Trying to calculate the correct size ceiling joists for the required span. What required ceiling joist load am I looking at with two layers of 5/8' drywall and green glue?
Ceiling Joist Loads
Originally posted at johnlsayers.com, topic 13992.
You should probably consult with a specialist if you don't know how to figure it out yourself. I can't tell you the answer, but I do know that span calculation depends on a lot more things than just drywall and green glue.
Brien can probably point you in the right direction, and explain it in detail.
It's easy enough to figure out what size lumber is needed for a given span as there's many sources of data to be found on the internet. It all references a given dead or live load to determine what is needed. The ceiling joists are for the new room only so there is no live load to be concerned with. I thought someone might be able to tell me approximate load values for joists supporting two layers of 5/8" rock with green glue sandwiched in between. I'm building "inside out" panels so the weight of the supporting timber associated with that and fabric/insulation etc. need to be taken into consideration too.
I'll most likely use conservative estimates and slightly overbuilt specs just to play it safe.
I came across this issue too, special K - nobody publishes "ceiling only" span tables for their materials because who would ever need to build that!?! :D
Just use the span tables for ceiling/attic joist - you need to calculate the weight of the ceiling joists - plus the drywall = plus the green glue - PLUS lighting - a ceiling cloud and any duct work above the ceiling, which is BEING CARRIED BY THE CEILING - would be considered live loads - and would have to be included in the calculations.
As long as all of your loads were well below the bottom - then you know that the smallest member listed would be more than adequate for your purposes.
For design purposes L/360 would be fine.
Rod
If you are willing to go to the slightly added expense of using BCI's from Boise Cascade http://www.bc.com/wood/ewp/simpleFraming/bciJoist.html or TJI's from Truss Joist. Give them a simple scale drawing of the span and detail the materials to be used in sheathing and they will ( or used to) engineer the specs for free as part of the sale . The other advantage of these over conventional lumber is they all are within about a 1/16 of inch height of each other, with no crowing or twisting to speak of . Where regular framing 2X material is sometimes up to 1/2 inch variance as well as often crowned, bowed and twisted
Also one person can easily set 20 ft joist by them selves.
And last but not least. They can use more cut off wood in the lam. of these units so they don't require as much hart area of big trees ( More Green oriented.)
Assuming the room in question has the head room.
Quite true. one approach if your talking about BCI's ect. or regular dimensional lumber, and what we have done in situations of tight head room is drop down a size in height and go to 12 " spacing if necessary . Or get the higher grade BCi's with less height but thicker top and bottom cords .Assuming the room in question has the head room.
I usually, on purpose, request room dimensions.
But since no one is giving them I can only agree in part with what you are suggesting.
The span of the room would be the only thing that will dictate if a wood I beam should or should not be used.
By and large, I don't see people of authority recommending them.
But, if they are laying around or you can get them at a comparative cost and they can fit into the environment, why not, right?
X, who are "people of authority" not recommending bci's or engineered lumber.Engineers? Architects? They are superior. I haven't seen plans with them not drawn in for years,except red iron and metal construction. They actually still call for 2x12 over engineered? Although, in the south they may still "frame" everything in, in conventional lumber. Just curious. One note.. when using engineered, follow manufactures recommendations on installation. most won't allow you to load the web at all.
People here who design what we are most interested in, recording environments.X, who are "people of authority" not recommending bci's or engineered lumber.
Ouch! A slam to the entire Southern Region on my behalf.Although, in the south they may still "frame" everything in, in conventional lumber.
Good advice. As soon as we here in the South figure out what engineered wood and possibly engineering in general is, I'll post a memo :) (That was for forgetting where we are and what we are doing) ;)...follow manufactures recommendations on installation. most won't allow you to load the web at all.
:D
Being that "we" are mostly building internal ceilings inside of external shells, wouldn't warrent going to the extermes of engineered joist!
Even though I did......
I should have went with 120mm standard timber then I could have bought an SM 57 with the money I saved :evil:
not a slam at all. the last construction I didn't see any engineered lumber on, was in Texas. We framed in everything with conventional lumber,including the roof. sorry you felt it was a slam, different regions = different building techniques. mostly I was just curious about the people in authority not recommending it. When I think authority I think police, gov. official, inspector, type is all. When you posted about the span being an issue I figured you hadn't dealt with it much, because it will out span conventional. You won't find them laying around and they are more expensive, at least last time I purchased them. I believe Knightfly or could have been Rod, recommending not using it because the web will transmit sound easier than 2x. So superior in conventional construction, studio construction..2x's all the way. Someone has had to work with TGI's,BCI's, or truss joists, converting a newer basement. Anyone care to share their experience, success or failure. Hey X what is your job title? Do you only do studio construction or design? I would love to see some pics of your work. Peace out.
Neither. What I do is gather the required information that people need to construct audio environments and then explain to them why they should use conventional methods and contemporary building practices. "When you posted about the span being an issue I figured you hadn't dealt with it much," You are incorrect, on both statements. I said "The span of the room would be the only thing that will dictate if a wood I beam should or should not be used." And that was in a typical building situation. Of which we are not involved. Engineered wood I beams are designed, part and parcel, for the ability to make a greater span then conventional methods with typical framing lumber, without the use of posts, support walls, etc. They are used largely for a floor system. Not a ceiling system. Even though when they work as a floor system they are intended to have a ceiling on the under side, just as another part of the assembly to aid in potential flexing and roll over. Like I said, no one in authority, might I add, >here< suggests using them. If you want pictures of what I have worked in, well, all I can say is that I am re-writing buildthisroom.com using joomla software to get a more interactive, logical and better presentation for what it is I do, want to do, have done or am considering doing. So let me answer your question direct: "Hey X what is your job title?" I do not have a title. Now I have a question: "the last construction I didn't see any engineered lumber on, was in Texas. We framed in everything with conventional lumber,including the roof." Was this a recording environment?Hey X what is your job title? Do you only do studio construction or design? I would love to see some pics of your work. Peace out.
Here's a rough sketch of the proposed area which is to be a tracking area for drums, guitars, etc. These are dimensions of the existing room and are within a few inches of accuracy. I'll be more exact after I get the existing sheetrock taken down. The new walls will be constructed in this space and I'll also be adjusting those dimensions for good room ratios and room modes so I'm sure the new walls are going to be shrinking things down a bit with shorter spans. I think I'd be safe with 2"x6"s on the shorter end however the span at the long end is too long for that size lumber. One thought I had was to build a wall turning the longer corner section into a machine room. This wall could support the weight and keep the spans down to 12' or so which seems fine with 2"x6"s.
Of course this is all about keeping the ceiling as high as possible. Right now I have 9' 11" from slab to the bottom of the existing ceiling/floor joists to the second floor.
If you nest your inner room ceiling joists between your outer shell ceiling joists you can maintain the maximum height.Of course this is all about keeping the ceiling as high as possible. Right now I have 9' 11" from slab to the bottom of the existing ceiling/floor joists to the second floor.
Thanks X. I don't have a job title either. Been retired for 6 years (am now 46). no it wasn't a recording environment. I asked what your job title was because I had thought, you were a craftsman. There are some that have knowledge and no construction skills. And vice versa. Rare to find one with both. Have a good one.
Actually this is quite interesting. The reason I am chiming in here is I am the one that first mentioned BCI's And TJI's or engineered framing members. So for starters In the interest of clarity Lets make a clear distinction between "general framing" practices i.e. residential const. AS opposed to framing practices specifically targeted to acoustic environment or here I'll call it "acoustic framing" The reason I make this distinction is it appears that in your third paragraph you are saying even in the "general framing" practices in your area that engineered lumber is only used for spans beyond a certain length and not used for spans of say for example 16 feet or less that regular 2X framing lumber comes in. If that is what you were saying then it is interesting and must be more of difference in regional practices . Because for example here in the Intermountain West as well as the North West, for aprox the last twenty years, in the "general framing" of residential const. the practice has been predominately engineered lumber for all span lengths in floors and all roofs where rafters are used instead of the typical 2X trusses Now back to topic it seems that some here have said that for "acoustic framing" that I beams are not as desirable as regular 2X lumber is this because of mass, or lack there of on I beam material ?Neither. What I do is gather the required information that people need to construct audio environments and then explain to them why they should use conventional methods and contemporary building practices. "When you posted about the span being an issue I figured you hadn't dealt with it much," You are incorrect, on both statements. I said "The span of the room would be the only thing that will dictate if a wood I beam should or should not be used." And that was in a typical building situation. Of which we are not involved. Engineered wood I beams are designed, part and parcel, for the ability to make a greater span then conventional methods with typical framing lumber, without the use of posts, support walls, etc. They are used largely for a floor system. Not a ceiling system. Even though when they work as a floor system they are intended to have a ceiling on the under side, just as another part of the assembly to aid in potential flexing and roll over. Like I said, no one in authority, might I add, >here< suggests using them. If you want pictures of what I have worked in, well, all I can say is that I am re-writing buildthisroom.com using joomla software to get a more interactive, logical and better presentation for what it is I do, want to do, have done or am considering doing. So let me answer your question direct: "Hey X what is your job title?" I do not have a title. Now I have a question: "the last construction I didn't see any engineered lumber on, was in Texas. We framed in everything with conventional lumber,including the roof." Was this a recording environment?
Engineered lumber gets used here in California all the time and was suggested by a contractor friend of mine. Seems like the dimensions for the engineered joists were larger than the required 2xX for my given span so they would end up eating more floor to ceiling height.
I saw the "nestled joist" idea in Rod's book. Only problem is that my existing joists above are running lengthwise with the room. I'd need to use 2x10's or 2x12's for that 20 foot span so probably would end up with the same ceiling height or less. This also wont work if I build "Inside out" walls and ceilings which I'm strongly considering.
It is not what I am saying. What I am saying is this. This is about recording rooms...not general construction. Engineered lumber, I joists and the like have their place and are used for many reasons not the least of which is to allow for greater spans between load walls to develop a more airy , larger room. I concede that it does not require that a large span be available to enlist the use of these types of products. So anything that cannot be applied directly that has support from someone in the field as say, John Sayers or Rod Gervias or quite a few others, doesn't matter to me how good it is, what it does, or if you can span or not span. That said, I do not doubt that at some time or the other, both of the people mentioned and those "quite a few others" may have actually used engineered wood products. But for the most part, they just do not get a lot of "air time" here (no pun intended, none taken I am sure :) ) That is what I am saying, while trying not to HIJACK this thread, and it seems it is too late for that.The reason I make this distinction is it appears that in your third paragraph you are saying even in the "general framing" practices in your area that engineered lumber is only used for spans beyond a certain length and not used for spans of say for example 16 feet or less that regular 2X framing lumber comes in. If that is what you were saying then it is interesting and must be more of difference in regional practices
What is stopping you from rotating the proposed room 90 degrees? If you are building more than one room then you issue may not be as difficult as you may believe. I am a big believer in pictures. People can see in a picture what they can only confuse with basic words and sketchup drawings.I saw the "nestled joist" idea in Rod's book. Only problem is that my existing joists above are running lengthwise with the room. I'd need to use 2x10's or 2x12's for that 20 foot span so probably would end up with the same ceiling height or less. This also wont work if I build "Inside out" walls and ceilings which I'm strongly considering.
If you used the detail in figure 4.25a in my book you would only need 2x4's - if all you carry on the ceiling joist is drywall you should only loose a few inches (depending on your existing joist sizing - this assumes that your existing joist can handle the added load of new joist and drywall. I used this for a pro-home mixing studio (with a smallish iso-booth) for Diamond Godfrey - so he could take work home and not have to live his whole life in the studio. The bottom of the 2x4 joist in this case was exactly 1" below the bottom of the xisting floor joists. I can see no reason whatsoever why this would not work with inside out walls - i cannot see why you need an inside out ceiling - which would mean you loosing tremendous headroom - which would not be to your benefit. RodEngineered lumber gets used here in California all the time and was suggested by a contractor friend of mine. Seems like the dimensions for the engineered joists were larger than the required 2xX for my given span so they would end up eating more floor to ceiling height. I saw the "nestled joist" idea in Rod's book. Only problem is that my existing joists above are running lengthwise with the room. I'd need to use 2x10's or 2x12's for that 20 foot span so probably would end up with the same ceiling height or less. This also wont work if I build "Inside out" walls and ceilings which I'm strongly considering.
Thanks Rod for the reference to your diagram. My two main reasons for not considering this is - 1. I don't have any experience working with these types of hangers so would need to actually learn something new. :wink: 2. I've got office spaces and a couple of VO studios on the floor above (the offices are directly above). I thought that having a completely isolated ceiling would work out better for isolation purposes. Not sure how much better or worse this would be hanging the new ceiling from the existing. I can't really reorient the room as xspace suggested. The room is currently a lounge and on the other side of an existing wall to a control room that has been in use since the early 90's for post production mixing. This is why that room has the angle in the front right corner. The control room is really nice and I want to leave it as is with the exception of building a door and window or sliding glass doors into the new tracking area. As I mentioned, these are just somewhat general questions that have been occurring during my research and design phase. I'll be getting much more detailed and start a thread with photos once I get the few rooms demo'd and ready to build. Hopefully that will be taken care of this week. In the meantime i've been trying to finish mixing a few projects before all the noise starts. Thanks to all for the suggestions and info.If you used the detail in figure 4.25a in my book you would only need 2x4's - if all you carry on the ceiling joist is drywall you should only loose a few inches (depending on your existing joist sizing - this assumes that your existing joist can handle the added load of new joist and drywall. I used this for a pro-home mixing studio (with a smallish iso-booth) for Diamond Godfrey - so he could take work home and not have to live his whole life in the studio. The bottom of the 2x4 joist in this case was exactly 1" below the bottom of the xisting floor joists. I can see no reason whatsoever why this would not work with inside out walls - i cannot see why you need an inside out ceiling - which would mean you loosing tremendous headroom - which would not be to your benefit. RodEngineered lumber gets used here in California all the time and was suggested by a contractor friend of mine. Seems like the dimensions for the engineered joists were larger than the required 2xX for my given span so they would end up eating more floor to ceiling height. I saw the "nestled joist" idea in Rod's book. Only problem is that my existing joists above are running lengthwise with the room. I'd need to use 2x10's or 2x12's for that 20 foot span so probably would end up with the same ceiling height or less. This also wont work if I build "Inside out" walls and ceilings which I'm strongly considering.