I have an end unit townhouse built in 1986. It's three stories including the garage level, and it's built on a slope. The garage level opens to the street in the back, but that level is below grade on the opposite side (front) of the house.

To accommodate the grade change, there is a vertical jog in the foundation wall on the side of the townhouse, so the foundation wall becomes a pony wall.

The problem is that the foundation wall jogs down too low too soon, and it is now below grade in one area, leading to a rotting sill plate and sheathing:

enter image description here

enter image description here

Note that the Great Stuff is my doing - a temporary fix to seal things up. There hasn't been meaningful water infiltration in this area, but it does appear that at some point mice got in there (they definitely haven't been there in at least a year).

The landscaping is in the control of the condo association. Although I could go to them and ask them to have the landscapers regrade, there's no guarantee in continuity in the landscaper, or any kind of institutional memory even if we retain the same one, so this problem could just reoccur the next time they add mulch.

So, since I need to replace the rotted sill plate anyway, I'd rather just try to come up with a solution that avoids the possibility of reocurrence by cutting away the rotted studs and sill and adding 6-12 inches of height in concrete along the ~2-3 feet of foundation pony wall. This would also require adjustments to the exterior siding, but that seems easy enough.

The questions are:

1) Does this make sense, or is there a better alternative?

2) Does the wall need to be supported while I do this, and if so, how? Can I just screw some 2x4s to the studs above where I'm going to cut them, and have those run down to the floor at an angle?

If it's relevant, this is a gable wall. Also, you can see the trusses running perpendicular to this wall that support the floor above - the light is attached to one, and the other is right above the wall on the right.

Appreciate any suggestions!

3 Answers 3


Since the soil should be 6" below (in my area code) I would verify building code and have association regrade the area as it is causing the rot from the violation. In a 3 story I would not want to try patch work on cement foundation without an engineering stamp of approval.

  • There's a sidewalk about 3 feet from the foundation, so there's a limit to how much it can be regraded while still sloping away from the foundation. But more importantly, I want a permanent solution that cannot be undone by landscapers in the future. Building codes are only relevant during construction, no? The inspector could have required them to fix it in 1986, but now the building is up.
    – Ken
    Feb 12, 2018 at 23:23

I like Ed Beal’s idea about regrading. It’s permanent and less expensive than adding a section of concrete wall. (There’s no guarantee that the concrete joint won’t leak either.)

The joist visible in the picture seems to rest on the wall that is above the plate that needs to be replaced. This is an indication of the floor joists above.

If you’re replacing just 2’ to 4’ section, then you won’t have a problem not bracing the upper wall, unless there’s a refrigerator or waterbed directly above that section of wall.

Btw, you say you’re in the end unit. That tells me you need an architect’s or engineer’s stamp to do the work. (4,000 s.f. Or 20’ high from lowest floor to highest ceiling.)

  • The problem with regrading is that it's not a sustainable solution. I want certainty that I will never have to worry about this again after I make the repairs, but since I don't control the landscaping it's not possible to ensure the regrading will not be undone. There is also a sidewalk about 3 feet from the side of the house, which limits the options as far as regrading. The soil needs to slope away from the foundation, so the area nearest the house has to be higher than the sidewalk. I don't plan on going through the association or pulling permits on this. It's a small area.
    – Ken
    Feb 12, 2018 at 23:18
  1. Build a 2-3 course retaining wall to hold back the soil. Excavate the area, create a base, completely bury the first course, and go from there. It doesn't need to be a long wall, but I would make it 2-3 feet long, just long enough to look like it belongs there. You're right about a simple regrade job not working over time.

  2. Screws and a 2x4 might work fine, but I would nail a 2x10 to the studs with 16d duplex nails. Open any windows above this area when you remove the sill plate so they don't break. Have a hydraulic jack and a 2x6 ready in case you have to jack the 2x10 up, or be prepared to go purchase one quickly. Replace the sill plate with treated southern pine so it doesn't rot again.

Don't add concrete here. If you really want to prevent the studs from rotting, then add a double/triple/quadruple treated sill plate. If you think that looks silly, you can also use a treated southern pine 4x4 or 6x6 to do the same thing.

  • When you say to nail a 2x10, do you mean horizontally across the studs above the area I'm cutting out? The issue with using a treated sill plate is the sheathing - that will still be plywood. The only thing I could think of with that is using King Starboard: totalplastics.com/products/253 but I'm not sure if that would work (I don't know the product well)
    – Ken
    Feb 12, 2018 at 23:12
  • Also - would you build the retaining wall perpendicular or parallel to the foundation?
    – Ken
    Feb 12, 2018 at 23:28
  • Yes, 2x10 horizontally across the studs with 3-4 16d duplex nails into each stud. It'll hold the wall up, and also give you a jack point if it does sag a bit. Replace the wall sheathing with pressure treated southern pine plywood if it's rotted out and you're not fixing the grade issue. If you fix the ground contact issue then the pressure treated lumber isn't as critical. I was thinking perpendicular, but whatever you think makes the most sense.
    – Dotes
    Feb 13, 2018 at 1:02
  • That sounds good to me. You guys have convinced me my concrete idea is a bad one. The reason I'm so concerned about alleviating even the potential for future ground contact is that I'm going to be finishing this wall, so I won't have access once it's buttoned up.
    – Ken
    Feb 13, 2018 at 2:38
  • Do you think it would be crazy to consider replacing that bottom piece of plywood that's rotted with a sheet of HDPE like King Starboard, rather than treated plywood? It might be overkill, but it's cheap insurance unless there's a downside to it
    – Ken
    Feb 13, 2018 at 2:40

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.