Question about how rafters are supported.

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Old 05-01-12, 06:52 PM
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Question about how rafters are supported.

House is single story, stick built, crawl space, 1926 Tudor Revival.

Ceiling joists are 2x4 16" OC. All joists run same direction, spanning from side to side of the house. Rafters also run from side to side. Approximately every 8 joists there is a 2x4 running vertically to the center of a corresponding rafter creating a triangle. The interior of the house has 14'x14' bedrooms and a 20'x14' living room. in the attic, on top of the joists, running perpendicular, there are 2x4s laid horizontally running roughly down the center of the bedrooms and the living room. The detached garage is framed in the same way, minus the ceiling joists (big open space).

From what I have been reading, I assume the horizontally laid 2x4s perpendicular to the joists are acting as support to keep the large open ceiling span from sagging.

My question lies in how the ceiling of the kitchen is structured.
The kitchen is 9'x16' with the joists running the 16' direction. There are 2 walls dividing the length of the kitchen into 3 separate parts (i.e.. utility section, main section, and eating section.) The floor joists are 2x6 and run perpendicular to the ceiling joists. The wall dividing the utility section from the main section has a centered doorway with a "header" of 2 2x4s laid horizontally nailed into studs on each side. There are no jack studs supporting this "header". This wall has a double top plate.
The wall dividing the main section from the eating section only extends 3', most of which is a doorway, also with the same "header" and no jack studs. The remainder is a built in cabinet. There is no structuring in/around the cabinet.
I plan to remove these 2 dividing walls. My question is should I replace them with a beam from below to support the ceiling joists due to the span, or should I support them from above with a beam and hurricane ties?
 
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Old 05-01-12, 07:44 PM
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First thing I'd do is try and figure out if you have any load bearing points in your crawl space, and locate them in relation to the kitchen. That might help you figure out where the weight of your headers can be transferred to.

Assuming there is no support in the crawl space where you need it (can't be that lucky, right?) I would think about this as a plan:

Build a temporary wall next to each of the existing walls, about 12" away. Then remove the walls you would like to remove. Open up a 16" wide slot in the ceiling plaster around the old top plate locations, to expose the bottoms of your ceiling joists. Open up a 16" wide slot in the plaster on each of the side walls, floor to ceiling. Snap 2 chalk lines on the bottom of the ceiling joists to represent where a new header will go. Mark one side with a square. Place temporary collar ties across every other rafter in the lower 1/3 of their span (assuming your roof is oriented in this direction) If using an LVL, cut each of the ceiling joists on your marks with a skilsaw so that you create a slot that will be 3 3/4" wide for your new header. Slide the new header in- if it is 10' long, it should be long enough to rest on the top plates of the side walls. Place joist hangers around the ceiling joists on each side and fasten them to the header using the correct sized nails for your hanger. Ensure you have 2 studs in the wall directly under the header to carry the new load point to the floor. Repeat this where the other wall will be removed. Then in the crawl space, support the two new load points with footings and piers, if they are not already supported. Remove the temporary collar ties.

Being in California as you are, I don't know if there are any special earthquake straps that would have to be included in this plan, but that might be what those horizontal 2x4's were for in 1926, besides being a nice thing to walk on.

Keep in mind that there is no substitute for having a structural engineer or at least a carpenter actually look at it with his own eyes. There might be something we are missing.

Keep in mind that 2x4 joists are no longer kosher, they really ought to be bigger. So it would almost be easier to scrap the whole ceiling and replace it with larger dimensional lumber, if possible.
 
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Old 05-02-12, 04:05 PM
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2x4 ceiling joists running 16' with no support is a long distance. You don't say how big your rafters are, but I am guessing that are on the small side as well. I wouldn't go adding additional load by hanging the ceiling from there. You can go wrong by adding a beam where the wall used to be. Make sure there is proper structure underneath the floor to carry the load from the posts to the ground.
 
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