Vaulting a ceiling

[Larry Sherman]

Hello all:


I am about to start a large project (for me anyway) and I need some advice. I will be vaulting a ceiling in a kitchen extension (12’ x 12’, 6/12 roof slope, 3 foot soffits on both sides, 2x6 framing of existing roof). The current ceiling height is 8’ and the space above the ceiling (at the ridge) is approximately 4’.

Questions:

• I will place 2x6 collar ties at the upper third of the rafters (or lower) – will this keep the walls from bowing – we are in NY’s Long Island – not a heavy snow area – but I don’t want to take any chances. Are the collar ties sufficient to prevent bowing of the walls?
• I am not sure if the ridge is structural or not - how can I determine if I even need to install collar ties?
• I have researched closed cell poly urethane sprayed on insulation, but at $1,500 it seems pricey. There are no soffit vents and there is no ridge vent – do I need to provide a 2” gap for air flow when there is no venting anyway? If I use regular fiberglass do you suspect I will have any issue with moisture – I intend on installing either pendent or track lighting to keep the integrity of the vapor barrier. Will this be sufficient “R” value – this is an extension over an unheated crawl space.

The ceiling will be covered in sheetrock and the collar ties will be enclosed, wiring and HVAC will go through the collar tie area and be covered by the sheet rock.

I have attached a few pics.

Is there anything I’m missing or anything else I need to know?

Thanks

[Larry D. Kage]

Hi Larry,

A rafter tie is located in the lower third of the roof framing to prevent rafter/wall spreading. A collar tie is located in the upper third of the roof framing and holds the rafter down to the ridge.

Most people undertaking a project like yours would benefit from an engineers/architects assistance.

Was there a previous fire in the attic area?

Others may have more input.

[Richard A. Hetzel]

The walls of that addition are partly kept from spreading by the end wall, and the main house wall. All you'd have to do is tie the middle of the wall, maybe with 2 steel bars fastened from top plate to top plate. You certainly don't need a rafter tie every 16 inches, because the top plate of the walls acts as a horizontal beam to help resist the rafter thrust. You could also run 2x4's or 2x6's across the space instead of rods, and you can then install your track lighting on top of them and bounce the light off the ceiling, which will give you excellent lighting. In a space that small, I'd use 2x4's. Another trick I've used is to use a deeper tie, maybe 2x6 or even 2x8, but cut the bottom in a gentle curve from zero near the ends to maybe 1 1/2 inches up at the center. It looks sensational.

For the record, your ridge is not at all structural; it's basically just a nailer.

Then you can place the rafter ties where they belong and use that space for whatever you need.

However, you probably should screw 2x4's to the bottom of each rafter, so you have enough room for at least R-19 or R-21 insulation, and preferably R-30. And you should install soffit vents and a ridge vent. Without ventilation you're risking two things: possible mold, and possible ice dams resulting in roof leakage.

A good local architect would probably be a good investment for you. Hunt for a low-key architect who specializes in additions and alterations. He or she can advise you on structure, insulation and ventilation.

[Kenton H. Shepard, CMI]

Richard is right about the ties.
Larry, if you have to ask questions like these, you should have somone more experienced running the job.

[Larry D. Kage]

Originally Posted by kshepard

Larry, if you have to ask questions like these, you should have somone more experienced running the job.

Bite me, Kenton!..you knew it had a fire?

Oh, that Larry...

Never mind.

[Kenton H. Shepard, CMI]

Originally Posted by lkage

Bite me, Kenton!..you knew it had a fire?

Oh, that Larry...

Never mind.

[Larry Sherman]

No, there was no fire in the attic. The black marks on the wood were from using a sawz all to cut through the roof shealthing with the asphalt shingle still attached.

A structural engineer will be on site tomorrow to determine what course to take to vault the ceiling.

[Larry D. Kage]

Originally Posted by Larry Sherman

No, there was no fire in the attic. The black marks on the wood were from using a sawz all to cut through the roof shealthing with the asphalt shingle still attached.

Of course, I wasn't looking with the right perspective. Thanks.

Originally Posted by Larry Sherman

A structural engineer will be on site tomorrow to determine what course to take to vault the ceiling.

Good decision. Good luck with your project.

Let us know how it turns out.

[Larry Sherman]

Ok - here's what I found, please see prior pictures for clarity.

The RAFTER ties are 2 x 6's and apparently sit on the exterior walls, the rafters themselves tie into the rafter ties. So, there is no (or very little) outward stress on the exterior walls.

My thought to vault the ceiling would be to get a "microlaminate" beam, place it below the ridge and construct a double 2 x 8 header above the existing back windows to support the "microlaminate" beam, tie the other end of the beam in to the existing doubled 2 x 12 header that is there and use Teco's to tie the rafters into the exterior walls. COLLAR ties (Bolted) would also be used as ADDITIONAL support.

I will clear this with my structural engineer - just curious of your thoughts.


Thanks

[Richard A. Hetzel]

What would support the 2-2x8 header? It needs a complete load path to the earth.