Here are the five steps I do in order to design for a bearing wall removal:
- Determine the load on the new beam that will replace the support wall. First determine the basic roof loads typically dead (D), roof live (Lr), wind (W) and snow (S). Next if this beam supports a story above in addition to the roof find the floor loads typically dead (D), floor live (L). Using the Allowable Stress Design (ASD) method I combined these loads using the following the following equations: D+L, D+(Lr or S), D+0.75L+0.75(Lr or S), D+0.6W and D+0.75+0.75(0.6W) + 0.75(Lr or S) to get the combination that produces the greatest beam loading. The last part of this step is to use beam design software to determine the most economical beam, multi-ply 2x lumber, LVL or steel that complies with shear, bending stress and deflection requirements.
- Next determine the beam support reactions at both ends to design the beam support columns. The support columns consists of multiple 2x lumber, solid wood or steel posts.
- Check the subfloor to ensure the loads from the beam support columns are transferred to the main support beam in the basement or crawlspace. This may require additional blocking between the subfloor and the beam.
- If there is an existing column under the main support beam in the basement or crawlspace, then check the offset between the new support column above and the post or pier in the crawlspace. If the offset is greater than 1/2 the depth of the main support beam in the basement or crawlspace, then an additional column or pier will be needed.
- Finally if there is a basement floor determine the total column load to be transferred to the floor slab. If the column load exceeds the capacity of a 4 inch unreinforced concrete slab then a footing design is required based on the underlying soil strength. In the case of a crawlspace a new pier and footing may need to be designed.
The purpose of this topic is to convey to your clients there is more to replacing a support wall then homeowners realize.