How to Build a Storm Cellar with Cinder Blocks

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How to Build a Storm Cellar with Cinder Blocks

The best place to be during a storm is in a shelter in the ground. While many companies offer prebuilt rooms, the cost of these rooms is often prohibitive. With just a little ingenuity and hard work, you can build your own in-ground shelter of cinder blocks. A storm cellar of cinder blocks covered with concrete on a firm foundation and with a sturdy concrete roof offers your family protection from harsh weather.


Choose the Location

Choosing the right location for the shelter is vital. Avoid locations where items are already in the ground. If your property has a hill, building the shelter into the side of the hill often saves major costs. Avoid areas that are prone to flooding. Additionally, consider placing the in-ground shelter close to your house for easy accessibility.


Determine the Room Size

Next, decide on the proper room size. When determining how large to build the room, determine its purpose besides keeping people safe during a storm. If you plan to use the room for storage, then it needs to be bigger. Also, consider the physical condition of the people using the shelter. Be sure to build the shelter to its minimum size for its intended use and occupants.


Physical Condition

Room Size per Person
(in sq. m.)

Able to walk and stand


Wheelchair bound





If you often entertain others, build the room larger. While homeowners with small children can use a smaller room, remember that children grow quickly. The best practice for able-bodied individuals is to create ample seating and standing space.


Start Building

Once you determine the room's location and the size, it is time to start building the room with cinder blocks. Because you need a large hole to house the shelter, it is best to obtain a backhoe to dig it. If there are underground wires and pipes present, make sure to mark their locations and check with utility providers. Before digging, decide on the shelter's height as well.

Dig the Hole

Start removing the dirt from the hole. Remove an additional metre of dirt beyond the size of the finished room. Dig the hole an additional 0.75 metres deeper than the shelter's intended height.

Frame the Foundation

The next step is to frame the shelter's foundation. This should be 20.3 cm wider and longer than the shelter's actual dimensions. Place an 8-mm thick moisture barrier across the bottom of the hole to keep moisture from seeping into it. Then, place a 5-cm square post every 46 cm. Once all the posts are in place, cover the entire frame with heavy plywood using extra-long self-tapping screws. Lay rebar in the foundation, securing with rebar stakes driven deep into the ground. Cover the rebar with cement and let cure for at least one week.

Build the Walls

First, install the shelter's doorframe. Attach the frame to the foundation using concrete bolts. Spread a thick layer of mortar along the edges of the foundation using a mason's trowel. Add the first cinder block next to the doorframe and press firmly into place. Once in place, spread a layer of mortar on the side and then add another block beside it, taking care to keep all blocks in a straight line.
Once the first layer is complete, add additional layers in the same manner until you reach the desired height. Let this all dry for a minimum of three days. Once dry, apply three thick coats of moisture barrier spray to the outside of the walls. Then, fill the empty spaces with concrete. Use plumbing brackets and concrete screws to install a 5-cm PVC pipe that is at least 92 cm taller than the finished building's height in each corner to help ventilate the shelter.

Add the Roof

Anchor 2.5-cm plywood over the top of the shelter using 9-cm concrete screws. Add large support beams in each corner and three in the middle of the shelter, spacing them at equal distances. Cover the top of the roof with another 8-mm thick moisture barrier. Cover the moisture barrier with another layer of concrete that is at least 4 cm thick. Let the concrete cure for at least three days.


How to Buy Storm Cellar Building Supplies on eBay

Sellers found on eBay offer a variety of supplies needed to build storm shelters with cinder blocks. To find what you need, use the search box that is accessible from every page. Because many of these supplies are heavy, consider using local sellers to reduce shipping costs. Additionally, make sure to read product descriptions carefully to ensure that a product is exactly what you need. While there is no way to place a value on your family's safety, using eBay is one way to save money while doing it.

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