How to Make an Underground Fort




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First I would like to say these can be extremely dangerous. I made mine by myself but that is HIGHLY not recommended and can lead to serious injury or even death. Do not be in denial about how dangerous this can be because it can be extremely dangerous. Always have someone there with you. I cannot stress enough how dangerous these can be.

In the middle of making this my camera broke and I couldn't take pictures of some of it but I will do the best I can to make this instructable good.

You can make your underground fort as deep as you want. Just keep in mind that the deeper you dig the bigger chance of collapse. Mine was made 6 feet on one side and 5 feet on the other because the area I made this on was going down hill. You can also make it as long and wide as you'd like.

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Step 1: What You'll Need

It kinda depends whether you would want wooden walls or use the dirt as walls. I used wood because I was scared of snakes and bugs. I can't guide you through the building part because It would be to complicated to explain and the way I made it was very complex and had unnecessary things. If you have a plan on how you'd like to make it you could just build it like a fort that is not underground as it does not matter once the hole is dug. Just use pressure treated wood so the rain does not destroy it. I will explain it as using the dirt as the walls as well as using wood though I will not explain HOW to make the walls and stuff.

What you will need:
A shovel
A bucket (If necessary. I didn't need one.)
A saw if there are any tree roots you need to cut
A weather treated sheet of wood for the roof
A wheelbarrow to move extra dirt
Treated Wood (if you are not using the dirt as walls and would like to build a room.)

Step 2: Digging, Digging and More Digging.

Use your shovel to dig how deep you want it. This can be very exhausting and time consuming but it was well worth it in the end for me.  In the photo it shows the pallet I used for the floor that I had put in. If you are using the dirt as walls that is not necessary and you do not need a pallet in there. If you are not using the dirt as walls you do not need to use a pallet as the floor only because I did. 

Step 3: Building Your Room

As I said before, You have to build your room your own way. I will briefly explain how I did mine though so I can give you an idea.

I put a pallet down in the hole and nailed wood planks onto it and used that as the floor.
I put four wooden beams up that were nailed to the pallet
I got 8 wooden planks and made 2 go across from 1 beam to the other on each of the 4 beams.
I nailed sheets of wood onto those wooden planks that are connecting the beams to make walls
I connected the beams at top with 4 wooden planks
I got a sheet of wood for the door and connected it at top with a hinge. 

Or you can skip all of that and just get a sheet of wood to cover the hole, cut a square out of that for the door, And get another sheet of wood to cover the hole in the door and connect it with a hinge. Just expect to see more bugs and snakes ect.

Step 4: Put Dirt Over Your Fort

Put dirt over your fort and fill in any extra space if there is room around it. Your goal is to make it as level as the dirt around it not put a pile of dirt on top of it so keep that in mind.

Step 5: Disguising Your Fort

Camouflage your fort so that no dug up dirt is visible. For instance, If the area has a lot of leaves, Disguise it in leaves. If the area has a lot of pine needles and sticks, Disguise it with pine needles and sticks. Use the surrounding materials to hide it. 

Step 6: Remove Excess Dirt.

Use your wheelbarrow to remove excess dirt around your fort. You can put the excess dirt where ever you like. After you remove it the ground still might look somewhat discolored from the dirt that was previously there. If that is the case also disguise that with the surrounding materials.

Step 7: Bugs and Rain Etc.

A while after I finished my fort it rained and pact down the dirt around it so I had to put more dirt there to make it level again. To prevent that just pact down the dirt yourself as you are building it. It was rained several times since then with no problems. 

As for bugs, I noticed a slug problem right away. The day after I made it there were around 3 slugs in it. I removed them but every time I go down there there is at least 1 slug  down there. I sprayed bug spray and that prevented spiders from going down there but there are still slugs. I just have to live with it.

If you spray bug spray in yours then don't go down there for a while because bug spray has lots of chemicals.

Step 8: Finished!

You can now enjoy your underground fort! 

Note: I have to clean mine up a bit

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    11 Discussions


    4 years ago

    Salt. its sadistic but I used to kill slugs and snails in my moms garden by sprinkling salt on them. They foam up and die. So its a reasonable idea that salt lick or something may be incorporated. The hard part will be sheltering the salt from the rain. Thinking about this Instructable make me feel like a kid again.

    1 reply

    Reply 4 years ago

    I should clarify. Don't salt the little slimies but they won't cross salt.


    5 years ago

    I read an instructable on here on how to build an electric slug fence using a 9V batterie thought it might be the answer to your slug problem. Cool hide out!


    6 years ago on Introduction

    This looks like great fun!

    Not to be a spoilsport, but:

    My comments are in regards shoring of the excavation sidewalls. You have zero-degrees of slope (i.e., vertical); in fact, this construct really is a vertical shaft. There is a very real risk of wall collapse - and typical, consolidated bulk soil densitiy of around 110 pounds/cubic foot. Clearly, it would be easy to become entrapped by only a few cubic feet of soil. Ever been buried in sand at the beach? Doesn't take a lot af material to become immobilized...

    OSHA requires a ladder for egress at 4-feet deep and a protective system to prevent collapse at 5-feet deep (yeah, I know this isn't a construction project).

    This type of excavation also constitutes a "confined space". be mindful of gases heavier than air that may collect in the space. Depending upon locale, frost heave may cause the walls to become unstable, too.

    Just some advice from a PhD / PE - be careful!


    7 years ago on Introduction

    if you have a problem with slugs and you don't want to use chemicals in an enclosed space (a very smart choice) ...

    salt kills slugs

    salt acts as a desiccant and dehydrates the slugs to death


    7 years ago on Introduction

    "How to build an Underground Fort"

    "I can't guide you through the building part because It would be to complicated to explain"

    I am confused...

    1 reply

    7 years ago on Step 5

    Great instructible weird. One thing we learned was you have to move a LOT of dirt! We would have to scatter it then cover it with leaves etc. A "new" hill near your fort won't help you hide it one bit. Just save some for the top and ALWAYS cover up before you go home for the day or somebody will probably find before you're finished. Be safe and good luck!


    7 years ago on Introduction

    As a kid, we were obsessed with doing this. It should be noted UP FRONT that when dirt dries out it acts like a fluid in slow motion. It WILL eventually fill itself in as the walls collapse. It should also be known that even if your head is ABOVE GROUND, if the dirt collapses on you, you may STILL DIE as the pressure exerted on your body will not allow you to inhale your next breath. Much like how a Boa Constrictor or simolar snake kills it's prey. we had a lot of fun but when my father (a very experienced guy)caught wind of it...well, he wasn't happy but did give us the idea as to risks we were taking. Kids would chase us (older, of course!) into the woods and "poof"! we disappeared! It was awesome!!


    7 years ago on Introduction

    What you have here is known as a Spider Hole like where they found Saddam.