Can we have a small secret cellar?
January 25, 2015 9:59 PM   Subscribe

We're building a small house on a small budget. We want to dig a small cellar (maybe 6'x6') into the ground below the crawl space entrance and support its walls with a wood framework. Is this feasible? Or will the house cave in if we do this? You are not our architect, you are not our structural engineer.

We'll have an 18"-deep perimeter wall foundation on top of an L-shaped footer. We are using light straw clay to infill the walls. It can have a density of up to 1200 kg/cubic meter, or around 20 lbs/cuft, if that makes a substantial difference.

Our most up-to-date house plans can be found at
posted by aniola to Home & Garden (19 answers total) 2 users marked this as a favorite
Root cellars! My grandma's house had one, and it was a magical place filled with all the fruits of her summer labor in the form of colorful mason jars.. It did have a single lightbulb that you turned on by pulling a string, otherwise it was pretty primitive.

You can buy a concrete septic tank to function as your cellar. The concrete might hold up to moist conditions better than wood.
posted by Ostara at 10:32 PM on January 25, 2015 [2 favorites]

I'm 12 months off qualified to design houses, work for an architect and have worked in construction. Honestly, the idea of doing this without a geoctech and/or structural engineer is totally insane. On top of that, timber is inappropriate. Yes you run the risk of your house subsiding.

If you did what you are suggesting here in Australia you wouldn't receive your occupancy permit at the end of construction and couldn't legally live in the house.
posted by deadwax at 3:31 AM on January 26, 2015 [11 favorites]

An unshored pit can collapse, killing the digger or occupant.

... and support its walls with a wood framework.

Or an improperly shored pit.

You are not our architect, you are not our structural engineer.

Nope, we're not.

Go call them and tell them you want a root cellar.
posted by sebastienbailard at 3:37 AM on January 26, 2015 [3 favorites]

Right, I just saw you are in Australia. I assume you have approved plans and are doing this on your own in variance to them? That's, um, brave.

It's totally a doable thing to do, but you need to take this back to an engineer, or your architect/building designer/builder does. It also needs to be documented properly for your building surveyor to sign off.
posted by deadwax at 3:37 AM on January 26, 2015 [1 favorite]

Also, doing this would void your home insurance.

I'm sorry I'm a little boggled. Just don't do this.
posted by deadwax at 3:42 AM on January 26, 2015 [6 favorites]

Perhaps you might consider purchasing a section of large diameter reinforced concrete sewer pipe.
posted by fairmettle at 4:49 AM on January 26, 2015 [1 favorite]

It is perhaps not as terrible as some have suggested... No, I take that back. If the slab is already poured you are kind of out of luck - at least you won't be able to so this inexpensively. If it is not yet poured you still have a chance to get an engineer/architect to hook you up.
Best of luck, default on the side of safe.
posted by From Bklyn at 4:52 AM on January 26, 2015 [1 favorite]

It wouldn't be cheap but check out

posted by koolkat at 5:10 AM on January 26, 2015

Best answer: When I was growing up in a small upscale neighborhood in Illinois, some people down the street had built their house such that they had a 30" "mini-basement" underneath most of their house. It had a full finished concrete floor and perimeter walls, and it was full of boxes and misc stored items.

It's a shot in the dark, but I'm tossing it out as a possible alternative that might be easier to get past code, and also safer than a DIY dig under your house. Given that your house doesn't seem large, the extra concrete might not be overly expensive.
posted by doctor tough love at 5:43 AM on January 26, 2015

I don't know why you wouldn't consult your architect and your contractor about this. Putting holes under structures is a pretty risky thing to do. If there's a statute against doing so, there's a very good reason for it.

If you want an underground structure, why not put one behind or beside the house? Fully permitted and built to purpose.
posted by Ruthless Bunny at 6:03 AM on January 26, 2015

It shouldn't be much more expensive to do this right, and there are real risks to doing it wrong (including collapse and your house subsiding), so count me in the consensus saying to talk with your contractor and/or building permit people before starting to dig.
posted by Dip Flash at 6:16 AM on January 26, 2015 [1 favorite]

No one here can answer the question because it's wholly dependent on the building codes in your jurisdiction and what the lay of the land your plan to build your home onto is like. If your rainy season is anything like our west coast winters the property you plan to build your home on may or may not be able to drain off moisture properly.
posted by squeak at 6:47 AM on January 26, 2015 [1 favorite]

Saw this question last night, but was unable to comment.

Glad everyone is telling you what a colossally bad bad idea this is as you proposed it. Danger and death first came to mind when I saw your question, too. Glad I don't have to document all of the things that can go wrong structurally since everyone else has covered it.

Be safe, not sorry. Build something you can use. Building codes, IMHE, really aren't just a nuisance - they keep you alive and uninjured.

Also, whenever you see deep holes dug by hand in the movies? Yeah, that's fake. In real life, the walls usually cave in before the hole gets too deep. Usually with the digger inside.
posted by jbenben at 8:50 AM on January 26, 2015 [1 favorite]

My son, who does custom home remodels, just spent six weeks jacking and shoring up under a house where someone had done just this. It was a bitch of a job. Now all the marbles don't roll to the midline of the house, but between that job, fixing the walls and screwed up flooring, plus the remodel, the owner of the house is going to look at more than double what they would have had to pay. We're talking almost as much as what they paid for the house.

Don't do it. Or if you do, make sure you have someone that absolutely knows what they're doing. It's possible to lift a house and put a basement in, but there's a good reason people don't usually do it.
posted by BlueHorse at 9:51 AM on January 26, 2015 [2 favorites]

In real life, the walls usually cave in before the hole gets too deep. Usually with the digger inside.

Especially so when the soil is also burdened by the weight of the house. Your house foundations kind of "expect" there to be earth there, not a void, and introducing a void compromises that. Plus, building anything that you expect to be permanent below grade with wood is a bad idea, never mind that a framed wall will almost certainly not be able to take the soil pressure.

It's certainly possible to have a small cellar, but it has to be planned for, the rest of the foundation of the house has to be designed to accommodate it, and it'll probably be made of concrete (either masonry or poured-in-place). I can't think of any way to do this DIY; you'd almost certainly have to have it professionally designed. A pre-cast concrete thing like a septic tank might work, but it would have to be designed to take the additional loads from the weight of the house on the earth into account (also known as "surcharge"), which is not something that normally happens so you couldn't just get a septic tank "off the shelf" and expect it to work either.
posted by LionIndex at 10:32 AM on January 26, 2015 [2 favorites]

This is a very dangerous idea - and I'm a devoted DIYer. Burial should never be DIY.
posted by IAmBroom at 1:57 PM on January 26, 2015 [3 favorites]

I am a geotechnical engineer, but not your engineer, and I strongly recommend you ask your engineer/architect to look over your plans. Like everyone covered above, doing this yourself could be dangerous and illegal. You included some specs in your question but I would need a lot more information to answer this; you should hire someone familiar with construction in your area.
posted by piper4 at 3:40 PM on January 26, 2015 [1 favorite]

Response by poster: That settles it - we will not be attempting this. Thanks everyone!
posted by aniola at 12:09 AM on January 27, 2015 [1 favorite]

Response by poster: When the time comes, we will lay tracks in the crawl space and make a train of tupperware bins.
posted by aniola at 2:43 PM on March 2, 2015

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