Hello All!
I am currently in the planning and design phase of building a very small outdoor control/mixing/vocal and acoustic recording space in Vermont, USA. This is in no way for professional work. It will be just me and the occasional friend working on my passion.
This is mainly a space dedicated to music that I can work in without distraction nor disrupting daily house activity or the neighbors.
The isolation requirements are not strict as I probably wont exceed 80 dB for mixing. Acoustic recording will be around that or most likely quieter. Also the building will be 40 feet from my house (Not a big concern) and 100 feet from the nearest neighbor.
I have emotionally budgeted $10,000-$20,000 on the entire project (Construction and Gear). I will be doing the building with the help of experienced workers and engineers.
This is a ground up construction so I have a lot design options to play with. The only restriction is that it must be uniform with garden shed it is being built against. The dimensions are 10x8x8ft with a 12ft peak at the roof. (See Pictures)
The biggest issue with the construction is that the shed is on 4x6 stilts about 4" - 8" off the ground. This, as I have learned, creates an isolation issue due to the "Drum Head" effect. So my main purpose of posting is to find what is reasonable to expect with a design like this so I don't invest all this money into a 50 dB reduction when my floor can only get 30 (Or whatever the case may be). I am not as concerned with higher frequencies as I am with Bass from the sub woofers getting amplified by the drum
After research I have not found much info on the limitations and capabilities of a design like this. Herein lies my questions:
- What are reasonable expectations for a design like this?
- Is it possible achieve a moderate level of sound reduction (40-60) by building on top of a stilt base
- Any design ideas? As Long as it "looks" the same I can do pretty much what ever I want aside from driving heavy trucks onto the yard.
Thank you very much
Kevin
Isolation Limitations of "Stilt" base construction
-
k.w.mcgreal
- Posts: 2
- Joined: Tue Feb 09, 2016 11:38 am
- Location: Vermont, USA
-
Soundman2020
- Site Admin
- Posts: 11938
- Joined: Thu Aug 21, 2008 10:17 am
- Location: Santiago, Chile
- Contact:
Re: Isolation Limitations of "Stilt" base construction
Hi Kevin, and welcome to the forum! 
Also, will the shed become part of the studio, or will they just share a wall? In other words, are you planning to take one wall of the shed and extend it outwards in some way to create the studio, or will the shed remain exactly as it is, with you just building another three walls onto one side of it, to create the studio?
If you wanted more than that, the ideal would be to pour a concrete floor on top of a plywood base, which in turn rests on joists. Obviously, your joists would need to be more substantial to handle the extra load of the concrete, but the results would get you into the 50-soemthing range easily, and feasibly into the low end of the 60's, for a thick slab done carefully. That would probably be the optimum solution.
You could still go more than that if you really wanted to (and have very deep pockets!) by building a second concrete slab over the first, on suitable acoustic resilient mounts. That would take you into the 70-soemthing range, and higher, depending on how much mass you put into each of the two floors, how much separation you provide between them, damping, and other factors.
I would suggest that your best bet is the single "concrete slab on plywood base". That is fairly simple to do, not excessively expensive, and gives good results. The only real issue here is how to get the concrete in if you don't want large trucks in your garden. There are three solutions for that: one is to rent a concrete pump to move the concrete from the truck out in the street to the location of the studio, less expensive bur more labor intensive is to get a team of helpers with wheelbarrows to do that job (I have done that, and it works, but you need probably twenty people with wheelbarrows, or maybe more if it is a long run from the street to the pour location. You only have a brief time window to empty the truck before the concrete starts hardening, and the trucking company starts charging you exorbitant extra fees for the delay). The third option is to rent a portable mixer, carry in sacks of dry ingredients, and mix the concrete right there, on site.
All of those are real options. I have done them all. The simplest is the concrete pump. Fast, accurate, simple, lowest labor. But more expensive, as you need to pay for renting it, and for the operator to run it.
However, there is another limiting factor here: How you build the rest of the building. If the outer leaf is also built on the slab, then you probably wont get more than about 50 no matter what you do. If you wanted to go beyond that, you'd to decouple the outer and/or inner walls from the slab in some form.
So in summary, What you want to do is feasible, you can get pretty good isolation, but you need substantial mass to do it.
- Stuart -
Is that the dimensions of what you want to build for your studio, or is it the dimensions of the existing shed?The dimensions are 10x8x8ft with a 12ft peak at the roof
Also, will the shed become part of the studio, or will they just share a wall? In other words, are you planning to take one wall of the shed and extend it outwards in some way to create the studio, or will the shed remain exactly as it is, with you just building another three walls onto one side of it, to create the studio?
For a floor that is not damped nor part of an MSM system, you are basically limited by mass law, regarding how much isolation you can expect. Therefore, the answer to your question depends on how you plan to put mass on your floor. If you plan to build it as a typical house floor (joists with wood subfloor then finish floor), you wont get much more than about 20-something to 30-something dB, at best, and that would not be very good at all in teh low end (drums, bass, bottom end of keyboards and electric guitar). To get more than that, you need to add substantial mass to the floor. If you wanted to build it up from several layers of plywood, drywall, MDF and suchlike, you could probably get into the region of 40-something dB, but still poor in the low end.- What are reasonable expectations for a design like this?
If you wanted more than that, the ideal would be to pour a concrete floor on top of a plywood base, which in turn rests on joists. Obviously, your joists would need to be more substantial to handle the extra load of the concrete, but the results would get you into the 50-soemthing range easily, and feasibly into the low end of the 60's, for a thick slab done carefully. That would probably be the optimum solution.
You could still go more than that if you really wanted to (and have very deep pockets!) by building a second concrete slab over the first, on suitable acoustic resilient mounts. That would take you into the 70-soemthing range, and higher, depending on how much mass you put into each of the two floors, how much separation you provide between them, damping, and other factors.
I would suggest that your best bet is the single "concrete slab on plywood base". That is fairly simple to do, not excessively expensive, and gives good results. The only real issue here is how to get the concrete in if you don't want large trucks in your garden. There are three solutions for that: one is to rent a concrete pump to move the concrete from the truck out in the street to the location of the studio, less expensive bur more labor intensive is to get a team of helpers with wheelbarrows to do that job (I have done that, and it works, but you need probably twenty people with wheelbarrows, or maybe more if it is a long run from the street to the pour location. You only have a brief time window to empty the truck before the concrete starts hardening, and the trucking company starts charging you exorbitant extra fees for the delay). The third option is to rent a portable mixer, carry in sacks of dry ingredients, and mix the concrete right there, on site.
All of those are real options. I have done them all. The simplest is the concrete pump. Fast, accurate, simple, lowest labor. But more expensive, as you need to pay for renting it, and for the operator to run it.
Stiffness isn't so much of an issue: mass is. The floor needs to be as massive as possible. Mass is what stops sound. Except for very low frequencies, where stiffness does become an issue.- Is it possible achieve a moderate level of sound reduction (40-60) by building on top of a stilt base
I would suggest sinking piles into the ground at key points, deep enough and large enough to take the weight of the building (your structural engineer will calculate that, not a problem), put suitable joists on them, pour the slab, then build on that.- Any design ideas? As Long as it "looks" the same I can do pretty much what ever I want aside from driving heavy trucks onto the yard.
However, there is another limiting factor here: How you build the rest of the building. If the outer leaf is also built on the slab, then you probably wont get more than about 50 no matter what you do. If you wanted to go beyond that, you'd to decouple the outer and/or inner walls from the slab in some form.
So in summary, What you want to do is feasible, you can get pretty good isolation, but you need substantial mass to do it.
- Stuart -
-
k.w.mcgreal
- Posts: 2
- Joined: Tue Feb 09, 2016 11:38 am
- Location: Vermont, USA
Re: Isolation Limitations of "Stilt" base construction
Thank you very much
The dimensions are for my planned space. It will be built separate from the existing building so no issues there.
I will look into the feasibility of pouring a slab on top of a ply base.
I don't really need more than 50 dB for what I am doing as I am planning on not even decoupling the ceiling/walls due to the limited space. Right now I am looking at just two layers of 5/8 drywall with green glue. I just wanted to make sure that that wouldn't be even more than my floor could do.
More will come soon!
Kevin
The dimensions are for my planned space. It will be built separate from the existing building so no issues there.
I will look into the feasibility of pouring a slab on top of a ply base.
I don't really need more than 50 dB for what I am doing as I am planning on not even decoupling the ceiling/walls due to the limited space. Right now I am looking at just two layers of 5/8 drywall with green glue. I just wanted to make sure that that wouldn't be even more than my floor could do.
More will come soon!
Kevin