We’ve got some old cinder blocks left over from a landscaping project, so could we use them to make a fire pit? Let’s find out…

Cinder blocks are cheap, light and can withstand high temperatures, so they are very good for making DIY fire pits. Cinder blocks can also be painted with heat resistant paint to create a great looking fire pit for under $100.

Let’s dive down into the subject of cinder block fire pits in greater detail, and discover some simple steps to turn these boring grey blocks into an attractive and efficient fire pit…

Are Cinder Blocks Fire Resistant? (What Temperature Can They Withstand?)

Cinder blocks make great fire pits, and one of the reasons is because they can withstand such high temperatures. They are lighter than concrete blocks, being made from aggregate ash, mainly coal cinders. Cinder blocks don’t have the tensile strength of concrete blocks (don’t use them for a retaining wall!) but they are incredibly tough.

Porous cinder blocks are better than dense concrete blocks for fire pits, as they vent the steam, reducing the risk of moisture build-up leading to explosions. Choose a fire-rated cinder block, which absorbs heat and protects you from sparks without the risk of it becoming damaged or dangerous. Check with the store whether the blocks are fire-rated or not. 

If you want to find out more about cinder blocks, read our earlier article. There are plenty of yard projects for these cheap and versatile blocks.

Is There a Difference Between a Concrete Block and a Cinder Block?

Isn’t a cinder block the same thing as a concrete block? Actually, no. Although they seem to be made from the same materials and certainly look similar, the two blocks have different properties and different uses.

Cinder blocks are lighter than concrete blocks (good news for your back), as they’re made from cinders, not cement. The concrete block contains stone and sand in its aggregate mix, whereas the cinder block is made up from much lighter ash.

Because of this, concrete blocks are far stronger, and are used in construction projects. You wouldn’t want to build your home extension out of cinder blocks as they simply don’t have the tensile strength, but they are a great material for smaller, non-load bearing projects such as garden walls.

Why would you choose cinder block over concrete block? Well, cinder block is cheap, and it’s far easier to lift and move around. As we discussed above, this lighter, more porous structure makes it a better choice for fires. The lighter texture vents steam rather than letting moisture build up inside the block, which can eventually build up so much pressure that the stone explodes.

We also like using it for general projects around the yard. It’s a quick and easy way to build a barrier, such as a sheltering wall around your vegetable patches or patio. Because it’s lighter to move around than concrete blocks, it doesn’t take a big team to build a cinder block wall.

How Many Cinder Blocks Do I Need For a Fire Pit?

You don’t need many cinder blocks to make a decent-size fire pit. The example we’re about to use (see the next section) is made from just 24 cinder blocks. You wouldn’t really want to go much bigger than this, as you’re making a backyard fire pit, not a massive bonfire. So, keep your fire pit a realistic size. Don’t build it too high, as then you won’t get so much benefit from the fire itself.

It’s tempting to build a large pit, however, as you can get so many blocks for just a few dollars. As a single cinder block costs well under two dollars, you can see why this is such a cheap way of making a fire pit.

Before we get too excited about a new cinder block fire pit, first check that domestic fire pits are permitted in your district. Some local authorities or home owner associations don’t allow fire pits in backyards, period. So, do your homework before you do the math.  

How Do You Make a Fire Pit Out of Cinder Blocks? (A Cheap One On a Budget)

This is a really simple DIY task, and you can create a great fire pit with just a bit of effort and a few dollars spent down at Lowe’s or Home Depot. 

Here’s a great little film about how to build a cinder block fire pit from Home Between The Oaks.

1. Head for the concrete aisle of the store, and find the 8 x 8 x 16 cinder blocks (the standard size). You’re going to need a trolley, as you’ll need 24 of these for this project. You’ll also need 2 x 8 x 16 cinder block caps. The fire pit needs 12, but pick up a couple of extra ones just in case 
2. Back in your yard… Measure out a space for the fire pit. You’ll need measuring tape and four stakes. Put the stakes where the four corners will go
3. Break up the ground inside this area using shovels. This is to create a nice, flat, grass-free space for your fire pit. Level the dirt as best you can
4. Area prepared, it’s time to lay the first cinder block in a corner… It’s really important to make sure this one is level. Once it’s level, add the next block alongside the first, again checking that it’s level
5. Keep working around the perimeter of the fire pit area, checking the levels as you go
6. When the perimeter is done, start adding the next layer of blocks, placing them on top of the base row
7. Next, it’s time to put the cinder block caps on top of the second layer of blocks. These need to be flush, so if there are any lumps and bumps on the cinder blocks, you may need to grind these down
8. Tidy the loose dirt around the edge of the new fire pit structure and tread it down. This keeps things looking tidy

The total cost? The husband-and-wife team from Home Between The Oaks built theirs in 2020, using blocks from Lowe’s. The whole set-up cost just under $58.

Can You Paint a Cinder Block Fire Pit?

Yes, you can make a real feature of your new cinder block fire pit by painting it in an eye-catching color. We won’t pretend that cinder block is the easiest surface to paint, but it is doable, provided you follow the right procedure.

We’ll be honest: most guides to painting cinder blocks don’t cover fire pits, just garden walls and decorative items like planters. However, we found this guide from SFGate that is specifically about painting cinder block fireplaces.

1. Clean the cinder blocks thoroughly. And we mean clean. Wire brush, bleach for mildew,  trisodium phosphate for any efflorescence… real deep cleaning. Rinse the blocks well after cleaning, then leave them to dry thoroughly
2. Any major cracks or holes? Fill them with siliconized acrylic caulk
3. Apply latex block filler. Without this coat, the porous blocks will simply absorb the paint
4. Next, apply latex primer, and give it the full drying time
5. Finally, the paint itself. A good-quality exterior acrylic latex masonry paint is the best option if you want it to last. See what it looks like once dry, as you may need a second coat

We’d still think twice about painting a fire pit though. That porous material is great for fires, and so it might give you the best results if you simply leave it be. The pale concrete is actually quite an attractive finish, and if you complete your fire pit with cinder block caps (like they did in the short film above), it can look really smart.

Summary

It’s good to know we can use our left over cinder blocks to build a decent fire pit. It doesn’t look like a project that will be too hard to complete in just one weekend.

I think we’ll paint ours though, as the grey color of the blocks makes them pretty unattractive in a well kept yard in my opinion.

I guess it’s down to personal preference but I’m thinking black or white would be a better color for our new fire pit. Each to their own! 🙂