Advice needed: Fixing 2" gap in firebox ceiling

[cj-8_jim]

Hi again,
Being new to fireplaces and wood inserts, I need your opinions and ideas on a firebox repair I'm going to make.

In the home we just bought, I noticed that there is a 2"-3" x 33" gap in the firebox's ceiling immediately behind the facing brick (and about 10" in front of the damper.

Since I'm installing a wood insert with a dedicated full-length chimney liner, I guess I don't need to repair it, but I'd like to fix it.
(The one and only time I used the fireplace, a good amount of smoke went up that gap and started coming out the ashbox in the fireplace on the floor immediately above it).

I was thinking of pushing in some rolled metal lattice in the gap and apply regular brick mortar to it.

QUESTIONS:
1) Is regular brick mortar sufficient and will it withstand the high temps 10-12" above the wood insert?
- Or must I use refractory cement?
- Since I'll probably have "gobs" of mortar > 1/8" max thickness for refractory cement (per label), I was thinking regular brick mortar might be better, but I don't know if regular mortar withstands high heat hanging from a firebox ceiling.

2) I don't trust my drilling/anchoring skills in masonry... Is rolled lattice without anchoring, held in only by the mortar sufficient?

Thanks again for your help,
Jim

 

[edthedawg]

Jim,

Sounds bad. like, real bad.

Any chance you could snap pix of this massive flaw in your fireplace? Kinda amazed the house is still standing if this fireplace ever saw a real fire in it. Ever.

:ahhh:

 

[Later]

There were a number of houses around here that were built so that you could reach up behind the fireplace opening and feel the 2x6 that was used for the lintel. It put the builder out of business.

 

[cj-8_jim]

Jim,

Sounds bad. like, real bad.

Any chance you could snap pix of this massive flaw in your fireplace? Kinda amazed the house is still standing if this fireplace ever saw a real fire in it. Ever.

:ahhh:

I'll try to get photos tonight.

The sellers/prior owners (there for about 15 years) had the fireplace mantel and brick facing remodeled. They told me they never really used that fireplace (I now know why!).

When I look up the flue, the square clay liner has the light orange-ish color... almost like it has not seen much/any use over 40 years! The firebox and smoke shelf is black though, but really no creosote buildup.

 

[cj-8_jim]

Here's the photo of the 2”-3” x 33” gap in the firebox’s ceiling between the red angle iron and the black angle iron (and about 10” in front of the damper).

I also just noticed that it looks like there is a second gap (about 1"x33" behind the facing marble immediately behind my head)

The plan is to install a wood insert and full-length SS chimney liner.

That being said, what's the best way and what's the cheapest way to plug this to limit heat escape off the top of the insert?
1) stuff some fiberglass insulation up there? If so, any special kind?

2) fill with regular brick mortar and lattice?

3) fill with refractory cement (says max thickness should be 1/8" which is not enough to do the job on this gap) and lattice?

4) just build a block of plate for the crack out of HVAC plenumn material

5) Other ideas???

Thanks for the advice,
Jim

FLICKER PHOTO:

ATTACHED PHOTO:

 

[afblue]

What year was the house built? The chimney looks to be just regular brick inside so I think the Full SS liner is madatory, but it willl also have to be an insulated liner too. I would consider stuffing the gaps above with a fire resistant insulation like Rock Wool, or steel wool, not fiberglass. The temps after the insert is installed are not going to be much over 200F if that so once you take up the majority of the dead airspace with insulation and a wire mortar combo will make it a permenent fix for your insert, butt never again for an open fire. Looks like you have a damper similar the one in my fireplace which is too narrow to fit the liner through, so it will probably have to be cut and this will prevent the fireplace from ever being used without an insert.

 

[cj-8_jim]

AFBLUE,
The house was built in 1969.
I agree, it's a trade-off to no longer use the fireplace for wood once the chimney is lined, insulated, and damper notched out.

got a question, when you say "take up the majority of the dead airspace with insulation and a wire mortar combo",
what kind of mortar? regular brick mortar? Or refractory cement?

I'd do refractory cement, but the label says don't apply more than 1/8" thick. With all the gaps I have, I'll have > 1/8".

But if I use regular brick mortar, will that withstand the heat?

Thanks,
Jim

 

[afblue]

I would say regular brick mortar. If you have large gaps that you need to fill I would use a non combustible insulation instead of trying to pack it with full of mortar. The state of the fireplace it should never ever be used again without an insert inside it confirmed further that the flue isnt lined, I can see that through the damper and see the flue is only brick. Personally I would think packing the gaps with just noncombustible insulation would be sufficent, the brick temps outside the fireplace insert wont get any higher than 200-300 degrees. The insert is bascially a firebox inside of a heat shield, and the blower draws air from the bottom front, and runs it in between the firebox and heat shield and sends the heat out the upper louver. The heat never makes it (High temps) to the brick enclosure besides right by the flue, which you will have an insulated SS flue liner connected to it. Since the current state of the fireplace its not suited for an open fire, I would not make any repairs that would lend someone (many years from now) to think the fireplace could be used alone, by mortaring the gaps closed. So I would go right ahead and cut the damper out and install a full Insulated SS liner.

 

[elmoleaf]

The problem you describe is typical for many fireplaces. There'll often be a gap between the face brick you see on the outside, and the firebox/lintel/smoke chamber structure behind. This gap behind the steel lintel will typically allow smoke up behind the face brick. Though a common problem, it's not normal and should be fixed.
I had a similar size gap. I filled it with a mixture of mortar and perlite....which makes a lightweight insulated filler, much like Thermix. You could also mix perlite or vermiculite with furnace cement to make a lightweight refractory filler for the gap.