Hi,
First time post here. We are thinking about knocking out a short wall between two doors. Trying to get an idea of how big header/lam beam will be needed to support the opening appropriately here. I'll try to spec as much info below, but might not have all the necessary info. Let me know.

-Span will be about 14 feet, and we want to drywall over it, so thickness needs to be around 5-1/2".
-Existing doorways are 6 and 3 feet wide, so we're wanting to knock out about 5 feet of wall.
-Wall is the "old" exterior of the house (@1900's construction 2x4 walls, 8 feet high).
-Doorways lead from old 1st story into a one-story greatroom addition.
-Wall supports the 2nd story "old" exterior wall, a traditional roof structure above the 2nd story, and the slightly-pitched roof structure over the greatroom addition (total span of each roof perpendicular to the subject wall is about 20 feet).
-We live in Seattle, so the roof live loads are an inch of water (just kidding--seems like it, though).
-Span supports can be 2x4s or 4x4s and I think will be well supported below by large framing timbers, joists and cinder block basement wall directly below.

Or should I call out an engineer?

Thanks for any help you can provide.

Dave

Much too complicated to advise here...consult an architect or structural engineer and get it right.

Okay,
Thanks, Richard.

Some lumber yards might help but I think Richard is correct. That a site vist by an engineer is the best wat to go.

Absolutely, consult a structural or Architectural Engineer. You will need drawings stamped by an engineer in order to pull your building permit, so the money will not be wasted. Additionally, the stamp is his guarantee that all the loads have been factored in, including load paths to the earth, wind load, etc., and that the recommendations on his stamped drawing are his guarantee of a proper solution to your problem. Finally, a licensed Professional Engineer carrys liability insurance and errors and ommissions insurance, in the unlikely event that a catastrophic collapse or other damage to your existing house occurs as the result of the contractor doing what the engineer recommended.

Most engineers will have no problem advising a competant contractor as to the best way to employ the recommendations on the drawing, if needed, in order to achieve what is desired as the end-product. By the way: make certain that the contractor you hire is also properly registered and insured. After all, we are talking about the house you live in, aren't we?

Trashmn,
W. J. Parker is exactly right--we are a 30 year design/build co. out of Dallas, and just completed a similar project on a client's home yesterday--and we don't "bull ahead" without the engineer for the engineered lumber (ours is thru the lumber yard) site inspecting, and processing his load report--in TX, this paperwork arrives with the TJ's or, in this case microlams. Engineered structural lumber is so much better than 'just a header' of 2 x whatevers, check with your local lumber company, whoever you buy your engineered wood from, should provide the engineering service contact, and as in TX, may be free of charge to your contractor. Also, you mention this was an exterior wall to the original home, you will want to pay attention to what may be in that stretch of wall--electrical wires, pipes, vents, etc. May not be much, if any, between two doors, but all kinds of surprises can be found opening walls! Good Luck!

After going through a similar issue, everything commented above is true. I have a old house (1834) which we wanted to open up the kitchen, opening a wall(former exterior double doors) like you are. It is also a two story. After hiring a structual engineer, it gets quite complicated, our second floor has three different roof lines merging together (built in different decades). New footing will need to be poored to support the addition weight. What we thought were decorative beams in the kitchen turned out to be former exterior wall support beams. Anyways, I'm only telling you this so take their advice, hire a engineer! (we are in Michigan so we need to worry about snowloads, etc) Good Luck!

A word of caution about getting a header size from a lumber yard:
Many lumber yards in my area “size” beams by going to the most closely appropriate size table – in this case the table for exterior walls supporting a second floor and roof load – and picking a size based on the home’s width and beam span. While this will get you close, and will give you an idea of size and pricing, it is not an actual design and doesn’t take into account individual situations, each of which is unique. I’ve seen many homeowners and some contractors use this “ballpark” size without any further investigation or design. Regardless of where you obtain the design services, be sure that it comes with documentation stamped by a licensed professional. The design should include a determination of existing loads, which can be made with a site visit and/or existing building plans, photos, measurements, etc. Exposing the adjacent framing members prior to the initial site visit, as well as locating any available building plans (including additions) will help to reduce the possibility of surprises later. An engineer will evaluate the calculated loads and can advise you on the numerous possible design solutions, and which would best fit your overall needs (header height and width, floor stiffness, etc.) In addition, having an engineer on board and involved in the initial design will help speed up design verification or changes if unexpected factors are uncovered during construction.

Hey trashmn,
Did you find out anything? I live in Shelton WA, I know exactly what you mean about the live load. I am going to be taking out two windows in my house and replacing them with a 14' slider. Same question for me. I've looked in some of my construction books from my apprenticeship and found a chart that said for a maximum 12' span a 4x`12 beam (grade 2) was required and for 16' span a 4x14 beam (grade `1) is required. I'm hoping the measurements are smaller for glue lams because I'll be bumping into rafters if I go more than 12". Let me know if you find anything. Marja
marjastowell@gmail.com

Microlams are about halfway between dimension lumber and steel for strength, but still, the condition ought to be examined by a competent professional...architect or engineer.

The header is one thing, but once installed, there are concentrated loads at the ends of the ehader that need to be carried to the earth somehow.

Not a matter for guesswork. Get it designed properly.

Adding to what was said previously: the fact that the house is 1900's vintage suggests that the framing may be "balloon", with the studs going all the way up the wall from the ground floor sole plate to the top plate of the top floor. If that is the case, there is the distinct possibility of side thrust coming into play as the existing loads get shifted around to allow for the enlarged opening. If the engineer determines that this is, in fact, your situation, then he/she probably will suggest some kind of exterior cribbing, along with an interior counterpart, with a connecting beams crossing through the exterior wall and resting on the cribbing, at each end of the proposed opening, with connecting ledger beams inside and outside, so that the wall will not belly outward and cause a collapse of the upper section of the building.

This scenario underscores the need for evaluation by a structural engineer before proceeding. Hope things work out to your benefit.