cleagl
Structural
- Nov 25, 2009
- 8
Hello Fellow Eng-Tips folks,
I have a footing I need to put right next to an existing basement wall. I have read the few posts there are, but alas none are really similar to this condition. This is a small house bump out (about 6ft x 25ft) along the entire side of the house. Bump out is one story, house is two, so they get a tiny balcony as a roof. (See attached)
The joists span in the direction of the bump out, so there is a beam spanning the distance to pick up the existing 2nd floor joists and wall. Column in the center(+/-) of the beam. The column comes down just at the edge of the foundation, so we need a pier. The contractor wanted to keep the pier footing at the same depth as the exterior wall footing. I looked at that and thought it was a bad idea. (Anyone have experience putting a footing higher up on a wall? Seemed like the combination of lateral soil pressure and pier footing settling would put a bunch of bending in the wall).
So even if I keep the new pier footing at the same elevation as the existing foundation footing, do I need to worry about the wall footing and/or the pier settling as well? I intend to pin them together and have a pretty big spread footing (SBC below 1500). I also plan on rebar and grouting the cores adjacent to the pier. The concentrated load will spread as it goes down the CMU wall from base plate to footing. Do you think I need to grout all the cores for that spread (about 5 ft.)? That would mean a lot of temporary shoring to the floor joist as you need to remove the existing sill plate, put grout (and bars) in and then replace the sill plate. Column load is 18k factored. Unknown existing strip footing. CMU is 8”, but unknown if grouted or reinforced. Access to basement for anything we need for work. Unknown soil conditions. We are not putting much additional load on the foundation as we are removing the outside wall, just changing it to three point loads (ends and center).
Any other worries I am not thinking of? TIA for any insights.
-CE
-cleagl
Eagleson Technical Services, LLC
I have a footing I need to put right next to an existing basement wall. I have read the few posts there are, but alas none are really similar to this condition. This is a small house bump out (about 6ft x 25ft) along the entire side of the house. Bump out is one story, house is two, so they get a tiny balcony as a roof. (See attached)
The joists span in the direction of the bump out, so there is a beam spanning the distance to pick up the existing 2nd floor joists and wall. Column in the center(+/-) of the beam. The column comes down just at the edge of the foundation, so we need a pier. The contractor wanted to keep the pier footing at the same depth as the exterior wall footing. I looked at that and thought it was a bad idea. (Anyone have experience putting a footing higher up on a wall? Seemed like the combination of lateral soil pressure and pier footing settling would put a bunch of bending in the wall).
So even if I keep the new pier footing at the same elevation as the existing foundation footing, do I need to worry about the wall footing and/or the pier settling as well? I intend to pin them together and have a pretty big spread footing (SBC below 1500). I also plan on rebar and grouting the cores adjacent to the pier. The concentrated load will spread as it goes down the CMU wall from base plate to footing. Do you think I need to grout all the cores for that spread (about 5 ft.)? That would mean a lot of temporary shoring to the floor joist as you need to remove the existing sill plate, put grout (and bars) in and then replace the sill plate. Column load is 18k factored. Unknown existing strip footing. CMU is 8”, but unknown if grouted or reinforced. Access to basement for anything we need for work. Unknown soil conditions. We are not putting much additional load on the foundation as we are removing the outside wall, just changing it to three point loads (ends and center).
Any other worries I am not thinking of? TIA for any insights.
-CE
-cleagl
Eagleson Technical Services, LLC
