Ridge Beam Support for Porch Addition

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Old 06-03-05, 10:03 AM
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Ridge Beam Support for Porch Addition

I am in the process of getting bids on a screened porch addition to my home. The construction of the porch will be ridge and beam, stick build rafter roof in order to have as open a cathedral ceiling inside as possible. Although most of my home is two stories, the area where the addition would be build is actually a story-and-a-half--it is a family room behind the garage, and the family room has a vaulted ceiling whereas the garage has a room above it (albeit you have to step down a few stairs to get from the upstairs of the two-story area to the bonus room over the garage). So the addition would be hipped into the existing roof over the family room (which as I stated is a vaulted ceiling inside).

My question is this: for a ridge and beam construction, the support on the end away from the house is easy to envision--a simple heavy post that extends down to the deck and then to the footers to support the load of the beam. On the other end, I can't envision how the load of the beam would be supported. The issue is that the wall where the end of the beam would sit has four windows in it with a steel lintel above. The contractor indicates that he would add an additional support beam to carry the load of the roof ridge beam and would do it above the existing roof without disturbing the structural integrity of the existing structure. Can anyone help me with a description of how this is done? Could this be done by using jacks on either end of the support beam (on either side of the windows)? The jacks would rest on the top plate of the existing exterior wall. Is this a legitimate method of support? Would the wall have enough strength to support this additional load?

Thanks!
 
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Old 06-03-05, 10:38 AM
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If I'm picturing this correctly, the ridge of the new roof will be terminating into the sloped side of your current roof, and your question is: how will this be supported when there are windows in the wall directly below this area?

Unless I'm way off base here, your rafters distribute the weight to the exterior walls, and the ridge really should not have any downward pressure on it once bottom chords have been installed to form some sort of triangle, whether it be cathedral or otherwise. There will be weight bearing down on the roof (the area of the new roof that extends onto the old roof) but it should be sufficiently distributed so as to not need additional support.

If I'm not picturing this correctly, then yes- the load would need to be supported with a header that would transfer the weight onto each side of the windows... you can't just frame straight down and assume that the window header is sufficiently sized so as to put even more load onto it.
 
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Old 06-03-05, 11:04 AM
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I would say that you are picturing this correctly in terms of the description you have in your first sentence. However, there will not be chords forming the bottom of the triangle as the addition's ceiling is completely open: not even tie rafters of any variety. Essentially, the roof is stick built and the load is carried primarily by the top ridge beam with minor contribution from the exterior addition walls. Therefore, the top ridge beam needs substantial support on both ends in order to carry the load sufficiently. This support on the gable end of the addition is easy--a large post heading straight down to grade and below. However, on the other end, the end terminating in the sloped roof of the existing house, the end of the ridge beam would be directly over windows in the exterior wall and would therefore need additional support in the form of another beam running perpendicular to the ridge beam and carrying the load to the sides of the windows. My question is how this perpendicular support beam is in turn supported on the existing exterior wall without disturbing the existing structural support and rafters of the existing roof. Are jacks in between the existing rafters, mounted on the top plate of the existing exterior wall, enough to support the load and would this be in compliance with most code requirements?
 
 

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