Fireplace Crack

[CR500]

Hi Everyone,

I started buring wood in the fireplace last winter. The front of the fireplace is all rock (real rock, the whole width of the room). About 5hrs into the fires the "keystone" rock would get too hot to touch. At the beginning of the winter I welded up some steel plate that mimicked the shape of a Rumford fireplace (very shallow with angled sides). I figured the rock was getting hot because the fire was too far forward.

The other day I pushed the plates further back in the firebox and looked up at the inside. This picture show what I found:
http://mysite.verizon.net/rjg1.mail/fireplace1.jpg

My guess is that flames were sneaking through the crack between the steel section. It looks almost like standard morter and it looks like it will come off easily. Should that be replaced with refractory cement (Rutland Black furnace cement or Stovo)

This picture is zoomed in on the cement and crack:
http://mysite.verizon.net/rjg1.mail/fireplace2.jpg

There is also a hairline crack further up. I scratched it with a screwdriver and it doesn't open up or fall out. Think I'll coat over that with also with one of the Rutland refractory products.

Thanks

Rob

[Wgoodrich]

Sounds like you have too hot of a fire for a masonry fire place. They are not designed for roaring fires only smaller fires. If you get too hot of a fire it will eventually crack the entire flue and block assembly.

Steel transmits heat. YOu probably didn't help your fireplace any by installing this alternative steel to your fireplace. A fire place box is supposed to be made of fire brick. Then insulation is placed between the fire screen and the fire brick box. The mortar you are using on that steel I suspect is not fire resistant mortar. I would call a fire place mason to help guide you not only in your repairs but proper fire sizing and types of wood to use. You are risking major fire damage to your home if this is not done correctly.

When this fire place was built did you install a footer and air chamber under the fire proof masonry fire box? Did you install an adequate size flue? Did you install a large enough cement block structure around the fire box and flue to ensure non heat transferal? Did you maintain minimum of 2" clearance from the cement blocks to wood in your attic. Did you build your chimney high enough to meet minimum height. Did you build your hearth large enough to meet minimum safety standards? Did you maintain minimum clearance for you fireplace mantel? All the above questions factors in safety from fire to your home.

I would call a fire place mason to look over your fire place to ensure your safety.

Be safe

Wg

[CR500]

Hi WG,

I was burning seasoned maple. I split about 6 cords two years ago. Don't know the lbs/log but it was consuming about 5 logs / hour.

I'm not the original owner of the house so I don't know the firebox construction. The back side of the chimney is in the garage. I measured the block temperature in the garage as well as in the attic and the walls surrounding the chimney. I didn't measure a temp rise on the walls. The garage blocks did indicate a temp increase, but it was very low. The stones at mantle height don't get hot like the keystone. I've also checked the block temps in the basement and don't see any increase. Gotta love the infrared thermometer!

I just put a "lock top" damper on. The flue is 13"x17" and only services the fireplace. The chimney top is well above the roof (I had to put a ladder on the roof and climb up about 10' - and I don't like heights!). This fireplace has the strongest draft I have ever seen and never comes close to dumping smoke.

I realize the steel insert conducts heat (you can hear it make noise as it expands), but there is a significant air gap between the back of the steel and the fire brick. I'll bet the firebrick behind the steel is at a lower temp than if the insert wasn't there.

You're probably correct in that the fire was too hot. That in combination with the crack between the steel headers and fire pulled forward caused the one stone to get hot.

Thanks

Rob