dimensions. For a wall, the length and the height. For a ceiling, the dimension that crosses the joists (the channel runs across them) and the other one.
Framing spacing. Centre to centre on the studs or joists; it sets the screws into the framing.
Channel spacing. Twenty-four inches unless your assembly says 16.
Overlap. Ten percent covers splices and offcuts on most rooms.
Common mistakes
- Board screws into the studs. The channel is shorted and the wall is no quieter. Short screws, into the channel only.
- Channel upside down on walls. Flange at the bottom.
- Hanging cabinets or TVs on a channel wall. The fixing shorts the channel. Plan backing or put heavy items elsewhere.
- Gaps at the edges. Leave a 1/4 in gap at the perimeter and fill it with acoustic sealant; rigid contact with the floor or the next wall carries sound.
- Channel without insulation. Channel works best with absorptive insulation in the cavity.
- Treating furring as channel. Wood strips do not isolate.
Questions people ask
- How many pieces of resilient channel do I need?
- Rows run across the studs or joists, one within 6 in of each edge and the rest 24 in apart (16 in for heavier board or some listings). A 12 × 8 ft wall takes five rows of 12 ft, 60 ft of channel, six pieces of 12 ft with overlaps.
- What is the spacing for resilient channel?
- Twenty-four inches on centre is the usual spacing on walls and ceilings in tested assemblies, with the first row 2 to 6 in from the floor or wall. Some assemblies and heavier double-layer ceilings specify 16 in; follow the listing you are building to.
- Does resilient channel really work?
- Yes, when it is installed so it floats. Gypsum Association and manufacturer test data show resilient channel adding roughly 5 to 10 STC points to a wood-stud wall or ceiling. Installed with screws that reach the framing, or channel the wrong way up, it adds little or nothing.
- What screws do I use with resilient channel?
- 1-1/4 in screws to fix the channel's mounting flange to each stud or joist, and 1 in fine-thread Type S drywall screws to fix the board to the channel. The board screws must be short enough not to reach the framing behind the channel.
- Which way up does resilient channel go on a wall?
- With the mounting flange at the bottom, so the weight of the board pulls the channel away from the stud rather than pressing it against it. On ceilings the orientation does not matter in the same way; fix it to every joist.
- Resilient channel or isolation clips?
- Clips with hat channel are more forgiving and usually perform better, especially on ceilings, because the clip, not a thin steel flange, does the isolating. Resilient channel is cheaper. The ceiling isolation clip calculator counts the clip system.