Cracking firebox mortar

[AlexT]

Hi everyone, first post here so I hope this is in the right place.

I have a question about our open fireplace. Our house was built in 1962, and aside from us installing some drystack veneer stone on the face of the fireplace, the rest is original.

When we first moved in five years ago, I noticed some of the mortar joints between the bricks of the floor were in poor shape. I chissled and dug out what I could, and repaired the missing mortar with a premixed fireplace mortar repair in a tube (pretty sure it was made by quickcrete). Not sure if this was ideal or not.

We had a chimney sweep come out to clean it at the same time and he gave us the all clear to use it, he did not find any issues aside from a poor design given our firebox is quite shallow.

We have since been using the fireplace over the last five years, only burning maybe five to ten fires a season (half of which are the wax/wood fire logs, the other half would be using decent hardwood. We only use the fireplace for ambience and have never had any real big hot fires in it.

Fast forward to now, and I noticed that some of the mortar again has some small cracks/gaps in it. I'm wondering if this is caused by thermal expansion/contraction, or could this be a sign of something else?

Is this something that should be repaired? Or will ash eventually fill in the cracks?

Here are a could pics, my apologies as they aren't of the best quality. Thanks in advance!

 

[AlexT]

Just bumping this back to the top

 

[Ludlow]

My opinion is it's just normal cracking due to settling and expansion/contraction. Firebox isnt shallow IMO. It would burn much better if you got a real grate instead of that ....thing. Looks too small and how high off the hearth is it?

 

[AlexT]

Thank you for the reply. I thought the same thing but just wanted a second opinion. Appreciate it!

 

[Ludlow]

Larger grate and larger fire and it would probably burn better. All the soot on the firebox tells a tale. From years of open fireplace burning I learned that big fires are best until you get a good hot bed of coals. Then you can reduce the wood amount and still keep a clean fire going. Be sure the flue is cleaned before building any "barn burner" fires though! A history of dirty little fires could mean a very dirty and dangerous creo buildup that a big fire will ignite and turn into a torch.