Dan F's One-Room Garage Studio

Dan, in your location you should just make sure you have earthquake insurance (can you even GET that in Ca anymore??!?) Then, if the slab cracks, just wait til the next shake and call your agent... :twisted:

:twisted: i think homeowners insurance companies are required to offer it ... and you are required to decline it (otherwise find another insurer).

Figgers; still not sorry I left when I did... :evil:

Figgers; still not sorry I left when I did

As in LEFT CALIFORNIA??? :shock: Don't tell my you were a Californian at one time Steve. And after all the needling you gave me... :lol: fitZ

Nope, just ended up there after military, more high tech stuff to do - decided to GTF out when the kids were still little (and drug-free) and while I still could pass for sane if people didn't look too close... :? Other than that, I'm more native than a REAL cutthroat trout (if you could even FIND one :cry: ) Steve

Xalky wrote:

I've been building houses and running construction jobs since I've been old enough to pick up a hammer, and I have an mechanical engineering degree.( i telling you this to qualify my statement as I'm new here.)

Cool! 8) We love it when you engineer types come to the party! :)

I think you're intuition is dead on about the weight of a car versus the weight of the wall. The car is exerting about 1000 psf, all in one spot (8x8" area). The load of the wall won't be nearly that much because the load is distributed over the width of the plate times the length of the wall. If you're paranoid about this you can distribute the load more by simply using a wider plate ie: 2x6 instead of 2x4. You can still however, use 2x4s for studs, just put the studs flush to the plate on the finished side of the wall. I don't think this is necessary however.

OK, that's cool. But... Why is it that in most houses, garage slabs are built to specifications that are inferior to the slab the house sits on? :? I believe my 5-year-old slab-on-grade home in Sacramento, California, has a 6" rebar-reinforced 3000psi mix slab, whereas my garage floor has a 4" 6x6 mesh-reinforced 3000psi mix slab, scored in multiple places. I'm guessing that the reason for this is that there are typically no load bearing walls on garage floors, whereas there are load bearing walls on most residential slabs. If I were to convert the garage into a large family room or something, I think the slab would be just fine. Any walls that attach to the garage floor would be simple room dividers and would be relatively lightweight. However, the kind of construction we're planning is not lightweight at all -- 3 to 5 layers of gypsum wallboards on each side, plus (and here's the kicker), supporting an equally dense ceiling. :shock: We're talking 10-15 tons in an area that is built for a single car and storage. :? Call me a worry wart, but I do consider worst-case scenarios. Suppose a garage floor is defective, or for some reason, not strong enough for the loads demanded of it. The worst that can happen (and indeed has happened two doors away from me) is that the slab fails, the contents of the garage are removed, and the slab is broken up, removed, and repoured. While that would be no fun whatsoever, consider the worst case scenario of a residential slab failure -- residents would likely be forced into a hotel during what would amount to major structural surgery on the house. A friend of mine went through that ordeal years ago -- "ugly" is an understatement, not counting the lengthy lawsuit against the builder for improper soil compaction. The point I'm making here is: by building such a :shock: heavy permanent structure :shock: on a garage slab, one is essentially demanding strucual-level performance from a slab that, for reasons that still escape me, is not built for. It stands to reason that it would probably perform well... But that's a gamble. I imagine the odds are good -- but considering the structural damage that a mere 1/2" settlement would cause to the most carefully constructed studio, I have to factor in the cost of the insurance against that happening (i.e., replacing the slab with one that is proven to perform at the required level)... And it sure seems the cost of that insurance policy is pretty low.

Agreed with everything BUT the idea that the reason for a heavier slab in the house is for load-bearing walls; these need to be planned for and extra footings poured during construction. I'm more inclined to think the reason for a heavier slab in the house is seismic; most people don't sleep in their cars in the garage, so local codes may be aimed at stronger construction where people may be asleep when the next "rock'n'roller" hits... Steve

Guys, Seismic has nada to do with it. 1st off - no one is concerned if a garage slab cracks....... it is a non-structural element to the construction. It isn't the same with slab on brade home construction. 2nd - garage slabs are considered short term duration loadings. This means they do not anticipate that people are going to leave their cars there forever. (even though they might - and then look at number 1 again) 3rd. I never said I was concerned with linear wall loadings on slabs. I did say that I was concerned with edge loading a cut slab - and also that I was concerned with loading a slab for a fully floating room. My concern (as I have noted numerous times in this and other threads) is that of the possibility of bad compaction in some area of the slab and thus a void below that area - which could occur somewhere that a tire never loads. I believe my presentation on this matter has been nothing other than consistent in that respect. IF there was settlement in such a location that did not occur prior to completion of the studio - repairing it would be a heck of a project. Dan, as far as floating a wood deck goes - tis all yours if you want it - but I still maintain that if you can't acheive a 10Hz center frequency with it - you would be better off without it. Good luck, Rod

Rod, Thanks for further clarifying what you've been saying. It sounds like you are implying that building a wall with several layers of wallboard that may approach 100lbs per lineal foot is not a problem. as long as it is not on the edge of a cut slab. actually, the load will be higher, because of the inner ceiling load. somewhere around 150 to 175 per lineal foot on the load bearing walls. and i am planning to build the walls fairly near the edges of the slab sections to take advantage of the natural isolation i will get (my inner leaf and outer leaf on one key wall will be built on different slab sections). my slab is as it exists is poured in sections, and i wonder if loading near the edge of these sections makes you worry in the same way a cut slab does? Pic Deleted Pic Deleted the "footprint" of the planned room will be on the two slab sections closest to the rolltop garage door. but the outer leaf would be built on the slab sections nearest the camera POV. the different sections do appear to be physically seperate. the gaps are full of debris but if you dig down there is a gap that goes down several inches at least. on the floating floor question, nobody has ever explained to me why you have to have a 10hz frequency for the floor but it is ok to have 25hz or 30hz for your walls. that is why i have concluded that the wood floor is an option; because the wall i'm planning has a predicted frequency in the low 20's ... so why would it matter if the floor was in the low 20's too? although my current thinking is against floating the floor, partly due to your reassurance that it isn't needed. thanks again for taking the time. dan

I'm not sure about construction methods in your area. Around here, 9 out of 10 times there will be a footing where the concrete wall sits, and the footing will have a 2-4" lip around the inside perimeter where the slab is poured directly on top. If thats the case most of the load will be bearing on the footings in those areas. The only way to know for sure is to bore a few test holes around the perimeter. Heres another consideration: even if the outer edge of the sound wall sound wall is inline with the edge of the footing below, the concrete would have to suffer a shear failure. I don't know what the #s are for shear failure of a 4" concrete slab is, but I know that is much higher than anything a sound wall could provide. A few test bores around the perimeter could put this mental masturbation to rest, and get you moving on your project.

In the area I am from(Northern California), typical residential slabs are integral with the footing AND flush with the top. Not only that, but the framing of the exterior wall is FLUSH with the exterior face of the footing, so shiething can extend over the edge of the footing to seal it, as in T-111 ply, OSB, Stucco or other types. Of course, my range of familiarity is based on living in lower Middle class type construction. More expensive type construction such as brick or other may have footings as you show, but that would have been out of my league. In fact, in this day and age of real estate prices, wll be out of MOST peoples league. I can't believe my 1958 tract house with a ONE car garage in Sacramento sold for almost 1/4 MILLION DOLLARS two years ago!!! Can't imagine building a new BRICK home now days. fitZ

Dan Fitzpatrick wrote:

Rod, my slab is as it exists is poured in sections, and i wonder if loading near the edge of these sections makes you worry in the same way a cut slab does?

Yes it does.......... it's one thing in the body of a slab - you can be pretty sure that the entire slab doesn't have a void - but cutting a slab or placing a bearing wall on a simple slab edge (no haunch to properly distributre a load) worries me.

on the floating floor question, nobody has ever explained to me why you have to have a 10hz frequency for the floor but it is ok to have 25hz or 30hz for your walls.

Who told you it was ok to have assemblies with thos TL values with a floated slab? If the remainder of the room values are not close to the slab - then you just threw all your money away on the slab. You isolation is as good as your weakest points,........... and if that's your walls and ceiling - then installing a slab with isolation values 2 to almost 800% better than your walls will gain you nothing. Sincerely, Rod

couldn't resist seeing how hard those cabinets were going to be to remove ... and checking out the interior of the wall behind ... stucco bows inward inside, will be a pain to add layers of wallboard without leaving gaps :( notice blue can in first and second picture (bottom right). somehow i dropped the cabinet on this stuff, which is on a small table, and that small dent in the can is all that happened. dan

close up ...

Stand back, folks -- "the man of action" is in action!

Dan Fitzpatrick wrote:

stucco bows inward inside, will be a pain to add layers of wallboard without leaving gaps :(

Oh mannnnnnnn... :roll: So, the "bowing" is between each stud? That does not look like fun. :( Steve did post a way to deal with this "uneven stucco" condition a few weeks ago:

knightfly wrote:

. . . if your stucco is that uneven, you should FIX it before trying to put inserts between studs - one way is to get a wide drywall knife (like 12") and mix up some slightly sloppy drywall mud, smear it liberally over the stucco, and while it's still very wet press the first layer of gypsum into the cavity until the mud RUNS OUT around the edges; then smooth off the excess, add the second layer, and fasten both in place with screwed in cleats fastened to the studs.

There's more at his post in aggybass' garage studio thread. How thick is that diagonal sheer brace?

"Oh mannnnnnnn... " indeed! thanks for that link, i knew i had read about that somewhere and couldn't remember offhand. as far as adding MULTIPLE layers of drywall to this area ... keeping in mind the post here: http://www.johnlsayers.com/phpBB2/viewt ... 6177#26177 but wondering ... since i'll be caulking EACH layer of wallboard, how do i hold each layer in place while it's being caulked, before adding the cleat. maybe a litte bit of liquid nails? on edges only? or maybe use OSB for the first layer, glued in, and screw subsequent layers of drywall to that? or maybe screw lengths of 1x4 to outside of studs, horizontally across multiple studs, and then wedge the layers of drywall against the leveled stucco with blocks and shims, temporarily, until the final layer and cleat is attached. then you could remove 1x4 structure. i'm kind of liking this last idea. at least it's something to fall back on if easier solutions dont' work out. oh, and i think that brace is a 1x4. yes that's a royal pain too isn't it?? :evil: dan

rod gervais wrote:

Dan Fitzpatrick wrote:

on the floating floor question, nobody has ever explained to me why you have to have a 10hz frequency for the floor but it is ok to have 25hz or 30hz for your walls.

Who told you it was ok to have assemblies with thos TL values with a floated slab?

Rod, i apologise for exaggerating. The resonance frequency in my walls should be around 18hz if i use 3 layers 5/8 gypsum and 12" air. if i go 4 layers it will be even better. about 16hz. these frequencies are pretty good. still, it isn't 10hz. i think the downfall with wood floors is that they need to have an airgap comparable to that of the walls you are building. most people would not want a 9 or 10 inch step up into their studio and headroom is an issue. but, if you did build a wood floor several layers thick, and had an airspace of 9 or 10 inches, you would achieve a resonance equal to that of the wall described above. you actually need less airspace because of the concrete slab. so if the resonance frequency in your floor is as good as that of your wall, you should be good to go. if not, you need to look at improving your floor AND wall (and ceiling for that matter) resonance frequencies. would you agree? you can get a 10hz frequency with a floating wood floor but the airgap would be ridiculous. but it would be even worse for a wall. anyway, i'm probably not going to float anyway. but i still think it's worth understanding. so if i'm missing something let me know. dan

Finally got around to checking to see if my room modes were anywhere near good, or if they sucked. I hadn't really considered the ratios in my design, i just hoped they would be good. BUT, i still have a chance to tweak my ratios if needed. So, better to check BEFORE building! this page has good info on room modes courtesy of Eric Desart: http://forum.studiotips.com/viewtopic.php?p=5570 Result: good news! my room, which is 1:1.5:2.2, has one of the better ratios. Phew! [Actual dimensions assumed/planned in feet: 7.25H x 11W x 16.25L] See chart number 8. Not that i understand ANYTHING about what these charts mean ... it's just abunch of colored diamonds to me. but at least i know it's good!

I'm glad you have some good, unqualified news to share about your project -- for a change! ;)

Dan, check out Studiotips for modesv2p.xls, it's in the OLD site's calculation tools. Complements of Jeff Szymanski, I use it daily. I can't get anything useful out of the little colored diamonds either... Steve

Ok, time for a report on today's progress ... it was a DAY OF DESTRUCTION :twisted: took off second of three cabinets ... third of three cabinets ... blammo!! gypsum is gone!! (i'd annoy you with more incremental pix of this process, but my wife took off with the camera for a few hours). side view: ceiling corner, side of garage: somewhat worrisome/annoying meter box, which will be a pain to work with: shot of interior of roof, aimed at roof peak: this was a surprise. i had already learned from my neighbor that the odd bi-level ceiling is normal. and i had kind of figured out that this is where the roofline of the main "body" of the house sits. the garage is "tacked on" to the main body of the house, it's a bit odd, but there is a "phantom" roof inside the attic that comes to rest on what i thought was a solid beam. it's not a beam. it is a truss. well it is a beam and a truss. you can see a second 2x8 beam behind the truss, which the roof sits on. the angle is bad, but you can see the phantom roof, with 1x4's and everthing, ready for shingles, under the "real" roof. weird man. the 2x8 seems nailed to the truss, but not the bottom part, they don't line up. the 2x8 is just slightly overlapping the bottom chord of the truss. so this is good news i guess, maybe ... i'm not sure about the strength of this assembly vs a standard garage door header, but the good news is that it isn't solid, so i may be able to work out ventilation fan maintenance through the truss. i was having a heck of a time figureing out how to keep that accessible. here's the bottom view, showing the hollow part of what i thought was a solid 4x? beam that's about it for pix. i have more, but i'll try to restrain myself. :) dan

so, a few comments about today's work. one, it is surprisingly quick and easy to pull down wallboard. at first i tried to get it down in big pieces, but then i gave up and it went much faster. some pieces came down big. i just swept up all the pieces that were small and shoveled them up with a square head shovel. a big crowbar is a very useful tool when tearning down wallboard. the second thing i realized, once i got to see the structure in reality, instead of in my fantasies, is it would be a huge PITA to do the ceiling wallboard up inbetween the ceiling joists instead of simply screwing them to the bottom. what really would suck is the sides where the roof comes down to the top plate. you would have to build some nailers so that you aren't screwing wallboard right into the roof itself, and you'd have to work around the roof beams where they come down to the top plate. the third thing is, if i added 2x8's going the short way across my ceiling, the nearest to the sides i could put one is about 4 feet, because the triangle gets smaller toward each side. but that might be ok, as long as i have room for say 4 or 5 of these 2x8's to reinforce my existing joists. one more thing. i'm concerned that i may have to build my walls in the 18 foot direction earlier than i want to, to support the new ceiling joists and the weight of the gypsum. i really don't want a wall to go up on the house side, because it will make it harder to work. maybe a compromise where i only put in some of the studs would work. maybe just a double stud in the center. as a post to hold everything up. dan

more destruction pix! almost all wallboard removed to make way for outer leaf beefing up ... just need to remove nails and a few bits here and there. and the part where my house's water line comes in, need to work on that seperately when i'm in a CAREFUL mood ... decided to bag up all the wallboard scraps in 3 mil garbage bags i found at the hardware store. i'll be using my wife's minivan for the dump run so i thought that would keep things pretty clean. i've done some and it seems pretty easy, shouldn't take more than another couple hours. dan

couple more ...

Nice (un)work! 8) Even cleaning up as you go! :mrgreen: