Issue: 1960s or 70s era, single story (with loft) home on sloped lot in Marin County, CA. Homeowner needs more space and wants to excavate part of sloped (max 1:2, avg 1:3)crawlspace. No evidence of hillside instability- floors are level, doors and windows open fine, just one minor diagonal crack in one footing wall (appears to be old settlement crack.) Concrete appears sound. Footprint is 40 feet wide and 24 feet deep (into the hill.)
Solution: Excavate the front 2/3 of crawlspace area and provide retaining wall, which will step back at about midway but still be held off the back wall by at least 5' to avoid undermining of the back footing. Might have to underpin a small length of the (e) side wall footings at the ends of the retaining walls depending on what we find during excavation. Wait 14 days to backfill.
Cap front (downhill) stem wall to raise height by 1'-8" max to be in line with finish slab. Cut/fill where needed and pour slab. Provide #4 @ 18" in new concrete, epoxy embed into (e) stem wall 24". Roughen (e) surface and use a bonding agent. Do not tie new slab into new capped wall.
Anyone see anything of concern here? The owner is concerned about the added weight from the cap and the added fill/slab, though I assure him that weight is nominal in terms of what footings are designed to carry, and considering the soil being removed, and that adding the cap is in no way detrimental to the integrity of the foundation or the house. I just want to be sure I'm not completely missing something here... thank you for any comments.
Solution: Excavate the front 2/3 of crawlspace area and provide retaining wall, which will step back at about midway but still be held off the back wall by at least 5' to avoid undermining of the back footing. Might have to underpin a small length of the (e) side wall footings at the ends of the retaining walls depending on what we find during excavation. Wait 14 days to backfill.
Cap front (downhill) stem wall to raise height by 1'-8" max to be in line with finish slab. Cut/fill where needed and pour slab. Provide #4 @ 18" in new concrete, epoxy embed into (e) stem wall 24". Roughen (e) surface and use a bonding agent. Do not tie new slab into new capped wall.
Anyone see anything of concern here? The owner is concerned about the added weight from the cap and the added fill/slab, though I assure him that weight is nominal in terms of what footings are designed to carry, and considering the soil being removed, and that adding the cap is in no way detrimental to the integrity of the foundation or the house. I just want to be sure I'm not completely missing something here... thank you for any comments.
