Basement Bottom Plate embedded in cement floor

[Big Bill]

Was helping my son do a radon mitigation this am. It's a 10 yr. old collonial w/full bsmt. While he was sealing cold sems in the basement he asked me about the 2x4 bottom plates embedded in the concrete (flush, 1-1/2 into). After inspection, the bottom plates in question were for the interior walls only, but where the abutted the ext. wall bottom plate they continued under and up to the poured wall.

Will they have concrete beneath them? Will it have air/barrior to the sub-grade? He asks.

I says sure, I dont know why they'd embed these bottom plates, but there should be 3" concrete there no matter what.

Later while doing a smoke test he found that, yes the air was drawing past the embedded bottom plate. so...

He's left sealing the 2x4's that he can access and hoping for the best.

I'm wondering who's seen this done and why?

It doesn't look loke a second pour. The ext. wall sill boards were typical. Sorry no pic, but its just bottom plate embedded flush...

[Jim Katen]

I think I'd have done a bit of discreet surgery on the embedded bottom plate to see what's under it. Maybe drill a 1 1/2" hole somewhere.

The whole thing sounds fishy to me.

[kurt]

I agree. I'd be digging some stuff up to see what's what.

It's a termite attractant, it's probably rotten, there's the air sealing inadequacy, and it's just plain cheesey.

There's no good reason for it. Only bad reasons.

[Big Bill]

I sure couldn't think of a reason, let alone a good reason for the plates to be 1-1/2" embedded. Perhaps they for some reason added the 1-1/2 inches of concrete to a bad floor (whatever) and then added a second plate to the perimiter framing, raising it the 1-1/2"s seen now...I was curious if there was a common practice I hadn't seen... Guess not!

We gotta get in there to complete the post mitigation test and I'll try and explore further...Thanks!

[ejager]

Was it a load bearing wall?

On a project I worked on, the interior basement wall was built on a footing long before the basement floor was poured. We formed and poured a curb at the same time as the footing, so the bottom plate would have appeared to be 'regular framing'. But I can imagine someone not going through that process, or given the project, the finished elevation for the slab was changed and so the bottom plate got buried.

[Big Bill]

Guess I assumed that it wasn't load bearing. Interior basement walls. 10 yr old bsmt. I-Joist (I viewed) to what I assumed was an I-Beam to pillar to footing. Most of the area was finnished. An area of 30'x35' maybe.

I'll see what I can do for pictures next week. The followup Radon measurement was delayed due to the homeowner unplugging the measuring device for us...

Thanks...

Sorry, my guy didn't get pictures as requested...

[Blochinger HI]

Isnt it likely that the plates were once flush with the concrete floor and that an additional layer of concrete was poured to level or smooth the basement floor? If the sill plates are of Pressure treated lumber you can simply leave them alone and lay nailers between the studs to secure sheetrock if not already installed. basment partition walls go up quickly enough that I, personally, would remove them, fill the troughs and reinstall.

[Steven Hockstein]

Was it a load bearing wall?

On a project I worked on, the interior basement wall was built on a footing long before the basement floor was poured. We formed and poured a curb at the same time as the footing, so the bottom plate would have appeared to be 'regular framing'. But I can imagine someone not going through that process, or given the project, the finished elevation for the slab was changed and so the bottom plate got buried.

That would be my guess. Bearing wall was installed (hopefully on a footing) before the floor was poured to save some time and a couple of bucks (the cost of an engineered girder and columns typically costs a little more than building a 2 x 4 bearing wall).

[leeboy]

We have done this on a few projects where we underpinned the foundations, by pouring the concrete with a additive allowing it to be runny with out losing strength, adding extra "head pressure" to the concrete to get it under the old footings to ensure contact. was it possible that the house was post and pad, then had a foundation poured after? What year was the house?