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-   -   Figuring out CEILING JOIST size for 18' room span (http://www.diychatroom.com/f19/figuring-out-ceiling-joist-size-18-room-span-176799/)

cloudburst51 04-10-2013 08:42 PM

Figuring out CEILING JOIST size for 18' room span
 
Hey all - I am constructing a recording studio and having to pick my ceiling joist sizes on my own with out an architect. How or where do I go to help figure this out. I have a 49' x 18' 2x4 framed stud wall system and the ceiling joists need to hold two layers of 5/8 drywall for sound isolation. And because of the limitation of the existing building we are constructing in and the fact that we need all available space for high ceiling in the studio rooms, I think I need to install the joists down under the top plate with a ledger board. This is also be the front 49' wall is a bit out of level with the back (badly leveled concrete floor ) the stud wall are following that bad dip and would make the ceiling joists unlevel. So I thought it might be wise to laser level the bottom of the ceiling joists on the studs and nail the end of them into the 2x4 studs and place a ledger board under the whole length of them. Is this viable to other veteran contractors? thanks for your time!

GBrackins 04-11-2013 09:28 AM

Welcome to the Forum!

there is not ceiling there now? if so, what is the current height? can you post a few photos? photos will aid in providing useful comments

as far as ceiling joist spans go to this link for span tables http://publicecodes.cyberregs.com/ic...9_8_sec002.htm these are the ceiling joist span tables from the 2009 International Residential Code

this will give sizing based upon the span, and the grade & species of wood joist used.

if this is just a ceiling joist and you cannot walk on the top of it then I'd use TABLE R802.4(1) CEILING JOIST SPANS FOR COMMON LUMBER SPECIES (Uninhabitable attics without storage, live load = 10 psf, L// = 240) as found in the link

if this will be an attic floor that you can walk on then these span tables would not apply and should not be used.

will hold off on comments regards ledger until you can post some photos

hope this helps!

jagans 04-11-2013 09:41 AM

Were I you I would be using an engineered webbed joist for that span, not dimensional lumber. Im with Gary on the ledger. This sounds like you are going to balloon type construction with a ledger let in to the studs but the pictures will help. This is a building within a building? Is the roof OK on the original building?

MJ Force 04-11-2013 09:42 AM

Have you considered a drop ceiling or suspended ceiling? I used this method in a Pub/Hotel as a sound barrier and fire guard. I added 5/8" FireGuard drywall on top of each 2'x4' sound proof panel. You can achieve a nice flat ceiling this way and have access for future lighting or wiring.

cloudburst51 04-21-2013 04:52 PM

Some photos and more
 
1 Attachment(s)
Thanks for all the replies- no we are just about to start the ceiling and I still haven't decided exactly but my brother who runs a construction company advised the same thing, using the engineered joists instead of dimensional lumber. Especially because this ceiling needs 2 layers of 5/8" drywall secured to it and that's a lot of weight. It's a recording studio so it's for the mass to absorb sound.

The height of the wall now with double top plate is 11'4 1/2" and is 17' 3" across. I could also double up 2x8s if I couldn't get the TGI's.

I've been able to lower the height of ceiling and the designer redrew room design and I can install on top of the top plate now. I'm going to find out how much those webbed joist can support at 8" as compared to 2x8 dimensional.

Daniel Holzman 04-21-2013 05:17 PM

This is a commercial project, therefore residential code does not typically apply. Assuming you need a permit, you really should check with your local building inspector, as they ultimately have a lot to say about the design. If no permit is required, and there is no building code to design to, then sizing of members typically is driven by the more restrictive case of deflection or strength, and you would have to supply the criteria (normally minimum criteria is supplied by the building code).

Msradell 04-21-2013 05:35 PM

Daniel brings up an interesting point. Is a building permit being pulled for this work? Especially considering the amount of electrical work, you will need to have done for a studio I can't imagine you'd wouldn't need one! You also didn't state where you are located, which could significantly affect the codes that the work must comply with.

joecaption 04-21-2013 05:52 PM

No headers over the door ways?

AndyGump 04-21-2013 06:10 PM

There are prescriptive means for dealing with this. It is in the International Building Codes, a link to which was already provided.

Look it up, if your designer can't do this for you, perhaps he is not the right designer for your project then.

And like Joe asked, where are the headers for the door ways? I assume that the wall you show in the picture is where C,J,s will be landing, correct?

Andy.

InspectorZo 04-21-2013 06:29 PM

Welcome!
 
I think a building permit for this project would be required in any State but will wait for the location to check and verify.

I have some concerns over your current project. I'm basing them on a visual observation of the single photo submitted.
1. You're constructing walls to be load bearing over a standard concrete slab (no footings). Not knowing what the bearing capacity is could prove problematic in the future.
2. Your studs appear to be a greater span of 16" o.c. (maybe 24"). This will change the load capacity (if even possible) in your particular area.
3. A header must be installed to span your door opening, not a flat 2x4 (as mentioned previously by joecaption). Also it appears you're missing trimmers under the flat 2x header. Maybe you're just planning to add them later, idk.
4. Mid span blocking are required at this wall height and are missing on the back wall shown.
5. It appears you're restricting access to the rear entrance of the shop. What provisions are you making for egress? This is a design change for exiting of the existing layout.
6. It also appears you're restricting required clearance access to the electrical panels on the existing exterior walls.

My suggestion cloudburst51: Draw a set of plans, take them to the city/county office of your building department, pull a permit, invite your inspector to come visit you and work off his/her concerns prior to putting more money into this.

Good luck! :thumbup:

InspectorZo


Quote:

Originally Posted by cloudburst51 (Post 1164391)
Thanks for all the replies- no we are just about to start the ceiling and I still haven't decided exactly but my brother who runs a construction company advised the same thing, using the engineered joists instead of dimensional lumber. Especially because this ceiling needs 2 layers of 5/8" drywall secured to it and that's a lot of weight. It's a recording studio so it's for the mass to absorb sound.

The height of the wall now with double top plate is 11'4 1/2" and is 17' 3" across. I could also double up 2x8s if I couldn't get the TGI's.

I've been able to lower the height of ceiling and the designer redrew room design and I can install on top of the top plate now. I'm going to find out how much those webbed joist can support at 8" as compared to 2x8 dimensional.


oh'mike 04-21-2013 07:40 PM

Sprinklers----no ceiling without lowering/adding to the system.

RWolff 04-21-2013 07:58 PM

Funny thing is my house was built in 1930, and they used typical rough cut 2x4 lumber for the rafters, but they were run the LONG way down the length of the room's 15 feet on either 16 or 24" centers I forget now, then they added on the usual lath and plaster ceiling!
When I bought the house that ceiling had a long standing 6" sag where one of the 2x4's had twisted and warped down in it's center. To make matters worse someone hung a huge heavy ceiling fan/light fixture there.

I wound up sheeting the ceiling with 3/4" CDX, jacking the ceiling up with floor jacks, then I ran a pair of 5/16" thick steel angle the 15' length of the two long walls and lag bolted them into every stud. Then I used a leg of each of those to support two steel channels across the width of the room, bolting them together, and boxing them in with pine.
Have to wonder about people thinking a 2x4 run 15' across the length of a room would work well as a rafter to support a plaster and lath ceiling!


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