Loose sand behind firebrick?

[newcomtd]

I am making final preparations to my existing firebox while I wait for my chimney liner to appliance adapter to arrive. In the diagram I've attached, the area shaded in yellow is a disgusting mess in my fireplace. It is filled with a sooty, black, grainy substance (creosote?). There are also small chunks of old firebricks and small animal bones! I have been reaching back there and scooping it out cup by cup. I seem to remember reading somewhere this area should be filled with sand. I could see sand being beneficial to keep pressure on the firebricks and also as an insulator. I don't have any sand on hand but I have plenty of roxul. Can I fill the area with roxul or should I go get some sand?

I'm installing a Jotul 550 with a full length insulated liner in an exterior chimney, if that affects the answer.

 

[begreen]

It's good that you are cleaning out the old creosote. I don't see any harm packing that area with roxul afterward.

 

[fossil]

Yeah, I don't think it really needs to be filled with anything. It's not going to fill back up with creosote because of your new liner. I'd say you can put about anything you want in there, so long as it's non-combustible. Rick

 

[Nick Mystic]

See if you can get the nozzle of a good size shop vac in there and suck it out clean. I had something similar in my chimney when I cleaned it out in preparation for my flex liner and free standing stove last February. I scooped out what I could reach and then hit it with my shop vac to finish cleaning out all the junk in there. I just left my compartment empty since nothing new could get in there with both the chimney cap up top and a block off plate down below.

 

[newcomtd]

See if you can get the nozzle of a good size shop vac in there and suck it out clean. I had something similar in my chimney when I cleaned it out in preparation for my flex liner and free standing stove last February. I scooped out what I could reach and then hit it with my shop vac to finish cleaning out all the junk in there. I just left my compartment empty since nothing new could get in there with both the chimney cap up top and a block off plate down below.

I should be able to get my vac hose back there. Thanks guys.