Rumford As Advertised but not the Firebrick and Mortar.


Hi Jim,

Hoping that you can give me some advice. Some time ago you gave me advice about the correct size Rumford to put in my family room--- a 36 inch Rumford.

Well, we finally closed on the house and had our first fire. It works just as you advertised. It draws beautifully. I have been building tipi fires which burn great, and, just as you say on the site, they collapse onto themselves as they burn. I have invited so many people that were doubting the design when the fireplace was being built and have turned them into believers.

But, I have run into a problem. After five fires, the mortar in the brickwork is starting to crumble. In one point it has crumbled out of the joint and there is a hole between the bricks. As well, on one of the bricks, a small portion of the face cracked off. This all seems to be happening in the area where the fire is being leaned on the fireback and lower.

My mason assured me that he used heat refractory mortar and it is obvious that the brick is firebrick. The fireplace was built about six months ago while the house was closed in, so, it cured for about six months.

Have you ever seen this happen? Can you provide me with any advice that I can give to my mason who will be doing the repair?

Thank you very much in advance for your help.

Robert Kulak


It would help me to know what state you live in. A picture of the fireplace would also help. Some firebrick does not even meet the ASTM standards for low duty firebrick. It would also be interesting to know what brand of refractory mortar your mason used. At least then we can ask the manufacturer for advice. Some masons still throw a handful of "fireclay" into regular mortar and call it "fireclay mortar" or sometimes erroneously "refractory mortar". Refractory mortar specified by the code must comply with ASTM C-199.

Whatever firebrick and mortar your mason used, the fix is about the same and pretty simple. Use HeatStop 50 or HeatStop II, which our dealers sell and we sell on line at to patch, tuckpoint and repair the damaged mortar. The damaged firebrick should be easy to remove and replace if the mortar is deteriorating.

The work is easy for your mason. Probably you can do it yourself. Wash the firebox. Force the HeatStop in the joints with a trowel or putty knife (a mason would use a pointing trowel) and wash the excess mortar off the face of the bricks within a half hour before it cures and becomes difficult to remove. The color might not match but use the fireplace after about 24 hours and you'll probably not notice the repair.

Glad to hear that you are enjoying your Rumford - otherwise. Thanks for the feedback.

Jim Buckley

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