Ridge Board Post Support Beam

[PreConGuy]

I am wanting to convert a 2nd floor storage room over the garage to a bonus room. The room would be approx 13' x 20'. The issue is there are two 2x6 posts that are supporting the ridge boards of the "L" shaped hip roof over the area. The posts are essentially at the intersection of the L's two legs running from the ridge board down to a steel beam that supports the 2nd floor joist framing. I am wanting to know what size beam I would need to span 13' and support the load from the two posts. The beam would run from the exterior wall to a new interior wall. I don't believe the load is huge since I can move the 2x6 posts back-and-forth with my hand fairly easily. I have attached a floor plan and a roof plan to help in understanding the situation. The floor plan shows the two ridge board's location in the proposed room as well as the location of the steel beam supporting the floor. The rafters for the 13' span are 2x6 @ 16"oc at a 8/12 pitch. I have installed 2x6 ceiling joists to the rafters in this location 8' above the floor. The rafters on the other leg of the "L" span 25'. They are 2x6's at 16"oc and 12/12 pitch. The other attached file shows the roof plan with a cloud around the area being questioned. I know the easy solution is the erect another wall and let the posts bear on it, but that cuts the room down about 40%. I am open to any other suggestions.

[Richard A Hetzel]

Before we get into beam sizes, is there a continuous load path from the points where the beam will be supported, running all the way doen to the earth? If not, then a beam won't do anything for you. If there is, then the beam should be designed by a qualified design professional, who can visit the house and examine all conditions that might affect the installation of a beam. We can't do it sight unseen, because of the risk that something we don't know could affect the design.

The actual load at one point in time may not be huge, but that does not enter into the design of a beam. Building codes specify definite load values for which a beam must be designed, and that is what a professional will determine after he or she has examined the house thoroughly.

[PreConGuy]

The beam would above the steel beam that is supporting the floor system.

[Richard A Hetzel]

Then someone will have to investigate that beam, to see if it can carry the new concentrated loads that would be imposed on it, and the footings that support whatever supports the beam must also be investigated. The loads have to be chased from wherever they begin directly to the earth without any gaps or breaks. That is why it is so important that someone examine the house first-hand.