Alternatives to rafter and collar ties

Reply

  #1  
Old 10-27-05, 01:38 AM
mikeklooster
Visiting Guest
Posts: n/a
Alternatives to rafter and collar ties

Im building a recording studio in my 22'x28' seperate garage. It is a 22' wide 4/1 pitch gable roof. It is constructed from 2x6 rafters spaced 24" apart. When I started building, we raised the 2x10 rafter ties that sat on the wall plates so that the bootom ridge is about half way up the rafter. They are spaced every 4'. The garage will be split into 3 rooms, a live room, a control room and an islation booth. The live and control rooms will be room in a room construction where the 2x6 wall frames do not touch the frame of the garage. The control room has a flat ceiling, but I would like to vault the live room.
We got an idea that the live room would have 2x8 rafters just under the garage roof rafters. The live room is 20' wide and from 11' to 16' wide. If during construction we temporarily remove collar ties in live room, and build the live room ceiling under the roof rafters and then place colar ties back on garage roof rafters so the collar tie's top ridge sit under the live room's ridge beam, I could put collar ties on the live room just under the garage collar ties. The ceiling would then pitch up until it reached the cottom of the live room collar tie, flatten out and hang on live room collar ties, then pitch back down the other side.
This would work, but through my reading I just realized something..the live room's ridge board is supported on both sides, 12' across, which turns the ridge board into a ridge beam. Ive read that this turns the rafters into joists and collar ties or rafter ties(flat ceiling joists on top of wall) are not neccessary. This would allow me to sheath all the way up the to the peak, instead of flattening out. If it werent for the garage collar ties which pass through the live room ceiling framing, I could sheath all the way up. Even if I needed ties in the live room I could leave them exposed and sheath all the way up. Is there any alternatives to collar ties or rafter ties that do not go horizontily across garage interior. Remeber that the other half of this building is fine like it is and no collar ties need to be removed. As well, as ties could be added in this part. The ridge board on the garage is NOT a ridge beam and not supported. If I could just not have protruding horizontal supports through the live room the ceiling would look and be amazing for my situation. The subsitution of a tie rod for collar ties and rafter ties, is a possibility. The cable, set on top of garage wall top plates would oass through the live room, but sinse the cables are thin(compared to a board) the vibrations picked up (which will hurt soundproofing) would be less, if any, but I would still have holes in me live room and also when two objects connect the two rooms wall frame it transfers sound(flanking). Ultimately a dangeruous endeavor since the results would be untested until completed. I would really love for another method, if possible, since this live room(with its ridge beam ) should need no horizontal supports at all so I can take advantage of the possible ceiling height.
These are some of the ideas I have...
1)over supporting in areas other than live room
2)tie rods(cables at lowest spot of rafter)
3)sistering rafters to support roof better
4)some combination of hurricane strapping
5)converting garage ridge board into a ridge beam by supporting

you can see my plans at http://www.**************.php?p=33242#33242
 

Last edited by mattison; 10-27-05 at 04:13 AM. Reason: Sorry, but no links to outside forums.
Sponsored Links
  #2  
Old 10-27-05, 10:57 AM
Join Date: Mar 2005
Location: USA
Posts: 6,126
Alternatives to rafter and collar ties

It sounds like you are trying to convert a very simple building into a sophisticated structure with a sophisticated use.

considering the goals, you need professional help, since the design is not a DIY project. With good plans, it could be.

If your have a firm understanding of acoustics, sound deadening, sound transmission then you could get buy with an engineer.

If you want a some consulting on sound and sound control products plus the structure, then an architect, who will probably hire out any tough structural problems.

Dick
 
  #3  
Old 10-27-05, 12:02 PM
mikeklooster
Visiting Guest
Posts: n/a
thanx for the post. Im an not an expert, but when it comes to the isolation and acoustics. I have a good handle, and understand the principles. the reason i described the studio aspect so much, was just to give enough insight and info for people to work from. The collar tie issue is one that Im chasing out of greed for ceiling height. I keep getting told I cant remove these collar ties, but then I read about these alternatives, and I cant help but think there is a way.I must admit, the alternatives Ive seen so far have not provided thesolution Im looking for. I do understand the principles that are making the people Ive talked to say it cant be done, but I keep thinking I need another view point that is knowledgeable yet can think out the box..
Any help will be greatly appreciated. thanx
 
  #4  
Old 10-28-05, 05:10 AM
Member
Join Date: Aug 2004
Posts: 1,150
So in simple terms, you want to create an acoustically isolated chamber and you are not concerned with vibration from vehicular traffic since you did not mention isolating the slab.

I'll address the ceiling as I go.

I would build walls using 3-5/8" 20ga. steel studs @ 24"oc. located to allow a 10" insulation cavity where they are parallel with the existing structure's walls,
Isolated from the slab by a 1/2" dense rubber pad, yet attached to the slab with drop-in anchors bolts. The walls are attached to the existing structure at there top, and maybe mid height, with brackets, also isolated from the walls with the same rubber pad at both ends.

The short section of the sloped ceiling, also of 20ga. steel studs, rests on, or is attached to the side of, the new wall and in both, the same rubber pad is used at that intersection.

At the top of the slope and the intersection of the ceiling or flat section, a steel support needs to be designed to carry the loads, I suspect an 18ga. or 16ga., which will be suspended from the relocated collar ties with adjustable, spring loaded isolation brackets.

There is a thin, narrow, self adhesive tape available from drywall suppliers which also aides in lessening sound transmission, use this between the first of two layers of 5/8" drywall throughout.

The wood member which occurs at 48"0C at the intersection of opposing rafters are the horizontal member of a carpenters truss, and they hold the place together, in part because they are also attached to the top plates.

Collar ties occur up the rafters and their location can be a design function based upon design roof loads, and you will need the assistance of a local civil or structural engineer.
 
  #5  
Old 10-28-05, 08:21 AM
Member
Join Date: Apr 2004
Location: Atlanta, GA
Posts: 143
Instead of double sided "tape" use a product called "Green Glue" mad by Audio Alloy. It is sandwiched between layers of drywall to improve sound isolation.

There is a thread over at avsforum.com about it.

BTW... I don't work for the company and I know I'm not supposed to plug websites and brands but this is a very specialized application and product.
 
  #6  
Old 10-28-05, 11:17 AM
Member
Join Date: Aug 2004
Posts: 1,150
"double sided "tape" "
The tape I mentioned is only one sided and is not for the purpose of adhering drywall to framing. Instead it has a peel away adhesive foam tape and is a standard product.
Thanks for the link, new products come around all the time.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes