Fire Brick Gaps

[jeffs]

I know lots of people have asked about this, but I've read conflicting answers so looking for something definitive.

I recently replaced a couple of fire bricks in our wood stove (Napoleon 1900). I bought Rutland bricks at Ace that are the size specified in the manual for our stove. (9" x 4-1/2" x 1-1/4")

When I put the bricks in, I'm ending up with 1/4" - 3/8" gaps. When I installed the original bricks (when stove was new), I had minor gaps (1/8" +). Bricks were not tight, I guess to allow for expansion/contraction. Now, comparing new bricks to originals, side-by-side, they are a little shorter (not a full 9").

If this was on the floor of the stove I wouldn't be concerned, just pack it with ash. But these gaps are on the sides and back wall, I can't get ash to stay in these vertical gaps.

What is an acceptable gap in fire bricks?

Would filling the gaps with refrac. cement, or some pieces of gasket rope be a good idea?

 

[firebroad]

For what it is worth, the bricks that came with my stove have the same gaps. I don't really worry about them, the stove doesn't seem to suffer because of it.

 

[jeffs]

Yeah, I wasn't worried about the original gaps, but some of these are so loose now the bricks feel like they could fall off each other.

There is a long, thin one on the front, just inside the door that stands on end, and literally has no bricks from the side touching it to hold it in place. It is so loose it feels like it could fall in. The gap there is in the corner, and probably a good 1/2" wide. I'm thinking about stuffing some gasket rope in the gap to put a little tension on the brick and keep it from being so loose.

 

[blueguy]

My 1450 has the same brick layout, and there are some small gaps along the back of the firebox that haven't affected anything negatively. The two small upright ones on either side of the door move slightly as you described, but they have never fallen in or moved in a way for me to think they would. In your case, I don't see why some gasket rope stuffed into the wider openings would have a negative effect either. I personally wouldn't worry about it, but if you do use the rope, just make sure room for expansion is left (i.e. don't pack it in tight).

 

[DougA]

My guess is that it won't get super hot in those gaps because air is trapped there and air makes a great insulator. When the gap is so large that you can get air creating an eddy in the gap, then I might get worried.

 

[jeffs]

Yes, the original bricks had small gaps. Not a problem. But the replacement brick is a little smaller and is leaving bigger gaps (approx. 1/2"). I don't know what's large enough for eddies of air, but that 1/2" gaps seem pretty big.

The brick along the side of the door is one I replaced, and last weekend when I had a fire it kept wanting to fall in (leaning in big-time).

Long story short, I bought some 1/2" gasket rope and put in the large gaps. It fit perfectly.

Annoying that Rutland's bricks are so much shorter and yet still called 9" in length.

 

[Chuck the Canuck]

Annoying that Rutland's bricks are so much shorter and yet still called 9" in length.

It wouldn't be the first time someone exaggerated the length of.... something.....

 

[BobUrban]

Buy an extra brick and cut it to fit the gap(s) with a grinder and a cutting wheel. They cut easy.