# Brick Fire Pit: What fireproof cement/bond do you use?



## TDBone

Last year I decided to make a fire pit in the back yard (First one, so I was bound to run into a problem or two.) and it's been pretty great so far. 

The one problem I've run into is the cement I used, to hold the bricks together and the structure in place, seems to be cracking and flaking because of the heat.

My question is: What type of cement or bonding stuff should I use that will hold the bricks together and not breakdown from the extreme heat?

Ideally I would like to be able to coat the inside of the fire pit with this 'fireproof' cement rather than starting all over again.

Here are a few pictures to give you an idea of the problem.

TIA


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## Twenty five ought six

There's a special high temp mortar you have to use.  Get it at a brick store.

Also regular brick will hold up for a while, but you should line it with firebrick.


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## Strych9

If you do just coat the inside of the pit like you said, I would really recommend taking the top 2 or 3 layers of block off, and stagering the joints(like a brick wall), so you don't have that one long joint going all the way to the bottom.


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## dawg2

Twenty five ought six said:


> There's a special high temp mortar you have to use.  Get it at a brick store.
> 
> Also regular brick will hold up for a while, but you should line it with firebrick.



What he said.  The interior should be lined with "firebrick."  You are using landscaping blocks.  PLUS, they don't overlap and leave one long continuous joint so even settling will cause it to crack.


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## CC Rider

*Fire Mud*

Mix fire clay (from masonry supply house) with portland cement. Remember a 10 pound bag of fire clay will do a whole fireplace, so don't mix too much with the portland. Make the mixx about the same consistancy that you would regular mortar. Do not use any type S,N, or sand in the mix. Hope this helps.


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## Doc_5729

Your pit reminds me of this. Saw it a couple of weeks ago.

http://www.thisoldhouse.com/toh/how-to/intro/0,,1636191,00.html

FWIW - Those blocks are interlocking and the joints should be staggered and overlapping. Any Masonry adhesive will be fine for the walls, but it's really not required. When properly stacked on a good solid footing those blocks will not move. (The lip you have pointing upwards, actually goes down. But you probably knew that.) 

Additional cutting may be necessary to achieve the tight angles of the diameter you choose, but they cut easily with a circular saw and a diamond tipped masonry blade available at any hardware or home improvement store. 

You can line the inside with a steel ring. You can usually get one at a local welding shop for 20-30 bucks or so. Cheaper than brick, sand and cement. Semi-trailer or farm tractor wheels work good as liners. So do tubs and drums from discarded washers and dryers.

If you're going to use fire brick, use Portland Cement not mortar mix. And don't use that ready mixed bagged stuff. One shovel of cement to 3 shovels of sand. Keep joints to no more than 1/4" and allow a quarter to a half inch of clearance between the firebrick and the block for expansion.


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## the r.o.c.

go to your hardware and but enough fire bricks, there about 2" thick and you can buy fire proof mortar in tubes like for a caulking gun.  very good stuff and very easy for non brick laying folks. the fire bricks will last for years, if your mortar cracks, just shoot some more in.


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## TDBone

Thanks a ton for all the information and advice. 

I look forward to getting some of the materials and fixing this thing up.


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## Nicodemus

One question on a fire pit like that. How does it get enough air for a good burn?


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## SELFBOW

I did one like yours w a 4ft opening. No cement just layered the bricks accordingly. It works just fine and is easy to take down to clean out and if one breaks its a simple fix(replace it)


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## SELFBOW

Nicodemus said:


> One question on a fire pit like that. How does it get enough air for a good burn?



My lowest layer has openings completely around it.


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## earl

Ya'll be careful. Those bricks will hold water and can explode with high temperatures. Fire brick should always be used on the inside, then put your decorative brick around the outside. For a small fire pit get a piece of clay chimney flue.Then use your deco brick.


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## Twenty five ought six

Ask around and find out if you have any potters in the area.

If so, they have to rebuild their kilns occasionally, and their discarded firebricks will work fine, and be  a lot cheaper than new.


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## jimbo4116

What everyone has said about lining with fire bricks or a steel ring ( with a steel ring you need to make is a little smaller and fill void with sand or clay).

What you have are not bricks but concrete blocks with a smooth finish, looks like you used a cement mix verses mortar.

Concrete does not bond to concrete well. You need to stagger the joints.  Although those are interlocking lanscape blocks for retaining walls, you will not be able to get the same configuration by just using the interlock ridges in a circle as each circle would become smaller. Just want work. If you stagger you will end up with voids between the edges of the blocks. Which wold not be a bad thing execpt for the top layer.

Configure it as you have and use galvanized metal ties laid in the mortar across each joint. This along with removing the the direct heat will maintain you vertical joints.  Hope that makes sense to you.

You also need to create a ventilation system at the bottom to have a good fire.

All that said I saw one built just like yours with with bricks with an small syrup kettle sat down on the top layer of stones. The edges had some broken spots and it was cracked but that gave it some character.  Would be easy to clean also.


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## TDBone

jimbo4116 said:


> What everyone has said about lining with fire bricks or a steel ring ( with a steel ring you need to make is a little smaller and fill void with sand or clay).
> 
> What you have are not bricks but concrete blocks with a smooth finish, looks like you used a cement mix verses mortar.
> 
> Concrete does not bond to concrete well. You need to stagger the joints. * Although those are interlocking lanscape blocks for retaining walls, you will not be able to get the same configuration by just using the interlock ridges in a circle as each circle would become smaller. Just want work. If you stagger you will end up with voids between the edges of the blocks. Which wold not be a bad thing execpt for the top layer.
> *
> Configure it as you have and use galvanized metal ties laid in the mortar across each joint. This along with removing the the direct heat will maintain you vertical joints.  Hope that makes sense to you.
> 
> You also need to create a ventilation system at the bottom to have a good fire.
> 
> All that said I saw one built just like yours with with bricks with an small syrup kettle sat down on the top layer of stones. The edges had some broken spots and it was cracked but that gave it some character.  Would be easy to clean also.



That's what I found when I started to assemble the bricks...that if I tried to interlock them then I would have gaps throughout it because they wouldn't be able to make the circle all the way around. 

As for air...I noticed that problem when I was finished. 

However, it didn't seem to be much of a problem as I have had great fires every time. 

But, when I fix it up this time I will take out two bricks from one of the lower levels, two that are on opposite sides of each other. In their place, I will replace 1/3 the size of the original brick in its place so that the bricks above them will still hold and air will be able to get in.

Thanks again guys!!


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## KDarsey

I thought about what you just said and thought I'd add that I would leave at least one out on the bottom and that would serve 2 purposes. Air & cleanout.


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## double b

When we built one in the past, we have dug a pit about 18"-24" deep, filled it with gravel, then put the fire bricks around it.  Then finally, surrounding the outside with decorative stones or bricks.  The gravel sure makes it easy to clean out, well actually it never really needs cleaning, everything just makes it way into the gravel.  We put spaces in the bottom 2 rows of bricks to allow for air flow. 

On the blocks you have used, they are designed for landscaping and small retaining walls, as someone said.  The lip is for the batter or set back.  If they are placed down, the wall would step back a certain degree as you go up, for support of the wall dirt behind it.  If you decide to use these as an outer ring, keep in mind that the top layer will be less in diameter than the bottom, so plan accordingly.


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## southwind

*pit*

I would get a metal fab shop to roll me a piece of iron a little smaller than the diameter of the landscape block for the ring then just stack the landscape block around (stagger bond) using no mortar or cement thus letting em expand and contract.


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