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How to i build a room under my shed so that is wont cave in during the winter or leak etc? Answered

Okay, so i have about 18 by 18 are that i can dig in and i really am not familiar with where my water and gas pipes are. (i also am not sure about electric wires) so any help on that would also help. this is in my back yard if that helps at all also. i really don't know much about how to support it as i build and also how to reinforce it. so let me know what you think. anything else that you need to know so you could help me out just ask and id be happy to answer.


Dial before you dig, you need to know where your utilities run before you start any work.
Anything subterranean needs waterproofing on the walled surface and drainage below the slab. Concrete and rebar are the way to go.
Seriously, dial before you dig.

Move the shed.
Dig your hole.
Concrete the floor.
Wall with bricks and mortar.
Replace the shed.


In my area water would leak through the bricks in a day or so.

I cannot move the shed.

Oh, that's going to be hard.
Can you post a picture of the shed and it's surroundings?


Electricity no problem.
What does ctitus know about french drains.


close to nothing.


6 years ago

Are you building a secret room, bomb shelter or prison ?

Not very secret several thousand if not millions of people could now know!!

Done without removing the existing building ?

Remove the floor
Build a big steel shell , out of say 8mm plate, in the centre of the room,
Dig out the soil in the centre of the shell, and let it settle down


1. unsure what is under the ground - dig by hand and go slow.

2. Big hole - ensure you support the sides and roof adequately - being buried is as bad as the shed falling on you,

3. for a permanent structure you can use it will need water proofing - look up tanking a basement - think about shuttering and using a lot of concrete. think about the cost and how much you really need such a big hole.

4. drainage. your going to get water in there.

Hi ctitus,
Just remember about ventilation/exhaust fans... especially if you plan to grow stuff down there ;)


6 years ago

First dig one outside corner pour a small base and raise a corner to support the
shed and repeat three more times a week apart.
If you are still alive after a month, it is time to dig out a side and wall it,
then another etc.
Finally make good support for the shed and put a small ditch on any high side
of the shed with a porous pipe to collect water to a sump hole that can be
pumped out in rain storm and keep the S_cret room dry.

You should consult with a builder. All I have ever built is an added Bath room
to my house (used a ex-contractor) moved a fuse box.



6 years ago

this will also most likely be built when its snowing. i didn't emphasize that.