What Are the Downsides of Soundproofing?
Updated
The biggest downside of soundproofing is that every extra point of blocking costs more than the one before it: doubling a single wall's weight buys you only about 6 dB, and NRC Canada concludes "it is not economical to continually double the wall or floor thickness" (CBD-239 (opens in a new tab)). PABCO says it straight: labor and material costs "keep escalating with each additional layer" (Sound Design Guide (opens in a new tab)).
Here are the other downsides:
- Weight: one layer of 5/8 in. drywall weighs 2.2 lb/sq ft (USG (opens in a new tab)), so an 8 by 10 ft wall picks up 80 x 2.2 = 176 lb for about 3 STC points.
- Stuffy rooms: once you seal things up, the air that used to leak in stops coming. Airport noise programs (opens in a new tab) that tighten up homes add "a quiet, low-volume exhaust fan or a balanced ventilation system if necessary."
- Results below the rating: code accepts STC 45 in the field for walls that have to rate 50 in the lab (LADBS, IBC Section 1206 (opens in a new tab)), and PABCO notes "failures with RC are common when the RC is installed upside down."
Watch out: acoustic panels skip most of these downsides because they're light and don't seal anything. That's also why they block so little. Their own drawbacks are in the disadvantages of acoustic panels, and the soundproof panels guide shows what each type does.
Seal first, and only add layers if the noise still bugs you. In PABCO's example, one unsealed 1/8 in. gap 1 ft long drops a wall from STC 46 to 36, so sealing gets points back for very little money. You'll find more answers in the soundproof panels FAQ.