complex isolated slab questions

This refers to my studio build, vibrations recording. More details are in my (vibrations1951) previous posts to be found in construction forum. It’s cold here and the ground is already covered with about 2’ of snow here in northern Maine, USA but it feels like spring is coming fast because I still have many questions before I break ground! Could anyone help by clearing up some specific questions that have come up between the contractor and I. We’re trying to save valuable building time by having materials, plans and alternate plans as ready as possible. (Most of the materials often need to be ordered months ahead and good subcontractors have to travel hundreds of miles and need to be booked soon. They can’t get onto the ground until June in a good year, rains settle down by July and the first frost is usually the 3rd week in August, making for a short window of good building weather.) So here goes: 1. We plan to build independent slabs to avoid flanking and increase sound isolation. I’m on a hilltop and that means ledge, likely only separated from some independent slabs by some leveling sand, 2” of Styrofoam and the vapor barrier. -Will the ledge defeat the sound isolation or actually help by being a sort of sound absorber of the low frequencies? 2. We want to form up the 5-6” slabs with 2 thicknesses of 2” Styrofoam and pour all 4 slabs at once because the slab guys are traveling 150 miles each way to do the job. I don’t want to have to do multiple pours, greatly increasing the cost here by putting the crew up for the night and paying for 2 days time! - So my question is, would it be unwise to leave the styro in place or should I plan to remove it once the slabs are cured a bit, (chop or burn them out???) 3. I plan to bring in my AC High Voltage wiring from above and then provide separate 4” plastic pipe chases below the slabs for Low Voltage and Line Level cables. -Will it be acceptable to bridge the gaps between slabs with flexible rubber connecting collars? Will this cause isolation or worse, weird sound anomalies? (I intend to stuff the open ends with rock wool.) 4. I think I would prefer to utilize metal Stage Pockets/Floor Boxes for the LV runs rather than punch more holes to later plug in the walls. Besides it could shorten the cables needed to mics etc. from the chase ends. I worry about the pockets being dirt collectors yet perhaps a small maintenance problem with greater gains. I’ve even considered constructing short podiums by the walls to accommodate the emerging chase with connector plates as another alternative to going through the room walls; or perhaps even coming up with the chases through the “inside-out” wall floor plates. -Any cautions or thoughts?? 5. Lastly (for now of course) I want to try and build single “super doors” that Rod describes in his book for many of my doors (good winter projects!) -But, if I were to use double entry or sliding glass door units between my drum and live rooms,(1 set per wall) do they need to have a degree difference (6-12 degrees that is?) or will parallel with 5-6” between work? -If non-parallel is needed, what should be the minimum angle used? - I’m trying to save valuable floor space without compromising my whole system on the door details. Below is the latest version of my floor plans, or I should say YOUR floor plans John! The more I learn and work with your ideas and other’s, the luckier I feel to have your help! Thanks again for your fabulous forum (which I read over and over and over and over…..) and generous support to us newbies and the rest! -------------------------------------------------------------------------------- --------------------------------------------------------------------------------

I'm not knowledgeable enough in construction detail to answer your questions.... Rod? I just wanted to say hello to a fellow Mainer.... Hodgdon, eh? You must have your contractors coming up from Bangor.... many here in southern Maine think Bangor is the northern border of the state.... LOL. They don't realize Bangor is still in the southern half of Maine..... heh Good luck on your build!

Ain't it the truth JWL :lol: Good to know you are that close by (so to speak!)! Congrats on the hook-up with Ethan. I'm sure I'll be tapping into your expertice in the future. Right now back home has about 3-4' of snow on the ground but we are at our Carribean time share, thank god! Gald we got it before I decided on the studio build :lol: .We're so lucky to have this 2 weeks a year cause without a break, it could be maddenning. I moved to ME in '77 by choice and would never move away.We may be bringing in most outside help from Bangor area and perhaps south of there. Stay tunned and thanks for the well wishes! jp

PAGING ROD...PAGING ROD...When you can, I could use your thoughts :? Thanks in advnce, jp

I would not do this...... First off - a 2" jopint is just too big........ 1" is perfect. My usual spec is the 1" iso board from Mason Industries - but I recently found out that they have discontinued that product. So I figured out a way to make your own. Buy the vinyl covered rigid fiberglass insulation from Home Depot - it is about 5/8" thick. Slice it into widths to match slab height at the joint Place 2 pieces back to back and join together with duct tape top and bottom. This places the vinyl to the outside face so the material doesn't soak up a lot of water. Fasten this to a piece of formwork using finish nails Set formwork so the face of iso is at the face of concrete (1/2" from centerline of the 2 walls. Pour your 2 outer slabs - and float - within 2 hour you should be able to remove the forms - pulling the finish nails through the iso-board. Set formwork with remaining boards and pour control room - float same - within 2 hours you should be able to remove form - Pour ramaining slab. Finish concrete slabs in order of pours - Your concrete contractor should not have any problem finish all of this within a long day. Keep concrete wet with poly over it for at least 6 days...... Remove poly - cut edge of iso board from edge of concrete to 1/2" below top of concrete to create a V-shaped recess in the caulk joint - apply caulk. Rod

Gotcha 8) Thanks for the quick and detailed reply. What you suggest is perfect and I acually think I understand it completely. To be sure, by

Pour your 2 outer slabs

you mean the smallest slab (iso/chill room) and drumroom, then only needing to form the front edge of the CR slab for the 2nd pour and then finishing with the live room requiring no form board, just the 2 layers of iso you describe on its outer edges for the final pour (3rd). Elegant :) Should I assume by your response that my question 1

Will the ledge defeat the sound isolation or actually help by being a sort of sound absorber of the low frequencies?

is not a concern with the ledge?? Also what of

Will it be acceptable to bridge the gaps between slabs with flexible rubber connecting collars? Will this cause isolation or worse, weird sound anomalies? Flanking?? (I intend to stuff the open ends with rock wool.) 4. I think I would prefer to utilize metal Stage Pockets/Floor Boxes for the LV runs rather than punch more holes to later plug in the walls. Besides it could shorten the cables needed to mics etc. from the chase ends. I worry about the pockets being dirt collectors yet perhaps a small maintenance problem with greater gains. I’ve even considered constructing short podiums by the walls to accommodate the emerging chase with connector plates as another alternative to going through the room walls; or perhaps even coming up with the chases through the “inside-out” wall floor plates. -Any cautions or thoughts?? 5. Lastly (for now of course) I want to try and build single “super doors” that Rod describes in his book for many of my doors (good winter projects!) -But, if I were to use double entry or sliding glass door units between my drum and live rooms,(1 set per wall) do they need to have a degree difference (6-12 degrees that is?) or will parallel with 5-6” between work? -If non-parallel is needed, what should be the minimum angle used? - I’m trying to save valuable floor space without compromising my whole system on the door details . I read and re-read your book on a regular basis as it is my bible so to speak. I pick out more understanding of the details you painstakingly addressed and I reccommend anyone using it to look deep into the wisdom you have shared. I can't express how grateful I am that someone with your expertice, knowledge and experience is willing to take the time with novices like myself to be so helpful. You are absolutley correct tht "the devil is in the details" :) Looking forward to any more advice you and/or others can share. ciao, jp