Guides On How To Build An Underground Room

My dad is the most creative person and the best DIYer I know, and building an underground room is among the reasons. The underground room he built for me and my brother is still there today, and I want to share the experience. It is exciting and fun, and it is very cool to have an underground mini fort at home. If your backyard has the right conditions to build an underground room, all you need to do is follow the steps.

1. Before Building

Before you start to build your mini fort, there are a few important factors that you have to consider. When you finally pick a location, you will also have to inspect that particular space so that everything is safe. Below are some of the first things that you have to have in mind before you start building an underground room.

1.1. Check The Area

A good spot is one thing, but you want to make sure that the location is also safe for a room. Because you are going to spend time down there, the room has to be as comfortable and safe as possible. Flooding risk is one of the most important parts that you must not overlook. Check if the area is prone to some sort of leaking that can cause flooding in the room or not. Consider changing the location if it is too close to the water pipe or other water sources.

Another important thing that you should not forget is whether or not it is legal to dig. Even if it is on the perimeter of your house, the depth that you want to go can be illegal. Let’s say you want to dig around 2 meters, but the authority in your area may not allow that. So you also want to check with your local authority to ensure that it is legal to build your underground room. Once the area is safe, then you may process to another step.

1.2. Determine The Size

The size of the underground room depends on the purpose that you want to build it for. If it is just a place that you want to chill, then a regular size room will do nicely. In case you want things to be so fancy, then the size is going to be bigger. The standard dimensions for an underground room are 3 feet by 3 feet, but you can also go up to 5. However, never go deeper than 6 feet because it is likely to collapse, which is not safe for you. This is also the reason why the room is rather in a square shape because it avoids the risks of collapsing.

1.3. Plan The Layout

The next thing to do is plan the layout of the underground room that you want to build. You want to design how you want the room to look, especially the space for comfortable movement. Think about the type of wall that you want, the furniture that you can fit in, and the power. Don’t forget to make sure that the room has proper ventilation as this part is very important. Once you have everything in hand, then go shopping for your tools.

1.4. Basic Underground Room Features

The tips below are optional, but they are helpful because those basic features are with a safe standard. They are also quite useful if you are a beginner, so check them out:

  • Include external perimeter HDPE perforated drainage pipes and filling to your structural retaining walls
  • Reinforce the concrete foundations and floor slab, then waterproof the floor and walls
  • Design and select space for roof opening and staircase
  • Look for durable and strong materials as a bunker roof

2. During The Building

Once you have everything you need, then it is time to build your underground fort. This can be a one-man project, but it does not have to be like that. You can save a lot of time when you have a few other helping hands, so reach out to your friends. When everyone is ready, then the building process may start.

2.1. Step 1: Site Clearance

This is the first step that you should always have in mind before you start building the room. Make sure that the location that you pick is all clear from roots, tree stumps, and more. Even trashes can get in the way during the digging process, so keep the spot clean before you start digging. Another thing to have in mind is to pick the right season to build your underground fort. Do it in summer because you wouldn’t want the rain to turn your underground room into a pool.

2.2. Step 2: Digging

When digging, there are 2 choices that you can choose either do it yourself or use professional excavators. Many people actually prefer to dig by themselves with some help from a few friends. It could take a whole day or way longer, but it saves so much money. In case the room that you want to build is quite large, then you can consider hiring professionals. You should also hire people to do the job for you if you don’t have all the equipment. If you cannot finish the digging in one day, make sure to cover it with a tarp for protection. This is to prevent people or pets from falling into the pit and protect the digging site lest it rains.

One more important thing, slope and shape the walls of the room so that they are slightly wider than the floor. By doing so, it helps to reduce the risk of collapsing which can be very dangerous. You can use a shovel to scrape each side of the walls to create the sloping shape. While you are at it, dig out some small nooks and shelves in the walls for additional storage. Once you have the layer of your safe room and walls, make sure to smooth them out. The walls of the room have to be free from rocks and roots while being smooth to ensure safety. When you are sure that everything is all perfect, then you can begin step 3.

2.3. Step 3: Secure The Wall

Some people apply this as an optional choice, but I recommend doing it for extra safety. Secure your walls by covering them with plywood boards in their sizes. This is to ensure that it keeps the dirt from falling or sliding, just in case. Once you cut the plywood to the size of the walls, drive 2 pressure treated 2×4 posts down their corners. Then you can lay the bricks for the walls or just use the plywood walls if it is okay. Another option is using cement to secure the wall before laying the bricks or plywood. All of them are safe and secure in their own ways, and the choice is all yours to choose.

2.4. Step 4: Room Decoration

It is advisable to paint the wall of your room before adding the roof due to proper ventilation. The smell of the paint can be irritating so painting the walls without the roof helps a lot. That also means the paint is going to dry fast when there is sufficient air circulation. Not to mention you can see better with all the sunlight, painting the room is going to be so convenient. This is also a good time to add the fans, lights, and other furniture to the room as well. The paint will dry by the time you finish furnishing your underground room, and then you can move to the final step.

2.5. Step 5: Roof & Upper Floor

The most common material for the roof and the upper floor is plywood because it is easy to find and use. You want to make sure that the roof that also functions as an upper floor is as strong as possible. This is to prevent it from breaking upon walking pressure which can lead to other bigger problems. The roof should be bigger than the fort so that it can cover the whole room very well. There are two methods that you can choose to create the roof, the lift-able roof or the walk-on roof.

The lift-able roof allows you to lift up the whole thing using a cord or rope. If you choose this type of roof, make sure that the plywood or wood that you have is not too heavy. This is to allow for easy lifts every time you want to get in or out of your underground room. In case you prefer the latter type, it is a fixed roof but with an entrance that you can enter. This type is rather convenient since you can easily walk down without lifting up the whole roof at all.

Bonus: Once everything is done, you can also build an A-frame roof on top of the upper floor. This is to add the taste of the fort to make it look even more appealing and interesting. Besides the look, this extra roof also protects the room from weather like heavy rain as well.

To make the building steps above more understandable, you can check out this video here.

3. 7 Underground Room Ideas

Just because it is an underground room does not mean it has to be dark and gloomy. You can always turn your room into an aesthetic or cozy space that you can enjoy can staying in. This is why I want to introduce you to some nice underground room ideas that you might like. Each design is nice and unique in its own ways, so let’s see if you like any of them.

3.1. Blanket Walls

You can always get creative with the design of your underground rooms, and this idea is among the best. The awesome thing about this blanket idea is that it does not only provide style but also warmth. In case the weather is cold, you can insulate your underground room by hanging thick sheets on the walls. Things are getting cozier and warmer, and the look in the whole place is also super cool. Plus, with some warm drinks and lights, you will surely love staying there.

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3.2. Bohemian Underground Room

A Bohemian design is always among the best and easiest ideas to achieve when it comes to room decorations. As for this one right here, it looks very cozy and relaxing. An underground room like this is a serene place that you can stay in for hours. Plus, with the lights and the small items around, all the aesthetics are there too. This is a perfect underground room idea for those who like boho style, and you will definitely love it.

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3.3. Chilling Underground Room

All you need is a mattress and some pillows, and you are going to achieve this chilling underground room theme. It is cozy yet very simple to create, and you don’t need a lot of things at all. The bookshelves are optional, but they are super chic to have if you love reading. Depending on the space that you have, the size of the mattress depends on you. You can also replace the mattress with a couch, and it still looks amazing.

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3.4. Kid’s Room

In case you build an underground room for your kids, you might want to consider this idea here. Because the room is small, the items in the room are not so many. However, you can still create a cool atmosphere for the kids with this look right here. You can use stickers on the floor and walls, then add some matching furniture to complete the design. They get a bed to sleep on with a table to study, and there is still space to play. Simple yet cool and cozy, this is clearly among the best underground room ideas for kids to have in mind.

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3.5. Minimalist Underground Room

Less is more, and this room idea says it all in one picture. This could be a great idea if you don’t like to paint your underground room. You can easily hang some sheets on each side of the wall to create this amazing look. Then you can add some lights, a cozy duvet, and some pillows, and that’s it. Simple as that, yet the whole looks are very comfortable and modern which is absolutely perfect. If you like minimalist designs, then this is the one to have in mind.

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3.6. Plants Underground Room

We all know that one person who adds plants to every room that they have, and this idea is just right. Because it is going to be a small room down there, plants can help to purify the air. This underground room idea does not only provides style but also a relaxing atmosphere at the same time. You can either hang the plants on the ceiling like that or just put them in pots. They look amazing either way, and they are beneficial to have. Here are some of the best plants that purify the air that you might like.

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3.7. Reading Underground Room

For those who build an underground room as an escape place for reading, this cozy design is it. Just get a cozy chair and a leg chair, and you can sit there to read for hours. Don’t forget to add some bright lights so that you won’t hurt your eyes when reading. The wall decorations are not necessary, and you can change those to bookshelves to complete the look. It is minimalist yet comfortable, and reading is to going to be peaceful and tranquil.

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4. 6 Useful Items To Have In An Underground Room

The room is small, so the number of furniture and other items that you can get there is limited. You can still make your underground room looks cool, and I have some amazing and space-saving items to suggest. Let’s see if you like any of them below.

4.1. Bean Bag

Don’t bother getting a chair and a couch because a bean bag can replace all of them while saving your space. Bean bags are so comfortable to sit and sleep on, and they are also very lightweight and portable. Placing a few of these in your underground room is way more convenient, and there is still space to spare. Not to mention that bean bags are inexpensive and easy to find, this is definitely something that you should not miss.

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4.2. Floor Mattress

In case you are not a bean bag person, the alternative to that is a floor mattress. The special thing about a floor mattress is that it is comfortable to sleep on even without a bed. At the same time, it is also very compact, lightweight, and portable which is so convenient to use. Floor mattresses come in different sizes and shapes, and there are many designs to choose from. All you need is to pick the one that you like the most, and that is it.

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4.3. Mini Shelves

In order to save space in the room, you can install mini shelves install of adding tables. Sturdy shelves can hold multiple items that you have in your underground room while looking nice. From books to plants and other small items, the shelves can handle them all for you. A room is a little incomplete without the shelves, so you might want to have one or two of those.

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4.4. Side Table

In case you have space, then it is only fair to have a small side table by the bed or mattress. There are many nice and space-saving side tables out there that you can find. I would say it does not really provide much storage room because it is small, but it looks good. Just make sure that it does not take up too much space in your underground room, and you are good. Some side tables are more for decoration rather than providing space, but you get get the idea.

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4.5. String Lights

One of the best room decorations is string lights, and they look incredible pretty much anywhere. These lights do provide not only illumination but also style and calmness to the room for you. There are so many types of string lights that you can find to match your room decorations and style. Some of them even have different modes that you can switch which is a total plus. They are better than lamps, so don’t forget to add some string lights to your underground room.

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4.6. Wall Decor Items

This is an optional item that you can add to bring out the style to the room. I recommend choosing wall décor items that are bright and illuminating so that it makes the room more interesting. From glow-in-the-dark stickers to various wall-hanging items, they are all great to have. Depending on your style, there are so many cool things that you can add. You might want to check some items that I suggest below. Those are not only easy to find but also stylish to have.

Final Thoughts

Building an underground room can be difficult, but the final results are always great. No matter if you want it as an additional room or a place to escape, it is ideal for them all. An underground room can also be a fun place for kids to play in or a quiet place for adults to relax. The best part is that there are so many cool decoration ideas that you can use for that particular room. With the tips on how to build an underground room and the ideas above, I hope things are easier for you. Always feel free to reach out if you have questions, I am always here to help out.