Hi Bob, I have a question for you. I have a house and it has cathedral
ceilings. It is a house of western red cedar and stone construction and
the ceiling material is also WRC planks supported by large thick beams
which in turn are supported by posts at the ends of the house and rooms.
I want to add a family room to my house and I want to add the room at right
angles to the exposed beams. The roof is colourbond steel. My question is,
is it possible to attach a roof to the existing roof at right angles when I
would have to remove the roofing steel, leave the WRC celling planks in
situ and use the beams to support a portion of the new roof which is
supported by studs where the new room is added. The roof I want to add is
not a cathedral type but is a normal cavity type with gyprock ceilings etc.
Would I be able to use the existing beams to support a portion of the new
roof line coming off the main roof. Hope this is clear enough for you.
Cathedral Ceiling Framing
Summary:
Framing a cathedral ceiling is not hard. A vaulted ceiling design can be created by transforming a traditional flat ceiling. Before you begin vaulted ceiling construction, be sure to consult with a structural engineer.
DEAR TIM: My ranch-style home was built in 1968. It has dreary low ceilings. I would love to create a cathedral ceiling. This past weekend, I poked my head into the attic to see how the roof was built. The roof was not framed with modern prefabricated trusses. All I could see were 2 x 6 rafters that meet at the top where they rest against a center-ridge board. Can I take out my flat ceilings and attach a finished ceiling to the underside of the rafters? Is it possible to install skylights at the same time? Stacy J., Tulsa, OK
DEAR STACY: The simple answer is you absolutely can create cathedral ceilings in your home and install any number of skylights. But before you start tearing out the flat ceiling and cutting away the flat-ceiling joists, we need to talk. The modifications you want to do are structural in nature, and if you don't adequately brace the roof, you can cause serious structural damage. In the worst case, your roof will collapse on top of you.
Traditional roof framing consists of two slanted rafters that are connected at their base with a horizontal piece of lumber. When fastened together, these three pieces of framing lumber create a very simple triangle that can be exceedingly strong. But the strength of the triangle relies on each and every one of the three pieces of lumber. Your existing roof consists of a series of these triangles spaced at either 16 or 24 inches on center.
Cathedral ceilings can be a dramatic look. The ceiling can be covered with wood or drywall. PHOTO CREDIT: Tim Carter
If you cut this horizontal piece of lumber, the force of gravity, along with the combined weight of the roof rafters, roof sheathing and roofing materials, immediately starts to push the roof structure down. The result is that your slanted roof starts to transform into a flat roof. This process can happen over a period of years, months or even seconds, depending upon how the house is built.
There are any number of satisfactory structural solutions that will allow you to create the cathedral ceiling. One solution is to install a properly sized beam just under the peak of the roof, where the top of the rafters connect to the ridge board. This beam will carry all of the roof load, but the ends of the beam must be supported by columns that rest on a solid surface. This surface might be a concrete footer in a floor, a steel I-beam that is used to support the floor of the home, or even the top of the foundation. A residential structural engineer can help you determine how to properly size and support this beam.
You can also install smaller, horizontal-framing members, called collar ties, that can be exposed as part of your cathedral ceiling. These collar ties are installed higher up than your current flat-ceiling joists, and they create a new bottom base of the triangle. Once again, the engineer can offer suggestions as to where to install these and how to properly fasten them to the slanted roof rafters.
Plywood gusset plates can also be installed high up in the rafters near the peak of the roof. These plywood pieces are cut in a triangular shape to match the slope of your roof. They are glued and nailed to the sides of the roof rafters. You would be surprised how small these gusset plates can be, yet they provide sufficient strength to prevent a roof collapse. If you use these gusset plates, you will end up with a small, flat ceiling area near the peak of the cathedral ceiling.
The slanted pieces of wood are actual roof rafters. The horizontal piece of wood is a collar tie. You can see how combined, all three pieces of wood make a strong triangle. This collar tie is not at the base of the rafters, yet it still imparts great strength. PHOTO CREDIT: Tim Carter
Once the new cathedral ceiling supports are in place, and the flat ceilings have been removed, you need to think about how you are going to insulate the ceiling. Do not fill the entire cavity with insulation, unless you happen to use newer breathable open-cell spray-foam insulation. If you use traditional fiberglass or cellulose, you need to create a 2-inch air space between the insulation and the roof sheathing. If you do not have ridge ventilation in place, you will need it after the job is complete.
Remember that the skylights need to be installed before any insulation work is performed. The engineer needs to know about the skylights, because you may have to strengthen the existing roof framing along each side of the new skylights depending upon their overall width.
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Comments:Welcome! I, Tim
Carter, don't answer questions
here. If you post a question here in the Comments Area,
perhaps another visitor will help you. You need to go to the Ask
Tim page if you want a question answered. Once there, look
closely at how many weeks behind we are. Please be patient as you use
this free service. If you have an emergency and need to talk to me,
there is an option there for you.
Jim Donnelly 06 Dec 2007, 22:43
AsktheBuilder 07 Dec 2007, 05:34
Jim,
Bob is out on medical leave. You are stuck with me. You need to call in an architect and/or a residential structural engineer. It is non-negotiable.
Sarah 07 Dec 2007, 16:44
Hello.I just purchased a 215 yr old stone house with high humidity and
mortar that needs to be replaced. The roof is asphalt shingled in fairly
decent shape, cathedral ceilings in the living room with what looks like
tongue and groove wood panelling for the A-frame ceiling. There is no
insulation whatsoever in the house and the average winter indoor room temp
is 35 degrees. it leaks heat like crazy. What is the best suggestion for
adding insulation to this ceiling? I know I'll probably lose the beautful
wood panelling. Thanks! Sarah
AsktheBuilder 07 Dec 2007, 17:00
Sarah,
You have multiple options. I would call in several remodeling contractors and see what type of creative ideas they float. Get back with what they say.
Stephanie 11 Dec 2007, 07:31
I have a log cabin with vaulted ceilings... no attic space. The roof has a
ridge vent. The rafters and roof have an overhand, but no soffits with
vents. I am getting hundreds of flies and wasps in the house, and I cannot
see any nests on the sides of the house or visible under the overhang. I
am suspecting air-space somewhere in this roof construction or ridge-vent
area where they are nesting. I am fairly certain the roof has 2 layers of
the styrofoam insulation sheets (house is in NC). It is a shingled roof.
Any ideas how this house may be harboring wasps??
AsktheBuilder 11 Dec 2007, 09:26
Stephanie,
Sure. You need insect screening over the ridge vent and any other place where those devils can squeeze into.
Beth 12 Jan 2008, 20:39
Hi Bob. I am building a cabin with 2 cathedral ceilings - one in a
downstairs room, and one in a higher, but connected loft area (you can see
down into the other room with its own cathedral ceiling from the higher
loft area), and I am planning on installing soffit and ridge vents in both
roofs, but I was wondering if I need some sort of gable vent in the gable
ends of the two rooms with cathedral ceilings.
I will be heating with passive solar and a wood stove, and I will not have air conditioning, just ceiling fans. I plan to keep a lot of windows open (and screened) in the summer. I live in North Carolina. Would it be enough to install some small, operable round windows in the gables of the upstairs, and maybe downstairs cathedral ceilings, or do I need to put some sort of gable vent with a fan in it in these gable ends. I was thinking about taking an attic gable vent with a fan, and creating some sort of insulated shutters that I can keep closed during cold weather, and then open them in hot weather to vent out the space, but if that's not necessary, I'd rather just put in windows that open up there. It gets up to over 100 degrees Fahrenheit here in the summer, and humid. Any ideas? thanks.
AsktheBuilder 13 Jan 2008, 07:18
Beth,
I don't know where Bob is. That rascal has not been showing up to answer questions. My idea would be for you to go to a sign maker and get this sign made: Free Sauna Experience - Come Stay in our Lofts and Sweat Your Life Away You can have as many windows or vents as you can fit into the gables, but it will still be like an oven up in those spaces.
Jay Reed 22 Jan 2008, 19:16
I have cathedral ceilings in an older house. That ceiling is very
attractive with exposed beams and a loft that does not need less head room.
The ceiling/roof is not well insulated and half of it is north facing.
The roof decking is of questionable quality and fells soft in about 10% of
the north facing side. There is not a ridge vent or appropriate air space
above the existing insulation in 2 x 10 rafters.
I'd like to add depth to the exterior of the rafters. The 2 x 10's and supportive structural beams exceed code for slope and snow load. The question: With this, can the roof be insulated further from outside with high density styrofoam? The plan would be to strip the old roof to the rafters, install high density styrofoam (2.5 or 3 inch -- R15 or so) directly to the beams, leave spacing for ventilation, and then add new roof decking (needed?), roofing materials and a ridge vent. This would be done without adding new wood to the rafters with 2x4's or 2x6's and assumes the strength of the high density styro would support roofing materials.
AsktheBuilder 22 Jan 2008, 19:55
Jay,
The answer is Yes. You simply must build in great ventilation. View all comments |
