Rod's book, floor questions

Hi all So I picked up Rod's book and so far it is so very well written and answered a ton of questions (excellent book HIGHLY recommended)... but one big one is still open for me. The floor section in the book was a little brief to say the least. (sorry Rod no offense meant) Okay so here is my dilemma. I will be building my studio as a project studio for paying clients, we will be tracking at all hours of the day and night (they pay I can't limit the times they want to track). There is only one house close to ours and it is far enough away that if I do a pretty good job of isolation I will be fine. The dilemma is that because of the topology of the building area the studio must be built on a post and pier foundation. I have been told by an architect that I can get a slab pored in a basin for a post and pier foundation but I am sure that the slab will be limited in thickness. The ground slopes away from the existing house so the posts will start at around ground level at one end and will end up about 4 or 5 feet off the ground at the other end. How thick is thick enough for this slab to not have major flanking to the outside? If I were to not go with a slab due to engineering considerations (not sure what that would be but...) is there a way to get enough mass with some sort of wood deck system? Thanks!!!

not_so_new wrote:

The floor section in the book was a little brief to say the least. (sorry Rod no offense meant)

None taken. Understand that any single chapter - any single subject matter - in this book - could (in and of itself) have an entire book written on (or about) it. Thus it wasn't possible for me to go entirelyinto depth about any one subject matter - or cover every contingency that one might encounter. The concept was to give you enough information that you would be able to ask the right questions - and not have be blind to what you were facing in your particular construction. It seems I have succeeded in this endevor- because you are here - and are asking a very specific question about a very specific subject that you now realize could well cause you problems. This makes life easier for me - becuase I do not have to ferret out your problems in the midst of a thousand post thread. On to the issue at hand

The dilemma is that because of the topology of the building area the studio must be built on a post and pier foundation. I have been told by an architect that I can get a slab pored in a basin for a post and pier foundation but I am sure that the slab will be limited in thickness. The ground slopes away from the existing house so the posts will start at around ground level at one end and will end up about 4 or 5 feet off the ground at the other end. How thick is thick enough for this slab to not have major flanking to the outside? If I were to not go with a slab due to engineering considerations (not sure what that would be but...) is there a way to get enough mass with some sort of wood deck system?

Ok - first off - with a pier and post foundation you can always install a series of grade beams around the perimeter of the building and backfill within that to effectively raise the grade of the 1st floor. If the existing earth is structurally sound - then this fill will suport a slab - and you will (in essence) be building a slab on grade building - thus with a little care to pour isolated slab assemblies (as outlined in chapter 4 - see detail 4.1) you would be just fine. But - please do not misconstrue the section on elevated wood isolating decks (which are specifically speaking about decks constructed on top of existing deck assemblies). In new construction - as long as your engineers understand the mass required - and the center frequencies needed to effectively create isolation - a wood frame deck assembly in post construction - can absolutely give you the isolation you need - this because form the very beginning the structure will be designed to carry the mass required to create that isolation. Part of this will require that an acoustical engineer be brought on-board to verify the design will meet the isolation - and that should be early on in the process - but either way - with an elevated wood deck - an elevated concrete slab or a slab over fill with grade beams at the building's perimiter - you can acheive the isolation you require. Sincerely, Rod

Hi Rod First thank you so much for the response very cool to be able to talk to you about things in the book. Yes I agree that the points in the book are a really really good primer for getting started. Actually, outside of the floor questions that I have, I think your book would probably be enough to take the process from concept to completion, at least for the little I have skimmed and read (just got it yesterday only on chapter 4). Anyway so this brings up another few questions. Sorry if this is covered in the book. I live in Pittsburgh P.A, not a cow town but not NY city or L.A. by any means. I work as a IT guy at a pretty large architectual firm so I have allot of building resources but I don't have any clue about were to find an acoustical engineer and I am not sure anyone at the firm I work for does either (I could be wrong about that). How does one go about finding an acoustical engineer in a given city and would you expect a city the size of Pittsburgh to even have one? Also how much do you think it would take to get someone to stop out? Exactly what do I need to tell them / ask them or if they are good enough will they know what I will need to do? When you say.....

In new construction - as long as your engineers understand the mass required - and the center frequencies needed to effectively create isolation - a wood frame deck assembly in post construction - can absolutely give you the isolation you need - this because form the very beginning the structure will be designed to carry the mass required to create that isolation.

... it sounds like I could get away with a wood deck? If that is the case can you give m a little detail how I would go about the decking, materials, layers and such? This is what I was looking for in the book that I could not find and I did a search here but most of the stuff seems to point to a slab. I am just trying to weigh the cost between slab (that someone else will have to pour for me) and wood (that I could do myself, I am more than pretty handy with building things). You have any take on this as well, cost someone pouring the slab vs. me building wood decking with enough mass for isolation? Again I can't thank you enough for your great work with the book and your taking the time to answer questions here.. sincerely thank you, thank you, thank you!