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If one HAS to build a raised house...

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Posted on May 9, 2007 at 09:07:44
marc g.
Audiophile

Posts: 3330
Location: New Orleans
Joined: October 14, 1999
 What tips could be utilized in reducing whatever negatives a suspended floor supposedly imparts? The best audio system I know of and consider a reference is located on a suspended floor so they can't be that bad (if they are I really don't care b/c it's a moot point - I am building up). I'd want to make it better since I'd have the luxury from starting from scratch and incorporating any ideas in the original construction.

Was thinking perhaps a couple extra pilings/supports in the middle of the room would tighten things up (not sure if tightening up the floor I what I even need to do though). Extra cross braces between the main floor joists? I do recall an installation whereby the owner had two cement columns poured up to the interior floor level to set the speakers on. Might be too extreme, maybe not?


marc g. - audiophile by day, music lover by night

 

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re: raised house, posted on May 9, 2007 at 09:22:48
geoff
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Posts: 3502
Joined: April 5, 2000
Contributor
  Since: September 10, 2003
 take your plans to a consulting structural engineer with your concerns. If you have retained or know an architect or a dilligent contractor, he/she can put you in contact with one or act as a go-between. I deal regularly with several engineers who will mark up a set of drawings or give you a field sketch on the spot, and bill you for an hour or two.

 

Overbuilding....., posted on May 9, 2007 at 09:33:35
pburant
Audiophile

Posts: 2285
Location: New Hampshire
Joined: January 9, 2002
 is generally a good idea with your goal in mind. You want the floor to be as stiff as possible, and extra supports will certainly help in that regard, as would larger joists (such as 2x12 if 2x10 are called for in the current plan).

In my previous house, when I added jacking posts beneath my listening room to stiffen the floor, it was one of the best tweaks I ever performed.

Making the floor non-resonant would also be worthwhile. One way you might do this would be to put a layer of 1/2" or even 3/4" MDF over the plywood subfloor.

Have fun,
Pete

 

Re: If one HAS to build a raised house..., posted on May 9, 2007 at 09:40:41
Door Nail
Audiophile

Posts: 745
Joined: August 27, 2005
 If you're going to pour cement columns for anything, pour one for your turntable. In fact it would be great if you could decouple the column from the floor altogether. I used this technique many years ago in disco installations.

 

Two ideas., posted on May 9, 2007 at 09:42:43
Al Sekela
Audiophile

Posts: 9169
Location: Northern California
Joined: February 18, 2002
 First is something I saw on This Old House. They had a long span for the second floor and did not want to use supporting pillars or make the joists wider. The solution was to sister the joists with heavy sheet aluminum between the two wood joists. The aluminum provided major stiffening without too much added weight.

Second is to recognize the vibration modes of any suspended floor. Between the supports, the floor acts like a drum head. Anywhere except in the exact center of the drum head, the motion is tilting as well as up and down. A rigid rack on the floor translates this into horizontal as well as vertical motion at the equipment.

CD players in particular suffer from horizontal vibration, because it fights with the laser pickup servo mechanism. I've found that a roller-ball suspension is a major upgrade for even a heavy player like my Wadia 861.

 

Here is what I did......., posted on May 9, 2007 at 10:50:15
Chuck Y
Audiophile

Posts: 4376
Joined: August 31, 2001
 Joists 16" on center (many building codes require 48" and some better builders upgrade to 24"), 2x6 tongue and groove planking laid accross (perpendicular) to the joists, 3/4" plywood sub floor, 3/4 inch T&G hardwood (oak is great). I placed piers 3' apart, but you just can't put in too many - its cheap. You can 'jump' on this floor and hardly get the needle to jump out of the groove. Highly recommended.

If you are using drywall you might consider double thickness in you listening room. And, although it might not have any effect on acoustics, I like 2x6 framing on all exterior walls, weight bearing walls, and for consistency walls between rooms (not closets etc). Cost a bit more, but it contributes to stability of your home in general.

Have fun.............

 

If you know where your system will go, put a footing there, posted on May 9, 2007 at 10:55:09
Norm
Reviewer

Posts: 31024
Joined: September 6, 2000
 Or afterwards, if you can get under your first floor, there are expansion metal poles that you can jack upwards between the earth and your flooring to give support where you need it. I used this once in a house were I had a partial basement but just a crawl space under where my system components were. I worked great.

 

Where do you find these support "poles"? (nt), posted on May 9, 2007 at 11:00:28
FrankC
Audiophile

Posts: 1230
Location: Silicon Valley
Joined: April 6, 2000
 .

 

Re: If one HAS to build a raised house..., posted on May 9, 2007 at 11:01:54
caffeinator
Audiophile

Posts: 1729
Location: Pacific Northwest
Joined: August 22, 2003
 My lessons learned on floor systems from building a couple of houses are first, if you use dimensional lumber for floor joists, go up to the next higher size lumber above what's specified on the plan. My plan spec'd 2x10 joists; I increased those to 2x12. As much flex as there was with even the 2x12, I can't imagine what it would have been like with the smaller sized material. Better still is to not use dimensional lumber at all but instead use something like a Trus-joist beam material. It is way stiffer and far more stable over time than dimensional lumber. Also watch the spans on the plan - often they may be structurally adequate, but still quite flexy (bouncy). On the same plan I mentioned before, even with upgraded lumber, in some areas you could literally see and/or feel the floor flexing as people walked across it. I ended up adding a couple of mid-span beams underneath in one area where the span was longest. Depending on what's underneath your floor system (like a basement) more posts and beams may or may not be possible, but it makes a huge difference.

Second lesson is regardless of joist material, glue and screw the floor deck down to the joists. While structure borne noise and vibration are issues to be sure, squeaks and creaks from a noisy floor system are a colossal PITA and very intrusive. Gluing and screwing generally avoids this issue entirely.

Finally, if you're really serious about preventing structure-borne vibration from finding it's way to your equipment, isolation is a very effective means of keeping it out. I saw an installation at someone's house where they'd cut four holes (about 6" dia each) in the floor and dropped a concrete-filled post through each into a footing below. The four feet of the equipment rack stood on these post-tops (though the post tops were concealed by the carpet). You could literally have an LP spinning and jump up and down right next to the rack with no visible movement of the turntable or rack. Of course, you have to be really, really sure where you want the rack to be!

Good luck with the project :)

 

Home Depot, etc., posted on May 9, 2007 at 11:41:18
caffeinator
Audiophile

Posts: 1729
Location: Pacific Northwest
Joined: August 22, 2003
 They are available at a lot of home-improvement or building supply stores. You can get pre-cast footing blocks (kind of pyramid shaped) with a jackscrew embedded in them that have a post saddle on top.

 

Re: Where do you find these support "poles"? (nt), posted on May 9, 2007 at 12:08:50
Glen B
Audiophile

Posts: 1081
Joined: October 4, 1999
 They're commonly called "jack posts." I use several of them under my wooden floors.

 

ICF, posted on May 9, 2007 at 12:33:04
lipmanl


 
Throwing out an idea--Insulated Concrete Form. Let me start by saying I've never heard of a raised ICF house, but don't see why it couldn't be done.

To build an ICF house, they lay build structural walls out of, essentially, big hollow styrofoam legos. They then stick in a bunch of rebar, and pour cement, filling the legos. The styrofoam stays, serving as form and insulation.

ICF structures have excellent wind resistance, are cheap to heat and cool, and should be stiff.

To me, a raised ICF structure would simply be a multistory structure with incomplete walls on the bottom floor (could be your garage).

I think you should look in to it, but I don't know if this would work for your goals.

 

Get Yourself Some, posted on May 9, 2007 at 13:38:20
Fishstink
Audiophile

Posts: 608
Location: Michigan
Joined: March 24, 2006
 Hurbies Raised House Silencers. Sorry, I just had to do it.

 

known in Britain as acros, posted on May 9, 2007 at 16:25:12
dave c
Audiophile

Posts: 32042
Location: Zigzag Street, Red Hill
Joined: April 17, 2000
 They are an affordable and effective solution.
If you have a reasonable floor or flat surface under the floor you want to brace just put them in position and wind them tight.

 

Re: If one HAS to build a raised house..., posted on May 9, 2007 at 17:58:15
Rod H.
Audiophile

Posts: 1918
Location: Oregon
Joined: May 18, 2005
 Acoustics aside, just remember for the rest of your house that rigid floors are hard on our bodies, especially as we get older. I think it's a great design feature that good old wooden floors in houses have some give.

Rod

 

That said, posted on May 10, 2007 at 07:49:22
jedinvest
Audiophile

Posts: 15168
Location: No. California
Joined: December 26, 2003
 Make sure that the joists are in the proper location with respect to your gear. If not, the structural engineer can easily change that.

 

Good idea, though I might change some of the specifics, posted on May 10, 2007 at 09:05:03
artemus
Audiophile

Posts: 15273
Joined: March 12, 2001
 You might not need a footer, but instead use 4" solid cinder blocks placed flat on the ground. Secondly, unless you have a pretty tall crawlspace, the adjustable metal posts will be too tall since they are generally used for basements. The cheaper alternative would be to use 4x4's placed on top of the 4" block and running up to a 2x4 or 2x6 under the 2-3 floor joists which are beneath the equipment. Put a 4x4 on each end of the 2x4.
FWIW, I am a builder and have used this approach in my house with good results


Life has lots of trials and lots of music to help us through them.

 

That'll work but will cost a fortune, posted on May 10, 2007 at 09:37:49
artemus
Audiophile

Posts: 15273
Joined: March 12, 2001
 It is definitely overkill.
One thing I might point out though is that no code that i am familiar with will allow 48" o.c. for floor joists
Life has lots of trials and lots of music to help us through them.

 

Lightweight concrete ! - and a couple of other suggestions, posted on May 10, 2007 at 09:46:54
Bambi B
Audiophile

Posts: 3304
Location: Los Angeles
Joined: March 24, 2005
 marc g.,

If you need to use a raised floor- the best case when the site has a lot of slope, then you can get rigidity and vibration damping with the use of a lightweight- non-structural- concrete on the floor. Double the bottom plate of the walls to create the "form" and pour the lightweight to the top of the plates- close to 3" thickness. The floor joists may need to step up a size to accomodate the extra weight- have the structural engineer check this.

A non-structural slab of this kind is very effective- for example if you put a bedroom over a garage, the isolation of noise and vibration can be almost total, plus a vastly improved fire separation.

Years ago I had a house on a raised floor and the transmission of vibration throught the floppy floor was extreme enough that there was feedback from speakers back through the Oracle turntable. I could see the tops of the speakers wobbling back and forth 3/4" while the woofers tried to make something like an 8Hz sound- and using about all 105W of the ARC D115! Lightweight concrete would've completely negated that problem, I had to move everthing around such that the equipment was almost in another room- (on another floor structure) from the speakers.

A couple of other recommendations if you're making a purpose built listening room:

1. If possible, have at least one wall non-parallel and a sloping or divided ceiling.

2. Avoid proportions that are multiples or that have common denominators: for example an 8' X 16' X 24' is not as good as 8' sloping to 11' X 17' X 26'

3. Use STC- "Sound Transmission Clips" on the drywall to reduce transmission through walls. Dual glazing of course really helps keep out outside noise and some companies offer specia sound reduction lines of windows.

4. Plan the furnishing to audio equipment layout carefully. Today, I'd include an Internet hookup and potential computer location nearby to the audio system. In my future home, I'm putting in a whole house local network so I can potentially have a computer device connected in almost every room.

5. Consider dedicated power circuits running in conduit and using a reasonably priced, high- grade outlet like Hubbell 8300 or Pass and Seymour 5362 (see VH Audio). In my future home I'm having three 20A circuits for the main system: two at the main equipment area with one for preamp and sources (actually feed for power conditioner), one for the power amp, and then at the wall next the speaker location another duplex 20A in case I ever want monoblocks. (Using Hubbell 8300 receptacles)

6. Oversize the AC/heating duct and air registers to reduce air velocity a bit. If you can, use smooth sheet metal rectangular ducts instead of the flexible round kind, these details will really quiet the A/C air rush sound. Also, locate the registers so the air is not directed at you when listening.

Plan three times and build it once!

Cheers,

Bambi B

 

Cost a Fortune?, posted on May 10, 2007 at 09:46:55
Chuck Y
Audiophile

Posts: 4376
Joined: August 31, 2001
 In comparison to the thousands that a a lot of folks spend for isolation/acoustic treatments, not to mention equipment? If we can be that anal about quality equipment the difference in lumber costs and a bit of extra labor is minimal! :-)

BTW, I built my house 15 years ago, perhaps the code has changed since, but at that time (where I live) it was 48" - and titled "How to build a wood trampoline". :-)

 

Short jack posts are available, and they are adjustable. I did put a 2x4 across three joists., posted on May 10, 2007 at 11:25:52
Norm
Reviewer

Posts: 31024
Joined: September 6, 2000
 I wish I could do it in my present home, but my room is on the second floor and my wife doesn't want a post in her kitchen for some reason.

 

Short jacks.., posted on May 10, 2007 at 12:03:52
Craiger56
Audiophile

Posts: 5574
Location: San Jose CA
Joined: April 3, 2002
Contributor
  Since: December 29, 2003

..like these from Economy Lumber work great.

Existing piers should be inspected also, if they can be turned or moved at all obviously they aren't holding much weight and need shims or replacement.

Cheers

 

Think about it this way, posted on May 10, 2007 at 12:34:50
MylesJ


 
Since you can do what you want without much extra expense in new construction how about having the components and the speakers on separate subfloors. I built a house on a hill. The entry level is 4 feet below the main floor. The entry level was made wider that it needed to be to host the audio gear and the fire place. Both of these face into the living room. Both appear to be at the same level as the living room. There is about a 1/4 inch gap between the standard suspended floor of the living room and the directly supported by the earth section of the mud room, fireplace and equipment. The speakers are spiked on the suspended floor. There is no direct transmission of the floor vibrations to the equipment side. You can dance without moving the turntable.

 

I haven't looked in some time but they were not a stock item here. They could be ordered, but I won't order anything, posted on May 10, 2007 at 13:19:39
artemus
Audiophile

Posts: 15273
Joined: March 12, 2001
 from the big boxes.
I'm sure that post in the kitchen would be somewhat of a challenge to sell.
Life has lots of trials and lots of music to help us through them.

 

You haven't priced a house lately have you?, posted on May 10, 2007 at 13:33:08
artemus
Audiophile

Posts: 15273
Joined: March 12, 2001
 Fifteen yrs ago they were about half of what they are today. Building prices start at $100 sf. now. Fifteen yrs ago that price was about $55. Thats in fly over country. I'm sure the prices are higher in other parts of the country, however the price increases are about the same in percentage.
I've been in building business for over 35yrs and I have never seen a 48" o.c. on a floor unless it was a poured concrete.
Life has lots of trials and lots of music to help us through them.

 

Thanks to all who responded..., posted on May 11, 2007 at 10:27:51
marc g.
Audiophile

Posts: 3330
Location: New Orleans
Joined: October 14, 1999
 Thanks for the tips and ideas folks. I think I'll be leaning towards some extra support pilings, cross braces, and double layer of plywood as a minimum. Good tips about the AC system.

FWIW - We are seriously thinking about building a round house from Deltech - see link below. If built raised, they have a subfloor system that I'm assuming are trusses. It's certainly not just pieces of dimensional lumber. My audio room would be a rectangular wing added ot the main structure and would utilize the same "web-tech" (think that's what they call it) subfloor system so beefing it up may not be possible as it would say, going to a 2*12 from a 2*10. I'm sure the extra pilings would address any extra support issues. Many of these homes built in high wind or hurricane areas have two layers of plywood on the floor for added strength - so the system can handle some extra weight.

marc g. - audiophile by day, music lover by night

 

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