|
| Author |
Message |
steveprsn
Member
|
# Posted: 19 Jan 2014 03:11pm
Reply
Looking for suggestions to convert from a flat ceiling to a cathedral ceiling on a 24' x 18' cabin with 2x4" outside walls and 2x6" ceiling joists and rafters on 24" centers. thanks.
|
|
rockies
Member
|
# Posted: 19 Jan 2014 03:39pm - Edited by: rockies
Reply
You want a cathedral ceiling over the entire cabin or just in one room? The rafters running across the cabin are providing the stability so that the walls don't bow out from the weight of the roof and any snow you might get on it, so I wouldn't cut them out. You might try doubling them up to make them look like timber beams. If you want to insulate the cathedral ceiling that is more tricky, If you have insulation in the attic space now it's sitting on top of the flat ceiling so you probably also have all the air venting you need in the attic space. Once the flat ceiling is gone the insulation will have to go up against the inside roof sheathing, and then you'll have to provide an air venting space above the insulation running from the bottom of each rafter bay right up to a ridge vent running across the entire roof. You'll also need a vapor barrier on the underside of the insulation before you put your finished ceiling in.
If you don't want to mess with any venting issues, you could just spray foam the underside of the roof sheathing and then add a vapor barrier and new interior ceiling treatment. Then you wouldn't need to vent the roof.
|
|
steveprsn
Member
|
# Posted: 19 Jan 2014 08:45pm
Reply
I was hoping to keep the ceiling joist in one end for approx. 10' feet with a loft above the bedroom/bathroom and adding a log or other tie(s) between the outside walls for the remainder. The wall at 10' for the bedroom/bathroom could act as the tie for the outside walls at that end of the cabin.
|
|
OwenChristensen
Member
|
# Posted: 21 Jan 2014 07:26am
Reply
To do it right, you need to take the whole roof off and start over.
|
|
Martian
Member
|
# Posted: 21 Jan 2014 09:07am - Edited by: Martian
Reply
I have done this a couple of times. Its not all that hard, but it is a damned dirty job!
On those projects, the ceiling support was installed at a different angle from the roof. This allows you to maintain ventilation of the attic space while having the cathedral look on the inside.
Start by removing the ceiling and insulation. Saw out the ceiling joist you don't want at the top plate, but leave the tails sticking out into the soffit. You need to leave enough joists to tie the walls together. Hang supports from each rafter pair at the ridge to hold the upper ends of your new ceiling joists. Install your new joist, insulation, and ceiling. I wrapped the remaining joist with cedar to give them a beam look.
Moving the lighting around can be difficult, but by using junction boxes in the attic space, you can usually extend any wires you may need to extend. Remember, the junction boxes need to be accessible after the new ceiling is in.
Tom
|
|
morock
Member
|
# Posted: 2 Feb 2014 12:50pm
Reply
Look up "scissor rafters" or "scissor trusses" it's a fairly easy conversion, but you should probably run it past structural engineer.
|
|
toyota_mdt_tech
Member
|
# Posted: 2 Feb 2014 01:19pm - Edited by: toyota_mdt_tech
Reply
You can not cut the rafter ties (ceiling joist) as they hold the walls in place, keep them from bowing out. You could convert the rafters to a type of scissor rafter system, it remove ceiling joist, run it from the bottom of one rafter tail like it is now, nailed into the ride of the rafter like it is now, then go across to the rafter at the opposite side, maybe a 3rd of the way down from the top. Then for the other side, same thing, but opposite side of the rafter. This will form an "X" that wont hook at the X, but have enough room between them for a 2X6 collar tie that can help the rafters plus a point where the rafter tie can hook at the bisect point. The ceiling wont be as high as the rafters, it must be lower. Of course, you will have to have an engineer look at it to determine if it will handle the snow load. This will raise your ceiling, but not nearly as high as the roof.
If you do this one rafter at a time, you can keep the roof on and in place. Final sheeting would go onto the scissor part. Insulate the ceiling, but not under the roof, make sure ventilation is adequate and you should be OK.
|
|
KinAlberta
Member
|
# Posted: 28 Apr 2014 07:12pm - Edited by: KinAlberta
Reply
Any thoughts on this:
Thinking that a horizontal beam along the top of each outer wall might prevent it from bowing out, I've wondered about leaving 8"- 12" of the ceiling joists sticking into the room but before cutting them off screwing & gluing a couple layers of 2x8" or wider boards to the bottom of those protruding rafters against the wall. Later maybe adding a layer on top bolted down to the bottom layer.
This would create a perimeter shelf look somewhat like some ceilings incorporating ceiling trays.
Then possibly scissor trusts or simply reinforcing the current rafters system possibly with new beams along the length of the room and possibly a couple or three black steel rods spanning the room at the former 8' ceiling height.
Imagine something like this (pictured in link below) with a cathedral ceiling instead of the "tray".
http://cdn.decoist.com/wp-content/uploads/2012/11/tray-ceiling-paint-ideas-for-the-be droom.jpg
Note: as the linked photo shows above, a fall back might just be building a ceiling tray. Reinforce the section to be cut out, put drywall jacks under it all, cut the perimeter, jack it up and tie it all back together - somehow. 
|
|
|
Don_P
Member
|
# Posted: 28 Apr 2014 10:00pm
Reply
That'll work, Frank Lloyd Wright's living room ceiling at Taliesin is basically this approach.
Remember that like any beam it needs to be sized appropriately and be well supported at its' bearing ends... it needs to be well tied to the gable endwalls. The horizontal component of the roof load needs to be resisted and delivered to ground from those walls.
|
|
KinAlberta
Member
|
# Posted: 29 Apr 2014 11:58pm - Edited by: KinAlberta
Reply
Do you mean this? It looks great. (Links below.) I was thinking that the beam would be supported along its length by the remnants of the original ceiling joists. Maybe tie each cut off ceiling joist to its rafter with a triangle of plywood. You raised a good point - how to tie it in at each end. ???
Note: The cabin I'm thinking of modifying (a guest cottage) is only 24' across the front, all glass fronted, gables at either end, 8' ceiling. Actually the floor plan of the whole cabin is only 24'x24'. One 12'x12' quadrant is 2 little bedrooms, the other three quadrants (L-shaped) is living room and kitchen, all open with 8' ceiling, ...1940s construction with uninsulated attic.
http://www.house-crazy.com/wp-content/uploads/2012/10/Taliesin-House81.jpg
http://www.steinerag.com/flw/Artifact%20Images/TalC1927-2a.jpg
Looking at the pictures above and imaging cutting off the ceiling joists, attaching vertical triangles and a horizontal hanging beam, I'd imagine there might be room between, the rafter and the sliced off protruding ceiling joist, to face it all with a standard beam on edge thus creating an L-shaped beam hanging from both the rafters and the remnants of the original ceiling joists. Or just use big angle-iron.
|
|
Don_P
Member
|
# Posted: 1 May 2014 07:45am
Reply
You've got the right pictures and idea. The glass wall in the right of the color pic is tied on the left side over the windows to a large stone wall on the left behind a piano area IIRC. His method provided the load transfer by way of a "collector", or "drag strut". A kind of fancy solution to that window wall problem. Getting the beams sized correctly and tied well to deliver the load to the foundation is the key though.
|
|
KinAlberta
Member
|
# Posted: 9 Jun 2014 10:54pm - Edited by: KinAlberta
Reply
Open Up a Ceiling with a Steel Sandwich
Bolted between rafters, an angled steel flitch plate can eliminate the need for rafter ties in cathedral ceilings
by Michael Chandler
Excerpt
"Everyone loves a cathedral ceiling, but when you remove the framing that makes most ceilings flat, you remove the lumber that keeps the walls from spreading apart. There are a few conventional solutions: a structural ridge beam, exposed collar ties, and scissors trusses. An unconventional option is to use a welded steel flitch plate sandwiched between two common rafters. This method gives more headroom than scissors trusses and is far cheaper."
http://www.finehomebuilding.com/how-to/articles/framing-cathedral-ceilings-with-steel -sandwich.aspx
|
|
KinAlberta
Member
|
# Posted: 2 May 2016 09:02pm
Reply
Quoting: Don_P That'll work, Frank Lloyd Wright's living room ceiling at Taliesin is basically this approach. Remember that like any beam it needs to be sized appropriately and be well supported at its' bearing ends... it needs to be well tied to the gable endwalls. The horizontal component of the roof load needs to be resisted and delivered to ground from those walls.
Realized later that one should be able to put the beam on the outside and tie it into the remnants of the joists that form the underside of the eaves.
|
|
Don_P
Member
|
# Posted: 2 May 2016 10:49pm
Reply
Yup Do take care of the end reactions though, they are sizeable.
|
|
KinAlberta
Member
|
# Posted: 3 May 2016 09:16am
Reply
Yeah. Tying the ridge and parallel beams into the gable end and spreading their loads should take away a lot of the outward pressures.
|
|
KinAlberta
Member
|
# Posted: 12 Feb 2017 10:10pm - Edited by: KinAlberta
Reply
On the cabin I'm thinking of removing the ceiling joists in, I believe the roof's truss design has the ceiling joists extending outside, forming the soffits ("cantilevered" not "overhang" truss? I don't know what it's proper name is but the rafters don't meet the ceiling joists over the wall plate for strong bearing point but instead the joists and rafters meet at the outer eaves). I'll have to look at it again but I believe the soffit is at a full 8' level, that is, there's no drop.
If that's the case then could the wall bracing / horizontal beam discussed above and used by Frank Lloyd Wright be built on the outside, screwed to the ceiling joists/soffit? (Maybe leaving maybe a 1/2"-1" screened slot for ventilation. Right now there are only two gable end vents and no soffit vents).
Anchoring it at either end to the corners would of course be critical to it all.
Could do/propose both I suppose. A beam on the inside and one on the outside.
Also, an article from a local paper:
Eyes up: Raising the ceiling can dramatically change a room
Architect Kevin Lichten says “the ceiling of any room has the potential to be the most dramatic and mood-altering part.â€
http://www.metronews.ca/your-home/2016/05/14/raising-the-ceiling-can-dramatically-cha nge-a-room.html
|
|
KinAlberta
Member
|
# Posted: 14 Mar 2017 07:14pm
Reply
Maybe a new strong roof would work, then remove the flat ceiling's guts.
A New Roof Over the Old One | GreenBuildingAdvisor.com
http://www.greenbuildingadvisor.com/articles/dept/green-building-blog/new-roof-over-o ld-one
|
|
|
