DIY Home Improvement Forum banner
1 - 20 of 29 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter · #1 ·
Hello everyone, I need some advice. Especially the advice of you brick masons out there. Thanks for your help. Here it goes!

I built a firepit using instructions I found on a DIY fire pit from the "Family Handyman" magazine. Maybe some of you are familiar with it. If not, the full instructions and article can be found by simply google searching "family handyman fire pit" easy enough. Without looking it up yourselves, I will briefly explain its construction (which I followed to a tee):

An 8" deep concrete foundation with rebar for strength with a diameter of about 42" or so, and about 6 1/2" wide (no issues here). On the interior of the circular foundation I installed firebrick, "soldiering" them on their ends, and using refractory cement to place them on the foundation and to each other. I also split firebrick in half in 4 places and created 4 openings along the circumference of the circle to allow for 'draw holes' through the bottom of the firepit, spaced evenly.

Around the outer portion of the foundation I layed 3 courses of ordinary clay brick, split in half by means of a hammer, and staggered courses/mortar joints properly (also leaving a one brick gap at the 'draw hole' location. After the 3 courses met the equivalent level with the top of the firebrick, I added one more course of ordinary clay brick on their sides all the way around, spanning both the top edge of the firebrick and the covering the top of the 3rd course of half brick. This gave a finished cap to the firepit.

I poured gravel into the middle of the pit for the full depth of the 8" foundation, to the bottom edge of the firebrick.

Thus completed the firepit, exactly according to the instructions found on the "Family Handyman" magazine article (where I first saw it as a subscriber) and according to the website article.

After letting the mortar cure for weeks, I had my first fire, and the firepit split from the top cap all the way through the wall of the firepit completely, along the mortar joints in a zig zagged fashion, to the top portion of the 'draw holes' I had left open, at all 4 spots! I think it is safe to assume that this happened due to thermal expansion. It probably split at those 4 locations because that was naturally the weakest point of the circular wall, which makes sense.

The article says, and I quote, that this firepit "will last forever". It didn't even last one fire. Needless to say, I am extremely disappointed in the "Family Handyman". However, I still have a problem, and I don't want to just accept that the firepit will soon be a pile of loose rubble after I spent so much hard work on it this summer (Hats of to you masons, its a lot harder than you guys make it look).

Obviously the culprit was thermal expansion. Nothing about that in the article. This is what I was thinking could be a solution. What if I chisel/grind out the mortar joints (or portions of it) along the already split part of the firepit due to the expansion, and fill it with a super high temperature caulk (I found one rated for 2500 + degree F) and essentially create control joints along the already split mortar joints? It might look funny, but at least water won't slowly (or quickly) infiltrate and destroy the whole thing.

Also, I was thinking about maybe raising the floor of the pit with a lot more gravel, thus reducing the amount of heat on the inside lower part of the firepit, and focusing it more outwards instead of being so low inside. That would probably cover up my draw holes at the bottom, but I could fit firebrick in those spots to cover those holes and then I could core drill a few holes up higher (I have a handheld Husqvarna wet core drill) when I raised the interior floor.

I've attached a picture of the firepit, before it split.

Thanks for reading this, I look forward to your responses.
 

Attachments

·
Registered
Joined
·
5,842 Posts
Because regular clay brick can crack at high temperatures, we’re using firebrick (also called “refractory” brick) to line the inside of the pit walls. Firebrick is a dense brick that’s kilned to withstand high temperatures. It’s larger, thicker and wider than regular brick, and you can find it at most brickyards. Firebrick is more expensive, but it will stand up to nightly fires for years to come. You’ll need 25 firebricks for a 3-ft. diameter pit.











We used SW (“severe weathering”) face brick (also called “common” or “building” brick) to line the outside pit walls. If your climate doesn’t include freeze/thaw cycles, you can use MW (“moderate weathering”) building brick. Home centers and brickyards carry a large variety of brick.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #4 ·
Tscarborough - It was a premixed bucket, about a one gallon pail. It was wet(ish). I found it difficult to butter firebrick edges with, because it wasn't very sticky, but the firebrick was set with very little gaps between each brick, almost touching.

Ron45- yes that is a copy/paste of the firepit I built.
 

·
Registered
Joined
·
1,605 Posts
That is what I thought. That type of refractory cement is not suitable for your firepit. It is designed for use in dry environments at a maximum joint thickness of 1/8". You can tear it out and reuse the brick, the cleanup of that material is easy.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #6 ·
That is what I thought. That type of refractory cement is not suitable for your firepit. It is designed for use in dry environments at a maximum joint thickness of 1/8". You can tear it out and reuse the brick, the cleanup of that material is easy.

Ok, I could probably chisel/grind out the joints and put the rights refractory cement in. This would just be yet another issue in the article of building this fire pit, as the instructions say, "Refractory cement comes premixed in a bucket and has the consistency of peanut butter." (which is exactly what I bought and used. Par for the course for this project.)

Should I be looking to purchase the stuff that is installed like caulk? And what is your opinion/thoughts of the existing split mortar joints on the outside? Just grind/chisel out and repair or do my control joint idea?
 

·
Registered
Joined
·
9,828 Posts
He said tear it out, not try to repair it.

Tear it out and rebuild is the only real fix for weak joints. Any halfway repair measures will take longer. And, you will be fighting bad joints for the life of the structure.
 

·
Registered
Joined
·
1,605 Posts
You won't need to chisel or grind, this type material is more of a chinking material than a mortar.
 

·
Registered
Joined
·
5,842 Posts
WOW!
Man I was just trying to help you figure out what went wrong. Posting the picture and some info could help others help you.

I thought your pit looked good and wanted to help.

Anyway..

This is what I think may have posed a problem, not saying it did.

The article states..
" The secret is to trowel the cement on thin, like you’re spreading peanut butter on toast, and use the tightest joints you can. "

Also you stated.
" Around the outer portion of the foundation I layed 3 courses of ordinary clay brick,"

The article states.
" Because regular clay brick can crack at high temperatures, we’re using firebrick (also called “refractory” brick) to line the inside of the pit walls "

The articles also states.
" We used SW (“severe weathering”) face brick (also called “common” or “building” brick) to line the outside pit walls. If your climate doesn’t include freeze/thaw cycles, you can use MW (“moderate weathering”) building brick. "
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #10 ·
Ron - wasn't trying to imply anything negative, I just didn't understand your post. Thanks for the compliment, too.

I did both use firebrick to line the inside of the pit wall as well as tight joints no more than 1/8 inch thick. The bricks around the outside really don't matter, they're just different colors and textures of ordinary brick, that was my attempt at creativity. In any case the bricks themselves didn't fracture, it fractured along the mortar joint all the way through. Like I said, I followed the instructions very well, that's why I'm so aggravated and displeased with the project. It took me a long time and the weather didn't help, and I suck as a mason!
 

·
Registered
Joined
·
1,605 Posts
You may have the interior face of the joints at 1/8", but the joints in a circle will always be a wedge and much wider than 1/8". Firebrick calls for full bedding, and your joints were cracking from shrinkage before you started firing. With refractory cement like you used, you fire right away, as it is a heat set material. With refractory mortar, you fire slowly to remove the moisture.

The weather rating of the brick is not important for a firepit, use what you have. You must expect some cracking of the mortar on the exterior of the firepit unless it is designed with a couple of soft joints at the air intake openings as they will be the weak points in the structure.

Ideally, you would have used soft joints at one corner of each opening. It is a firepit, not a house, fire it up!
 

·
Concrete & Masonry
Joined
·
3,882 Posts
Never been a big fan of split firebrick resting tight against face brick, w/o some kind of airspace or insulating castable between them. Just too much potential for thermal issues, like you've now seen.

At this point, I would move forward as you you're suggesting, high heat sealant in the cracks and build up the center with clear stone, so that air & water can still find it's way through, and the vast majority of the heat exits above the brick line........



The correct kind of refractory cement for this kind of work:

http://www.heatstoprefractorymortar.com/productDetail.php?HEAT-STOP-II-HEAT-STOP-50-1


The wrong kind of refractory for this kind of work:

http://alsey.com/products/residential-mortar-indoor/
 

·
Registered
Joined
·
217 Posts
For this project, tearing and rebuilding is the real fix for those weak joints. If you still want to go for halfway repair measures, just remember that the process will surely take a longer time and those bad joints will be a fear for the life. Along this, weather rating of the brick is not important for the firepit. Hence, you can cut down on this part easily.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #14 ·
Thanks for all the advice. I hope to do some sort of repair next spring, probably not until then because now is the weather for using the damn thing. Since it's already cracked, I suppose the stress from the heat expansion is probably no longer a big issue. I should have made sure to leave a gap like momama suggested - and I didn't necessarily fill it solid, but I did let the mortar fall in between the outside face brick and the back side of the firebrick as I was building it, so it's all attached and a solid structure. But a gap filled with small stone would have been better in hindsight. Over the weekend I'm gonna try and get some pictures of the cracks, and post here the beginning of next week.
 

·
Registered
Joined
·
6,734 Posts
wouldn't lining the thing w/carboline or other intumescent material be much easier & faster ? just askin',,, are there no expansion jnts in this small structure to help it withstand temp diffs ?
 

·
Registered
Joined
·
1,605 Posts
"Repair" would indicate return to original condition. If the original condition was not correct, what is there to repair? The real option is either live with it, patch it to extend the life, or tear it out and do it correctly.

For a firepit, I lean heavily upon the "use it until it decomposes" theory as opposed to patching it or repairing it.
 
1 - 20 of 29 Posts
Top