Wall to roof truss question

rapg635 · #1 04/30/14, 09:05 AM

Hi all. This is my first post here. If anyone can help in any way with this question, thanks in advance. I had an oversized garage that used roof trusses, 2x4 24" oc. I used part of the extra space and had a contractor convert that space to an interior room. The new separating wall spans approximately 20 feet (at one end is a solid wood fire door which has heavy use). The wall runs parallel with the roof trusses. However, the contractor placed the wall approximately 6 inches from the closest truss. Therefore, the complete wall is only tied into another supporting wall by the 2 ends. The top plate merely runs along the sheetrock, and literally is held to the ceiling by spackle and tape. With the frequent use of the heavy wood door, plus the extreme difference in room/garage temperatures, the wall "moves" thus tearing the ceiling spackle joint. I had planned to cut 2x4's to place between the trusses, then nail them to the trusses and top plate, securing the wall to something.
My problem is, since I am not an engineer, can the trusses be nailed together as stated (or secured in any other manner) or do they need to be "free-floating" in order to function properly? (sorry for the long first time post). Thanks for any info and help.

Rich G

Ramblin Wreck · #2 04/30/14, 09:18 AM

No, they don't need to be free floating. Whenever I use trusses on barns, I usually build a "catwalk" from end to end on the joists to tie them all together. I brace the rafters also, to each other and to the side walls.

rapg635 · #3 05/09/14, 05:44 AM

I appreciate the feedback. Another project added to the list! Thanks again

1shotwade · #4 05/09/14, 06:53 AM

I don't know where you are but I would be concerned about a 2x4-24oc roof. It will not hold much of a load. If you get snows etc it may fail on you. So,that might be another consideration while you are dealing with tying the wall to roof.Just a thought.

Wade

Hornacopia · #5 05/10/14, 09:45 AM

My roof trusses are 24" OC, gambrel roof with cathedral-style ceiling. My inspector was OK with me connecting them with 1x4 strapping on 16" centers. This greatly strengthens the structure, and drywall is easier to attach. The trusses are attached together at the roof surface -- there is no reason they can't be bridged at the lower chord.

Understand that trusses move slightly. You really shouldn't make a completely rigid connection between the truss and the wall below. They make special metal clips for this purpose, that have a slotted hole for nailing to the truss. This allows some up/down movement.

Check this link: http://www3.telus.net/selkirk99/selk.../ceilings.html

If you can, I would recommend strapping the underside of the trusses.

Horn

wharton · #6 05/10/14, 12:45 PM

Quote:

Originally Posted by 1shotwade

I don't know where you are but I would be concerned about a 2x4-24oc roof. It will not hold much of a load. If you get snows etc it may fail on you. So,that might be another consideration while you are dealing with tying the wall to roof.Just a thought.

Wade

No idea where you got that silly idea, but it's wrong. Any properly engineered TRUSS roof system is done with engineering that guarantees that it will support the design load requested. In my area we use a very location specific design load of 50 lb ground snow load, and add additional live and dead loads. That said, truss roofs in this area at typically constructed of 2x4 stock, installed on 24" centers and rarely fail. Failure is typically traced to installation by somebody who ignored the drawings provided. In my location I have seen everything from double wides with trusses made of 2x2s to new barns with trusses on 8' centers. All engineered, code approved, and doing just fine.

As to the OP's question. Yes, the wall needs to have a ladder of flat 2x4's installed on top of the sheetrock. In this case, I would install them on 48" centers, with additional pieces on each side of the door. If you have a helper cutting and handing them up, and you install them with a battery impact gun and 3-1/2" deck screws, the job will only take a few minutes. Be careful, falling through a ceiling sucks.

wharton · #7 05/10/14, 12:53 PM

Quote:

Originally Posted by Hornacopia

My roof trusses are 24" OC, gambrel roof with cathedral-style ceiling. My inspector was OK with me connecting them with 1x4 strapping on 16" centers. This greatly strengthens the structure, and drywall is easier to attach. The trusses are attached together at the roof surface -- there is no reason they can't be bridged at the lower chord.

Understand that trusses move slightly. You really shouldn't make a completely rigid connection between the truss and the wall below. They make special metal clips for this purpose, that have a slotted hole for nailing to the truss. This allows some up/down movement.

Check this link: http://www3.telus.net/selkirk99/selk.../ceilings.html

If you can, I would recommend strapping the underside of the trusses.

Horn

As the OP stated, the ceiling is sheetrocked, and the wall was added later. As for strapping, it is a regional thing, and makes for a better sheetrock installation, but it's too late here. I use the slide clips, and they are routinely ignored by 99% of other builders here. They can be important, but IIRC they prevent truss uplift damage caused by the temperature and moisture differential from a heated to unheated space. So, I doubt they would be of much use in a typical garage and like the strapping, of little value at this stage, since all the rock is up already.

1shotwade · #8 05/10/14, 01:15 PM

Quote:

Originally Posted by wharton

No idea where you got that silly idea, but it's wrong. Any properly engineered TRUSS roof system is done with engineering that guarantees that it will support the design load requested. In my area we use a very location specific design load of 50 lb ground snow load, and add additional live and dead loads. That said, truss roofs in this area at typically constructed of 2x4 stock, installed on 24" centers and rarely fail. Failure is typically traced to installation by somebody who ignored the drawings provided. In my location I have seen everything from double wides with trusses made of 2x2s to new barns with trusses on 8' centers. All engineered, code approved, and doing just fine.

As to the OP's question. Yes, the wall needs to have a ladder of flat 2x4's installed on top of the sheetrock. In this case, I would install them on 48" centers, with additional pieces on each side of the door. If you have a helper cutting and handing them up, and you install them with a battery impact gun and 3-1/2" deck screws, the job will only take a few minutes. Be careful, falling through a ceiling sucks.

YEA! O.K.,senior moment there. I read trusses and was thinking rafter.Thanks for the correction.

Wade

wharton · #9 05/10/14, 06:35 PM

Quote:

Originally Posted by 1shotwade

YEA! O.K.,senior moment there. I read trusses and was thinking rafter.Thanks for the correction.

Wade

No worries. One interesting thing to think about in the truss situation, however is that design loads on rafter are factored to do a lot of sagging, and even a few individual rafters splitting and failing without the whole mess caving in. Trusses, OTOH tend to be capable of their design value, and not a whole lot more.

Years ago we had a few nasty winters with radical amounts of snow. Heading south from here there were many collapsed building and lots of pole barns down, few if any, were stick built roofs. I asked my truss company what had happened and they said you could draw a line through the damage and call it the "20lb-30lb divide. The whole area was overwhelmed with snow load, but the existing codes called for 20lb loads in one area and 30lb loads in the next counties north.
Turns out that 20lbs was just a hair too light. OTOH, my local lumber yard has many buildings that are at least 32-36' deep, with a 6/12 pitch and rough sawn, full sized 2x6s on 24" centers. They are covered with board sheeting and shingles. They are nearly 100 years old, and still standing. The rafters are sagging, and in places the sidewalls needed to be cabled back into place, when they bowed, but those rafters would need to be at least high grade 2x12s on 16" centers in today's world.

haypoint · #10 05/11/14, 08:32 PM

Most garage trusses are built with a zero bottom chord load. dry wall over loads those trusses. Yes, I know people do it.

wharton · #11 05/11/14, 09:44 PM

Quote:

Originally Posted by haypoint

Most garage trusses are built with a zero bottom chord load. dry wall over loads those trusses. Yes, I know people do it.

Must be a regional thing. Here attached garages get 5/8" type X rock as standard procedure. Also, current IRC requirements call for a default bottom chord live load of 10lbs, so any recently build truss structure in a code area, should easily handle the load. OTOH, even in a small garage, 5/8" rock can easily impose additional dead loads of over 200lbs, per truss, so it's pretty to easy to see how saving a few bucks, and cutting the job to the bone, could result in trusses that, in theory, wouldn't handle a rocked ceiling.