Basement ceiling

M

marshall409

Active member
I'm back again!

Finally started my long talked about work on my basement. Stripped the walls and ceiling completely...bare foundation walls are painted. Concrete floor is going to be either painted or vinyl tile to keep cost down.

I've got a huge space here...rough 24x20. Divided down the middle by a metal support beam complete with annoying pole in the middle of my room.

Anyways the only part I have yet to decide on is the roof. I wanted to do the simple fluffy pink insulation+fabric covering idea to complement my hard floor, but my mom said shes not letting me do anything unless its going to stop sound at least a little bit. So i've come up with a few ideas from some research:

1. Seal up the floor boards with a layer of drywall or MDF and caulking right up in between the joists and then do the fabric/insulation roof

OR

2. Seal up the floor boards as above, then resilient channel or rubber pads on the joists, then a layer or two of drywall (if a structural engineer approves it of course).

Now, I'm not going all out here. I will not be able to do any serious modifications or treatments to the HVAC system and my room is probably not going to be perfectly sealed in other areas. But I know that either of these options will help A BIT and thats all I'm looking for.

My question is, will the the first idea help significantly less since I'm only adding mass to the already exisiting leaf(the floorboards)? Will the second one be well worth the cost of material and labour?

Any other cheap and somewhat isolating ceiling ideas would be greatly appreciated.

Thanks guys,

Adam
 
Hi Adam

For an alternative idea that may help, consider adding compressed cellulose fiber boards to the materials mix. AKA soundstop or homasote.

Prior to building my studio I met a guy that builds movie theaters. You know the cinaplex, bunch of theaters all together kind of places. He said they used tons of this stuff and multiple layers was pretty standard. I looked into the NRC values of it and because it was fairly cheap and light, I ended including it in my materials list. You can cut the boards with a utility knife and trim around electrical and plumbing very easily.

My local drywall vendor had a non-homasote "brand x" stuff that I used multiple layers of on the outside (room in a room) of my studio to further reduce the noise going to the outside.

For my studio design on the 3rd floor, the added layers of drywall was getting heavy and I still wanted a little extra reduction. I reached the limit of mass the structure would support so I so I had to use some lighter weight insulative materials.

So I used 2x6 framing insulated with fiberglass, sinlge layer of drywall on the inside wall, double on the outside, with a layer rigid fiberglass covered by double layers of the sound stop boards fastened by long roof nails on the verticals. The ceiling angles were a little harder to install as I didn't have much room to work with between the roof and studio structure. When the kids were little, I could get pretty damn loud in there without disturbing their sleep. Now I go to bed before them.

What I am suggesting for your basement is seal the floor if there are any openings to above first. Insulate thoroughly. Add one or two layers of sound stop then drywall using longer drywall screws. The soundstop is easy to handle. Stagger the layers if you use two. Use roofing nails to hold them in place until the drywall is up. Make sure everything is sealed well.

Will it stop the sound transmission. Not completely but neither will using resilient channel. It will however get you very good attenuation levels without breaking the bank and without adding tremendous weight to the project. This is its biggest advantage. You want to know how much? Look up the STC ratings on all the materials you're planning on using and add it up. Then decide if it is enough.

One layer of drywall with two layers of soundstop and fiberglass insulation should be able to be supported by the floor joists unless this is a really old sub-standard structure and its not a budget buster. Hence the reason for suggesting it.

You will still need to treat the ceiling to deal with acoustics on the inside but this will go a long way towards your problem on the outside.

Don
 
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Another question along the same lines...

If I were to stick homasote soundboard or sheetrock in between the joists right up against the floorboards...should it be screwed in or green glued?

Adam
 
Hi Adam

I'm not sure I understand you or perhaps you misunderstood my suggestion. My advice was an alternative to your #2 idea. I'm suggesting you put insulation (the fluffy pink stuff) in between the floor joists, then seal it up using 4x8 sheets of sound stop/homasote, then cover that with drywall.

Your suggestion was to use resilient channel. That helps the STC by mechanically decoupling the drywall from the floor joists. The soundstop works similarly (not quite as well but it does add insulative/mass where the channels do not). Resilient channel is really easy to screw up negating its purpose/effectiveness. I've seen drywall contractors do this all the time.

Glueing or screwing drywall directly to the floorboards is not going to help you much with sound transmission loss. The gap between floorboards (separated by the floor joists) and the ceiling below is an essential element in the attenuation plan. What you want to achieve is a combination of mass, insulation and mechanical separation. Insulation with drywall and resilient channel does this. The alternative I suggested also does this. The one other downside to using channel is that it is not possible to use two layers of drywall (adding more mass if the structure can support it). What I laid out is a decent alternative with minimal cost (not much difference between channel and generic soundstop boards).

Don
Folkcafe
 
Just get a truckload of old, smelly eggcrates and SuperGlue them to the ceiling, maybe on the concrete floor too.;)
 
Dodgeaspen

Compare the STC ratings of a non-insulated and an insulated wall and let me know if you wish to revise that statement.

From stcratings.com
Sound absorptive material can be installed inside of a partition's air space to further increase its STC rating. Installing insulation within a wall or floor/ceiling cavity will improve the STC rating by about 4-6 dB, which is clearly noticeable. It is important to note that often times, specialty insulations do not perform any better than standard batt insulation.

While not a ton better than the airspace in between the floor and ceilng layers, every bit of the plan is helpful. Hence a multi-pronged solution. Mass, mechanical isolation and insulation will net you the biggest result.
 
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