Parging

[Easy Livin’ 3000]

My fireplace used to be an old open cooking fireplace dating from the late 1700's. Later, a brick firebox was built inside the larger opening. They put lath and plaster over that entire wall.

I've torn down the plaster and lath, and see the mortar work between the bricks, that was intended to be hidden, looks very porous.

I need to make sure I'm not just sucking all the hot air up into the chimney through the porous brickwork. I was thinking I should try to airseal it. Parging is the only way I can think of to do this. It's right above the fireplace insert, which is attached to a top sealed chimney liner.

If I parge, is there something special I should add to the mortar? Is there another solution to this?

 

[Simonkenton]

The chimney, which the smoke goes up through, should be a separate structure from the bricks you see there on the front of the fireplace. So, it should not matter if there are flaws in the mortar there.
On such an old fireplace, however, there could be leaks so I think it is a good idea to cover the mortar joints. Sorry don't have much experience in parging, I have done it once long ago, I think you use more mortar mix and less sand.

 

[Easy Livin’ 3000]

The chimney, which the smoke goes up through, should be a separate structure from the bricks you see there on the front of the fireplace. So, it should not matter if there are flaws in the mortar there.
On such an old fireplace, however, there could be leaks so I think it is a good idea to cover the mortar joints. Sorry don't have much experience in parging, I have done it once long ago, I think you use more mortar mix and less sand.

Thanks Simon. I was up in there when I installed the liner and stove. There's a smoke shelf made out of bricks that angles up and back towards the outside, but above that, it's hard to say. The heat is going somewhere, I'm guessing this area is one of the culprits.

 

[Ashful]

Why not remove all of that "modern" brickwork, and get it back to original? Mine was built in, identically to yours, and that's what I did.

In case you need some inspiration...

Before:



Behind the stove... brick firebox like yours:



Removed framed surround and brick firebox:



Removed newer firebox floor:



Cut back old flooring (it went right to firebox edge, as shown above), recessed new subfloor between existing joists, and laid new hearth and extension flush with old floor:



New block-off plate, liner, stove:



I even found some neat surprises, behind that old brick firebox:



Fireplaces are like internal-combustion engines... there's no replacement for displacement.

 

[Easy Livin’ 3000]

That some fine inspiration! I've been mulling over a more thorough restoration, but am a little worried about the structure. I'd need to get a professional assessment before proceeding on this one (@bholler, if you are ever in the neighborhood...). Did you do this yourself? Your stonework looks like the local professional stonemason did the old, original work. I'm pretty sure the poor subsistence farmer who lived here did the masonry himself. Hence, my structural concerns.

I've another fireplace at the opposite side of the room that looks more like yours, they put in a smoking fireplace in that one, but the structure is massive behind it. Eventually, I'll get to that one, too. Then, we can have two stoves going at once in one room, and really get the house warm.