Thread: Strange Box in Basement Floor

Does anybody have a clue as to what this is? This is somewhat new construction, and is in one side of an attached townhouse (sounds sexier than calling it a duplex)- main floor with a finished walk-out basement. This is basically a rough 2 x 4 frame embedded in the floor pour, and extending under an interior wall. This is in an unfinished room. That dark thing at the rear is one of the beam support posts. The inside of the box is presumed to be free of concrete, but what you're looking at is what appeared to be a debris covered plywood piece with a threaded rod or bolt (with the end turned down to a smaller diameter) holding it down. I didn't examine it any more closely than that, but the client and I are both curious as to what the heck it is. Thanks a lot for any enlightenment on what it is, or it's intended purpose.

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Future toilet drain? Cutout for a floor safe? Sump?

Originally Posted by Benjamin Thompson

Future toilet drain? Cutout for a floor safe? Sump?

Thanks for having a better imagination than I've got. There were no stub outs anywhere close to this, and the place already had two full bathrooms in the finished portions of the basement. The sump was in the utility room, so it has to be "sump-thing" else. A cutout for a floor safe might be a "safe" bet, but they've either misplaced it or the interior wall that's over the end of it. Hey, thanks again for some good guesses!

My guess is that is was for a "maybe" sump for someday, just a little forethought from the builder. That would be the nice thought.

On the other had, maybe a piece of a engineered floor truss fell to the floor prior to the concrete pour and the concrete guys just left it.


If you are curious enough you'd pull that dang thing off and snap a picture for us. You've made me curious-er.

Originally Posted by Michael Chambers

Thanks for having a better imagination than I've got. There were no stub outs anywhere close to this, and the place already had two full bathrooms in the finished portions of the basement. The sump was in the utility room, so it has to be "sump-thing" else. A cutout for a floor safe might be a "safe" bet, but they've either misplaced it or the interior wall that's over the end of it. Hey, thanks again for some good guesses!

I agree it looks like a void left in the concrete for future utilities or something. try digging in to see if there is a drain stubbed to that location. I saw a shower drain stubbed to a framed opening like that once. Could be plumbing, elect or there may be a cleanout plug down there. A little excavating may reveal a utility of some sort. Maybe thats where they hid the loot? LOL

I love mysteries! Dig it up and post the results. One thought: a very good earth ground??

Maybe it was something the builder started to install but plans were changed after the first step(s). Find the builder and ask.

Originally Posted by Michael Chambers

This is somewhat new construction, and is in one side of an attached townhouse (sounds sexier than calling it a duplex)

While it may sound sexier than calling it a duplex, calling it a townhouse is incorrect, so maybe the person inside the sexy dressing is not who you think it is.

(underlining and bold are mine)
TOWNHOUSE. A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from foundation to roof and with open space on at least two sides.

It could cover plumbing drain access for future restroom, or the finishers ran out of concrete and blocked out the space.

An opening to the sub-slab space that could be used to detect Radon and then seal around a duct to vent Radon if high levels were found? Not logical or standard procedure. Also, an opening to create a sump if needed for draining? Probably none of the above. But certainly no problem for the inspector.

Possibly a palmer valve or plumbing clean-out underneath. Covers of such are quite often "crudely" done.

Bruce Low
Bottom Line Home Inspection
Serving Northeast Wisconsin

I did not hear "back flow preventer". Here in Utah, back flow preventers are required for the main sewer line. Usally they will put an irigation box over them and sometimes what ever is lying around.

A Palmer Valve is a backflow preventer.

Bruce Low
Bottom Line Home Inspection
Serving Northeast Wisconsin

Hey Cliff, How you doing. Might have a energy audit for you. Good answer, I wasn't sure what they were either. Usually when I look in these all I see is gravel.

Originally Posted by cliff douthit

I did not hear "back flow preventer". Here in Utah, back flow preventers are required for the main sewer line. Usally they will put an irigation box over them and sometimes what ever is lying around.

What! A backflow preventer on the main sewer line? I have never heard of such a thing and I have been designing systems for 30+ years in this Pretty Great State. Please enlighten me.

It may be something totally legit, but it could also be something like an open sewage drain with a piece of plywood covering it up. This would eventually cause the owner a problem. I would just report it as an unknown and suggest the client have it further investigated (cya). I would be curious also, but wouldn't want the responsibility if I was to open it up.

Originally Posted by Michael Chambers

Does anybody have a clue as to what this is? This is somewhat new construction, and is in one side of an attached townhouse (sounds sexier than calling it a duplex)- main floor with a finished walk-out basement. This is basically a rough 2 x 4 frame embedded in the floor pour, and extending under an interior wall. This is in an unfinished room. That dark thing at the rear is one of the beam support posts. The inside of the box is presumed to be free of concrete, but what you're looking at is what appeared to be a debris covered plywood piece with a threaded rod or bolt (with the end turned down to a smaller diameter) holding it down. I didn't examine it any more closely than that, but the client and I are both curious as to what the heck it is. Thanks a lot for any enlightenment on what it is, or it's intended purpose.

If it was for a sump in would be encased in concrete on below grade. Aggrogate would be visable.
It must have been asked to be installed by the owner. Flooring safe, or speed way for wiring in the future if it is installed under a main wall.
It is a recessed bulkhead for passing some system that will or might be added on at a later date.

Regardless of what it might be, it seems to be made of untreated wood in direct contact with the ground. WDO/WDI concerns if nothing else.

Originally Posted by Bruce Low

Possibly a palmer valve or plumbing clean-out underneath. Covers of such are quite often "crudely" done.

Bruce Low
Bottom Line Home Inspection
Serving Northeast Wisconsin

My guess,,access to the clean outs,that go to the street.

It's probably a chase access to piping connection/cleanout or vacant conduit. You should look into it to answer your question.

Looks like an oversight. You've all seen good plans go awry and then the result is a bad patch job. I'd agree that the WDI issue would be a concern.

Originally Posted by James Risley

I guess you have never seen what happens when a city main becomes blocked and the people up hill from your designed systems keep on flushing........

a backflow preventer is found on a water line. a backwater valve is installed on the sewer for the problem you speak of

Secret passage to the house next door.

Originally Posted by Ron George

Maybe thats where they hid the loot?

Or maybe another Howard Hughes will?

Well, I think we have an explanation - of sorts! I was back in there last week to check corrected items during the final walk-through inspection, and the buyer's agent said that the seller's (a bank) representative said that it was where they anchored a brace during construction, and that the wood just never got removed and the hole patched. I didn't get any more details than that, and this was related from a bank person talking to a R/E agent.

I'm guessing that they still had their brace in place when they wanted to pour the basement floor, didn't want to concrete it in, so they just built a quick box around it. Maybe someone with construction experience can hazard a better guess based on that. If it's any help, this foundation was at least a foot taller than usual, and maybe they were bracing the forms from the inside during the foundation pour.

Originally Posted by Michael Chambers

Well, I think we have an explanation - of sorts! I was back in there last week to check corrected items during the final walk-through inspection, and the buyer's agent said that the seller's (a bank) representative said that it was where they anchored a brace during construction, and that the wood just never got removed and the hole patched. I didn't get any more details than that, and this was related from a bank person talking to a R/E agent.

I'm guessing that they still had their brace in place when they wanted to pour the basement floor, didn't want to concrete it in, so they just built a quick box around it. Maybe someone with construction experience can hazard a better guess based on that. If it's any help, this foundation was at least a foot taller than usual, and maybe they were bracing the forms from the inside during the foundation pour.

Thanks for the follow up response!

I'm not buying the bank representative's story. I saw something that I did not see at first. Look at the small hairline crack that runs from top left of wood frame and continues to the left. This is usually an indication that there is a drain line under slab. Do you ever see the exterior foundation walls poured and then the slab poured before removing the forms for walls? I liked Ken Bates answer and if it's not for radon mitigation (sub-slab depressurization) it would be a good idea so that you do not have to cut concrete later on. Just my 2 cents.

I agree with Tom, bogus story about brace left in for why?
The shape and location suggest a toilet may have been in the plans. As a few guys suggested ages ago.
That hairline crack could be where the floor has settled over the edge of the footing.

Isn't it more important to find out than to guess? If it's really just a bolt holding it on (or lag screw, probably), and I was the homeowner I would have investigated long ago! Will it damage the interior wall to do so, is that the problem?