designerdale

I live in southern New Jersey, near Philadelphia. I plan to open up an exterior bearing wall to a new addition. The bearing wall supports the only the roof rafters, and not the ceiling joists (which run parallel to the wall to be removed). The existing roof rafters (and ceiling joists in the existing room) are 2x6's. The rafters are 24" OC and on a 5.5/12 pitch. Based on a 50lb/sf total load (figuring for some of our weird winter snowstorms), can a double 2x6 adequately span the new 10'-4" clear opening that we want in the bearing wall, or should we simply plan on using a triple 2x6 as the header for the opening? I want to use 2x6 members, and not increase to 2x8s or 2x10s, if at all possible, to make it easier to extend the attic floor level above. The supporting studs on each end of the header can be as many as needed, based on the header's required thickness, as the addition will create an L with the existing house exterior. The 2x6s to be used would likely be select hem fir. Any feedback would be greatly appreciated! THANKS!!

CallMeVilla

From what I can see, your 2x6 plan will not work. You need at least 2x10 and one table actually calls out a triple. I am not an East Coast guy, so others might have better experience.

Check out these specs to be sure: https://docs.google.com/viewer?a=v&q=cache:7rqE2RWhz-wJ:napasolanoicc.org/Links/IBCSpanTables_NapaSolanChapterFinal.pdf+header+spa n+table&hl=en&gl=us&pid=bl&srcid=ADGEESgNcBsNx0Jfx WrmaPqQ4C7BxiPVGY-f6O4ApDqe-TT4GoidjtNoWb7fRhFutOzVr5F_SRjAvxG3smBbcppDZYHc7Ql 29PbYAAp80R5zKhIzrqPKjr8AqPQlZRa84WKhVXKaKVHA&sig= AHIEtbRjBABRJnH3UR24wZJzig9Vu9D1Ww

GOOD LUCK with your project.

designerdale

CallMeVilla
Thanks for your thoughts. I had actually previously reviewed the table you linked. And, like all of the other tables I'm finding online, none is actually addressing the question of a header dimension. This (and all the other) tables only address floor joist, ceiling joist, or rafter size requirements, based on the OC distances between the individual members, which actually spreads the load out. If I were simply putting a 10'4" clear span window opening into the wall, I wouldn't be able to add to the header material's thickness (it would need to match the wall's thickness), and I could easily understand the need for larger height (i.e.: 2x10) lumber. Since I have the option of actually using a triple 2x6 (a "6x6") or even a quadruple 2x6 (an "8x6") to span the opening, I would think that the 6" height dimension would suffice. Unfortunately, I have yet to find a table specifically noting header dimensions, based on load, that includes triple and quadruple dimension lumber. I may even have to consider using an engineered product to get the strength I need in the 6" dimension.
One table I reviewed stated that a single 2x6, with a 50lb/sf load, can span a 10'-6" opening. Figuring that as a basis, I thought that I could easily double or triple (or even quadruple) the 2x6, to strengthen the load bearing capacity.
Your thoughts on this?
Anyone else have an opinion?
Thanks again, fellow handypeople!!

nealtw

Any amount of 2x6 will not do the job, spend a few buck on an engineer.

CallMeVilla

Neal went where I was about to go. Doubling or tripling the 2x6 does add to carrying capacity but you need a specific calculation . . . won;t cost much for such a simple problem . . . but the assurance of a structural engineers review is worth it.

AndyGump

You should (I think) be looking towards using something more like 3 2x12 for the span yo are thinking of.

are you getting this permitted?

Andy.

BridgeMan

Looking at Weyerhaeuser's Microllam header data sheet, even those would be overstressed if limited to the 5-1/2" deep units. You either have to go with increasing the member's depth, or consider adding a steel flitch plate on the bottom of the stacked 2 x 6 header. If going with the latter, an engineer should compute what you need based on (present and future) loads being applied.