• Possibility #1 - Foundation is experiencing small settlement in that corner examined (see next page for possible causes), the crack in Fig 3 could be related but could also be related to water penetration and a naturally weak area given the hole above.
• Possibility #2 - Rusting of the rebar in the thickened edge of the slab causing spalling of the concrete - seems to large of a crack though to be related to this and there are also signs they have tried to stop the movement with the added concrete
Options - Short Term
• Add gutter on side shown in Fig 3 (water contributes to movement)
• Hardscape (sidewalk at least 3’ wide) around the sides to flow the water better away from the foundation
• Patch crack (high grade exterior caulking) & monitor
• Investigate the area a bit closer to see if you can see rebar exposed and whether the concrete pops off or not.
Options - Long Term
• Going deeper to support the footer is the only way this can be full stopped which is called ‘underpinning’, it would likely involve 3-4 piles and connections (for the corner examined - approx 8’ total) which would run in the $4K/pile range (budgetary range). Note: doing hand excavations into the 5’+ range and pouring underpinning footers would be one path that would improve the performance but only by going deep would you guarantee to stop the movement in the long run.
The fact that the exterior & interior isn’t showing signs of cracking and the floor is mostly level indicates that it’s still relatively minor. I’d recommend improving the water/drainage as mentioned above, seal the crack to limit water entry and monitor and if you start to see interior or exterior cracks start looking into underpinning.
DRAINAGE ISSUE - CRAWLSPACE
Concise Overview Discussion
In some areas of the Bay Area, the ground is fully saturated this time of year, many crawlspaces I enter are wet, some are completely dry, just depends on your area and that’s something you can’t really control other than to do a full subsurface drainage system (See Attachment 2, Fig 1) which get expensive at roughly $500/linear ft and should run the entire perimeter of the house and is very disruptive to the exterior and is ultimately quite costly. Plugging holes will just push the water elsewhere and likely eventually make it’s way into the crawlspace through the next weakest area. Water running under the foundation can cause settlement issues, if you have concerns related to that then you should have that inspected (see my website for details)
Gutters are key - they need to be fully functioning as does the subsurface drain pipe so get the gutters fully flowing and get the drainage pipe they are going into scoped by a a plumbing company to make sure they are intact, if they are broken then they need to be repaired/replaced.
Verify the slope of the sidewalk area - it should slope as shown in Attachment 2, Fig 4. If they are flat or sloped back to the house then this needs to be corrected. Also, the gap shown with the yellow arrow should be sealed.
With these two surface areas improved I’d then monitor next winter - odds are that now that it’s unlikely to rain much until next fall/winter that the amount of water will drop quite a bit but this should be monitored. Lastly, a sump pump may also be desired depending on what you observe next season - many homes in this area have pumps.
DRAINAGE ISSUE - EXTERIOR
• Water is getting into the garage. The trench appears to be the main issue, combined with the fact that 3 downspouts are going into it
• No idea why the trench it’s there but doesn’t terminate into a pipe from what we can tell, and it doesn’t have a grate over it and has exposed reinforcing wire mesh inside of it - possibly in the past it was a trench drain?? (we have no history on it)
• Option 1: dig the dirt from the end and see if there is a pipe there and see if it flows and if that’s all working good then possibly install a grate over the area. Odds are though that this system is past it’s useful life or maybe was never done right to start.
• Option 2: fill in the trench and slope the area away from the house and towards the street so it flows that way to the extent possible - to get full & proper slope it might be a case where the entire sidewalk needs to be redone so to reduce the necessity for this I’d recommend hard piping all of the downspouts into a common downspout mounted on the wall and sloped to the end of the house where it then drains away and then it’s not as crucial to have all of the sidewalk area draining to the street (most of the water is from the downspouts vs. surface drainage given that it’s a small area.
Summary of recommended work:
• clean and fill the trench and slope it away from the house,
• seal all other gaps around the house to sidewalk interface
• redo the downspouts as mentioned above.