When do cracks in the firebrick become a concern (for a fireplace)?

[Swamp_Yankee]

For those that have been following my other threads I've decided to keep my fireplace open and let the wood stove on the other side of the house do the heating. I am going to get some sealed doors for when it is not in use however. In any event I just gave the firebox a good cleaning and took a good look at two small cracks in the brick as well as some deterioration of the mortar. How bad is this? Should the brick be pulled out, replaced and repointed soon? I should add that I have a 1/2" steel fireback on the way. Admittedly it will be more for looks than heat retention but I understand that it should protect the rear wall of the firebox as well.

Thoughts? The rest of the brickwork and mortar are completely solid.

 

[Easy Livin’ 3000]

For those that have been following my other threads I've decided to keep my fireplace open and let the wood stove on the other side of the house do the heating. I am going to get some sealed doors for when it is not in use however. In any event I just gave the firebox a good cleaning and took a good look at two small cracks in the brick as well as some deterioration of the mortar. How bad is this? Should the brick be pulled out, replaced and repointed soon? I should add that I have a 1/2" steel fireback on the way. Admittedly it will be more for looks than heat retention but I understand that it should protect the rear wall of the firebox as well.
View attachment 268505
Thoughts? The rest of the brickwork and mortar are completely solid.

I have similar cracks. I don't think it's an issue, but look forward to the expert opinions.

 

[bholler]

For those that have been following my other threads I've decided to keep my fireplace open and let the wood stove on the other side of the house do the heating. I am going to get some sealed doors for when it is not in use however. In any event I just gave the firebox a good cleaning and took a good look at two small cracks in the brick as well as some deterioration of the mortar. How bad is this? Should the brick be pulled out, replaced and repointed soon? I should add that I have a 1/2" steel fireback on the way. Admittedly it will be more for looks than heat retention but I understand that it should protect the rear wall of the firebox as well.
View attachment 268505
Thoughts? The rest of the brickwork and mortar are completely solid.

Nothing to worry about yet. A fireback will help protect the brick

 

[Swamp_Yankee]

Nothing to worry about yet. A fireback will help protect the brick

What would constitute a problem crack? Something say 1/16" or more wide?

 

[bholler]

What would constitute a problem crack? Something say 1/16" or more wide?

If any brick are loose or large cracks. Probably 1/8"