Dear Ask Me Help Desk, I am renovating my kitchen (see related threads on water flow and gas lines in plumbing) and need help on calculating the size of a beam for a supporting wall. I live in L-Shaped 2900 square feet 1963-built rancher in Atlanta, GA. The kitchen is on one side of a long run at the end of the house. Imagine a center line the length of the long run of the house, which divides the kitchen from an adjoining common room. The rooms are divided by a common supporting wall. There is an interior door at one end. Below the floor, in an open unfinished basement, there is a double joist, exactly corresponding to the length of this supporting wall, where each joist is 10x1.5 inches. The run is 13.5 feet. The two joists sit on the foundation on one end, and at the other end on a slightly unorthodox "post" consisting of three 2x4s that converge as a result of two standard interior walls meeting at a corner with intermittent 8 inch extra 2x4 pieces between two of the 2x4s along the length of the "post." (This same posts supports the center beam in the other direction.) I plan to put a metal post under the end with the 2x4s and it will directly support the end of the 13.5 run of 2 joists. I think the foundation support is adequate. Upstairs in the kitchen, I want to open the supporting wall between to the kitchen and the adjoining room. The joists that support the ceiling in both the kitchen and the adjoining room are perpendicular to and supported by the plate in the superior aspect of the supporting wall. There is an A-frame roof above the ceiling. The perpendicular joists in the ceilings of the two rooms anchor 45 degree joists that hold up the A-frame roof joists so that there is nothing directly tied to the joists resting on the plate on top of the supporting wall in question. How big of a joist do I need to replace this supporting 13.5 foot run? Since the basement only has two 10x1.5s supporting the entire situation up through to the roof, then two 10x1.5s (or less) should be adequate? Also, do you have any tips for how to do this? In the past, with smaller jobs, I have built two temporary supporting walls to support the ceiling on both sides while I do demolition and construct the new beam. A friend said I should put a piece of plywood between the two 10x1.5s. Another friend said I should find a new prefabricated building material that is light-weight, easy to cut, with an I-beam-like plywood design. Value your opinions, Thanks, Michael

labman

For 13.5' spans, 2 x 10's should be adequate for joists. Headers used to always be two 2 X 12's with a sheet of half inch plywood between to space it out to 3 1/2''. The engineered wood I-beam like things are being used more and more now. Haven't noticed them at the home centers. You may need to go to a real lumberyard. I think they come in various constructions depending on the span.