I tried to look this up but everything seems to be related to exterior load bearing walls…

A month or so ago, we noticed a good amount of water coming through the concrete porch into our basement. This portion of the 1940’s basement below the porch used to be a garage, and sometime in the 90’s (according to dates on portions of the sheetrock) they put in a wall where the garage entry was to expand the living space. I don’t think this was load bearing when they put in the wall.

It seems like this leak was happening in 2017 as well, since new sheetrock was added and they tried to fix it with spray foam (which is obviously not water tight and did not fix the problem).

Anyway, I ended up ripping off the sheetrock to see the damage. All four sides of the framed wall are at least partially rotted, with the top and bottom plates completely compromised on the corners. This means that I should probably replace the entire wall, which would be “easy” if it wasn’t load bearing…

However, over time and possibly accelerated with water intrusion, the concrete above has a long, horizontal crack which may go through both sides. The crack doesn’t line up perfectly on both sides, but it’s definitely possible that it’s cracked all the way through. If that’s the case, it means that this wall has now become load bearing, possibly holding up a portion of the porch above.

My thinking is that I could get a jack post (or a bottle jack and 4x4 post), put it in the middle, and then build framing on both sides with pressure treated 2x6s. Then I could remove the jack, and attach blocking between the two portions of new framing.

The other, more expensive but safer option would include talking to a structural engineer. I got a quote from one, and he wanted $900 to come take a look. I can afford it, I suppose, although I’m worried that he’ll end up telling me what I already know.

Pictures below. Note that this is concrete on all 4 sides, and that the drywall has now been removed from both sides.

Here’s the wall: Wall with exposed studs, showing damage and concrete on all 4 sides

And here’s the crack on one side: Horizontal crack in concrete above wall

  • DagwoodIII@piefed.socialEnglish
    19·
    15 days ago

    Pay the $900.

    I mean, ask around and find a good person, but it makes no sense to gamble with your investment.

  • perestroika@slrpnk.net
    1·
    14 days ago

    Disclaimer: not an engineer, but I’ve built a house and squatted half a dozen.

    Questions:

    • how much load might it be supporting (what is the porch made of?)
    • how high and long is the concrete beam and approximately how many decades old? if it’s truly from the 1940-ties and has seen water just as long, you should assume that the rebar is entirely corroded and will slip in concrete (read: highly compromised load bearing ability)
    • what percentage of the vertical span of the beam looks compromised? (e.g. is it 30 cm tall and 10 cm is compromised or only 20 cm tall and 10 cm is compromised?)

    Ideas:

    • don’t remove woodwork until you have investigated the cracked concrete, removing bits that come loose without hammering; I would determine for sure if the concrete is fully compromised or partly so

    • if concrete is only partly compromised, one method would be cutting off the compromised layer (e.g. with a cutting disc) and casting a filler

    • if you end up removing rebar, you should re-calculate the load bearing ability of the beam as if the filler was nothing (if there is a choice, preferably clean and don’t remove rebar)

    • if it’s critically important and cannot be removed, I’ve seen concrete structures renovated by cutting off parts with a pressure sprayer (not a method one would use in domestic settings, sprayers that cut concrete are expensive and dangerous), cutting off bad rebar with a cutting disc, cleaning the end of good rebar, tying new rebar to the old, and casting fillers

    • after this you’d have a concrete beam that can be more effectively supported from below (it won’t compress at the crack)

    • if you use a jack and a pillar, prefer a mechanical (not hydraulic bottle) jack, people sell and rent such instruments for temporary support, it’s a steel pillar made of 2 parts that you rotate against each other to extend

    • in a pinch, you can create a screw-type jack from a wooden pillar, a short length of serious threaded bar (e.g. M24, M32) and some appropriate washers and nuts

    • your plan to offer support from the center and replace the framework from sides makes sense

    • if water if a frequent visitor there, use treated wood (or make sure that water doesn’t return)