View Full Version : Drywalling with 48"oc trusses?


Rick98Z
01-20-2011, 09:19 AM
Okay, I am probably thinking too much into this like normal...here's the situation. In my 40x60 garage I am going to section off two rooms along the 40' span. One is a 20x20 photo studio for my wife with a bathroom and closet behind it and then the rest is for my manroom area with couches, tv, etc. I want to drywall the ceilings for those rooms. The trusses are 48" oc currently with the bottom chord of them being a 2x6 I believe, I need to have something inbetween for the drywall to acheive 24" oc but not sure what the best method is...I guess I will be using 5/8 drywall also so it wont sag.

willymakeit
01-20-2011, 09:28 AM
If the truss's are designed for it, use 2X4's hung perpendicular between the truss's on 16 or 24 inch centers with joist hangers. You might also get away with 2X4 strapping acros the bottom on the same centers.

Fastback
01-20-2011, 09:29 AM
Or, just use a lot of 1x4 as furring strips, the more the better to prevent sagging.

bczygan
01-20-2011, 09:35 AM
First determine if the trusses were designed to carry the load of a finished ceiling. If not, a good way to solve the problem is to simply use ceiling joists bearing on the walls of the new rooms. Either put these below the existing truss bottom chords, or if the chords will support additional weight, put the joists as intermediate members even with the existing truss bottom chords. Be careful to get the same rigidity so there won't be different deflections. That could be a cause of cracking in the DW finish or nail pops. That may be a good reason to use all ceiling joists and set them with their bottoms just a little lower than the bottoms of the existing trusses. Then offset these ceiling joists from the trusses so they don't fall at the same locations. They will be independent systems.
Understand?

Bill

Rick98Z
01-20-2011, 10:03 AM
I will see if I can dig up the truss specs, doubt I will even know what I am looking at with them though :) There will be a 2x4 stud wall going across to seperate the rooms as well which will be directly along the middle of the lines of trusses so that should add additional support for the trusses right? I am no carpenter by any means, but know the basics and can get things square...how I managed to build this pole building myself is amazing!

Older'n dirt
01-20-2011, 10:36 AM
I'd feel much safer using Bill's description above. You'll be putting a pretty good load on your existing trusses if you hang additional 2x4s or 2x6s AND 5/8 drywall on them, ...... especially at 48" centers. If you have the headroom I think I'd let the new interior and existing exterior walls take the load of the new ceilings. Even at that, a 20' span might warrant using 2x6's minimum for your ceiling...... probably 8s or 10s.
I'm no engineer or architect so I'm just offering an uneducated opinion.

Red05GT
01-20-2011, 11:03 AM
The deflection on a 20' span 2x6 ceiling joist under load from drywall won't be acceptable. I would not be afraid of framing it as willymakeit stated. The 2x's perpendicular or the strapping. If the specs show you're close on loading you could
beef up the bottom chords by laminating 12" to 16" rippers of 1/2" plywood to the sides
of the bottom chords to prevent deflection.

Rick98Z
01-20-2011, 11:11 AM
Ok I have the truss spec sheet but really don't know what I am looking at...it looks greek to me :( When we set the trusses we ran 2x4 bracing horizontally along the 60' span in two rows on top of the trusses bottom chord for bracing, and I have since added three more rows. The bottom chords are stiff as hell now and don't move now that I have added the extra bracing. I know this is just a garage and I shouldn't get too crazy with this stuff but I don't want it looking all jacked up either!

Rick98Z
01-20-2011, 11:24 AM
I am going to try to scan a layout of the garage and rooms so it makes more sense. I am a need to see it kind of guy, pictures help me alot more than reading!

Rick98Z
01-20-2011, 11:38 AM
Okay here we go:
First is truss spec sheet
Then overall bldg with truss layout shown and then closeup of sectioned area

Rick98Z
01-20-2011, 11:42 AM
Cost is a factor too I should add. Drywall is only going in these two shown rooms...Rest of garage is going to have a white plastic wrap ceiling which simply uses black strapping one way and fur strips on bottom of trusses to hold up and then blown insulation on it...

Falcon67
01-20-2011, 12:12 PM
The way I read the truss diagram - an I'm not an engineer or even a conductor - is:
Top chord live load = 20 lbs sq/ft
Top chord dead load = 5 lbs sq/ft
Bottom chord live load = 0
bottom dead load = 5 lb sq/ft.

Which says to me - no shingles on roof (says so on plan), no allowance for any storage or weight in the attic space and a bare minimum ceiling. Figure 1.7~2 lbs sq/ft just for drywall, so all the other support materials would need to be figured and have to stay under 5 lb sq/ft. You didn't say what the height is, but if it was me I'd build the rooms using a whole separate 2x8 set of ceiling joists that just snug up under the trusses and not use the truss structure for anything.

Rick98Z
01-20-2011, 01:05 PM
The concrete floor to the bottom chord of truss height is just under 12'. I see what your saying now falcon, but those ratings are with a full 40' span, they wouldn't take into account adding a wall along the middle to support weight attached to the concrete floor...ugh, I certainly am not an engineer so I don't have a clue how to figure this out...I live outside the city with mostly farms around. All the local farmers have similar buildings and just slapped stuff together and didn't take into account "loads" and all theirs are still standing just fine and have told me to stop worrying and just do it...Thats just not how I like to do things. My neighbor is a local contractor and he agreed with just adding 2x4s between the bottom chord or running 2x4's on the bottoms of the chords as well...I hate doing something halfassd though but I don't want the added cost of running 2x8's underneath the chords to just have a dedicated ceiling for "playrooms"...ugh I hate this economy and my need to be CHEAP!!! If it sags a tiny bit, I don't care...I just don't want the ceiling to collapse on itself!

csp
01-20-2011, 01:10 PM
You didn't say what the height is, but if it was me I'd build the rooms using a whole separate 2x8 set of ceiling joists that just snug up under the trusses and not use the truss structure for anything.

Winner! You have the headroom for a setup like this.

bczygan
01-20-2011, 01:21 PM
The concrete floor to the bottom chord of truss height is just under 12'.

Rick,
Your trusses weren't designed to have ANY additional load on them. Just build your room walls to a convenient height and run ceiling joists across them. If a standard 8' wall is desired you could size the joists for storage above and throw a plywood deck on top. If you want the walls to the bottom side of the trusses do as I outlined above and put the joists just under the trusses and independent of them. Also, 20' is a pretty long span for dimensional lumber. I would use engineered joists. And you will need some kind of ledger at the outside wall if you don't frame a wall there as well.

Bill

bczygan
01-20-2011, 02:12 PM
You're reading it wrong. It means 0 load is figured on the bottom chord. That is the live load of 0.
You are right about building the room separate though. This roof structure is designed to support only itself, PERIOD!

The way I read the truss diagram - an I'm not an engineer or even a conductor - is:
Top chord live load = 20 lbs sq/ft
Top chord dead load = 5 lbs sq/ft
Bottom chord live load = 0
bottom dead load = 5 lb sq/ft.

Which says to me - no shingles on roof (says so on plan), no allowance for any storage or weight in the attic space and a bare minimum ceiling. Figure 1.7~2 lbs sq/ft just for drywall, so all the other support materials would need to be figured and have to stay under 5 lb sq/ft. You didn't say what the height is, but if it was me I'd build the rooms using a whole separate 2x8 set of ceiling joists that just snug up under the trusses and not use the truss structure for anything.

bczygan
01-20-2011, 02:19 PM
The concrete floor to the bottom chord of truss height is just under 12'. I see what your saying now falcon, but those ratings are with a full 40' span, they wouldn't take into account adding a wall along the middle to support weight attached to the concrete floor...ugh, I certainly am not an engineer so I don't have a clue how to figure this out...I live outside the city with mostly farms around. All the local farmers have similar buildings and just slapped stuff together and didn't take into account "loads" and all theirs are still standing just fine and have told me to stop worrying and just do it...Thats just not how I like to do things. My neighbor is a local contractor and he agreed with just adding 2x4s between the bottom chord or running 2x4's on the bottoms of the chords as well...I hate doing something halfassd though but I don't want the added cost of running 2x8's underneath the chords to just have a dedicated ceiling for "playrooms"...ugh I hate this economy and my need to be CHEAP!!! If it sags a tiny bit, I don't care...I just don't want the ceiling to collapse on itself!

Rick,
You are trying to talk yourself into the answer you want to hear because you don't want to face the truth of what it costs. The local farmers are IDIOTS!!! (Emphasis added). The whole idea of engineering things and figuring loads and stresses is so you know with some certainty how strong something is and approximately when it will fail. If you don't do that, you won't know where the difference is between a little more deflection and failure. Nothing heavier than lights should be hung from this roof structure.

MoonRise
01-20-2011, 02:19 PM
Like Bill in Detroit said, NO hanging things off those trusses. They weren't designed for it.

Want drywall ceilings in your two rooms? Frame the rooms and put ceiling joists (of the appropriate size and spacing for all framing members) in there and drywall to -that- framing, NOT to the roof trusses.

IMNSHO.

Also consider putting sound insulation in the rooms, so that noise from one 'space' doesn't 'encroach' into another space. An air impact wrench in the main shop/garage area may not be all that conducive to a photo session in the photo studio area or some movie viewing in the 'man cave' section or whatnot. Hmmm, let's see, maybe some mild smooooth jazz and a very mellow portrait session going on in the photo studio and the subject/model is finally getting relaxed and in a 'groove' with the photographer, "Yeah that's nice, now lean just a little to your left and let you arm down just a little more ..." and then BRRRRRRaaaaPPPP an air impact goes off. Model/subject jumps, wife jumps because of that and big $$$ lens falls to floor. Oooops.

Or you have the sound system -cranked- for a movie and then the scene hits the spaceship rumbling into spacedock just as the main fusion plant explodes from the sabotage just as the wife is adjusting that fancy delicate glass sculpture for the still-life shots she is setting up after adjusting the lighting for two hours so far to get the studio shot JustRight. Oooops.

You get the idea.

Rick98Z
01-20-2011, 02:42 PM
Oh there won't be wrenching or playing when she has a session...I will be inside the house 125ft away watchin the kids :) I know the loads for the 40' span say nogo, but doesn't adding the wall down the middle carry load down to the concrete and help? UGH...I wish I knew of this site when I was building this damn garage. It would have saved alot of headaches, now what should be a enjoyable project for me is turning into a constant stress!

creativecars
01-20-2011, 02:53 PM
Rick, I was faced with a similar situation, but on a smaller scale (only 12X12 rooms) . Decided to frame up and insulate 2X4 walls, and used 2X8’s for the ceiling joist with ¾ Advantech on top. I think I have got my money back for the extra spent on materials to offset for the storage area. I now have a sturdy storage space above my rooms. It’s not as easy to get too as some storage, but storage is storage. I am very happy I went that way and would do it again.

With the span table I have it looks like you could use 2X10s on 16”centers (24” is cutting it close) to have a useable storage space.

bczygan
01-20-2011, 03:07 PM
Rick,
One more thing. If you did what you propose it would probably stand on it's own for some time. You will have excessive deflection. You will have cracking and nail pops in the drywall. And on that one perfect day when you have the maximum snow and or wind load you will have wracking of the roof structure and maybe some damage to the roofing or sheathing or roof or wall structure and just maybe a partial or total structural failure. Engineer it properly, do a good spreadsheet on costs for materials and you will know how much money to save up. Or you could do it in phases. Walls first with drywall only on the inside, no ceiling. Hang temporary lighting from the trusses. Later do the ceiling framing and electrical and then insulate walls and ceiling. Then throw decking on top for storage. I'll size the engineered joists when I get a chance. What are your sidewalls?

Bill
And hey..........you've got a 40 x 60 building!!! You lucky rat bas*@#d!

socapots
01-20-2011, 03:07 PM
nice drawings..
only thing i can add to this is dont forget the doors for your mancave

georgiadave
01-20-2011, 03:12 PM
If you frame rooms in your garage, do not rest the bottom of the trusses on the room framing header. For the truss to function as designed, it can not touch the room framing.

Red05GT
01-20-2011, 04:05 PM
The talk of 20' ceiling joist and 20' engineered joist to span these rooms is interesting
to say the least. If you were to use 2 x 4 framing set 16" on center hung in joist hangers
it would take 4- 8' 2xs to hang each 4x8 sheet of drywall. 4 2xs wouldn't weigh half as
much as a sheet of drywall. If as many have said nothing should be hung off of the
trusses, this would preclude ever insulating or hanging light fixtures, and definately no
storage racks hung from the bottom chord as many threads have talked of on this forum.
There have been many who have talked of using metal liner panels directly on the
chords and then blowing in insulation or using batts. This would definately push the 5lb's per sf number. The weight of a 20' wide storage mezzinine transferring load on to
the floor slab if not thickened could also be a concern.

JayClay
01-20-2011, 04:27 PM
Im working on a simular project but my building is much smaller 24x32. So my span is only 24'. My trusses are 2x6s so I used 2x6s to make it 24" oc and am going to hang the drywall on that. My roof is only tin so its not very heavy. And there is only bubble insulation on that.

6768rogues
01-20-2011, 06:31 PM
If the trusses were designed for 4-foot spacing and the bottom chord dead load is 5 lbs., you can add 2x4s between the trusses and be ok. Think of it this way: An 8 foot sheet of drywall is 32 square feet. With an allowable 5 lbs. per square foot of dead load, you can put on a dead load of 160 lbs. over the area of that sheet of wallboard. If you add the equivalent of 2x4s every 2 feet, you will be adding 3 2x4x8 foot boards (the equivalent of one would be shared with the next sheet of drywall, so the calculation is conservative) and a sheet of drywall for every 32 square feet. That assembly will not weigh 160 lbs.

racerock
01-20-2011, 08:46 PM
The way I read the truss diagram - an I'm not an engineer or even a conductor - is:
Top chord live load = 20 lbs sq/ft
Top chord dead load = 5 lbs sq/ft
Bottom chord live load = 0
bottom dead load = 5 lb sq/ft.

Which says to me - no shingles on roof (says so on plan), no allowance for any storage or weight in the attic space and a bare minimum ceiling. Figure 1.7~2 lbs sq/ft just for drywall, so all the other support materials would need to be figured and have to stay under 5 lb sq/ft. You didn't say what the height is, but if it was me I'd build the rooms using a whole separate 2x8 set of ceiling joists that just snug up under the trusses and not use the truss structure for anything.

I did not open the specs but if the above is right - I would have never accepted that design...

I think I have over 100' per square foot with shingles on mine with drywall below as my spec. I have a 20 ' width loft with 8' headroom on a span of 30' on mine.

24" spacing

Drywall is very stable.

About a 10/12 pitch on the roof.

6768rogues
01-20-2011, 09:04 PM
Dead load is permanent construction. Live load is a load that is temporary, such as storage items, snow, ice, wind, etc.
Asphalt shingles are considered as lightweight roofing. If you have a good shingle that is 250 lbs. per square, that is only 2 1/2 lbs. per square foot. 5 lbs. per square foot is plenty for plywood and a shingle roof. Additionally, you have 20 lbs. per square foot live load, that being wind load, snow load, etc. In western NY, we use 35 lbs. per square foot live load, so you are probably just right for your area. You do not have a roof that will support heavyweight roofing, such as concrete tiles.
The bottom chord dead load is enough for additional framing and drywall, and even some insulation. If you are concerned, do the math and add up the weight of your materials and figure out how much they weigh per square foot. You are installing a uniform load, so you can figure out the load exactly.
Zero bottom chord live load means NO storage items. They are live load.

Rick98Z
01-21-2011, 07:34 AM
The center wall I was framing down the middle could certainly be bumped up to a 2x6 wall I guess as well. In reply to someones question about the rest of the framing, in between the post I was going to frame in 2x4 walls even with the inside edge of the posts and insulate with 6" insulation. The cap boards on those would butt right up underneath the 2x12 carrier that is attached to the posts. As far as the roof is concerned it is metal with the double bubble insulation underneath it. I bought the building materials as a package from a local pole barn company. I just decided to put it up myself to save the 5-6000 install price tag. I don't know anything of loads and such so looking at the truss sheet I wouldn't have known any different. All the building specs were submitted to my county for permitting as well and approved, so nothing would have thrown a red flag up to me that my trusses were shit...

Rick98Z
01-21-2011, 07:36 AM
nice drawings..
only thing i can add to this is dont forget the doors for your mancave

Thanks, yeah I just didn't take time to add them in CAD when I was drawing it up. It will have an entrance door and window in the wall to see into the garage.

darkk
01-21-2011, 08:09 AM
From what I'm reading here. The OP is finding it necessary to 2x4 or 2x8 the lower part of the trusses to hang ceilings from. Since the cost is going to be about the same. just use the wood to make a ceiling the height he wants "under" the existing roof. He needs to buy the lumber anyways....

Rick98Z
01-21-2011, 01:39 PM
Correct I need to buy lumber anyway, I am just trying to find the easiest method that doesn't brake the bank. I am tight on funds now after building this monster, but I want to keep moving on this project and get these two rooms going now that I have elec to the building. What about if I use 2x8's from the new middle wall and run them inbetween the trusses to create 24" oc using the trusses as well to attach drywall to. I am just trying to come up with all possibilities to achieve the same eventual end result...

Oh from the new middle cross wall would be like 19 something feet span and the trusses are currently sitting on 2x12 carriers bolted on both sides of my 6x6 posts...

mobetta
02-11-2011, 04:11 PM
id be tempted to do 7'6" walls and a storage mezzanine above., even if you have to buy the lumber one board at a time....

but the dead load specs on those truss' is typical, ok for DW