Re: Sound Class Transmission Rating
From: Sharon Villines (
Date: Sat, 7 Mar 2015 08:27:10 -0800 (PST)
> On Mar 7, 2015, at 10:57 AM, R Philip Dowds <rpdowds [at]> wrote:
> Severe budgeting problems forced compromising on Cornerstone construction 
> standards, so our walls and floor/ceilings are of the most basic assemblies:
> PARTITIONS between units are 5/8” firecode gypsum board each side of 2x4 or 
> 2x6 studs, insulated.  We are not happy.  US Gypsum manuals put this kind of 
> construction at STC 46.
> FLOOR/CEILING ASSEMBLIES between units are typically hardwood over structural 
> plywood; 2x10 floor joists; and 5/8” firewood gypsum board on strapping.  We 
> are not happy.  The manuals say STC 39 and IIC 56.

Our ratings are probably the same as CornerStone's. The developer described 
them as "better than most" but they are not better than condos I have 
previously lived in. I knew, for example, when my upstairs neighbor acquired a 
new vacuum cleaner. I know when they are out out of town because a teenager 
comes to feed and play with their cats. He stays to play computer games on a 
humongous TV screen. I've asked him to take off his shoes (work boots). 

My downstairs neighbor complains when I have more than one child in the 
apartment. I hear loud voices in through my bathroom wall. Since people rarely 
yell in the bathroom and we and rarely are in there at the same time, it isn't 
a problem. I hear containers knocking against the wall when neighbors clean 
their counters in the kitchen after dinner.

Some have installed "party walls" in bedrooms -- one to muffle the sound of an 
early morning coffee grinder next door and one next to almost constant loud 
music playing neighbor.

What did help was people moving in and adding heavier and soft furniture in 
addition to rugs. For various reasons, many had moved in with almost no 
furniture. The units were like drums amplifying sound.

Most condos require that 80% of upstairs unit floors be covered with rugs. I 
highly recommend it. I often wish we would have everyone go through walking 
training. I only hear one of my upstairs neighbors and it is the thinner one. I 
once knew the heavier walker was angry because she stomped around for two weeks.

Silence from the sounds of others gives a great feeling of luxury and conveys 
an impression of quality construction.

Acoustics are very hard and expensive to fix once you move in. Spend every dime 
you have on them.

Sharon Villines
Takoma Village Cohousing, Washington DC

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