Modifying a Load Bearing Wall
I remember the first load bearing wall I modified. I was in my early twenties and had never done it before. It was in a massive old home in Clifton, an inner city suburb in Cincinnati, Ohio. I was working as a sub-contractor for a remodeling company and knew just enough to be extremely dangerous. Fast forward . . . The house didn't collapse and in fact the enlarged opening I created has not sagged to this day. But I must tell you I had lots of luck that day. All sorts of things could have gone wrong.
Knowing the Loads
Creating archways or openings in bearing walls can almost always be accomplished. It simply becomes a matter of where the loads are going to be concentrated. A typical bearing wall tends to transmit a fairly equal amount of load down to the floor below via the wall studs. If you decide to create a large opening in the wall, then the loads above the opening must be shifted to the sides of the opening using a properly sized beam. Will a double 2 x 6 be enough? How about a single 2 x 12? The truth is, only experienced carpenters who have successfully installed beams, or structural engineers who are trained to size and specify beams, should make the call. Do not try to conjure up your mystic powers and guess.
If you want to install a beam in an existing bearing wall, there are all sorts of tricks and methods. If it is an interior wall, there is a cool way to install a beam without building any temporary support walls. You need to have access to both sides of the wall into which the beam is going to be placed. All that you do is simply install half of the beam at a time. You make 1.5 inch deep notches at the top of one side of the wall and slide the beam into this recess. Add the king studs at each end of the beam that run from top plate to bottom plate. You then add the jack studs next to the king studs. These framing members actually support the load from the beam. If the rough opening of the new beam is 72 inches or less, you generally only need one jack stud at each end. Once all of this is in place and the jack studs are solidly supported from beneath, you can take out the remaining old notched wall studs as the weight of the wall will be carried by the one half of the beam that is secure and in place. Be sure to have the second half of the beam already cut and ready to slide in place!
When You Need One
Often you can't do the cool trick I described. Perhaps you are working on an outside wall and want to salvage the wall finish on the exterior side of the new beam. You need to build a temporary wall 3 feet back from the existing bearing wall.
But stop! Before you start to build the wall, you must build the beam and lay it on the floor next to the existing wall. Why? Many a rookie carpenter has built the temporary wall, created the hole in the existing wall only to find out they can't get the beam threaded into the narrow space between the old and temporary walls!
The temporary support wall needs to have a top and bottom plate, and the studs of this wall need to fall as closely as possible under and above the floor and ceiling joists. The studs are cut tight so they have to be tapped in place. I simply add a few toe nails that just penetrate partially into the top and bottom plates. Be careful about ruining finished floors and ceilings!
Don't even think about creating an opening in a masonry wall without help from a professional. Masonry walls are very heavy. The weight from steel roof members and floor loads can be enormous.