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Low-rise Foam Between Interior Walls


Kutch's Avatar
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Join Date: May 2009
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MI

07-07-10, 09:17 AM   #1  
Low-rise Foam Between Interior Walls

I have a situation where a spare bedroom adjoins my master bathroom. The problem is the noises in the master bathroom are easily heard in the spare bedroom. Whether it's the shower or someone using the toilet, every noise comes through.

We're going to be taking on an exchange student this fall, and I would like to reduce the amount of sound going through the walls. The problem is, I don't want to turn this into a major constuction project. My first thought is injecting a low-rise foam between the walls. Does anyone have any ideas on the effectiveness of this? Is this something I could easily do myself or should I have it professionally done? I haven't yet researched the cost involved either way.

 
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07-07-10, 09:45 AM   #2  
Adding the foam will reduce some of the noise from one of several sources. In other words, a 25% reduction in 25% of the noise will only result in a 6% overall reduction. Sound travels many paths. Air paths, through openings around receptacles or heat and ac vents. Mechanical paths where wall framing conducts sound directly from wall to wall. Up and over, down and under, and out and around, all add up to the total of the sound heard from one room to another. Even if the foam was 100% effective, it would only be eliminating one component of the sound.

Unfortunately, with the lack of competing sounds/noise, our hearing gets more acute, which complicates the problem.

Here are some thoughts:
Where the foam will only affect the cavity, a wall covering will reduce the sound across the entire wall.

Seal around all electrical boxes on that wall from both rooms.

If there is a basement below or attic above, consider adding extra insulation in those areas.

Supply and return ducts are often sound conducting paths between rooms.

If the heat is baseboard hot water, check for paths between the rooms.

By looking at the many paths and adding up the small gains that can be achieved on each, your end results will be better.

If adding any insulation for sound adsorption, consider high density or mineral wool.

Bud

 
Kutch's Avatar
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07-07-10, 11:59 AM   #3  
Thanks, Bud. It's on the 2nd floor. I'm not looking to completely deaden the sound, but more toward an overall reduction as cheap as possible. The attic has insulation, but I'm sure it's to the minimum code allowed here in Michigan. I wish that I had this house built. I would have put deadening insulation between every floor and wall in the house and sealed everything. The additional cost of materials would have been minimal.

 
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07-07-10, 01:00 PM   #4  
Your evaluation of what could be done next time is being echoed across our country. The realization is that 90%+ of our existing housing stock is not built for today's energy costs and certainly not tomorrows. And yes, the cost during construction is minor compared to retrofitting.

Roxul makes a sound proof batting, but their regular mineral wool batts are very dense. Trouble is, you can't stuff it into a hole . Removing all of the sheetrock on one side and constructing a double wall to eliminate the mechanical coupling and double the insulation depth would be the most effective.

I have never used the slow rise, but the typical estimate of $1.00 per board ft. would be close. That's $3.50 per sq ft of cavity space and you really don't know what you are going to get.

Rooms can be sound proofed, so that a noise on one side of the room isn't heard on the other. Walls can absorb sound, which reduces what they can transmit. The room on the other side can again absorb sound so that what gets through dissipates quickly.

Stuff helps, that's pictures, wall coverings, furniture, drapes, as they all absorb energy or break it up so it can't go anywhere.

Good luck,
Bud

 
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07-07-10, 03:52 PM   #5  
Maybe a layer of quietrock will help.

 
hironomous's Avatar
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07-09-10, 04:31 PM   #6  
as noted above, our hearing is more acute where there is no competing noise. The sound of a bathroom fan is less unpleasant than the other sounds you mention, so having the fan run full time with the lights or on a motion sensor might also help. In work spaces requiring confidentiality (e.g. counselling offices) white noise is often used this way.

 
Ted White's Avatar
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09-02-10, 10:44 AM   #7  
Kutch, what did you wind up doing?

 
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