# Couple of Flooring Questions



## Albertan (Jun 16, 2012)

My house was built back in 2008, but I am just getting to finishing the theater room now. I have two rows of seating and wanted to build a riser for the back row. I've done a fair bit of reading but I haven't found an answer to a couple of questions I have. As this site seem to have the best answers every time I google something, I figured I should just register here and seek answers. 


Should I place the riser on top of the existing carpet, or on the concrete itself?
I've read about recommendations to use DRI-core as a subfloor, but I think this is more for temperature control. The concrete floor in my home theater room has in floor heating so that's not really a concern. Is there another reason to put a subfloor in I am not aware of?
Are the U-boats to keep the riser off the concrete the best way to go/necessary if it should be on concrete, and how do I determine where to place them? I've spent a fortune on QuietRock drywall, and I plan to do some other acoustic treatments in the room as well. So I might as well do the riser right.


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## ALMFamily (Oct 19, 2011)

Albertan said:


> My house was built back in 2008, but I am just getting to finishing the theater room now. I have two rows of seating and wanted to build a riser for the back row. I've done a fair bit of reading but I haven't found an answer to a couple of questions I have. As this site seem to have the best answers every time I google something, I figured I should just register here and seek answers.


First off - welcome to HTS! :wave:



Albertan said:


> Should I place the riser on top of the existing carpet, or on the concrete itself?


As carpeting provides sound absorbtion (like furniture, people, etc), I personally would be hesistant to put down an additional layer of carpeting (over the riser) before I had taken measurements to determine how much absorbtion was needed. 



Albertan said:


> I've read about recommendations to use DRI-core as a subfloor, but I think this is more for temperature control. The concrete floor in my home theater room has in floor heating so that's not really a concern. Is there another reason to put a subfloor in I am not aware of?


The main reason for Dri-Core is moisture control. It provides a gap with breathability so that if you ever experience a leak in your foundation, it does not soak your foam / carpet. Standard subfloors do not provide that gap.



Albertan said:


> Are the U-boats to keep the riser off the concrete the best way to go/necessary if it should be on concrete, and how do I determine where to place them? I've spent a fortune on QuietRock drywall, and I plan to do some other acoustic treatments in the room as well. So I might as well do the riser right.[/LIST]


Honestly, it is the best thing I have found so far to provide a dampening gap between the concrete and riser. However, I have not made it to building my riser yet and have not researched that part completely yet - hopefully, someone else has a more imformed opinion.


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## Albertan (Jun 16, 2012)

Thanks for your assistance. I really appreciate it. The more I read, the more I want to do. I just ran to work and grabbed my wide angle camera to take some pictures. I'm going to post a build thread that I can ask questions as I go, rather than start several different threads. The journey is half the fun.


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## ALMFamily (Oct 19, 2011)

Albertan said:


> Thanks for your assistance. I really appreciate it. The more I read, the more I want to do. I just ran to work and grabbed my wide angle camera to take some pictures. I'm going to post a build thread that I can ask questions as I go, rather than start several different threads. The journey is half the fun.


No problem at all - we love questions here!

A couple suggestions:

1. Use the post padding thread to get to 5 posts - you need 5 to be able to post pictures. You can find it here.

2. Post in the new member forum and introduce yourself - it helps everyone get to know you as not everyone monitors the Construction subforum.

3. Check out and start a thread in the Equipment List subforum. There are a number of giveaways that happen, and you need to have a post there to qualify - also, check the sticky there that describes how to do the list in your profile.

4. And, definitely enjoy the journey - take lots of pictures! :bigsmile:


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## Albertan (Jun 16, 2012)

ALMFamily said:


> No problem at all - we love questions here!
> 
> A couple suggestions:
> 
> ...


All done! Thanks for the site tips. Now to get to work on the build thread.


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## fitzwaddle (Aug 25, 2010)

>>Should I place the riser on top of the existing carpet, or on the concrete itself?

If the room is already carpeted go over it; if not, go over concrete. If on concrete, building code may dictate specific construction (in my area, that meant green/treated lumber in contact with the concrete).

>>DRI-core as a subfloor

ALM already covered it, it is used to mitigate water leak damage. I was surprised to find that many folks have to tear it all out and replace when water leak actually does occur. It prevents water from damaging other stuff though.

>>Are the U-boats to keep the riser off the concrete the best way to go/necessary if it should be on concrete

No, not necessary, but I've seen them used under risers that will be used as a platform for tactile transducers, to let the riser shake vs. being anchored to the floor.

Another thing to think about before building the riser is whether you intend to use it for additional bass trapping - since that will require specific construction technique.


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## Ted White (May 4, 2009)

If building on a wood subfloor, or if you need to run wires under the floor, then the rubber Joist Isolators are appropriate. Takes up huge headroom, which usually is a deal breaker in a basement.

Consider a 3/8" acoustic mat, then a plywood topper. This will protect the slab from its coincidence frequency weakness.


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## Albertan (Jun 16, 2012)

Ted White said:


> Takes up huge headroom, which usually is a deal breaker in a basement.
> 
> Consider a 3/8" acoustic mat, then a plywood topper. This will protect the slab from its coincidence frequency weakness.


Could you explain this a bit better please Ted. Because I have both front and rear risers planned, I was going to take up the carpet and go back down to the concrete. It wouldn't be a big deal to treat the floor while its up. Thanks.


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## Ted White (May 4, 2009)

The 3/8" thick mat would be applied to the entire floor. Then the riser rests on this. The stage should be placed directly on the slab. No rubber mat. The floor section between the two raised areas would simply receive a layer of ply.

No need for the rubber joist isolators


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## Albertan (Jun 16, 2012)

Here is a scale drawing of my room with the riser and stage drawn in.










So if I understand correctly, starting with a bare concrete slab, build the two-tiered front stage on the concrete slab. Then lay down the 3/8" thick rubber mat on the reamining concrete slab. Next, build the rear riser on the mat. And finish by covering the remaining mat with plywood. Does the thickness of the plywood matter? 

And could you explain to me exactly what improvements this would yield over a normal underlay/carpet on the floor? Thanks again Ted.


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## Albertan (Jun 16, 2012)

Also, could someone recommend a good source for the 3/8" acoustic mat? Thanks.


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## Ted White (May 4, 2009)

Try a Google for "Serenity Mat"


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## Albertan (Jun 16, 2012)

Thanks Ted.


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