Help with proper weight and compression of floated floor

Hi. After almost a year and a half of reading and posting and learning on this forum, I've learned that I'm limited in my options in reguards to my project studio build. http://johnlsayers.com/phpBB2/viewtopic.php?t=4131 My floor's weight capacity is capable of supporting an additional 28lbs psf dead load on top of the 50 lbs psf live load. I can't float a concrete slab because that would be too heavy. I know concrete slabs are ideal because of their mass but it just isn't an option for me. I was wondering if I could get some help with figuring out weight and compression etc. etc for floating a wooden floor using rubber. About what can I hope to do with 28lbs psf?

Chris, please PM me as a reminder; I'm in the middle of the "dark hours" ATM so next time I get time to be here I'll see it and try to help you work out a plan. Also, post on this thread how much headroom you can afford to give up, if it's required (and it WILL be :wink: ) Thanks... Steve

What's up Steve? Yeah so my existing ceiling is just over 8ft (actually 10ft but sprinkler heads and trusses drop down).Sprinkler heads need to be exposed but the trusses are actually a couple inches higher then the heads. As long as I have roughly 7.5ft in ceiling height after new construction, then I'd be okay with that. So I've got about 7-8 inches to play with. I figure with green glue and proper construction, a pretty good floor can still be built.

Oh yeah, Green Glue IS recommended for floors now. (Perhaps it always was...?) I have a feeling that will be a lifesaver for you. Any chance you can leave the existing sprinklers in place, then run new lines to the studio interior with exposed pipe? Mason Industries makes pipe penetration resilient seals - fire rated too as I recall. Any U.S. supplier for Sylomer? :roll: That's the awesome elastomer Paul Woodlock used. --Keith :mrgreen:

Keith, unfortunately I can't alter the existing sprinkler system. My old man doesn't want to go there(owner of the building). I have some thick butyl rubber caulk/gasket sealant http://johnlsayers.com/phpBB2/files/stu ... 02_170.jpg http://johnlsayers.com/phpBB2/files/stu ... 01_149.jpg that should be pretty affective at minimizing any flanking issues with the pipes by wrapping them and sealing off the ceiling penetrations generously. It even passed the Knightfly "see how well it damps" test. Plus, I can use as much as I need seeing as how my dad is letting me use as much as I need.

Here is a small sketch to help illustrate what I mean in reguards to the sprinklers and trusses and the ceiling height limitations they bring.

Chris, where did this "extra" 28 PSF of capacity come from, and would this include the weight of any walls you add? Is it a uniform loading calculation, or just total weight of additional dead load divided by square footage of the floor? Also, will your ceiling need TWO leaves of mass inside those trusses or will one of those be fulfilled by construction OUTSIDE of the trusses? (Sorry, don't remember all your details and am REALLY crunched for time)... Steve All I have to do today (yeah, right) is take a fresh computer out of the box, trash all the "media edition" junk, reformat with new copy of XP Pro, delete all the fluff (no MS office, no .net, no games, no ANYTHING that isn't necessary), install 6-7 new software packages including Vegas 7 +DVD, Samplitude, Sonar Producer, Magix MEP 10+, get them all registered, update all drivers, set up 8-port MIDI interface, 8-channel Layla, Canopus TwinPact 100, Matrox triple monitor driver, add 10krpm drive, 2 external fw HDD's and 2 external fw dual layer opticals, then capture 4 hours of DV tape and a few dozen hi-res stills, and edit/design into a short "operator" version and a longer "maintenance" version video of how to, and how NOT to, use/fix a Varian vacuum leak detector. OH, did i mention that I'll be doing this in Vegas, which I've not used before? (Need the more professional DVD setup choices, etc) The GOOD news - high placed person in my company quote, uttered last week - "we've been looking at your last video and comparing it to the ones we've gotten from the "big guys back east", and we're wondering why we're still using them for anything"... The BAD news - who needs sleep anyway??!? Holy crap... :?

All I have to do today (yeah, right) is take a fresh computer out of the box, trash all the "media edition" junk, reformat with new copy of XP Pro, delete all the fluff (no MS office, no .net, no games, no ANYTHING that isn't necessary), install 6-7 new software packages including Vegas 7 +DVD, Samplitude, Sonar Producer, Magix MEP 10+, get them all registered, update all drivers, set up 8-port MIDI interface, 8-channel Layla, Canopus TwinPact 100, Matrox triple monitor driver, add 10krpm drive, 2 external fw HDD's and 2 external fw dual layer opticals, then capture 4 hours of DV tape and a few dozen hi-res stills, and edit/design into a short "operator" version and a longer "maintenance" version video of how to, and how NOT to, use/fix a Varian vacuum leak detector.

That's it. I thought you said you'd be busy.

Chris, where did this "extra" 28 PSF of capacity come from, and would this include the weight of any walls you add? Is it a uniform loading calculation, or just total weight of additional dead load divided by square footage of the floor?

The extra 28psf came from the analysis of the floor I had done back in Dec. 05 by a structurall engineer. Yes, I would have to figure any new walls into the equation. I think it would be best if I posted the "official" results here rather than try and explain them with my limited knowledge.

Also, will your ceiling need TWO leaves of mass inside those trusses or will one of those be fulfilled by construction OUTSIDE of the trusses? (Sorry, don't remember all your details and am REALLY crunched for time)... Steve

Sorry for the misleading drawing. I always asume people remember things too often. Anyway, to answer your question: I'll only need one leaf of mass under the trusses because there is an existing ceiling above the trusses constructed of corrugate steel with 3 inches of epdm rubber on top of the steel.

This is the email conversation the engineer and I had about the results for additional weight capacity of the floor.(Also, at the very bottom is a link to the pdf of the drawing and explanation of the work the engineer did. In case it's hard to see, the "hatched" area of the drawing is shown where diagonal lines run.) I've also attached a link to arough drawing I did of existing construction as a guide to the engineers sketch. http://www.johnlsayers.com/phpBB2/download.php?id=5621 Q and A b/w the engineer and I: me: "Ken, thank you very much. Just to make sure I'm understanding the >results, > >am I correct in saying that the area of the slab where I want to build >the > >studio will be able to hold an additional 28lbs per square foot or no? So >a > >new floated slab at 45 or 50lbs per square foot is out of the question >then > >right? Just making sure I'm understanding what I read and saw." engineer: "The hatched area can hold an additional 28 psf of superimposed dead load > >such as a new concrete floor, new insulated floor, etc. I provided you > >with > >maximum thickness of concrete allowed based on the concrete being > >lightweight or normal weight. Keep in mind that although your studio may > >extend beyond the hatched area, there is no additional load capacity." me: "So then would new walls and then a new ceiling on top of the new walls in >addition to a new slab be too much load?" engineer: "Yes it may be too much load. As you add more loads from walls and a >ceiling >you reduce the allowable live load which in this case is 50 psf. However >for your use of the room, music equipment and a few people, it may be >reasonable to reduce the allowable live load to 40 psf allowing you to gain >10 psf of superimposed dead load capability." me: Sorry to keep bugging you Ken but in your opinion, do you think I'm better off going with an alternative solution for the floor so I can for sure safely build my new thick walls and ceilings, or will that extra 10 lbs per square foot you mentioned in the last email give me enough capacity to safely build the new slab and walls etc, etc. Forgive me for being a little slow with this stuff." engineer: "I would look at a lighter alternative to the concrete such as a rubberized floor membrane and wood finish. This would allow you to build up the walls like you would like."

Awesome report. 8)

Just in case this is an issue, I thought I'd clear this up. In relation to the engineers drawing and mine, the views are slightly different. Both are birdseye but the engineers sketch is rotated 90 degrees clockwise in relation to mine.

Hi Cyeazel - You engineer said you could use up to 38 psf if you accept a 40 psf live load. I would expect that 40 psf is just fine... that's the standard live load for a residential floor. So if you'd be comfortable putting your studio stuff on a second floor of a house, then the 40 psf is fine. I looked at Keith's (sharward) isolated floor. My quick estimate is that it is about 60 psf dead load or a tad more. This is a long shot, but... if you can find a soils report for your property and your engineer didn't know about it... he may be able to get a design load from the soils report and give you better allowable loading. Sometimes the building department has a copy. Creatch

Chris, was anything mentioned about any extra support capability of your existing ROOF trusses? Don't have time to read a lot of stuff and probably won't for quite a while the way it's going, but if you were able to suspend your inner sound leaf ceiling from existing trusses then this wouldn't add to floor dead load, and all you'd need to concern yourself with would be a wooden floated floor and your inner (maybe outer) walls - if this is the case, we might be able to reach a compromise weight by distributing all the allowable extra weight between walls (green glue will be a MUST here, to save weight) and floor (also GG between layers of this, likely resting on 2x6's/u-boats for the added air space to compensate for the lower mass) Just a thought... Steve

Been sick this week so I haven't had a chance until now to check my thread.

Chris, was anything mentioned about any extra support capability of your existing ROOF trusses? Don't have time to read a lot of stuff and probably won't for quite a while the way it's going, but if you were able to suspend your inner sound leaf ceiling from existing trusses then this wouldn't add to floor dead load

Steve, I've thought of this idea too, many times. The engineer did not look at additional weight capacity for them because I didn't think to ask at the time. If I were to use the trusses, I'd have to build some more joists parallel to the trusses because they are currently at 5.5 ft centers. I'd imagine drywall (or anything) would sag with that kind of spacing, right?

This is a long shot, but... if you can find a soils report for your property and your engineer didn't know about it... he may be able to get a design load from the soils report and give you better allowable loading. Sometimes the building department has a copy. Creatch

Thanks for the advice but unfortunately there are no existing documents for my building anywhere. I've already looked into that and the building dept has no records.

Yeah, that long a stretch won't work for drywall. You need to get your engineer guy back and have him evaluate those trusses - tell him you want to hang 2 layers of 5/8 drywall and at least a foot of unfaced 1 PSF fiberglass insulation on them, suspended INSIDE your similar inner walls on the kip/rim system on your floor (see your other thread) and see if he thinks it's OK... Steve (if so, then 2 layers of 5/8 DW with green glue between AND the insulation as your inner leaf, similar choices for walls (inner AND outer for the room(s) where there's no concrete backing up the inner wall) Keep in mind though, that a double framed wall with 2 layers of 5/8 DW each side (assuming 8 feet tall) will exert approx. 80 PSF on your floor (80 PLF as well) so in order for this to work, your walls upstairs would need to coincide with a support wall DOWN stairs or your 28 PSF limit would be destroyed...