Tight "owner's envelope," construction make for quiet high-rise condos

New Construction Corner

Tom Corbett

Robert Frost wrote, “Good fences make good neighbors.”

I think most homeowners would agree. The aphorism (from Frost’s 1919 poem “Mending Wall”) is something to keep in mind as you shop for a home in a high-rise. The owner of a house can build a fence or plant a row of trees to shut out his or her neighbors. The owner of a high-rise condo, living in a box stacked in a tower of other boxes, has no such recourse. If your neighbors are Metallica lovers or aspiring bagpipers, you could end up with some sleepless nights.

But there are steps developers can take to seal off what I’ll call the “owner’s envelope” – the floor, ceiling and walls of each unit – to limit sound transmission.Here are some steps to take and issues to consider if peace and quiet are important to you:

  • Confirm in writing that the developer has installed a sound-deadening assembly of materials. Contrary to what you may have heard, insulation plays a relatively small part in blocking noise. The key is proper construction detailing. If you were paying attention in science class, you remember that dense hard surfaces are the best transmitters of sound.
  • To inhibit sound from passing from the floor above, builders should install a “Z” channel in the ceiling. This piece of sheet metal, shaped (as you might expect) like the letter “Z,” has soft material in the middle that absorbs sound.
  • The U.S. Gypsum Handbook” (a manual by a major drywall manufacturer that serves as a Bible for home inspectors) recommends leaving a gap of about an eighth of an inch between the drywall of ceilings and walls – another way to block sound. That gap should be filled with caulk, which absorbs sound vibrations.
  • Developers should also install a sound-deadening layer made of sheet cork or Homosota board, an absorbent material, between floors. This detail has become fairly common in multi-unit buildings today, and any high-end building should have it. But be aware that some developers don’t install cork or Homotosa, even though the blueprints call for them.This was the case at two big complexes I inspected within the last month.That’s why you should ask to look at the blueprints before you sign a contract. Make sure that plans call for cork or Homosota board. If your home inspector finds these items are missing in the condo, demand changes in writing before you buy. And if you’re buying in an existing building, always read the condo board minutes. You may unearth complaints there that you won’t find anywhere else.
  • Builders can also trap and deaden sound through “doubled” or “staggered” walls. The builder creates a second wall inside a wall, complete with new studs and drywall. This is done routinely for plumbing purposes, but if added to a wall that separates your condo from your neighbors; it can go a long way toward reducing sound, especially if sound-deadening insulation is added to the second wall.This is basically the same principal at work in high-end recording studios, which are built by creating a studio within a studio, mounted on hard rubber so there’s no place where interior walls touch exterior walls.
  • Consider where the condo is located within the building. Are you near the garbage chute? Where are the parking garage, exhaust fans, elevators? Proximity to these elements can create noise. Which side of the building is the condo on? The north side can be windier – and therefore noisier – during the winter.
  • The hallways of multi-unit condo buildings should always be carpeted. You can reduce hallway noise even more by installing carpet up to your front door on the inside of your unit. Just be sure you don’t block any gaps between the floor and the door. These are sometimes required for safe air flow.
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