this post was submitted on 14 Nov 2025
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Hey, I've got a cold room in my place that is concrete on all sides, I'm going to be framing it in and insulating and I don't really need any help there unless there's anything cold room specific I should know, however.

As you can see I have a floor that appears to be a stepped concrete pit, filled with quite a lot of dirt, and what I believe is probably a tie in to the sewage drain.

Can I just get rid of the dirt? The whole room spells like petrichor because of it.

Assuming the pit continues to step down, can I just build the floor over it regardless, and do I need to support the pipe in some way if the dirt is removed?

Or, if I'm completely off base please let me know what I should be doing.

Thanks

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[–] semisimian@startrek.website 15 points 1 day ago (2 children)

Where are you building? I'm assuming this is the basement or the ground floor. What is the rest of the subfloor on that level?

Wood resting on dirt is a big no, so that is an obvious red flag. Whatever floor you put in, I'd preserve your access to that clean out. Once you answer my Qs above, I can help give you a recommendation.

[–] TheJesusaurus@sh.itjust.works 6 points 1 day ago* (last edited 19 hours ago) (1 children)

Basement yep. The rest of the basement subfloor is poured concrete. Other than this cold room the basement design seems to be very typical poured concrete foundation dug under grade, typical of eastern Canada.

[–] semisimian@startrek.website 8 points 1 day ago (2 children)

https://www.owenscorning.com/en-us/insulation/commercial/enclosure/below-grade-under-slab-foamular-xps-insulation

I'd remove the existing wood, grade the soil flat and compact it. I'd then put down 2 in foam board (like in the link above) to decouple the flooring from the Earth. I would pour concrete to match the subfloor in the rest of the basement, but you don't have to. You can go back with a pressure treated subfloor product on top of the foam, etc.

A few things to keep in mind would be making sure that you get the right height of the soil so that you have the finished flooring height you desire. Also, all this work assumes you are maintaining access to that clean out. Good luck.

Thanks for this! Whatever happens I'm fairly certain I'll need this eventually

[–] classic@fedia.io 2 points 1 day ago (1 children)

Random reader here. What's a clean out?

[–] TheJesusaurus@sh.itjust.works 4 points 1 day ago (1 children)

He's referring to the capped pipe in the centre of the room. I'm not entirely certain either

[–] schwim@piefed.zip 3 points 23 hours ago (1 children)

It's a septic or sewer clean out. Code requires them at certain distances of the drain system to allow for access to clear any blockages. You can use that access to run a snake.

[–] CompactFlax@discuss.tchncs.de 3 points 23 hours ago (1 children)

It’ll save your ass from a big bill if your kids flush something they shouldn’t vs calling a plumber.

[–] TheJesusaurus@sh.itjust.works 2 points 20 hours ago (1 children)
[–] CompactFlax@discuss.tchncs.de 1 points 20 hours ago (1 children)

Just be careful opening it. If there’s a blockage downstream of this clean out, you’ll see symptoms of the blockage somewhere else, and the pipe will therefore be full from the blockage right to the symptomatic drain. Hopefully it’s a floor drain, but it could be a lot of water with some possible pressure behind it so really think the situation through before cracking it open, and have a plan.

[–] TheJesusaurus@sh.itjust.works 1 points 20 hours ago

That's very good advice

[–] Onomatopoeia@lemmy.cafe 4 points 1 day ago

Like who the hell built that with wood right on dirt?

That took more effort than just finishing that area with concrete like the rest of the floor.

Sometimes I just don't get how builders think.