# building soffit



## 44070dart (Nov 18, 2009)

building a room in my basement ..need to build soffit to cover 2 heat ducts a waste water pipe and steel support beam ..they are close enough together so I will be building a 6' x 14' soffit to cover them ....if I do it out of 2 x 2 's will the 6' span bow ?.... I cant support it in the center because of heat duct ....guess if I had to I could make two soffits but I think it would look better with one ..thanks


----------



## Bob Mariani (Dec 1, 2008)

it will bow. Support at the center with threaded rod into a screw in stud anchor. This way you can use a driver to insert the rod in between the two ducts from below. Set the nuts into the studs to keep it all flush.


----------



## Gary in WA (Mar 11, 2009)

2x4 with a 10# live load (ceiling joist) will span 7'2" at 24"on center. The 5/8" drywall needs 24"o.c. also, if you wet texture it.
Be safe, Gary


----------



## Bob Mariani (Dec 1, 2008)

OP said using 2X2 and will it sag?? did I miss something?


----------



## 44070dart (Nov 18, 2009)

threaded rod ... why didn't I think of that ...thank you :thumbup:


----------



## Gary in WA (Mar 11, 2009)

"if I do it out of 2 x 2 's will the* 6' span bow* ?" ---- Yes, as Bob already said it will bow.
"I *cant support it in the center* because of heat duct " ---- So your span is 6'. *Minimum* residential *code for ceilings is 2x4* for a 6' span. I don't have load ratings for 2x2 anywhere, but if you took 1/2 the span for the 2x4 I said earlier, it would only be 3'7".



Drywall, 1/2", weighs 2.2# per square foot, so your 6' x 2.2# x 24"o.c.= *26.40# *5/8" drywall is *33#.*

If 16"o.c., is* 17.69#* 5/8", 16"o.c. is *22.11#* http://www.bc.com/dms/wood/ewp/3_Gu...erials/GE-1 Weights of Building Materials.pdf


Be sure to read the footnotes below and go to the article as it may answer other questions you might have:
Table 1
Maximum Framing Spacing
For Single-Layer Gypsum Panel Product
Gypsum Panel Gypsum Panel Maximum
Product Thickness Product Orientation Framing Spacing
in. (mm) to Framing in. (mm) o.c.
Ceilings:
3/8 (9.5) A Perpendicular B 16 (406)
1/2 (12.7) Parallel B 16 (406)
1/2 (12.7) Perpendicular B 24 (610)
5/8 (15.9) Parallel 16 (406)
5/8 (15.9) Perpendicular 24 (610)
Walls:
3/8 (9.5) Perpendicular 16 (406)
or Parallel
1/2 (12.7) Perpendicular 24 (610)
 or Parallel
5/8 (15.9) Perpendicular 24 (610)
or Parallel
A Shall not support thermal insulation.
B On ceilings to receive hand or spray-applied water-based texture
material either i) 1/2 in. (12.7 mm) gypsum ceiling board (ASTM
C 1396/C 1396M shall be applied perpendicular to framing; or ii)
other gypsum panel products shall be applied perpendicular to
framing and board thickness shall be increased from 3/8 in. (9.5
mm) to 1/2 in. (12.7 mm) for 16 in. (406 mm) o.c. framing and
from 1/2 in. (12.7 mm) to 5/8 in. (15.9 mm) for 24 in. (610 mm) o.c.
framing. See Appendix A.2. From: http://www.gypsum.org/pdf/GA-216-07.pdf

Ah, Bob hit the nail on the head between my answer, Good job, Bob!.
Be safe, Gary


----------



## xuc318 (May 17, 2009)

I am glad that I found this thread because I have a very similar situation as OP. 

I am finishing my basement, already done most of the framing. Only have some soffits left. The heat and cold return trunks in my basement run next to each other with about 2 inch gap between them, and the span is about 4 - 5 feet. My plan is to use 2x2 for the joist ledger, and 2x4 lookout in 16 in o.c. Will this be strong enough? Does the joist ledger need to be 2x4 too?

As far as using threaded rod to support the center, I don't have a clear picture of how it would be done. Could you please explain a little bit more?

Thanks in advance

(Attached is a picture of the trunks)


----------



## baum (Jul 14, 2009)

I believe this is what they are trying to say to do. 

as you can see the wood goes around the ducts and a threaded rod goes from the floor joists between the ducts and you bolt the cross 2 x 4 through it.


----------



## Bob Mariani (Dec 1, 2008)

The threaded rod can be screwed into a threaded lag bolt that is made for this purpose. The nuts at the bottom get recessed into the studs so the drywall is flush.


----------



## Gary in WA (Mar 11, 2009)

Please read the fire-blocking article here: http://www.diychatroom.com/f98/how-fireblock-framing-37190/

You need it at the soffit line in the wall to stop a fire (maybe from an outlet) from leaving the wall cavity into the soffit/mechanical chase easily and quickly spreading to distant parts of the house unseen.
Be safe, Gary


----------



## xuc318 (May 17, 2009)

Thanks for the replies. The picture doesn't show how the top end of the threaded rod is attached to the floor joist. Is it screwed to the lag bolt which hangs between floor joists? And if I use 2x4s, will it be strong enough without the threaded rods?

GBR, I read the fire-blocking thread several times. Very informative. I already fire blocked the gaps between top plates and the wall. Do I still need to fireblock at the bottom of the soffit?


----------



## Gary in WA (Mar 11, 2009)

Yes, the new ceiling/wall level is at the soffit bottom. Picture a fire behind the drywall in a stud cavity. It can go up the wall, into the tin-work chase from the wall side. Then anywhere the tin-work goes AND into each ceiling/floor joist bay anywhere across the length of the chase, popping up next to a floor register above, or up to the *next* floor - if not fire-stopped there. 
Be safe, Gary


----------



## tpolk (Nov 7, 2009)

wish i had the ability to post pics like some of the smart folks here so i will try to do with words. they make a lag with a threaded end for nuts. In this case you could add a coupling with a piece of allthread rod to the length you need and run it into the joists between the duct. To get the torque you need to set the lag part thread two nuts together and they should stay in place while tightening


----------



## xuc318 (May 17, 2009)

Tpolk, you have pictures showing how the rod is attached to the joist? I am new to home improvement work, still doesn't have a clear picture of how it would be done.

Posting picture is easy. When you reply a post or create a new one, in the section of 'Additon Options', click on 'Manage Attachments', then browse the pictures in your computer, and upload. Or email the pictures to me if you could.

Thanks a lot.


----------



## firehawkmph (Dec 12, 2009)

Dart,
I have used 1 x 6 T&G pine to span the hvac trunklines like you show. I build a 2 x 4 wall on each side a 1/2" below the lowest hanging structure. The pine easily spans it and looks nice to boot. 
Mike Hawkins


----------



## xuc318 (May 17, 2009)

Thanks Mike. What made you using 1x6 T&G pine instead of 2x4s? to save head space? Did you have any support in the middle?


----------



## tpolk (Nov 7, 2009)

sorry no pics to upload and not sure how to find one or draw one to show you, less than computer savy. I beleve a hardware store will have a threaded stud for attatching a standard nut and washer on one end and a lag on other end. This is a one piece bolt, hopefuly someone will read this post and be able to direct you a little better. I have used these in the pst but do not know a tech name for them


----------



## Kevin M. (Nov 26, 2009)

tpolk said:


> sorry no pics to upload and not sure how to find one or draw one to show you, less than computer savy. I beleve a hardware store will have a threaded stud for attatching a standard nut and washer on one end and a lag on other end. This is a one piece bolt, hopefuly someone will read this post and be able to direct you a little better. I have used these in the pst but do not know a tech name for them


You can use a hanger bolt and coupler attached to the threaded rod. If you ever plan to remove it, put lock nut or epoxy in the coupler.

http://www.boltdepot.com/dimension.aspx?cc=39&cs=180&cm=106


----------



## tpolk (Nov 7, 2009)

thank you kevin:thumbsup: exactly so


----------



## Kevin M. (Nov 26, 2009)

tpolk said:


> thank you kevin:thumbsup: exactly so


You're welcome


----------



## firehawkmph (Dec 12, 2009)

XUC,
I just wanted to try something different and maintain as much headroom as I could. Plus the pine goes up easy and is fun to do. Stain before hanging. I used a couple pieces of lattice to make an outside corner on the bottom corners. Since doing these, I miter the corners of the pine so a small piece of outside corner will cover. The miters don't have to be tight, just reasonable close. Here's some pics.
Mike Hawkins


----------



## Gary in WA (Mar 11, 2009)

Very nice! Others may want to do some research first, as you probably did. At installation, maybe wrap the ducting with some suitable insulation or rigid foam to keep the heat in the supply trunk line, not exposing the wood. Watch the flammability ratings for such use. Otherwise, over time, the constant heat could dry the moisture content down to change the size of the individual boards causing open gaps at the t&g joints or splitting if they are securely nailed. Be sure to use a finish that is compatible with baking in an oven, on low heat, for extended periods of time. Or maybe just acclimating it for awhile to like wood flooring. It's amazing how much wood can move with humidity changes: http://www.woodfloorsonline.com/techtalk/woodwater1.html
I like the checkerboard floor!
Be safe, Gary


----------



## firehawkmph (Dec 12, 2009)

Thanks Gary,
I took those pictures yesterday. As you can see, we are getting ready to have everyone over on Christmas day. That wood has been up for 6 years now with no noticable shrinkage. The black and white floor is ceramic and was supposed to be the bar area. Turned out to be the music room. My son and I would use it at different times for band practice.
Mike Hawkins


----------



## Gary in WA (Mar 11, 2009)

:thumbsup:

Be safe, Gary


----------

