How Do I Seal Gap Under Wood Fireplace Insert

[ArmyMP]

Hi Everyone. Just moved into this house last October and we have a wood burning fireplace insert. Recently, all of the material between the bottom of the insert and the brick is crumbling and cracking apart and coming out. (See photos)

What do I need to replace this stuff with? High-temp silicone seal?

Do I need to put anything in there? I would like to fill the gap with something, just not sure what. Any help is greatly appreciated.

Thanks

 

[Rickb]

Someone else with more expertise then me will have better info, but I would think you could just scrap it all out and vacuum it up then use stove cement.

 

[Ludlow]

Is it even necessary? Looks like crap.

 

[blacktail]

Unless it needed to be shimmed up to level it with the hearth, I don't think there should be anything under there. In that case it would be some kind of brick or stone.

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[begreen]

Looks like maybe someone painted the edge of some cement board? One option would be to clean it out to solid material, vacuum and then run a neat bead of black silicone to seal around the edge.

 

[sportbikerider78]

Whatever that is, I would remove it till i couldn't see it and call it a day.

 

[coaly]

I would be concerned that the Insert is not connected to a liner that allows cleaning without removing insert. It was common to slide an Insert into hearth using the much larger existing fireplace flue. This is no longer acceptable and the Insert must now be connected to a liner the same size as the Insert outlet. Remove the fireplace front cover at top to be sure it has a pipe connected to Insert, extending up chimney flue.
The main reason is the exhaust gasses expand into the larger chimney area, cooling below the condensing point forming creosote.
Also, without direct connection, you have to pull the Insert out each time the chimney is cleaned and that could be the cause of crumbing of shim material under it. It should set on a clean brick hearth bottom.

 

[begreen]

Good thought Coaly. Before fixing the problem have the flue system for the insert checked and cleaned. Have the sweep verify if and how the insert is vented.